HK1059794A - Process for the preparing of stabilized polycarbonate - Google Patents

Description

Process for the preparation of stabilized polycarbonates

Technical Field

The present invention relates to a process for the preparation of polycarbonates, and more particularly to an interfacial polycondensation process.

Background

In the preparation of polycarbonates by the so-called interfacial process, dihydroxydiarylalkanes in the form of their alkali metal salts are reacted with phosgene in heterogeneous phase in an inorganic base such as sodium hydroxide solution and in an organic solvent in which the product polycarbonate is readily soluble. The aqueous phase is distributed in the organic phase during the reaction, after which the organic polycarbonate-containing phase is separated from the aqueous phase and washed several times with an aqueous liquid, during which electrolyte, residual monomers and, in particular, catalyst are removed. Subsequently, the washing liquid was separated off as much as possible. Finally, the organic solvent is removed from the polycarbonate and converted into a form which can be readily processed further, for example in the form of pellets.

Such known interfacial processes are described in detail, by way of example, in the following publications:

schnell, "polycarbonate chemistry and Physics", volume 9, International science Press, New York, London, Sydney, 1964, p.33;

d.c.prevorsek, b.t.debona and y.kesten, research center of company, union chemical company, Morristown, new jersey 07960: "Synthesis of Poly (ester carbonate) copolymer" [ J.Polymer science & Polymer chemistry album, Vol.18 (1980) ], p.75;

freitag, u.grigo, p.r.muller, n.nouvertn, bayer, "polycarbonate", volume 11, second edition, 1988, p.651; and finally

Dres.U.Grigo, K.Kircher and P.R.Muller, "polycarbonates", Becker/Braun headquartered in Plastic handbook volume 3/1, polycarbonates, polyacetals, polyesters, cellulose esters, Carl Hanser Press, Munich, Vienna, 1992, p.118 and 138.

These publications relate to the corresponding synthesis of polycarbonates according to the so-called "interfacial process" which is carried out in a two-phase reaction mixture composed of an inorganic phase (water, base) and an organic phase (organic solvent, insoluble in water, mostly chlorinated hydrocarbons such as methylene chloride and/or chlorobenzene).

The products of the synthesis are an organic phase (synthesis solution) comprising the polycarbonate in dissolved form, and an inorganic aqueous alkaline phase comprising the salts formed during the synthesis, such as sodium chloride, sodium bicarbonate, soda ash, in addition to residual phenolate, bisphenolate and sodium hydroxide used, as well as catalysts and secondary products thereof, and water-soluble compounds from the starting materials or impurities formed as by-products. If a different basic compound is used instead of sodium hydroxide, the aqueous alkaline phase contains the salts or secondary products of the corresponding analogs.

The subsequent work-up is carried out with the aim of separating off the inorganic aqueous phase as completely as possible and of removing from the organic phase as completely as possible the alkaline residues of the inorganic compounds remaining, in particular, contained in the water soluble and dispersible in the separated organic phase. This is achieved by a washing operation, optionally in conjunction with several acidification steps. These purification operations may, if desired, be carried out before the concentration of the organic phase, if the concentration is to be achieved by thermal means.

The purification of the synthesis solution is achieved by washing the organic solution with water once or more. Generally, this is achieved by one or more acidification operations and washing with water, mostly in several steps.

Acidification involves either the total potential base of the synthesis or, preferably, after phase separation at alkaline pH range, only neutralizing those residual components of the aqueous phase that are dissolved or dispersed in the organic phase, or those present in a mixture with the residue of the aqueous phase. Aqueous solutions of inorganic acids, in particular hydrochloric acid and phosphoric acid, but also aqueous solutions of organic acids, are used for this acidification.

Such washing and acidification are likewise the subject of numerous patents and publications.

For example, EP-A0023570 describes a process for working up alkaline synthesis solutions with a disperser which generates shear energy, optionally in combination with a dispersing agent.

