POLYCARBONATE, USE THEREOF, PRODUCTION THEREOF, AND PURIFICATION THEREOF

Abstract: The polycarbonate of the invention includes ones based on sucrose, oligosaccharides other than it, and monosaccharides each having a specified cyclic structure; ones derived from specified saccharides not containing any cyclic structure; ones having a skeleton of pentaerythritol, neopentyl glycol or trimethylolethane; and specified ones. The lubricant and electrical insulation oil of the invention contain the polycarbonate.

Description: The present invention relates to novel polycarbonates and uses thereof, more particularly to polycarbonates which are excellent in compatibility with hydrogenated fluorocarbon (HFC) used as a refrigerant for refrigerators such as Freon R-134a or R-152a which is nondestructive to the ozone layer, hydrogenated chlorofluorocarbon (HCFC) which is small in ozone depletion potential such as Freon R-22, R-123 or R-124, and mixtures of the above-mentioned hydrogenated products and also excellent in lubricating properties. This invention also relates to lubricant oil comprising such polycarbonates as mentioned above, particularly those suitable for use in refrigerators where Freon which is nondestructive to the ozone layer is used as a refrigerant. Further, the present invention relates to polycarbonates excellent in compatibility and lubricating properties as aforesaid and also excellent in electrical insulation properties, and to lubricant oil and electrical insulating oil comprising such polycarbonates as mentioned above, particularly lubricant oil suitable for use in refrigerators where Freon which is nondestructive to the ozone layer is used as a refrigerant, and lubricant oil and electrical insulating oil suitable for use in electric refrigerators. Furthermore, the present invention relates to processes for preparing and purifying the polycarbonates as mentioned above. TECHNOLOGICAL BACKGROUND With the alteration of refrigerant gas for refrigerators to hydrogenated fluorocarbons such as Freon R-134a (CH 2 F-CF 3 ) which is an ozone layer-nondestructive HFC, mineral oils or alkylbenzenes which have heretofore been used as lubricant oil for refrigerators have come not to be used therefor because they have no compatibility with the refrigerant gas. Accordingly, such compounds as polypropylene glycol, polypropylene glycol monoalkyl ether and polypropylene glycol dialkyl ether have come to be used as lubricant oil for refrigerators. However, the above-mentioned compounds are low in compatibility with Freon R-134a, and there was such a problem that among the compounds mentioned above, those having such high viscosity as a kinematic viscosity at 100°C of more than 15 cSt are particularly low in compatibility with Freon 134a, and hence exhibit low performance as a lubricant oil for refrigerators, for example, a lubricant oil for a rotary automatic air-conditioner. By the way, polycarbonates are materials which are usable as various lubricant oils or components thereof. However, polycarbonates known heretofore have a volume resistivity of the order of 10 11 to 10 12 Ω·cm, and they were not always sufficient to show good electrical insulation properties when used in the fields of lubricant oils and electrical insulating oils where the electrical insulation properties are required. Accordingly, there has heretofore been desired not only the advent of highly viscous compounds excellent in lubricating properties as well as electrical insulating properties and also in compatibility with Freon R-134a but also the advent of lubricant oils for refrigerators containing such compounds as mentioned above. French Patent No. 2,321,477 discloses tricarbonate of trimethylolpropane represented by the following general formula. CH 3 - CH 2 - C[CH 2 - O - CO- O -R] 3 In the above general formula, R is branched or non-branched alkyl of 4-12 carbon atoms, cycloalkyl, allyl or aralkyl which may be substituted sometimes with lower alkyl. Accordingly to the above-cited French patent, it is alleged that the disclosed tricarbonate can be used as a main component of lubricants stable to heat, and the lubricants containing this tricarbonate may be used particularly in supersonic aircraft. Of the polycarbonates, particularly those having an alkyl group at the molecular terminals have such an advantage that they are low in hygroscopicity. Japanese Patent L-O-P Publn. No. 3865/1971 discloses a process for preparing such polycarbonates. That is, this Japanese publication teaches that such polycarbonates as mentioned above may be obtained by allowing 1 or 2 mols of a diol to react with 1 or 2 mols of a monoalcohol in a mixture of n mols of the diol and (n-1) mols of diphenyl carbonate. For example, the above-cited publication discloses a process for preparing a polycarbonate having a decyl group at the molecular terminals by allowing n-decanol as the above-mentioned diol to react with polyethylene glycol as the above-mentioned diol while heating under a reduced pressure. In the above-mentioned process, highly reactive diphenyl carbonate is used preferably as a starting carbonate. The reason why highly reactive diphenyl carbonate is used as the starting carbonate in preference to other carbonates is that this diphenyl carbonate has a high boiling point and so it is easy to preset the reaction conditions therefor. In contrast thereto, when dimethyl carbonate or diethyl carbonate which is low in reactivity and has a low boiling point is used as the starting carbonate in the above-mentioned process, it is not easy to terminate the molecular terminals of the resulting polycarbonate substantially only with an alkyl group. Furthermore, a catalyst must be used when such a low reactive carbonate as mentioned above is used as the starting carbonate, but it is also not easy to remove the catalyst having a high boiling point from the reaction product. It is, however, industrially an economically advantageous to use, as the starting material, dimethyl carbonate or diethyl carbonate which is available at a low price as compared with diphenyl carbonate. It has already been known, in general, that a polycarbonate can be obtained by a reaction of a monoalcohol with a carbonate such as dimethyl carbonate. However, no desired polycarbonate can be obtained in good yield by the prior art process for preparing polycarbonates by allowing a polyol instead of a monoalcohol with the carbonate, distilling off the remaining unreacted carbonate by heating after completion of the reaction, and neutralizing the catalyst with an acid, because polymerization of the above-mentioned unreacted carbonate takes place at the stage of distilling off said unreacted carbonate. As the process for preparing polycarbonates, there has heretofore been known, for example, a process for preparing polycarbonate which comprises reacting a polyol such as diethylene glycol with a carbonate such as dimethyl carbonate by heating in the presence of a basic catalyst, distilling off the unreacted carbonate by heating, and neutralizing the catalyst with an acid such as an organic acid. In the polycarbonate obtained by the above-mentioned process where the catalyst contained in said polycarbonate is merely neutralized, however, an ionic compound remains therein. Accordingly, the polycarbonates obtained by the above-mentioned process involve such a problem that their characteristics such as electrical resistance properties will deteriorate. FR-A-1367493 relates to lubricants obtained by reacting propylene oxide and/or butylene oxide with the reaction product of saccharose and ethylene oxide. DE-AS-1006565 discloses mixed polycarbonate esters of the following formula wherein x, n and y are at least 1 and A and B are derived from alcohols having 1 to 60 carbon atoms. Sorbit is mentioned as one of many examples for alcohol components usable in the above polycarbonate. The present invention is intended to solve such problems associated with the prior art as mentioned above, and an object of the invention is to provide polycarbonates excellent in compatibility with an ozone layer-nondestructive hydrogenated fluorocarbon such as Freon R-134a, with hydrogenated chlorofluorocarbon having small ozone destruction power and further with mixtures thereof, particularly highly viscous polycarbonate excellent in compatibility (mutual solubility) with Freon R-134a. A further object of the invention is to provide polycarbonates excellent not only in compatibility as aforesaid but also in lubricating properties as well as in electrical insulation properties. Another object of the invention is to provide lubricant oils and electrical insulating oils comprising the above-mentioned polycarbonates, particularly lubricant oils suited for use in refrigerators where an ozone layer-nondestructive Freon is used as a refrigerant, and lubricant oils and electrical insulating oils particularly suited for use in electric refrigerators. A still further object of the invention is to provide a process for preparing polycarbonates having an alkyl group at the molecular terminals in high yields and in an economical manner by aid of simplified preparative step. A still another object of the invention is to provide a