Use of Perfluoroalkanesulphonic Acid Amides and/or Cyclimmonium Salts of Perfluoroalkansulphonic Acids as Mold Release Agents

Aromatic polycarbonates are employed in numerous technical fields of application because of their typical tough and elastic properties. A disadvantage is their poor mold release when injection-molded which frequently results in relatively long cycle times. However, for economic and technical reasons it is desirable to shorten the cycle times as far as possible so as to manufacture larger numbers of moldings per unit time on the injection molding machines. This can be achieved, for example, by injection molding at higher temperatures. However, for this purpose the polycarbonate melt must be so modified that the release of the molding from the mold wall takes place with low release forces and at high temperatures without sticking of the solidified melt to the mold wall. Easy mold release at high temperatures is in particular also desired in the case of complicated moldings which are produced in molds with parts which cannot be cooled (for example cross-webs, cores and the like).

In the past, long-chain aliphatic carboxylic acid esters of monohydric and trihydric alcohols have been added to improve the mold release of aromatic polycarbonates in accordance with DOS (German Published Specification) NO. 2,064,095, DOS (German Published Specification) No. 2,220,185, U.S. Pat. No. 3,784,595 and U.S. Pat. No. 3,836,499. However, a disadvantage of these mold release agents is the deterioration of the mechanical properties of the aromatic polycarbonates on prolonged heat exposure as a result of which the aromatic polycarbonates which have been modified according to DOS (German Published Specification) No. 2,064,095 and DOS (German Published Specification) No. 2,220,185, U.S. Pat. Nos. 3,784,595 and 3,836,499 in order to give easy mold release no longer satisfy certain technical requirements.

U.S. Pat. No. 3,775,367 discloses the use of specific perfluoroalkanesulphonic acid derivatives as additives to polycarbonates to improve the flame resistance of polycarbonates, but makes no mention of the mold release properties of the additives.

It is now the object of the present invention to provide a mold release agent for aromatic polycarbonates which imparts to the polycarbonates, which are to be released from the mold, release properties which are adequate for all industrial applications, while on the other hand the release agent leaves the level of mechanical properties of the pure aromatic polycarbonates essentially unaffected even after prolonged heat exposure. In view of the advantages described above, a mold release agent for higher mold release temperatures is particularly desirable.

Accordingly, the subject of the present invention is the use of perfluoroalkanesulphonic acid amides and/or cyclimmonium salts of perfluoroalkanesulphonic acids as mold release agents for thermoplastic, high molecular weight, aromatic polycarbonates.

High molecular, thermoplastic, aromatic polycarbonates are in particular those based on dihydroxydiaryl compounds of the formula I ##STR1## wherein

R are identical or different and are H, C.sub.1 -C.sub.4 alkyl, Cl or Br and

X.sup.1 is C.sub.1 -C.sub.8 alkylene, C.sub.2 -C.sub.8 alkylidene, C.sub.5 -C.sub.15 cycloalkylene and C.sub.5 -C.sub.15 cycloalkylidene.

Perfluoroalkanesulphonic acid amides are in particular those of the formula IIa

wherein

R.sub.F is a linear or branched aliphatic perfluoroalkyl radical with 1 to 12 C atoms or a cyclic aliphatic perfluoroalkyl radical with 3-12 C atoms and

X is NR.sup.1 R.sup.2,

wherein

R.sup.1 and R.sup.2 are identical or different and can be hydrogen, C.sub.1 -C.sub.18 alkyl, C.sub.7 -C.sub.20 aralkyl and C.sub.5 -C.sub.20 cycloalkyl, and furthermore R.sup.1 and R.sup.2 can form a heterocyclic structure with the N atom.

Cyclimmonium salts of perfluoroalkanesulphonic acids are especially those of the formula IIc

wherein

R.sub.F has the meaning indicated for IIa and

X is ##STR2## wherein

R.sup.1 can be C.sub.1 -C.sub.18 alkyl, C.sub.7 -C.sub.20 aralkyl or C.sub.5 -C.sub.20 cycloalkyl and ##STR3## is an aromatic heterocyclic compound containing

1 hetero nitrogen atom, such as ##STR4##

The mold release agents according to the invention are employed in amounts of about 0.001 to 1% by weight, preferably about 0.001 to 0.01% by weight, relative to the weight of polycarbonate.