Disclosure of Invention

According to the invention, polycarbonates are to be understood as being those based on suitable diphenols, such as, for example, hydroquinone, resorcinol, dihydroxydiphenyl, bis (hydroxyphenyl) -alkanes, bis (hydroxyphenyl) -cycloalkanes, bis (hydroxyphenyl) sulfides, bis (hydroxyphenyl) ethers, bis (hydroxyphenyl) ketones, bis (hydroxyphenyl) -sulfones, bis (hydroxyphenyl) sulfoxides, α' -bis (hydroxyphenyl) -diisopropylbenzenes and also their nuclear-alkylated and nuclear-halogenated compounds.

Preferred diphenols are hydroquinone, resorcinol, 4 '-dihydroxydiphenyl, 2-bis (4-hydroxyphenyl) -1-phenyl-propane, 1-bis (4-hydroxyphenyl) -phenyl-ethane, 2-bis (4-hydroxyphenyl) propane, 2, 4-bis (4-hydroxyphenyl) -2-methylbutane, 1' -bis (4-hydroxyphenyl) -m-or-p-diisopropylbenzene, 2-bis (3-methyl-4-hydroxyphenyl) -propane, bis (3, 5-dimethyl-4-hydroxyphenyl) -methane, 2-bis (3, 5-dimethyl-4-hydroxyphenyl) -propane, bis (3, 5-dimethyl-4-hydroxyphenyl) -sulfone, 2, 4-bis (3, 5-dimethyl-4-hydroxyphenyl) -2-methylbutane, 1' -bis (3, 5-dimethyl-4-hydroxyphenyl) -m-or-p-diisopropylbenzene and 1, 1-bis (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane.

Particularly preferred diphenols are resorcinol, 4 '-dihydroxydiphenyl, 1-bis (4-hydroxyphenyl) -phenylethane, 2-bis (4-hydroxyphenyl) -propane, 2-bis (3, 5-dimethyl-4-hydroxyphenyl) -propane, 1' -bis (3, 5-dimethyl-4-hydroxyphenyl) -1-or-p-isopropylbenzene, 1-bis (4-hydroxyphenyl) -cyclohexane and 1, 1-bis (4-hydroxyphenyl) -3, 3, 5-trimethylcyclohexane.

These and other suitable diphenols are described, for example, in U.S. Pat. Nos. 3, 3028635, 2999835, 3148172, 2991273, 2271367,4982014 and 2999846, in DE-A1570703, 2063050, 2036052, 2211956 and 3832396, in French patent Specification 1561518, in the monograph, H.Schnell, from polycarbonate chemistry and Physics, International scientific Press, New York, 1964, from p.77 and in JP-A62039/1986, 62040/1986 and 105550/1986.

In the case of homopolycarbonates only one diphenol is used, whereas in the case of copolycarbonates a plurality of diphenols is used, it being possible, of course, for the diphenols used, as are the other chemicals and auxiliaries added to the synthesis, to be doped with impurities from their own synthesis, although it is desirable to use starting materials which are as clean as possible.

As carbonate precursors, it is possible to use halogen derivatives of carbonic acid, as described, for example, in the cited literature, in particular phosgene.

The catalysts include ammonium and/or phosphonium compounds or tertiary amines as described in the literature, in particular N-ethylpiperidine, N-methylpiperidine, triethylamine and tributylamine or mixtures thereof, it being possible for these catalysts to be added in one metered amount or, alternatively, in several metered amounts at certain time intervals (batch process) or space intervals (continuous process).

As the alkaline component, any alkali metal and alkaline earth metal hydroxides may be used as long as they are soluble or dispersible in water, but sodium hydroxide, potassium hydroxide, magnesium hydroxide and/or calcium hydroxide (suspension of calcium oxide in water) or a mixture thereof is preferred.