process for purifying polycarbonates by removing basic substances from the polycarbonates containing the same and thereby obtaining polycarbonates excellent in electrical insulation properties. DISCLOSURE OF THE INVENTION The first novel polycarbonates of the present invention are those represented by the following general formula [I]. Su - O - R wherein Su is a group represented by the following formula (A) and R is a group selected from the groups represented by the following formulas (B), (C), (D), (E) and (F). In the above-mentioned formulas (A), (B), (C) and (D), R 1 is a group represented by the following formula (E) or (F). - (C 3 H 6 O) n COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n is an integer of 1 to 12. - (C 3 H 6 O) n (C 2 H 4 O) p COOR 2 wherein R 2 is as defined in the above-mentioned formula (E), and n and p are each an integer of 1 to 12. The second novel polycarbonates of the invention are those represented by the following general formula [II]. (R 1 O) CH 2 [CH(OR 1 )] m CH 2 (OR 1 ) wherein R 1 is a group represented by the following formula (E) or (F), and m is an integer of 1 to 6. -(C 3 H 6 O) n COOR 2 wherein R 2 and n are as defined above, respectively. -(C 3 H 6 O) n (C 2 H 4 O) p COOR 2 wherein R 2 , n and p are as defined above, respectively. The lubricant oils of the present invention, such as those for refrigerators, are characterized by containing the above-mentioned first and second, polycarbonates of the invention. The lubricant oils of the invention are excellent in lubricating properties as well as in detergency, and they are easy to decrease in viscosity at low temperature, hence the present lubricant oils can be used for wide applications such as industrial gear oil, automotive engine oil, automotive gear oil, lubricant oil for refrigerators such as automotive air-conditioner and electric refrigerator, lubricant oil for the textile industry and lubricant oil for the rolling mill. The present lubricant oils are excellent not only in such characteristics as mentioned above but also excellent in compatibility with an ozone layer-nondestructive Freon such as Freon R-134a dn R-152a, with a hydrogenated fluorocarbon having a small ozone destructing force such as Freon R-22, R123 and R-124, and with mixtures thereof, hence they can be used as lubricant oil for refrigerators wherein the above-mentioned ozone layer-nondestructive Freon, hydrogenated fluorocarbon and mixture thereof are used as refrigerant. In the present invention, lubricant oils containing, besides the above-mentioned polycarbonates, an ozone layer-nondestructive Freon such as R-134a, a hydrogenated fluorocarbon having a small ozone destructing force such as Freon R-22 and mixtures thereof may also be used as lubricant oil for refrigerators. In the present specification, the term "lubricant oil" used is intended to include lubricant oils comprising the polycarbonates of the invention and other components and also lubricant oils comprising the polycarbonates of the invention only. The processes for preparing and purifying polycarbonates of the present invention are defined in claims 9-13. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1 and 2, are graphs individually showing IR absorption spectra of polycarbonates obtained in Examples 1 and 9, respectively. PREFERRED EMBODIMENT OF THE INVENTION The polycarbonates, uses thereof and processes for preparing and purifying the same according to the present invention are illustrated below in detail. First of all, the first and second novel polycarbonates of the invention and the uses of the same are described hereinafter. The first novel polycarbonates of the invention are sucrose polycarbonates, oligosaccharide polycarbonates other than the sucrose polycarbonates and monosaccharide polycarbonates, all being represented by the following general formula [I]. Su - O - R wherein Su is a group represented by the following formula (A) and R is a group selected from the following formulas (B), (C), (D), (E) and (F). In the above-mentioned formulas (A), (B), (C) and (D), R 1 is a group represented by the following formula (E) or (F). - (C 3 H 6 O) n COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n is an integer of 1 to 12. - (C 3 H 6 O) n (C 2 H 4 O) p COOR 2 wherein R 2 and n are as defined in the above-mentioned formula (E), and p is an integer of 1 to 12. The second novel polycarbonates of the invention are those derived from sugar having no cyclic structure and having the following general formula [II]. (R 1 O) CH 2 [CH(OR 1 )] m CH 2 (OR 1 ) wherein R 1 is a group represented by the following formula (E) or (F), and m is an integer of 1 to 6. -(C 3 H 6 O) n COOR 2 wherein R 2 and n are as defined in the above-mentioned formula (E). -(C 3 H 6 O) n (C 2 H 4 O) p COOR 2 wherein R 2 , n and p are as defined in the above-mentioned formula (F). In the present invention, the ratio of n to p (n/p) in the above-mentioned formula (F) is 0.5 to 20, preferably 1 to 10 and especially 2 to 5. In the above-mentioned formulas (E) and (F), the hydrocarbon group as R 2 includes aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, aromatic aliphatic hydrocarbons and glycol ethers represented by the following general formula - (R 3 - O) q - R 4 wherein R 3 is an alkylene group having 2 to 3 carbon atoms, R 4 is a hydrocarbon group having not more than 28 carbon atoms. Concrete examples of the aliphatic hydrocarbon group as the above-mentioned R 2 include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, pentyl, isopentyl, neopentyl, n-hexyl, 2,3-dimethylbutyl, isohexyl, n-heptyl, isoheptyl, n-octyl, 2-ethylhexyl, isooctyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, isoundecyl, n-dodecyl, isododecyl, n-tridecyl, isotridecyl, n-tetradecyl, isotetradecyl, n-pentadecyl, isopentadecyl, n-hexadecyl, isohexadecyl, n-heptadecyl, isoheptadecyl, n-octadecyl, isooctadecyl, n-nonyldecyl, isononyldecyl, n-eicosanyl, isoeicosanyl, 2-ethylhexyl and 2-(4-methylpentyl). Further, concrete examples of the alicyclic hydrocarbon group as the above-mentioned R 2 include cyclohexyl, 1-cyclohexenyl, methylcyclohexyl, dimethylcyclohexyl, decahydronaphthyl and tricyclodecanyl. Furthermore, concrete examples of the aromatic hydrocarbon group as the above-mentioned R 2 include phenyl, o-tolyl, p-tolyl, m-tolyl, 2,4-xylyl, mesityl and 1-naphthyl. Still further, concrete examples of the aromatic aliphatic hydrocarbon group as the above-mentioned R 2 include benzyl, methylbenzyl, β-phenylethyl (phenetyl), 1-phenylethyl, 1-methyl-1-phenylethyl, p-methylbenzyl, styryl and cinnamyl. Concrete examples the alkylene group as the above-mentioned R 3 include ethylene, propylene and isopropylene. Further, the hydrocarbon group as the above-mentioned R 4 includes aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. Concrete examples of these hydrocarbons mentioned above include the same examples exemplified as the aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons of the above-mentioned R 2 . The glycol ether group represented by the above-mentioned general formula -(R 3 -O) q -R 4 includes concretely ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monoethyl ether and tripropylene glycol mono-n-butyl ether. When the first and second novel polycarbonates of the invention are used as lubricant oils for refrigerators wherein an ozone layer-nondestructive Freon gas such as Freon R-134a is used as a refrigerant, the above-mentioned R 2 represents desirably lower alkyl such as methyl, ethyl, isopropyl or n-butyl, or alkylene glycol monoalkyl ether such as ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monoethyl ether or tripropylene glycol mono-n-butyl ether. The first novel polycarbonates of the invention represented by the above-mentioned general formula [I] include concretely, for example, those having the following formulas as mentioned below, respectively. Further, the second novel polycarbonates of the invention represented by the above-mentioned general formula [II] include concretely, for example, those having the following formulas as mentioned below, respectively. The polycarbonates represented by the above-mentioned general formula [I] or [II] may be prepared, for example, by a process as mentioned below. First, a mixture comprising (a) a polyol represented by the general formula [III] or [IV] as will be mentioned later, and (b) a carbonate represented by the general formula [V]: R 5 OCOOR 5 wherein R 5 are corresponding to R 2 as mentioned above and each dependently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, R 5 OH resulting from said carbonate during the course of reaction with said polyol being lower in boiling point from that of said polyol as will be represented by the general formula [III] or [IV], and the carbonate being used in such an amount that the molar ratio of this carbonate to the polyol of the general formula [III] or [IV] is from 3 to 80, is heated in the presence of a basic catalyst, and the mixture is allowed to undergo reaction so as to proceed to a reaction ratio of not less than 95%. In carrying out the above-mentioned reaction, it is desirable that the reactor used therefor is nitrogen substituted, though this is not