According to the present invention, the following advantages are achieved:

The mechanical properties of the polycarbonates and their molecular weight are uninfluenced by the added mold release agent. Even after heating for 300 hours at 130.degree. C, no molecular weight degradation and no deterioration in the mechanical properties is observed. This is specifically of particular advantage in relation to multiple extrusion and reprocessing of scrap.

The mechanical properties of the polycarbonates to which the mold release agents of the invention have been added are identical with those of the pure polycarbonates. Because of the unusual heat stability and complete solubility of the perfluoroalkanesulphonic acid derivatives of the invention in the polycarbonate melt, the polycarbonate molding materials to which the mold release agents of the invention have been added remain transparent and completely colorless.

By using the mold release agents of the invention, excellent mold release of polycarbonate moldings is achieved, a particular advantage being that the mold release can take place in a very broad temperature range. As a result, the injection molding cycles become independent of temperature fluctuations in the injection mold, and this is a great advantage for the plastics processor.

The surprising feature of the invention is that compared to known mold release agents, such as, for example, the fatty acid esters of glycerol, mold release properties which are far superior to those with known mold release agents are achieved with far smaller amounts of the mold release agents according to the invention.

Aromatic polycarbonates used in the sense of the present invention are understood to include homopolycarbonates and copolycarbonates based, for example, on one or more of the following bisphenols: bis-(hydroxyphenyl)-alkanes and bis-(hydroxyphenyl)-cycloalkanes, as well as their nuclear-alkylated and nuclear-halogenated compounds. Further aromatic dihydroxy compounds are described, for example, in U.S. Pat. Nos. 3,028,365; 2,999,835; 3,148,172; 3,271,368; 2,991,273; 3,271,367; 3,280,078; 3,014,891 and 2,999,846, in German Offenlegungsschriften (German Published Specifications) Nos. 1,570,703; 2,063,050; 2,063,052; 2,211,956 and 2,211,957, in French Pat. No. 1,561,518 and in the monograph "H. Schnell, Chemistry and Physics of Polycarbonates, Interscience Publishers, New York, 1964".

Examples of preferred bisphenols are: 2,2-bis-(4-hydroxyphenyl-propane, 2,4-bis-(4-hydroxylphenyl)-2-methylbutane, 1,1-bis-(hydroxyphenyl)-cyclohexane, 2,2-bis-(3-methyl-4-hydroxyphenyl)-propane, 2,2-bis-(3-chloro-4-hydroxyphenyl)-propane, bis-(3,5-dimethyl-4-hydroxyphenyl)-methane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane, 2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-2-methylbutane, 1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-cyclohexane, 2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane.

Examples of particularly preferred bisphenols are: 2,2-bis-(4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane, 2,2-bis-(3,5-dichloro-4-hydroxyphenl)-propane, 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane and 1,1-bis-(4-hydroxyphenyl)-cyclohexane.

Preferred aromatic polycarbonates are those based on one or more of the bisphenols stated to be preferred. Particularly preferred polycarbonates are based on 2,2-bis-(4-hydroxyphenyl)-propane and optionally one of the other bis-phenols stated to be particularly preferred.

The aromatic polycarbonates can be manufactured according to known processes, e.g., in accordance with the melt transesterification process from bisphenols and diphenyl carbonate, and in accordance with the two-phase boundary process from bisphenols and phosgene, as described in the above-mentioned literature.

The aromatic polycarbonates can also be branched as a result of the incorporation of small amounts of polyhydroxy compounds having more than two aromatic hydroxy groups, e.g. 0.05-2.0 mol-% relative to the bisphenols employed. Polycarbonates of this nature are described, for example, in German Offenlegungsschriften (German Published Specifications) Nos. 1,570,533; 1,595,762; 2,116,974 and 2,113,347, British Pat. No. 1,079,821 and U.S. Pat. No. 3,544,514. Some examples of the polyhydroxy compounds which can be used are phloroglucinol, 4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptene-2,4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl)-heptane; 1,3,5-tri-(4-hydroxyphenyl)-benzene, 1,1,1-tri-(4-hydroxyphenyl)-ethane, tri-(4-hydroxyphenyl)-phenylmethane, 2,2-bis-[4,4-(4,4'-dihydroxydiphenyl)-cyclohexyl]-propane, 2,4-bis(4-hydroxyphenyl-isopropyl)-phenol, 2,6-bis-(2'-hydroxy-5'-methylbenzyl)-4-methylphenol, 2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane and 1,4-bis-(4',4"-dihydroxy-triphenyl-methyl)-benzene.