The solids content of the polymer solution to be washed can vary depending on the polymer molecular weight in the range of 0.5% to 30% by weight of polymer; when the molecular weight (weight average "Mw") is 8000 to 50,000, the polymer solid content is preferably 2 to 25% by weight of the polymer, preferably 5 to 22% by weight of the polymer, and particularly preferably 7 to 20% by weight, and when the molecular weight (Mw) > 50,000, the polymer solid content is preferably 2 to 15% by weight of the polymer.

Molecular weights (weight average Mw) were determined using Gel Permeation Chromatography (GPC) with dichloromethane as eluent. Detection is achieved by means of ultraviolet light or Refractive Index (RI). Polystyrene gel-based columns previously calibrated for polycarbonate were used. In the context herein, HP1050 is used.

Organic solvents for washing the polycarbonate solution include the solvents discussed for polycarbonate and which form a two-phase mixture with water. These solvents include aliphatic, optionally branched, partially halogenated or perhalogenated solvents of 1 to 10 carbon atoms with chlorine or bromine as halogen, for example dichloromethane, trichloroethane, tetrachloroethane, and optionally substituted aromatic compounds of 6 to 18 carbon atoms, for example benzene, toluene, o-, m-and/or p-xylene, methoxy-or ethoxy-benzene, biphenyl, diphenyl ether, chlorobenzene, o-, m-and/or p-dichlorobenzene, or even mixtures of such solvents. Preferred solvents are dichloromethane and chlorobenzene, especially chlorobenzene.

Suitable chain terminators are both monophenols and monocarboxylic acids. Suitable monophenols are phenol, alkylphenols such as cresol, p-tert-butylphenol, p-n-octylphenol, p-isooctylphenol, p-n-nonylphenol and p-isononylphenol, halophenols such as p-chlorophenol, 2, 4-dichlorophenol, p-bromophenol and 2, 4, 6-tribromophenol and mixtures thereof.

Suitable monocarboxylic acids are benzoic acid, alkylbenzoic acids and halobenzoic acids.

The amount of chain terminators to be used is 0.5 mol% to 10 mol%, based on the moles of diphenols used in a particular case. The addition of chain terminators may be carried out before, during or after phosgenation.

Suitable branching agents are the tri-or polyfunctional compounds known in polycarbonate chemistry, especially those having three or more phenolic hydroxyl groups.

Suitable branching agents are, for example, phloroglucinol, 4, 6-dimethyl-2, 4, 6-tris (4-hydroxyphenyl) -heptane, 2, 4, 6-dimethyl-2, 4, 6-tris (4-hydroxyphenyl) -heptane, 1, 3, 5-tris (4-hydroxyphenyl) -benzene, 1, 1, 1-tris (4-hydroxyphenyl) -ethane, tris (4-hydroxyphenyl) -phenylmethane, 2-bis [4, 4-bis (4-hydroxyphenyl) -cyclohexyl ] -propane, 2, 4-bis (4-hydroxyphenyl-isopropyl) -phenol, 2, 6-bis (2-hydroxy-5' -methyl-benzyl) -4-methylphenol, 2- (4-hydroxyphenyl) -2- (2, 4-dihydroxyphenyl) -propane, hexa- (4- (4-hydroxyphenyl-isopropyl) phenyl) -orthoterephthalate, tetra- (4-hydroxyphenyl) -methane, tetra- (4- (4-hydroxyphenyl-isopropyl) -phenoxy) -methane and 1, 4-bis (4', 4 "-dihydroxy-triphenyl) -methyl) -benzene, as well as 2, 4-dihydroxybenzoic acid, 1, 3, 5-trimellitic acid, cyanuric chloride and 3, 3-bis (3-methyl-4-hydroxyphenyl) -2-oxo-2, 3-dihydroindole or mixtures thereof.

The amount of branching agents which is optionally used is from 0.05 mol% to 2.5 mol%, preferably from 0.1 to 1.0 mol%, based on the moles of diphenols used in a particular case.

The branching agents may be used initially in the aqueous alkaline phase together with the diphenols and the chain terminators or they may be added to a solution in an organic solvent before phosgenation.