essential thereto. Subsequently, the basic catalyst is removed from the reaction product, and the unreacted carbonate is distilled off from the reaction system to obtain the polycarbonate represented by the above-mentioned general formula [I] or [II]. In the process as illustrated above, there is a possibility that there are formed not only the polycarbonates obtained by carbonation of all the hydroxyl groups of the starting polyol but also small amounts of the polycarbonates obtained by carbonation of parts of the hydroxyl groups of this polyol. The general formula [III] representing the above-mentioned polyol (a) is as follows: Su - O - R 6 wherein Su is a group represented by the following formula (G), and R 6 is a group selected from those represented by the following formulas (H), (I), (J), (K) and (L). In the above-mentioned formulas (G), (H), (I) and (J), R 7 is a group represented by the following formula (K) or (L). -(C 3 H 6 O) n H wherein n is an integer of 1 to 12. -(C 3 H 6 O) n (C 2 H 4 O) p H wherein n and p are each an integer of 1 to 12. Concrete examples of the polyol represented by the above-mentioned general formula [III] include those represented by the formulas as mentioned below. In these formulas, n is an integer of 1 to 12. (5) - (8) Polyols (5) to (8) are those represented respectively by the same chemical formulas shown in the foregoing (1) to (4) polyols, except that the -(C 3 H 6 O) n H groups in each formula have been substituted with the -(C 3 H 6 O) n (C 2 H 4 O) p groups. The polyols (1') to (4') are represented by the following general formula [IV] (R 7 O)CH 2 [CH(OR 7 )] m CH 2 (OR 7 ) wherein R 7 is a group represented by the following formula (K) or (L), and m is an integer of 1 to 6. - (C 3 H 6 O) n H wherein n is an integer of 1 to 12. - (C 3 H 6 O)n(C 2 H 4 O) p H wherein n and p are each an integer of 1 to 12. Concrete examples of the polyols represented by the above-mentioned general formula [IV] include those represented by the following formulas. In these formulas mentioned below, n is an integer of 1 to 12. (3') and (4') Polyols (3') and (4') are those represented by respectively by the same chemical formulas shown in the foregoing (1') and (2') polyols except that the -(C 3 H 6 O) n H groups in each formula have been substituted with the -(C 3 H 6 O) n (C 2 H 4 O) p H groups. The carbonate represented by the above-mentioned general formula [V] which is used preferably in the above-mentioned process for preparing the polycarbonates represented by the general formula [I] or [II] includes concretely dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, dihexyl carbonate, dioctyl carbonate, dicyclohexyl carbonate, di-2-ethylhexyl carbonate and di(2-methyl-methoxyethyl)carbonate. In this process, the carbonation reaction is allowed to proceed while distilling off alcohol resulting from this reaction from the reaction system, hence the thus formed alcohol, that is, alcohol represented by R 5 OH, must have a boiling point lower than that of the above-mentioned polyol. Further, the carbonates exemplified above are used in such an amount that the molar ratio of the carbonate to the polyol of the above-mentioned general formula [III] or [IV] is 3 to 80, preferably 3 to 50. By using the limited amount of the carbonate as defined above, it is possible to inhibit the formation of polycarbonate of high polymerization degree. In the process mentioned above, the reaction is carried out by heating the above-mentioned polyol and carbonate in the presence of a basic catalyst in the reactor so as to proceed to a reaction ratio of not less than 95%, while distilling off the resulting alcohol from the reaction system. After removing the basic catalyst from the reaction product, the unreacted carbonate is distilled off from the reaction system. By the expression "...so as to proceed to a reaction ratio of not less than 95%" as used herein is meant that the reaction is continued until the above-mentioned resulting alcohol is formed not less than 0.95 times the molar quantity of the polyol represented by the above-mentioned general formula [III] or [IV]. The basic catalyst preferably used in this process includes alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, alkali metal carbonate or hydrogen carbonate such as sodium carbonate or sodium hydrogen carbonate, alkali metal alcoholate such as sodium methoxide, potassium methoxide, lithium methoxide or cesium methoxide, and alkali metal compound such as sodium hydride or sodium amide. Of these basic catalysts, particularly preferred is the alkali metal alcoholate. In addition thereto, there may also be used, for example, alkaline earth metal compound such as magnesium hydroxide or calcium hydroxide, organic amino compound such as trimethylamine, triethylamine, imidazole or tetramethylammonium hydroxide. These catalysts are used in such an amount that the molar ratio (the number of moles of the catalyst/the number of moles of the polyol) is usually 10 -1 to 10 -7 , preferably 10 -2 to 10 -5 . In the process of the invention mentioned above, the reaction is carried out at a temperature of usually 50 to 300°C, preferably 60 to 200°C, and the reaction time is usually 0.5 to 200 hours, preferably 1 to 100 hours. Removal of the catalyst after the completion of the reaction is carried out by washing with water or by neutralizing with acid. The acid used herein includes solid acids such as sulfonic acid type ion exchange resins; inorganic acids such as carbonic acid, ammonium chloride, hydrochloric acid, sulfuric acid and phosphoric acid; and organic acids such as acetic acid and phenol. In carrying out the water washing as mentioned above, such a salt as ammonium carbonate may be added to the water. According to the process of the invention carried out in the manner now described, polymerization of the polycarbonate can be inhibited, said polymerization being caused by distilling off the unreacted carbonate in the presence of the basic catalyst, by removing first the basic catalyst and then distilling off the unreacted carbonate under reduced pressure, and hence the desired polycarbonate can be obtained in high yield. The thus obtained polycarbonate may be freed from a trace amount of impurities, if necessary, by treating it with adsorbents such as activated clay and activated carbon or by washing it with water. In particular, a trace amount of ionic or polar compounds can be removed by such treatment as mentioned above from the polycarbonate obtained above, the polycarbonate thus treated can be stored stably. When dimethyl carbonate is used as the starting carbonate in the reaction of the above-mentioned process of the invention, an azeotrope former such as cyclohexane, benzene or hexan may be added to the reaction system before initiation of the reaction, whereby methanol produced may be removed from the reaction system as an azeotropic mixture with the azeotrope former instead of removing methanol as an azeotropic mixture with dimethyl carbonate from the reaction system. The azeotrope former is usually used in an amount of 5 to 100% by weight based on 100% by weight of dimethyl carbonate. According to the procedure mentioned above, methanol is removed during the course of reaction as an azeotropic mixture with the above-mentioned azeotrope former from the reaction system, and the unreacted dimethyl carbonate is recovered from the reaction mixture after completion of the reaction, and hence the recovery thereof can be increased. There is another procedure wherein methanol is recovered as an azeotropic mixture with dimethyl carbonate as described above, the above-mentioned azeotrope former is then added to the azeotropic mixture to remove methanol as an azeotropic mixture with said azeotrope formed from dimethyl carbonate, and dimethyl carbonate can be thus recovered. According to the process of the invention as illustrated above, the desired polycarbonates can be obtained in high yields, because the basic catalyst used is removed from the reaction product after completion of the reaction of the polyol with carbonate, and the unreacted carbonate is then removed from the reaction system. Furthermore, the polycarbonates represented by the general formula [I] or [II] may also be prepared by the process as will be mentioned hereinafter. First, a mixture comprising (a) a polyol represented by the aforementioned general formula [III] or [IV], (b) a monoalcohol represented by the following general formula [VI]: R 8 OH wherein R 8 is the same as R 2 defined in the aforementioned general formula (E), and (c) a carbonate represented by the following general formula [VII]: R 9 OCOOR 9 wherein R 9 are each independently an alkyl group having 1 to 2 carbon atoms, R 9 OH resulting from said carbonate during the course of reaction with said polyol and monoalcohol being lower in boiling point of those of said polyol and monoalcohol, and said carbonate being used in such an amount that the molar ratio of the carbonate to the polyol of the general formula [III] or [IV] is 3 to 80, is heated in the presence of a basic catalyst, and the mixture is allowed to undergo reaction so as to proceed to a reaction ratio of not less than 95%, while