The aromatic polycarbonates should as a rule have molecular weights M.sub.w of about 10 000 to more than 200 000, preferably of about 20 000 to 80 000.

Perfluoroalkanesulphonic acid derivatives in the sense of the present invention are in particular those of the formula

as explained above.

The amides of the formula IIa can be obtained analogously according to known processes, in the absence of water, by reaction of the perfluoroalkanesulphonic acid halides with secondary or primary amines or ammonia: see Gmelin Handbuch (Gmelin's Handbok), supplement to 8th edition, volume 12, part 2, pages 158 et seq.

Examples of compounds of type IIa are: N-cyclohexyl-perfluorooctanesulphonamide, N-methyl-perfluorooctanesulphonamide, N-methyl-perfluorodecanesulphonamide, N-butyl-perfluorooctanesulphonamide, N,N-dimethyl-perfluorooctanesulphonamide, N-benzyl-perfluorodecanesulphonamide, N-stearyl-perfluorooctanesulphonamide, N-stearyl-N-methyl-perfluorooctanesulphonamide and perfluorooctanesulphonamide.

The cyclimmonium salts of the formula IIc are obtainable in accordance with the reaction, described by V. Beyl, H Niederprum and P. Voss in Liebigs Ann. Chem. 731 58-66 (1970), of perfluoroalkanesulphonyl fluoride with silane in the presence of the corresponding heterocyclic nitrogen compounds.

Examples of compounds of type IIc are: N-methyl-pyridinium perfluorobutanesulphonate, N-methyl-pyridinium perfluorooctanesulphonate and N-methyl-quinolinium perfluorooctanesulphonate.

The use, according to the invention, of the perfluoroalkanesulphonic acid derivatives of the formula IIc as mold release agents for polycarbonates was surprising inasmuch as it was to be expected at the polycarbonate processing temperature of about 280.degree. C and above, that quaternized nitrogen compounds of this type would decompose thermally, as described by A. W. v. Hofmann, with ring scission (compare H. Beyer, Lehrbuch der org. Chem., (Textbook of Organic Chemistry), 1963, page 632). The use, according to the invention, of the perfluoroalkanesulphonic acid derivatives of the formula IIa as mold release agents for polycarbonates was surprising inasmuch as it was to be expected at the polycarbonate processing temperature of about 280.degree. C and above, that the amides of the formula IIa which generally are liquid at a temperature of about 20.degree. C, are distilling off the polycarbonate melt. This doesn't happen.

The mold release agents according to the invention are incorporated, for example, by applying the substances, onto the granules of the polycarbonate by tumbling respectively by spraying, and subsequently extruding the material on a twin-screw extruder at about 280.degree. C to from a ribbon, which is granulated.

However, the mold release agent can also be incorporated into the polycarbonate during the manufacture of the polycarbonate. In that case the perfluoro compound is either admixed, as a solution in a solvent, before reaching the devolatilization screw, or is metered, without solvent, into the polycarbonate melt.

In view of the small amounts of mold release agents to be used according to the invention it is advantageous, for uniform metering and incorporation, first to prepare a concentrate of the perfluoro compounds to be used according to the invention in polycarbonate, according to customary methods, and to meter this concentrate into the polycarbonate melt.

The use according to the invention of the mold release agents has no adverse effect either on the transparency or on the color of the polycarbonates.

Optionally, dyestuffs, pigments, stabilizers, flame-proofing agents, fillers and glass fibers and other materials can also be added to the polycarbonate without thereby impairing the effectiveness of the mold release agent.

Suitable glass fibers in this context are all grades and types of glass fiber which are commercially available, i.e., cut glass fibers (long glass fibers and short glass fibers) and rovings or staple fibers, provided that they have been finished with suitable sizes to make them compatible with polycarbonate.