All these measures for the preparation of polycarbonates are known to the person skilled in the art.

Preferred methods for preparing the polycarbonates used according to the invention are the known interfacial processes.

The molecular weight (Mw) of the polycarbonates according to the invention is from 12,000 to 50,000, preferably from 12,000 to 40,000, particularly preferably from 15,000 to 40,000. The molecular weight is determined by the GPC method already mentioned above.

High purity polycarbonates are used for optical and magneto-optical data storage means, optical lenses and prisms, glazing for motor vehicles and headlamps (glazing), other kinds of glazing, such as greenhouses.

During the injection molding process, higher melting temperatures must be used during the process for producing molded articles in order to shorten the processing time, which leads to increased yellowing and thermal damage of the polycarbonate; in addition, under such conditions, the release aid may react with the polycarbonate. It is therefore an object of the present invention to achieve a high stabilizing effect with the lowest concentration of the known stabilizers without any change in other properties of the polycarbonate and of the molded articles produced therefrom.

It is known that the following attempts have been made to achieve a corresponding stabilizing effect:

-JP 10060247 a: 0.001 to 0.01 part by weight of phosphoric acid is added to PC, and the PC is used for optical data storage means, lenses and the like, and has excellent transparency, excellent thermal stability, no decomposition and no yellowing.

JP 04081457 a UPAB: 5-50 ppm phosphoric acid is added into polycarbonate, and no spots or defects are generated after the polycarbonate is exposed to high temperature and high humidity.

-JP 01315459 a: 0.0005 to 0.01 part by weight of phosphoric acid, is well suited for optical data storage means, lenses and prisms, and can be processed at 300 to 380 ℃ without thermal damage.

-JP 2001031859 a: at least one phosphorus-based stabilizer in an amount of 0.0001 to 0.15 wt%, and has excellent thermal stability.

-JP 07126505 a: 0.05 to 5ppm of PC for CD, phosphoric acid, etc. is added to PC.

This prior art discloses the metering of phosphoric acid together with a mold release agent into a polycarbonate melt. This improves the thermal stability, but does not reach a satisfactory level. The release agent as a whole therefore still reacts with PC, especially during further processing into moldings. The stabilizing effect achieved by the prior art is therefore still insufficient. Further improvements in this area are highly desirable.

Disclosure of Invention

It is therefore an object to provide an improved process for stabilizing polycarbonates.

Surprisingly, it has now been found that thermally stable polycarbonates can be prepared by improving the interfacial polycondensation process. The improvement comprises introducing into the washed polycarbonate solution an emulsion of a small amount of phosphoric acid in an organic solvent. The introduction is effected by intensive mixing of the emulsion into the polycarbonate solution. The polycarbonates obtained and the articles molded therefrom feature improved thermal stability. For the purposes of the present invention, phosphoric acid is an inorganic acid which contains phosphorus.

According to the invention, phosphoric acid is understood to mean any desired phosphorus-containing inorganic acid, preferably phosphoric acid in the form of ortho-, meta-or poly-phosphoric acid, phosphorous acid and hypophosphorous acid, etc., particularly preferably phosphoric acid in the form of ortho-, meta-or poly-phosphoric acid, most particularly preferably orthophosphoric acid.

In the process of the present invention, whether the nature of the phosphoric acid or its amount in the polycarbonate is not critical, it is critical that the phosphoric acid emulsion is formed in the organic solvent mixture and that the phosphoric acid emulsion thus prepared is distributed in the PC solution after washing of the polycarbonate. The phosphoric acid remains in the polycarbonate solution which is fed to the subsequent process of concentration by evaporation for the isolation of the polycarbonate. This stabilization occurs whenever an acid other than phosphoric acid is used to remove the catalyst from the previous wash.