distilling off the resulting alcohol (R 9 OH) from the reaction system. In carrying out this reaction, it is desirable that the reactor used therefore is nitrogen substituted, though this is not essential thereto. Subsequently, the basic catalyst is removed from the reaction product, and the unreacted carbonate is distilled off from the reaction system to obtain the polycarbonate represented by the above-mentioned general formula [I] or [II]. Even in this process as illustrated above, there is still a possibility that there are formed not only the polycarbonates obtained by complete carbonation of the hydroxyl groups of the starting polyol but also small amounts of the polycarbonates obtained by partial carbonation of the hydroxyl groups of this polyol. In this process, the carbonation reaction is allowed to proceed while distilling off alcohol resulting from this reaction from the reaction system, hence the thus formed alcohol, that is, alcohol represented by R 9 OH, must have a boiling point lower than those of the above-mentioned polyol and monoalcohol. Further, the carbonates exemplified above are used in such an amount that the molar ratio of the carbonate to the polyol of the above-mentioned general formula [III] or [IV] is 3 to 80, preferably 3 to 50. By using the limited amount of the carbonate as defined above, it is possible to inhibit the formation of polycarbonates of high polymerization degree. In the process mentioned above, the reaction is carried out by heating the above-mentioned polyol, monoalcohol and carbonate charged in the reactor in the presence of a basic catalyst so as to proceed to a reaction ratio of not less than 95%, while distilling off the resulting alcohol from the reaction system. After removing the basic catalyst from the reaction product, the unreacted carbonate is distilled off from the reaction system. By the expression "...so as to proceed to a reaction ratio of not less than 95%" as used herein is meant that the reaction is continued until the above-mentioned resulting alcohol is formed not less than 0.95 times the molar quantity of the polyol represented by the above-mentioned general formula [III] or [IV]. With respect to the basic catalyst, reaction temperature, reaction time, removal of the catalyst after completion of the reaction, removal of impurities from the end product and recovery of the unreacted dimethyl carbonate, this process of the invention as mentioned above is carried out in the same manner as in the process of the invention as mentioned previously. In the process of the invention as first mentioned, the carbonates other than dimethyl carbonate and diethyl carbonate represented by the general formula [V] must be synthesized when they are used, because they are difficult to avail commercially. On the other hand, in the process of the invention just described above, the desired polycarbonates can be prepared by using easily available carbonates represented by the general formula [VII] (dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate), hence this process is more economical than the process as first mentioned. Furthermore, the desired polycarbonates can be obtained in high yields in the manner similar to the case of the process as first mentioned. The polycarbonates of the present invention are excellent in lubricating properties as well as in detergency and, at the same time, they are also excellent, though they are highly viscous, in compatibility with an ozone layer-undestructive hydrogenated fluorocarbon such as Freon R-134a, with a hydrogenated chlorofluorocarbon having a small ozone destructive power such as Freon R-22 and further with mixtures thereof. Accordingly, the polycarbonates of the invention can be utilized as lubricant oils for refrigerators wherein highly viscous lubricant oils are used. The lubricant oils of the invention such as lubricant oils for refrigerators contain at least one of the polycarbonates of the invention as mentioned above, that is, the polycarbonate represented by the general formula [I] or [II]. Accordingly, the lubricant oils of the invention such as lubricant oils for refrigerators may contain both the polycarbonate of the general formula [I] and the polycarbonate of the general formula [II]. In addition to the polycarbonates of the general formulas [I] and [II], the lubricant oils of the invention such as lubricant oils for refrigerators may contain further other polycarbonates, for example, those derived from lower aliphatic hydrocarbon polyether glycols. The lubricant oils of the invention such as lubricant oils for refrigerators may contain other components in addition to the polycarbonates as mentioned above. In addition to the polycarbonates of the invention, the lubricant oils of the invention may be loaded with other usable components such as glycol ethers, for example, polyether glycol of a random copolymer of ethylene oxide and propylene oxide, carbonates derived from this polyether glycol, and mineral oils, for example, neutral oil or bright stock, and further with α-olefin oligomer such as liquid polybutene, and liquid decene oligomer, carboxylic acid esters such as diisooctyl adipate, diisooctyl sebacate and dilauryl sebacate, or vegetable oils. Particularly, in the case of the lubricant oils of the invention used as a lubricant oil for refrigerators wherein HFC, for example, Freon R-134a is used as an ozone layer-nondestructive refrigerant, the above-mentioned other usable components are limited to glycol ethers or carboxylic acid esters from the standpoint of compatibility. In that case, however, the amount of these usable component loaded to the lubricant oil must be limited to less than 60% by weight based on 100% by weight of the total amount of the lubricant oil, otherwise the lubricant oil thus loaded will deteriorate in heat resistance, compatibility with Freon R-134a and hygroscopicity. Further, the lubricant oils for refrigerators of the invention may also be loaded with an epoxy compound as a chlorine complementary agent used against inclusion into the lubricant oil of a phenolic stabilizer, defoaming agent or chlorine refrigerant. Furthermore, in the present invention, it is possible to contain in the lubricant oils of the invention for use in refrigerators such known additives for lubricant oil, for example, detergent-dispersants, antioxidants, anti-load agents, oiliness improvers and pour point depressants as disclosed in "Additives for Petroleum Products", compiled by T. Sakurai, Saiwai Shobo, 1974 in such an amount that the objects of the present invention can be accomplished without hindrance. Still further, the lubricant oils for refrigerators of the invention may also contain an ozone layer-nondestructive Freon (HFC) such as Freon R-134a, Freon (HCFC) having a small ozone-destructive force such as Freon R-22 and mixtures thereof. Further, when the polycarbonates represented by the general formulas [I] and [II], of the present invention, from which the aforementioned lubricant oils are prepared, are used as rolling lubricant oils, metal working oils and lubricant oils for fibers, it is also possible to use these carbonates in the form of an emulsion in water. The polycarbonates obtained respectively by the above-mentioned processes contain basic substances. The process for the preparation of polycarbonates according to the present invention may comprise a purification step. Removal of basic substances from polycarbonates containing the same may be performed by the following three process steps. (1) A process step for the removal of basic substances from polycarbonates, which comprises removing the basic substances from the polycarbonates containing the same by washing said polycarbonates with water. In carrying out this process step, it is desirable that the basic substances contained in the polycarbonates is neutralized with an aqueous weak acid solution, and the polycarbonates are then washed with water. Useful aqueous weak acid solutions in this process step include those of inorganic acids such as ammonium carbonate, carbonic acid, ammonium chloride, etc.In that case, if necessary, a non-polar solvent may be added to the polycarbonates containing the basic substances prior to subjecting them to such removal treatment as mentioned above.The non-polar solvent referred to above includes concretely aromatic hydrocarbons such as toluene, benzene, xylene, etc., and saturated hydrocarbons such as hexane, octane, etc. (2) A process step for the removal of basic substances from polycarbonates, which comprises bringing the basic substances contained in the polycarbonates into contact with an inorganic ion exchanger. In this process step, if necessary, a non-polar solvent may also be added to the polycarbonates containing the basic substances prior to subjecting said polycarbonates to such removal treatment as mentioned above.Useful inorganic ion exchangers in this process include concretely zeolite and "IXE inorganic ion exchangers" produced by Toa Gosei Chem. Ind. Co. Ltd., for example, inorganic ion exchangers of the cation exchanger such as GRADE IXE-100 (ingredient: zirconium compound), IXE-300 (ingredient: antimony compound), etc., and inorganic ion exchangers of the