The length of the glass filaments, whether bundled to form fibers or not, should be between 60 mm and 6 mm in the case of long glass fibers, whereas in the case of short glass fibers the maximum length should be between 5 mm (5000.mu.m) and 0.05 mm (50 .mu.m).

Two types of glass fiber are particularly preferred:

I. Long glass fibers having an average fiber length of 6,000.mu.m, a diameter .phi. of 10 .mu.m and a powder content (-50 .mu.m) of about 1% by weight, and

II. Ground short glass fibers having an average fiber length of 230 .mu.m, a diameter .phi. of 10 .mu.m and a powder content (<50 .mu.m) of about 5% by weight.

Usable glass materials are alkali-free aluminum-boron-silicate glass ("E-glass") and also alkali-containing "C-glass".

Suitable sizes which can be used are those known from the literature; the known aqueous size for short glass fibers (compare DT-AS (German Published Specification) No. 1,201,991) has proved particularly suitable for polycarbonate compositions.

Further details regarding glass fibers and their use in plastics, especially in polycarbonates, are known from Harro Hagen, Glasfaserverstarkte Kunststoffe (Glass fiber-reinforced plastics), Springer-Verlag, Berlin, Gottingen, Heidelberg, 1961 (especially pages 182-252) and from U.S. Pat. No. 3,577,378 (Ue 2,159-Cip).

In the present context, the glass fibers can be used in the customary amounts, preferably in amounts of 1% by weight to 30% by weight, relative to the total weight of glass fibers + polycarbonate.

The thermoplastic polycarbonate molding materials which have been modified with the mold release agents according to the invention so as to have good mold release properties are employed wherever moldings are manufactured fully automatically, in large numbers and with short cycle times, by the injection molding process. This applies, for example, to the use in the electrical industry and the optical field, for example for terminal bars, bobbins, housing components such as projector housings, floors of switch cabinets and the like, and for particularly complicated moldings which are molded in molds in which these are zones which differ greatly in temperature. When manufacturing such articles, no mold release difficulties are found even at elevated temperatures.

The effectiveness of the perfluoroalkanesulphonic acid derivatives is measured in terms of the mold release forces required for the mold release of injection molding materials. In the examples which follow, these forces are measured by rendering visible, via an optical and at the same time recording indicator instrument, the pressure which builds up in the hydraulic cylinder of the ejector system during mold release.

The examples which follow are intended to explain the subject of the invention in more detail:

Preparation of a polycarbonate and preparation of one mold release agent of each of the formula IIa and IIc.

Approximately 454 parts of 4,4'-dihydroxydiphenyl-2,2-propane and 9.5 parts of p-tert.-butylphenol are suspended in 1.5 liters of water. The oxygen is removed from the reaction mixture in a 3-necked flask, equipped with a stirrer and gas inlet tube, by passing nitrogen through the reaction mixture for 15 minutes, while stirring. 355 parts of 45% strength sodium hydroxide solution and 1,000 parts of methylene chloride are then added. The mixture is cooled to 25.degree. C. While maintaining this temperature by cooling, 237 parts of phosgene are added over a period of 120 minutes. An additional amount of 75 parts of a 45% strength sodium hydroxide solution is added after 15-30 minutes or after the absorption of phosgene has started. 1.6 parts of triethylamine are added to the resulting solution and the mixture is stirred for a further 15 minutes. A highly viscous solution is obtained, the viscosity of which is regulated by adding methylene chloride. The aqueous phase is separated off. The organic phase is washed with water until free from salt and alkali. The polycarbonate is isolated from the wash solution and dried. The polycarbonate has a relative viscosity of 1.29-1.30, measured in a 0.5% strength solution in methylene chloride at 20.degree. C. This corresponds approximately to a molecular weight of 32,000. The polycarbonate thus obtained is extruded and granulated.

N-Methyl-perfluorooctanesulphonamide is obtained in accordance with U.S. Pat. No. 3,636,085 of Ciba-Geigy Corp. (E. K. Kleiner) from perfluorooctanesulphonyl fluoride and methylamine in ether as the solvent, at a reaction temperature of -30.degree. to 0.degree. C and with a reaction time of 2-3 hours. The melting point is 101.degree.-103.degree. C.