The phosphoric acid emulsion is prepared by emulsifying 6 to 10 wt.%, preferably 7 to 9 wt.%, particularly preferably 8 wt.% aqueous phosphoric acid in an amount of 500 to 2000ppm, preferably 800 to 1200ppm, particularly preferably 1000ppm, in an organic solvent mixture comprising monochlorobenzene and dichloromethane. The content of dichloromethane in the solvent mixture is 10 to 70%, preferably 20 to 60%, and particularly preferably 50%. The phosphoric acid-solvent emulsion remains stable by virtue of the continuous mixing of the two phases. For example, a mixing pump or a powerful high-speed stirrer may be used as the mixing element.

The metering of the phosphoric acid emulsion is carried out after the washing of the polycarbonate and before the isolation process, i.e.into the washed PC solution. The phosphoric acid emulsion is metered in such an amount that a phosphorus content of 0.15 to 2ppm, preferably 0.3 to 1.5ppm, particularly preferably 0.6 to 1ppm, most particularly preferably 0.8ppm, based on the carbonic acid ester, is achieved. In the case of orthophosphoric acid, this corresponds to 0.5 to 5ppm, preferably 1 to 4ppm, particularly preferably 2 to 3ppm, most particularly preferably 2.5ppm, of phosphoric acid, based on polycarbonate.

All percentages in this context are to be understood as wt.%, unless explicitly stated otherwise.

Preferred, particularly preferred or most particularly preferred are those embodiments which employ the parameters, compounds, definitions and explanations mentioned with preference, particularly preferred or most particularly preferred.

However, the definitions, parameters, compounds and explanations mentioned above generally or in the preferred ranges can also be combined with one another as desired, that is to say between the respective ranges and the preferred ranges.

The distribution of the phosphoric acid emulsion in the polycarbonate solution can be carried out by means of a high-speed dynamic mixer. A mixing chamber, such as a mixing pump or a disk separator, may be used for this purpose.

The present application also relates to polycarbonates prepared by the process according to the invention and their use in the production of extrudates and molded articles, especially those used in applications requiring transparent resins, most particularly preferably in optical applications, for example, sheets, multiwall sheets, glass, headlamp lenses, lamp housings or optical data storage means such as audio CDs, DVDs, minidiscs, in their various read-only or recordable, optionally also writable, forms.

The present application also provides extrudates and molded articles produced from the low defect polymers of the present invention.

Further areas of application, which do not constitute a limitation of the subject matter of the invention, are, for example:

1. safety glass, as is well known, is required in many fields, including buildings, motor vehicles, aircraft, and also helmets.

2. Production of films, in particular ski films.

3. Production of blow molded articles (see, e.g., U.S. Pat. No. 2964794), e.g., 1-5 gallon water bottles.

4. The production of transparent sheets, in particular hollow sheets, is used, for example, for covering buildings, such as railway stations, greenhouses and lighting installations.

5. Production of optical data storage means.

6. For producing traffic signal light housings or road signals.

7. For producing foamed materials (see, for example, DE-B1031507).

8. For producing threads or filaments (see, for example, DE-B1137167 and DE-A1785137).

9. Translucent plastics containing glass fibers for illumination purposes (see, for example, DE-A1554020).

10. As translucent plastics or organic polymer acrylate rubbers containing barium sulfate, titanium dioxide and/or zirconium oxide (EP-A634445, EP-A269324) are used for producing transparent and light-scattering mouldings.

11. For the production of precision injection-molded parts, such as lens holders. For this purpose, polycarbonate containing glass fibers is used, optionally additionally containing about 1 to 10 wt.% MoS₂Based on the total weight.

12. For the production of optical instrument parts, in particular lenses for cameras and cinematographic cameras (see, for example, DE-A2701173).