amphoteric ion exchanger such as GRADE IXE-600 (ingredients: antimony, bismuth compound). In the present invention, there may also be used as the inorganic ion exchanger such inorganic materials as acid clay and dolomite, but they are low in ion exchange ability.As is well known, the ion exchangers include inorganic ion exchangers and organic ion exchangers, but an organic ion exchanger having a sulfone group as an exchange group is low in ion exchange ability. (3) A process step for the removal of basic substances from polycarbonates containing the same, which comprises employing a combination of the treatment for the removal of basic substances by means of water-washing as described in the foregoing (1) with the treatment for the removal of basic substances by means of an inorganic ion exchanger. In this process step, the above-mentioned treatment (1) may first be carried out followed by the above-mentioned treatment (2), or the treatment (2) may first be carried out followed by the treatment (1).In the present invention, it is desirable that the basic substances are removed from the polycarbonates containing the same by the above-mentioned process steps (1) or (3), followed by dehydration treatment. EFFECT OF THE INVENTION The first and second polycarbonates of the present invention, that is, those represented by the general formulas [I] and [II] as mentioned previously, are excellent in lubricating properties and detergency and, at the same time, excellent in compatibility, though they are highly viscous, with an ozone layer-nondestructive HFC such as Freon R-134a or 152a, a bydrogenated chlorofluorocarbon (HCFC) having a small ozone-destructive ability such as Freon R-22, R-123 or R-124 or mixtures thereof. Of the polycarbonates of the invention, even those having a high kinematic viscosity at 100°C as high as 15 cSt or more are also excellent in compatibility with Freon R-134a. The first and second polycarbonates of the invention having such effect as mentioned above may be used as lubricant oils for refrigerators wherein an ozone layer-nondestructive Freon R-134a is used as a refrigerant, for example, a lubricant oil for rotary car air conditioners, and also as lubricant oils for refrigerators wherein a conventional Freon is used as a refrigerant, automotive engine oils, automotive gear oils, rolling lubricant oils and lubricant oils for fibers. According to the process for preparing the polycarbonates of the present invention, after completion of the reaction of polyol with carbonate, the basic catalyst used may be removed from the reaction mixture, followed by removal of unaltered carbonate, and hence it is possible to obtain polycarbonates. In the present invention, moreover, when the polycarbonates are prepared, there is no need for preparing the starting carbonate compound in advance, because the carbonate compound used in the invention may be dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate which is easily available. Accordingly, in accordance with the present invention, there can be prepared polycarbonates with economy. In accordance with the process step for purifying polycarbonates of the present invention, there can be obtained polycarbonates of such high purity that the amount of a residual base is not more than 0.1 ppm and the total acid value is less than 1. The present invention is illustrated below with reference to examples, but it should be construed that the invention is in no way limited to those examples. In the following examples, the results of analysis and evaluation of performance of the polycarbonates were obtained by the following test methods. (1) Analytical method a. Average molecular weight Using a GPC system of Shimadzu Seisakusho Ltd., the average molecular weight of the polycarbonate obtained was determined on the basis of polystyrene. The conditions under which the average molecular weight was determined are as follows. Column: Four (4) pieces of polystyrene gel (G-2000HXL + G-2000HXL + G-3000HXL + G-4000HXL) Sensor: Differential refractometer Solvent: Tetrahydrofuran Rate of elution: 0.7 ml/min b. Infrared absorption spectrum The determination is conducted using the specimen spread between KBr plates by means of an infrared spectrometer manufactured and sold by Nippon Bunkoh K.K. c. NMR analysis The n value of the formula [E] representing R 1 in the general formulas [I] and [II] is obtained by the proton NMR method JNM-GX270 manufactured and sold by Nippon Densi K.K. (2) Evaluation method a. Kinematic viscosity JIS K-2283 b. Viscosity index JIS K-2283 c. Pour point JIS K-2269 d. Load bearing capacity After a 5-minute warming-up operation under a load of 250 lbf using a Falex tester, the load is increased continuously, and a value of the increased load obtained, at which burn markings have appeared, is taken as a value of load bearing capacity. e. Volume resistivity A volume resistivity of the polycarbonate obtained was determined in accordance with ASTM D 257. f. Compatibility with Freon R-134a (1) A test tube of 10 mm in inside diameter and 20 cm in depth is charged with 1 ml of the specimen and, while cooling the test tube on a dry ice/acetone bath, Freon R-134a is introduced gradually into the test tube from a bomb and stored so as to reach a volume slightly larger than that of the specimen. The mixture in the test tube is then stirred by means of a spatula, and the test tube is transferred onto a cooling bath kept at -20°C to investigate a solubility of the specimen in Freon R-134a at the time when the volume ratio of the specimen/Freon R-134a has become 1/1. At the time of the investigation, when the resulting mixture is a perfectly homogeneous solution, the rating is taken as o, and when the specimen does not dissolve in Freon R-134a, the rating is taken as x. (2) In order to investigate the solubility of the carbonate product in Freon R-134a more in detail, a lubricant and Freon R-134a are encapsulated in various proportions into a glass tube to obtain a critical temperature at which the two compounds become compatible with each other. Example 1 A 5-liter reactor equipped with a distillation column of a 10-sieve tray was charged with 764 g (0.97 mol) of a propylene oxide adduct of sucrose having an average molecular weight (Mn) of 740 (SU-460 of PPG-polyfunctional Series, a product of Mitsui Toatsu Chem. Inc.), 2370 g (26.33 mol) of dimethyl carbonate and 0.73 g (0.004 mol in terms of NaOCH 3 ) of a methanol solution of 28% by weight of NaOCH 3 . The resulting mixture was heated at 110-120°C at atmospheric pressure to carry out reaction while distilling off the resulting methanol as an azeotropic mixture with dimethyl carbonate, whereby the effusion of the methanol ceased after 9.0 hours. The amount of the methanol formed was 189 g (5.0 mol), and the yield of the methanol was about 100%. The reaction mixture thus obtained was charged with hexane and, the catalyst was neutralized with an aqueous solution containing ammonium carbonate in an amount of five times the molar quantity of the NaOCH 3 used. The reaction mixture thus treated was washed with water, and the hexane and unaltered dimethyl carbonate were removed from said reaction mixture containing the same to obtain 1067 g of a polycarbonate. The polycarbonate thus obtained is a viscous liquid, and from the results of 1 H-NMR, 13 C-NMR, IR and GPC analysis, it was found that the polycarbonate has a structure represented by the following formula. wherein R is -[CH 2 CH(CH 3 )O] n COOCH 3 in which n = 0-3, and an average value of n is about 1.1. The polycarbonate obtained was analyzed by means of 13 C-NMR, whereby such peaks as mentioned below appeared in the chart. In this case, CDCl 3 was used as the solvent therefor. 16-17 ppm, 54-55 ppm, 66-67.5 ppm, 69-70 ppm, 70-72 ppm, 72-73 ppm, 73-74 ppm, 74-76 ppm, 76.5-78 ppm, 78-79 ppm, 79-80 ppm, 80-81.5 ppm, 81.5-83 ppm, 83-85 ppm, 88-90 ppm, 103-105 ppm, 154-155 ppm The infrared absorption spectrum of the polycarbonate obtained are shown in Fig. 1, wherein the main peaks observed are as in the following. νC-H 2800-3000 cm -1 δC-H 1440 cm -1 νC=O 1745 cm -1 νC-O 1250-1290 cm -1 νC-O-C 1100 cm -1 The results of GPC analysis of the polycarbonate obtained are shown below. Weight-average molecular weight (Mw)/number-average molecular weight (Mn) GPC : 1.51 Weight-average molecular weight measured by the polystyrene conversion method : 1337 Amount of sodium remaining in the product: Not more than 0.01 ppm Total acid value in the product: Not more than 0.01 Results of evaluation of fundamental performance as lubricating oil are shown in Table 1. Example 2 The same procedure as described in Example 1 was repeated to obtain 526 g of a polycarbonate, except that 352 g (0.44 mol) of a propylene oxide adduct of sucrose (SC-800, a product of Asahi Denka K.K.) having an average molecular weight of 800 was used instead, and the amounts of the dimethyl carbonate and the methanol solution containing 28% by weight of NaOCH 3 used were changed to 1632 g (18.12 mol) and 0.3 g (0.0016 mol in terms of NaOCH 3 ), respectively. The amount and yield of methanol as formed were 111.9 g (3.49 mol) and 99%, respectively. The polycarbonate thus obtained was viscous liquid, and from the results of 13 C-NMR, IR and GPC analysis it was found that the polycarbonate has a structure represented by the following formula. wherein R is -[CH 2 CH(CH 3 )O] n COOCH 3 in which n = 0-3, and an average value of n is about 1.3. The polycarbonate obtained was analyzed by means of 13 C-NMR, whereby such peaks as mentioned below appeared in the chart. In this case, CDCl 3 was used as the solvent therefor. 