151 g (0.5 mol) of perfluorobutanesulphonyl fluoride, 30 g (0.025 mol) of dimethyldimethoxysilane, 39.5 g (0.5 mol) of pyridine and 200 ml of acetonitrile as the solvent are mixed in a flask, and stirred; the second phase originally present disappears over the course of about 10 hours. The solvent, and the fluorosilane formed, are then distilled off and the residue is washed with benzene. After drying, the desired compound is obtained in a yield of about 85% of theory.

Their viscosities are measured at 25.degree. C in methylene chloride at a concentration of 5 g/1.

A. An aromatic polycarbonate based on 4,4'-dihydroxy-diphenylpropane-2,2 (bisphenol A) and having a relative viscosity of .eta..sub.rel. = 1.30, and M.sub.LS = 28,000 (M.sub.LS = molecular weight determined by light scattering).

B. An aromatic polycarbonated based on 90 mol% of bisphenol A and 10 mol% of 4,4'-dihydroxy-3,3',5,5'-tetrabromodiphenylpropane-2,2 (tetrabromobisphenol A), having a relative viscosity of .eta..sub.rel. = 1.33, and M.sub.LS = 37,000. (M.sub.LS = molecular weight determined by light scattering).

C. An aromatic polycarbonate based on 70 mol% of bisphenol A and 30 mol% of 4,4'-dihydroxy-3,3',5,5'-tetramethyldiphenylpropane-2,2 (tetramethylbisphenol A) having a relative viscosity of .eta..sub.rel. = 1.28, and M.sub.LS = 31,000.

D. An aromatic polycarbonate based on 4,4'-dihydroxydiphenylpropane-2,2 (bisphenol A) having a relative viscosity of .eta..sub.rel. = 1.32 and M.sub.LS = 30,000, with a glass fiber content (sized long glass fibers, average fiber length, 6 mm, diameter 10.mu., powder content < 50.mu., approx. 1%) of 20% by weight. It is obtained by extruding 80 kg of a polycarbonate of relative viscosity .eta..sub.rel. = 1.32, and M.sub.LS = 30,000 in a twin-screw extruder at 310.degree. C. At the same time, 20 kg of glass fibers (sized long glass fibers, average fiber length 6 mm, diameter 10.mu., powder content < 50.mu., 1% by weight) are added. The polycarbonate which has been glass-fiber-reinforced in this way is granulated in accordance with customary techniques. The properties are described in Tables 1 and 2.

E. Glycerol triesters with acid radicals of stearic acid, palmitic acid and myristic acid in the ratio of 1:1:0.1, melting point 48.degree. C. (Obtainable in accordance with customary ester syntheses; compare also DT-OS (German Published Specification) No. 2,064,095 and U.S. Pat. No. 3,784,595).

G. N-Methyl-perfluorooctanesulphonamide C.sub.8 F.sub.17 SO.sub.2 NHCH.sub.3, melting point = 101.degree.-103.degree. C.

H. N-methyl-pyridinium perfluorobutanesulphonate, C.sub.4 F.sub.9 SO.sub.3 .sup.- [CH.sub.3 N.sup.+C.sub.5 H.sub.5 ], melting point = 83.degree.-85.degree. C.

The mold release behavior of the polycarbonates A, B, C and D is tested on a conical cylinder of 35 mm length and of 40 and 42 mm diameters, and 3 mm wall thickness, by measuring the pressure which builds up in the ejector system. The mold release pressures and temperatures are indicated in Table 1. A molding injection-molded from these polycarbonates at 270.degree. C has the mechanical properties described in Table 2.

0.5 kg of mold release agent E is applied to 99.5 kg of polycarbonate A by tumbling in a drum at room temperature and the material is then extruded to a ribbon on an extruder at 280.degree. C, and is granulated. The mold release behavior is tested as in Example 1. The properties are described in Tables 1 and 2.

0.1 kg of mold release agent G is applied to 99.9 kg of polycarbonate A by tumbling in a drum at room temperature and the material is then extruded to a ribbon on an extruder at 280.degree. C, and is granulated. The mold release behavior is tested as described in Example 1. The properties are described in Table 1 and 2.

100 kg of polycarbonate D, during the manufacture of which 10 g of a mold release agent H are metered in together with the glass fibers. The properties of the granules obtained after extrusion are described in Tables 1 and 2.

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.