13. Optical transmission carriers, in particular as optical cables (see, for example, EP-A10089801).

14. As electrical insulating material for electrical conductors and for socket and plug connectors.

15. Production of a mobile phone cover having improved resistance to perfume, shaving lotion and perspiration.

16. A network interface device.

17. As a carrier material for organic photoconductors.

18. For producing lamps, for example headlights in the form of headlight lamps, headlight lenses or inner lenses.

19. For use in the medical field, for example, oxygen generators, dialysers.

20. For use in the food field, for example, bottles, kitchen articles and chocolate molds.

21. For use in the automotive field, wherever there is a possibility of contact with fuels and lubricants, for example bumpers, optionally in the form of suitable blends with ABS or suitable rubbers.

22. For sporting goods, e.g., slalom poles or ski boot buckles.

23. For household articles, such as kitchen sinks and letter box cases.

24. As housings, e.g. electrical distribution boxes.

25. An electric toothbrush housing and a blower housing.

26. A transparent washing machine, ox eye, has improved resistance to washing liquid.

27. Safety glasses, optical correcting glasses.

28. Lampshades for kitchen appliances having improved resistance to kitchen vapors, particularly oil vapors.

29. A medicine packaging film.

30. Wafer cassettes and wafer shelves.

31. For other fields, e.g. stable doors or animal cages.

The application also relates in particular to the field of optical applications and corresponding molded articles, such as lenses, spectacles, optical recording media, such as CDs, CD-R, CD-RW, DVDs and the like, and magneto-optical recording media.

Detailed Description

The examples given below are intended to illustrate but not limit the invention.

Comparative example

Removing the solvent from the polycarbonate solution washed by hydrochloric acid in steps in the process of evaporation and concentration; to the melt conveyed on a ZSK type twin-screw extruder, PC together with glycerol monostearate (mold release agent) and 5ppm of phosphoric acid were added in the melt by means of a side-draw extruder, and the entire mixture was mixed. The yellow index of the PC granules obtained in the way is 1.5-1.8; 95-100% glycerol monostearate reacts with polycarbonate to form GMS carbonate.

Examples

The PC solution washed with hydrochloric acid was emulsified in an amount of 1000ppm from 8% phosphoric acid by means of a continuously operated mixing pump in a mixture of 90% monochlorobenzene and 10% dichloromethane and mixed into the PC solution by means of the mixing chamber of a disk separator after washing. The polycarbonate is then isolated in a conventional manner. The amount of phosphoric acid used was 3ppm based on polycarbonate. The mold release agent was metered in the same manner as in the comparative example, but without the addition of phosphoric acid, and then mixed in; the release agent is present in a particulate form and has a yellowness index of 1.2 to 1.3. The release agent does not change even during processing into a CD molded article.

If the results of the prior art process (comparative example) are compared with those of the process according to the invention, it will immediately be seen that, on the one hand, the polycarbonates obtained by the process according to the invention surprisingly exhibit an excellent yellowness index, and, on the other hand, that, unlike the prior art, the mold release agent does not change during further processing. This behaviour is surprising and unexpected in view of the prior art.

Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.

Claims (10)

1. A method of making an emulsion, the method comprising: an aqueous inorganic acid containing phosphorus is mixed in an organic solvent, the mixing being continuous and of sufficient intensity to form a homogeneous emulsion.

2. The method of claim 1, wherein the aqueous inorganic acid containing phosphorus is 6 to 10 wt% phosphoric acid aqueous solution.

3. The process of claim 1, wherein the inorganic acid is present in the organic solvent in an amount of 500 to 2000 ppm.

4. An emulsion prepared by the process of claim 1.

5. In a method of making polycarbonate by the interfacial process, the improvement comprising mixing a washed organic polycarbonate solution, which has been washed without a phosphorus-containing inorganic acid, with the emulsion of claim 4.

6. The process of claim 5, wherein the emulsion is used in an amount to produce a phosphorus content of 0.15 to 2ppm relative to the weight of the polycarbonate.

7. A polycarbonate prepared by the process of claim 5.

8. A molded article comprising the polycarbonate of claim 7.

9. An extrudate comprising the polycarbonate of claim 7.

10. An optical information storage medium comprising the polycarbonate of claim 7.