16-17 ppm, 54-55 ppm, 66-67.5 ppm, 69-70 ppm, 70-72 ppm, 72-73 ppm, 73-74 ppm, 74-76 ppm, 76.5-78 ppm, 78-79 ppm, 79-80 ppm, 80-81.5 ppm, 81.5-83 ppm, 83-85 ppm, 88-90 ppm, 103-105 ppm, 154-155 ppm Data of the infrared absorption spectrum of the polycarbonate obtained are shown in Fig. 1, wherein the main peaks observed are as in the following. νC-H 2800-3000 cm -1 δC-H 1445 cm -1 νC=O 1740 cm -1 νC-O 1240-1295 cm -1 νC-O-C 1100 cm -1 The results of GPC analysis of the polycarbonate obtained are shown below. Weight-average molecular weight (Mw)/number-average molecular weight (Mn) GPC : 1.43 Weight-average molecular weight (Mw) measured by the polystyrene conversion method : 1076 Amount of sodium remaining in the product: Not more than 0.01 ppm Total acid value in the product: Not more than 0.01 Results of evaluation of fundamental performance as lubricating oil are shown in Table 1. Example 3 The same reactor as used in Example 1 was charged with 377 g of a propylene oxide adduct of sucrose having an average molecular weight (Mn) of 580 (SU-450M of PPG-Polyfunctional Series, a product of Mitsui Toatsu Chem. Inc.), 901 g of isopropanol, 1351 g of dimethyl carbonate and 2 g of a methanol solution containing 28% by weight of NaOCH 3 . The mixture thus charged was allowed to undergo reaction at atmospheric pressure at 90-140°C for 18 hours. After removal of the catalyst from the reaction mixture thus obtained, diisopropyl carbonate was distilled off to obtain 570 g of a polycarbonate. The polycarbonate thus obtained was viscous liquid, and from the results of 13 C-NMR, IR and GPC analysis it was found that the polycarbonate has a structure represented by the following formula. wherein R is -[CH 2 CH(CH 3 )O] n COOCH(CH 3 ) 2 , in which n = 0-3, and an average value of n is about 1.1. The polycarbonate obtained was analyzed by means of 13 C-NMR, whereby such peaks as mentioned below appeared in the chart. In this case, CDCl 3 was used as the solvent therefor. 16-18 ppm, 21-22 ppm, 54-55 ppm, 71-72 ppm, 74-75 ppm, 74.5-75.5 ppm, 76.5-78 ppm, 89-90 ppm, 104-105 ppm Data of the infrared absorption spectrum of the polycarbonate obtained are shown in Fig. 1, wherein the main peaks observed are as in the following. νC-H 2800-3000 cm -1 δC-H 1450 cm -1 νC=O 1740 cm -1 νC-O 1240-1290 cm -1 νC-O-C 1100 cm -1 The results of GPC analysis of the polycarbonate obtained are shown below. Weight-average molecular weight (Mw)/number-average molecular weight (Mn) [GPC] : 1.48 Weight-average molecular weight (Mw) measured by the polystyrene conversion method : 2736 Amount of sodium remaining in the product: Not more than 0.01 ppm Total acid value in the product: Not more than 0.01 Results of evaluation of fundamental performance as lubricating oil are shown in Table 1. Example 4 The same reactor as used in Example 1 was charged with 402 g of a propylene oxide adduct of sucrose having an average molecular weight (Mn) of 740 (SU-460 of PPG-Polyfunctional Series, a product of Mitsui Toatsu Chem. Inc.), 400 g of polypropylene glycol (molecular weight 2,000), 805 g of n-butanol, 980 g of dimethyl carbonate and 0.9 g of a methanol solution containing 38% by weight of NaOCH 3 . The mixture thus charged was allowed to undergo reaction at atmospheric pressure at 110-160°C for 18 hours. After removal of the catalyst from the reaction mixture thus obtained by the addition thereto of water, dibutyl carbonate was distilled off to obtain 997 g of a polycarbonate having a structure represented by the following formula. wherein R is -[CH 2 CH(CH 3 )O] n COOC 4 H 9 , in which n = 0-3, and an average value of n is about 1.1. Results of evaluation of fundamental performance as lubricating oil are shown in Table 1. Lubricating properties of the polycarbonates as prepared in Examples 1-4 evaluated on the basis of the compatibility of said polycarbonates with Freon R-134a and load bearing capacity of said polycarbonates were excellent. Example 5 A car air-conditioner (TV-12EC, a product of Nippon Denso Co.,Ltd.) was started by an electric motor (2,000 rpm) using 120 cc of the polycarbonate of Example 4 as an oil for refrigerator and 700 g of Freon R-134a (HFC) as a refrigerant, whereupon it was possible to carry out the air-conditioning operation as is evident from the data shown in Table 2. In this case, the outdoor temperature was 23°C. Referential Example 1 Example 5 was repeated exactly in the same manner, except that in place of the polycarbonate of Example 4, a commercially available oil for refrigerator (Denso Oil-7, a product of Nippon Denso Co., Ltd.) was used and in place of Freon R-134a (HFC), Freon R-12 (CFC) was used. The results obtained are shown in Table 2. In this case, the outdoor temperature was 23°C. Example 6 Example 1 was repeated to obtain 412 g of a polycarbonate, except that in place of the propylene oxide adduct of sucrose, a propylene oxide adduct of lactose having an average molecular weight of 798 was used. The polycarbonate thus obtained was a viscous liquid, and from the results of 13 C-NMR, IR and GPC analysis, it was found that the polycarbonate has a structure represented by the formula mentioned below. wherein R is -[CH 2 CH(CH 3 ]O] n COOCH 3 , in which n = 0-3, and an average value of n is about 1.3. The compatibility of the polycarbonate thus obtained with Freon R-134a as measured by the test method (1) mentioned in Table 2 was rated o. Example 7 Example 1 was repeated to obtain 386 g of a polycarbonate, except that in place of the propylene oxide adduct of sucrose, a propylene oxide adduct of isomaltose having an average molecular weight of 856 was used. The polycarbonate thus obtained was viscous liquid, and from the results of 13 C-NMR, IR and GPC analysis, it was found that the polycarbonate has a structure represented by the formula mentioned below. wherein R is -[CH 2 CH(CH 3 ]O] n COOCH 3 , in which n = 0-3, and an average value of n is about 1.5. The compatibility of the polycarbonate thus obtained with Freon R-134a as measured by the test method (1) mentioned in Table 2 was rated o. Example 8 Example 1 was repeated to obtain 506 g of a polycarbonate, except that in place of the propylene oxide adduct of sucrose, an addition product of propylene oxide and ethylene oxide of sucrose was used. The polycarbonate thus obtained was viscous liquid, and from the results of analysis of 13 C-NMR, IR and GPC analysis, it was found that the polycarbonate has a structure represented by the formula mentioned below. wherein R is -[CH 2 CH(CH 3 )O] n [CH 2 CH 2 O] p COOCH 3 in which n = 0-3, an average value of n is 2.2, p = 0-3, and an average value of p : about 1.0. The compatibility of the polycarbonate thus obtained with Freon R-134a as measured by the test method (1) mentioned in Table 2 was rated o. Example 9 Example 1 was repeated to obtain 535 g of a polycarbonate, except that 356 g (0.59 mol) of a propylene oxide adduct of sorbitol (SP-600, a product of Asahi Denka Kogyo K.K.) as a polyol, and the amounts of dimethyl carbonate and the methanol solution of 28% by weight of NaOCH 3 used were changed to 1607 g (17.84 mol) and 0.34 g (0.0018 mol in terms of NaOCH 3 ), respectively. The amount of methanol formed was 110 g (3.44 mol), and the yield of methanol was 97%. The polycarbonate thus obtained was a viscous liquid, and from the results of 13 C-NMR, IR and GPC analysis, it was found that the polycarbonate has a structure represented by the following formula mentioned below. wherein R is -[CH 2 CH(CH 3 )O] n COOCH 3 in which n = 0-3, and an average value of n is about 1.2. The polycarbonate obtained was analyzed by means of 13 C-NMR, whereby such peaks as mentioned below appeared in the chart. In this case, CDCl 3 was used as the solvent therefor. 16-17.5 ppm, 54-55 ppm, 66-68 ppm, 68.5-70 ppm, 70-72 ppm, 72-73 ppm, 73-74.5 ppm, 74.5-76 ppm, 76-78 ppm, 78-79 ppm, 79-80 ppm, 154-156 ppm. The infrared adsorption spectrum of the polycarbonate obtained is shown in Fig. 2. The results of GPC analysis of the polycarbonate obtained are shown below. Weight-average molecular weight (Mw)/number-average molecular weight (Mn) GPC : 1.23 Weight-average molecular weight (Mw) measured by the polystyrene conversion method : 778 Amount of sodium remaining in the product: Not more than 0.01 ppm Total acid value in the product: Not more than 0.01 Results of evaluation of fundamental performance as lubricating oil are shown in Table 3. Example 10 The same reactor as used in Example 1 was charged with 557 g of a propylene oxide adduct of sucrose having an average molecular weight (Mn) of 1380 (SP-21P, a product of Toho Kagaku Kogyo K.K.), 1747 g of diisopropyl carbonate and 2.1 g of a methanol solution of 28% by weight of NaOCH3. The resulting mixture was allowed to undergo reaction at atmospheric pressure and 120-150°C for 7 hours. The polycarbonate thus obtained is a viscous liquid, and from the results of 1 H-NMR, IR and GPC analysis, it was found that the polycarbonate has a structure represented by the formula mentioned below. wherein R is -[CH 2 CH(CH 3 )O] n COOCH(CH 3 ) 2 , in which n = 0, 3-4, and an average value of n is about 3.4. The polycarbonate obtained was analyzed by means of 1 H-NMR, whereby such peaks as mentioned below appeared in the chart. In this case, CDCl 3 was used as the solvent therefor. 1.1-1.2 ppm, 1.25-1.32 ppm, 3.25-3.45 ppm, 3.45-3.60 ppm, 3.6-3.8 ppm, 4.8-4.9 ppm. Data of the infrared absorption spectrum of the carbonate obtained are shown below, wherein the main peaks are as shown in the following. νC-H 2800-3000 cm -1 δC-H 1450 cm -1 νC=O 1740 cm -1 νC-O 1240-1290 cm -1 νC-O-C 1100 cm -1 The results of GPC analysis of the polycarbonate obtained are shown below. Weight-average molecular weight (Mw)/number-average molecular weight (Mn) GPC : 1.23 Weight-average molecular weight (Mw) measured by the polystyrene conversion method : 2936 Amount of sodium remaining in the product: Not more than 0.01 ppm Total acid value in the product: Not more than 0.01 Results of evaluation of fundamental performance as lubricating oil of the polycarbonate obtained are shown in Table 3. Example 11 Example 10 was repeated to obtain 867 g of a polycarbonate, except that 700 g of an addition product of propylene oxide and ethylene oxide of sorbitol having an average molecular weight (Mn) of 1530 (SP-21P, a product of Toho Kagaku Kogyo K.K.) was used instead, and the amounts of diisopropyl carbonate and the methanol solution of 28% by weight of NaOCH 3 were changed to 2344 g and 14 g, respectively. The polycarbonate thus obtained was a viscous liquid, and from the result of 1 H-NMR, IR and GPC analysis, it was found that the polycarbonate has a structure represented by the formula mentioned below. wherein R is -[CH 2 CH(CH 3 )O] n [C 2 H 4 O] p COOCH(CH 3 ) 2 in which n = 0-6, an average value of n is about 3.5, p = 0-2, and an average value of p is about 1.0. The polycarbonate obtained was analyzed by means of 1 H-NMR, whereby such peaks as mentioned below appeared in the chart. In this case, CDCl 3 was used as the solvent therefor. 1.1-1.18 ppm, 1.25-1.32 ppm, 3.25-3.45 ppm, 3.45-3.60 ppm, 3.6-3.8 ppm, 4.8-4.9 ppm. Data of the infrared absorption spectrum of the polycarbonate are shown with reference to the main peaks as mentioned below. νC-H 2800-3000 cm -1 δC-H 1450 cm -1 νC=O 1740 cm -1 νC-O 1240-1280 cm -1 νC-O-C 1100 cm -1 The results of GPC analysis of the polycarbonate obtained are shown below. Weight-average molecular weight (Mw)/number-average molecular weight (Mn) GPC : 1.29 Weight-average molecular weight (Mw) measured by the polystyrene conversion method : 2989 Amount of sodium remaining in the product: Not more than 0.01 ppm Total acid value in the product: Not more than 0.01 Results of evaluation of the fundamental performance as lubricating oil of the polycarbonate obtained are shown in Table 3. Example 12 Example 10 was repeated to obtain 1100 g of a polycarbonate, except that 1050 g of polypropylene glycol having a molecular weight of 1500 was used instead, the amounts of diisopropyl carbonate and the methanol solution of 28% by weight of NaOCH 3 used were changed to 1533 g and 4 g, respectively, and the reaction temperature and reaction time were changed to 140-150°C and 10 hours, respectively. The polycarbonate thus obtained had a kinematic viscosity at 100°C of 21 cSt, the compatibility of the polycarbonate with Freon R-134a measured by the aforesaid test method (1) was rated o, and the critical temperature of the polycarbonate as measured by the aforesaid test method (2) was 59°C at the high temperature side and -65°C at the low temperature side. This polycarbonate (A) and the polycarbonate (B) of Example 10 were mixed together in a weight ratio [(A)/(B)] of 25/75 to obtain a polycarbonate having such lubricant characteristics as shown in Table 3. The polycarbonates obtained in Examples 9-12 were all excellent in lubricating properties as defined on the basis of the determined compatibility with Freon R-134a and load bearing capacity. Reference Example 2 A 3-liter reactor equipped with a 10 sieve tray distillation column was charged with a mixture containing 802 g (2.00 mol) of polypropylene glycol having an average molecular weight of 400, 1,804 g (20.03 mol) of dimethyl carbonate and 0.39 g (NaOCH 3 : 0.0020 mol) of a methanol solution of 28% by weight of NaOCH 3 . The mixture was heated at 110-120°C and ordinary pressure to carry out the reaction while distilling off the resulting methanol as the dimethyl carbonate azeotrope, whereby the methanol ceased to distill after 8 hours. The methanol thus formed was 127 g (3.97 mol), and the yield of methanol was 99%. The reaction mixture thus obtained had the Na content of 44 ppm. The reaction mixture was then charged with hexane and an aqueous solution obtained by dissolving 0.96 g (0.01 mol) of ammonium carbonate in 1 liter of distilled water, stirred thoroughly to neutralize the catalyst, and left at rest followed by separation of an aqueous phase. Subsequently, an oily phase remained was washed three times with 1 liter of distilled water, and the hexane and unaltered dimethyl carbonate were removed from the oily phase containing the same to obtain 1,032 g of a polycarbonate. Shown in Table 4 are the results of analysis of inorganic elements and free ions contained in the polycarbonate thus obtained. By virtue of the water-washing treatment mentioned above, the Na content in the polycarbonate reduced up to 0.036 ppm, and other elements and free ions were all below the limit of detection. The electrical insulation properties of this polycarbonate as measured in terms of a volume resistivity which is regarded as a measure of said properties was 7.0 x 10 11 Ω.cm. This polycarbonate charged with 1 liter of toluene and 20 g of an inorganic ion exchanger (Grade IXE-600, a product of Toa Gosei Chemical Industry Co., Ltd.) was allowed to undergo ion exchange by heating with stirring at 100°C for 3 hours. Subsequently, the resulting liquid thus treated was cooled and filtered to remove the toluene therefrom, whereby 1,011 g of a purified polycarbonate. Shown in Table 4 are the results of analysis of inorganic elements and free ions contained in the purified polycarbonate thus obtained. This polycarbonate was found to have a volume resistivity of 4.2 x 10 12 Ω.cm, and it was understood that the polycarbonate has improved in electrical insulation properties by virtue of the above-mentioned treatment with inorganic ion exchanger. The polycarbonate obtained was a viscous liquid which, on analysis by means of proton NMR and GPC, comprises polypropylene glycol dimethyl carbonate as a main constituent. The weight average molecular weight/number average molecular weight ( M w/ M n) ratio as measured by means of GPC in the polyolefin was 1.1. Reference Example 3 Reference Example 2 was repeated except that in place of the polypropylene glycol and dimethyl carbonate there were used 106 g (0.55 mol) of tripropylene glycol and 1,575 g (5.51 mol) of di-[2-ethylhexyl]carbonate, respectively, and the amount of the methanol solution of 28% by weight of NaOCH 3 used was changed to 0.11 g (NaOCH 3 0.0006 mol). The reaction gave 2-ethylhexanol in an amount of 143 g and in 100% yield. The reaction mixture thus obtained contained 10.1 ppm of sodium. This reaction mixture was subjected, in the same manner as in Reference Example 2, to neutralization, water-washing and removal by distillation of unaltered di[ethylhexyl]carbonate, whereby 244 g of a polycarbonate was obtained. Shown in Table 5 are the results of analysis of inorganic elements and free ions contained in the polycarbonate thus obtained. The electrical insulation properties of this polycarbonate as measured in terms of a volume resistivity which is regarded as a measure of said properties was 2.8 x 10 12 Ω.cm. This polycarbonate was subjected, in the same manner as in Reference Example 2, to treatment with an inorganic exchanger (Grade IXE-600, a product of Toa Gosei Chemical Industry Co., Ltd.), whereby 239 g of a purified polycarbonate was obtained. Shown in Table 5 are the results of analysis of inorganic elements and free ions contained in the purified polycarbonate. This purified polycarbonate was found to have a volume resistivity of 2.1 x 10 13 Ω.cm, and it was understood that the polycarbonate has improved apparently in electrical insulation properties by virtue of the above-mentioned treatment with inorganic ion exchanger. The polycarbonate obtained was a viscous liquid which, on analysis by means of proton NMR and GPC, comprises polytripropylene glycol-di-[2-ethylhexyl]carbonate as a main constituent. The weight average molecular weight/number average molecular weight ( M w/ M n) ratio as measured by means of PGC in the polyolefin was 1.05. Treatment method Element Free ion Na Cl Cl - NO 3 - PO 3 3- SO 4 -2 HCOO - Water-washing 0.66 Not more than 0.1 Not more than 0.5 Not more than 1.0 Not more than 1.0 Not more than 1.0 Water-washing and ion exchange treatment with inorganic ion exchanger Not more than 0.01 Not more than 0.1 Not more than 0.5 Not more than 1.0 Not more than 1.0 Not more than 1.0 Unit : ppm

Claims: A polycarbonate represented by the following general formula [I]: Su - O - R wherein Su is a group represented by the following formula (A) and R is a group selected from the groups represented by the following formulas (B), (C), (D), (E) and (F). (in which R 1 is a group represented by the following formula (E) or (F)) -(C 3 H 6 O) n COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n is an integer of 1 to 12, -(C 3 H 6 O) n (C 2 H 4 O) p COOR 2 in which R 2 is as defined in the above-mentioned formula (E), and n and p are each an integer of 1 to 12. A lubricating oil containing a polycarbonate represented by the following general formula [I]: Su - O - R wherein Su is a group represented by the following formula (A) and R is a group selected from the groups represented by the following formulas (B), (C), (D), (E) and (F). (in which R 1 is a group represented by the following formula (E) or (F)) -(C 3 H 6 O) n COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n is an integer of 1 to 12, -(C 3 H 6 O) n (C 2 H 4 O) p COOR 2 in which R 2 is as defined in the above-mentioned formula (E), and n and p are each an integer of 1 to 12. The lubricating oil as claimed in claim 2 wherein said lubricating oil is a lubricating oil for refrigerator. The lubricating oil for refrigerator as claimed in claim 3 wherein said lubricating oil contains an ozone layer-nondestructive Freon. A polycarbonate represented by the following general formula [II]: (R 1 O) CH 2 [CH(OR 1 )] m CH 2 (OR 1 ) wherein R 1 is a group represented by the following formula (E) or (F), and m is an integer of 1 to 6; -(C 3 H 6 O) n COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n is an integer of 1 to 12, -(C 3 H 6 O) n (C 2 H 4 O) p COOR 2 wherein R 2 , each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon containing an ether bond and having 2 to 30 carbon atoms, n and p are an integer of 1 to 12. A lubricating oil containing a polycarbonate represented by the following general formula [II]: (R 1 O) CH 2 [CH(OR 1 )] m CH 2 (OR 1 ) wherein R 1 is a group represented by the following formula (E) or (F), and m is an integer of 1 to 6; -(C 3 H 6 O) n COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n is an integer of 1 to 12, -(C 3 H 6 O) n (C 2 H 4 O) p COOR 2 wherein R 2 , each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, n and p are an integer of 1 to 12. The lubricating oil as claimed in claim 6 wherein said lubricating oil is a lubricating oil for refrigerator. The lubricating oil for refrigerator as claimed in claim 7 wherein said lubricating oil contains an ozonelayer-nondestructive Freon. Process for the preparation of a polycarbonate represented by formula [I]: Su - O - R wherein Su is a group represented by the following formula (A) and R is a group selected from the groups represented by the following formulas (B), (C), (D), (E) and (F): in which R 1 is a group represented by the following formulae (E) or (F): -(C 3 H 6 O) n COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n is an integer of 1 to 12; -(C 3 H 6 O) n (C 2 H 4 O) p COOR 2 in which R 2 is defined as in the above-mentioned formula (E), and n and p are each an integer of 1 to 12; comprising the step of heating in the presence of a basic catalyst a mixture comprising (a) a polyol represented by the general formula [III]: Su - O - R 6 wherein Su is a group represented by the following formula (G), and R 6 is a group selected from those represented by the following formulas (H), (I), (J), (K) and (L): wherein R 7 is a group represented by the following formula (K) or (L): -(C 3 H 6 O) n H wherein n is an integer of 1 to 12; -(C 3 H 6 O) n -(C 2 H 4 O) p H wherein n and p are each an integer of 1 to 12; and (b) a carbonate represented by the general formula [V]: R 2 OCOOR 2 wherein R 2 is defined as above; R 2 OH, which results from said carbonate during the course of reaction with said polyol of formula [III], displaying a lower boiling point than said polyol of formula [III] and the carbonate being used in such an amount that the molar ratio of this carbonate to the polyol of the general formula [III] is from 3 to 80, wherein the mixture is allowed to undergo reaction so as to proceed to a reaction ratio of not less than 95%. Process for the preparation of a polycarbonate represented by formula [I]: Su - O - R wherein Su and R are defined as in claim 9; comprising the step of heating in the presence of a basic catalyst a mixture comprising (a) a polyol represented by the general formula [III]: Su-O-R 6 wherein Su and R 6 are defined as in claim 9; (b) a monoalcohol represented by the following formula [VI]: R 2 OH wherein R 2 is defined as in claim 9; and (c) a carbonate represented by the following general formula [VII]: R 9 OCOOR 9 wherein R 9 are each independently an alkyl group having 1 to 2 carbon atoms; R 9 OH which results from said carbonate during the course of reaction with said polyol of formula [III] and said monoalcohol of formula [VI] displaying a lower boiling point than said polyol of formula [III] and said monoalcohol of formula [VI], and said carbonate being used in such an amount that the molar ratio of the carbonate to the polyol of formula [III] is 3 to 80, wherein the mixture is allowed to undergo reaction so as to proceed to a reaction ratio of not less than 95%. Process for the preparation of a polycarbonate represented by formula [II]: (R 1 O) CH 2 [CH(OR 1 )] m CH 2 (OR 1 ) wherein R 1 is a group represented by the following formula (E) or (F), and m is an integer of 1 to 6; -(C 3 H 6 O) n COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n is an integer of 1 to 12, -(C 3 H 6 O) n (C 2 H 4 O) p COOR 2 wherein R 2 is each independently a hydrocarbon group having not more than 30 carbon atoms or a hydrocarbon group containing an ether bond and having 2 to 30 carbon atoms, and n and p are an integer of 1 to 12; comprising the step of heating in the presence of a basic catalyst a mixture comprising (a) a polyol represented by the general formula [IV]: (R 7 O)CH 2 [CH(OR 7 )] m CH 2 (OR 7 ) wherein R 7 is a group represented by the following formula (K) or (L), and m is an integer of 1 to 6: -(C 3 H 6 O) n H wherein n is an integer of 1 to 12; -(C 3 H 6 O) n -(C 2 H 4 O) p H wherein n and p are each an integer of 1 to 12; (b) a carbonate represented by the general formula [V]: R 2 OCOOR 2 wherein R 2 is defined as above, R 2 OH, which results from said carbonate during the course of reaction with said polyol of formula [IV], displaying a lower boiling point than said polyol of formula [IV] and the carbonate being used in such an amount that the molar ratio of this carbonate to the polyol of the general formula [IV] is from 3 to 80, wherein the mixture is allowed to undergo reaction so as to proceed to a reaction ratio of not less than 95%. Process for the preparation of a polycarbonate represented by formula [II]: (R 1 O) CH 2 [CH(OR 1 )] m CH 2 (OR 1 ) wherein R 1 and m are defined as in claim 11; comprising the step of heating in the presence of a basic catalyst a mixture comprising (a) a polyol represented by the general formula [IV]: (R 7 O)CH 2 [CH(OR 7 )] m CH 2 (OR 7 ) wherein R 7 and m are defined as in claim 11; (b) a monoalcohol represented by the following formula [VI]: R 2 OH wherein R 2 is defined as in claim 11; and (c) a carbonate represented by the following general formula [VII]: R 9 OCOOR 9 wherein R 9 are each independently an alkyl group having 1 to 2 carbon atoms; R 9 OH which results from said carbonate during the course of reaction with said polyol of formula [IV] and said monoalcohol of formula [VI] displaying a lower boiling point than said polyol of formula [IV] and said monoalcohol of formula [VI], and said carbonate being used in such an amount that the molar ratio of the carbonate to the polyol of formula [IV] is 3 to 80, wherein the mixture is allowed to undergo reaction so as to proceed to a reaction ratio of not less than 95%. Process for the preparation of polycarbonates according to any of claims 9 to 12, which process comprises as further step the removal of basic substances contained in said polycarbonates by washing with water and/or by bringing into contact with an inorganic ion exchanger.

Inventors: FUJIMOTO TADAAKI, HAYASHI TETSUO, KISO YOSHIHISA, MIZUI KINYA, NAKAMURA KOSEI, SHIMAMOTO KENJI, TAKAHATA KAZUNORI, TANAKA MASAHIDE, FUJIMOTO, TADAAKI, HAYASHI, TETSUO, KISO, YOSHIHISA, MIZUI, KINYA, NAKAMURA, KOSEI, SHIMAMOTO, KENJI, TAKAHATA, KAZUNORI, TANAKA, MASAHIDE, FUJIMOTO, TADAAKI, MITSUI PETROCHEMICAL IND. LTD., HAYASHI, TETSUO, MITSUI PETROCHEMICAL IND. LTD., KISO, YOSHIHISA, MITSUI PETROCHEMICAL IND. LTD., MIZUI, KINYA, MITSUI PETROCHEMICAL IND. LTD., NAKAMURA, KOSEI, MITSUI PETROCHEMICAL IND. LTD., SHIMAMOTO, KENJI, MITSUI PETROCHEMICAL IND. LTD., TAKAHATA, KAZUNORI, MITSUI PETROCHEMICAL IND. LTD., TANAKA, MASAHIDE, MITSUI PETROCHEMICAL IND. LTD.
Applicants: MITSUI CHEMICALS INC, MITSUI CHEMICALS, INC.
Application year: 1991
Main classification: C07C69
IPC codes: C07C69, C10M171, C10M105, C08G64, C07H15, H01B3