EP0894111A1

EP0894111A1 - Polyarylene sulphides with a narrow molecular-weight distribution and method of producing them

Info

Publication number: EP0894111A1
Application number: EP97916446A
Authority: EP
Inventors: Michael Haubs; Reinhard Wagener; Otto SCHÖNHERR
Original assignee: Ticona GmbH
Current assignee: Ticona GmbH
Priority date: 1996-04-11
Filing date: 1997-04-07
Publication date: 1999-02-03
Also published as: CN1220678A; DE19614126A1; WO1997038040A1; JP2000508359A; KR20000005338A

Abstract

Proposed is a method of producing, from prepolymers with halogen terminal groups, polyarylene sulphides with a narrow molecular-weight distribution, an absolute polydispersivity of less than 1.8 and a very low content of organic impurities.

Description

description

Polyarylene sulfides with a narrow molecular weight distribution and process for their preparation

The invention relates to polyarylene sulfides, in particular polyphenylene sulfide (PPS), with a narrow molar mass distribution and a process for their preparation.

According to the prior art, PPS is produced with a broad molecular weight distribution of the polymers. It contains undesirably large amounts of low molecular weight impurities and oligomers and, due to the presence of molecules of different sizes, is polydisperse. In general, the polydispersity D (D = M _w / M _n ), that is to say the ratio of the weight (M _w ) and number average (M _n ) of the molar mass, is from 2.5 to 6 for linear PPS and is branched from linear PPS is D even 4 to 10. High molecular weight PPS with large M _n and a high polydispersity value D = M _w / M _n offers the guarantee of good mechanical properties, but is extremely difficult to process due to its extremely high melt viscosity. It may have to be processed at temperatures high enough to damage the polymer. Polyarylene sulfides with high molar masses and simultaneously low polydispersity D are therefore of interest for technical applications.

EP-A-0527055 describes the production of high molecular weight polyarylene sulfide with a narrow molar mass distribution by ring-opening polymerization of cyclic arylene sulfide oligomers. The cyclic oligomers can only be produced with a low yield. Halogenated phenols or thiophenols and metal compounds (Lewis acids) are used as catalysts for the polymerization, which lead to impurities (metal ions, chlorinated benzene derivatives) in the polymer. It is not disclosed how polyarylene sulfides with a Polydispersity below a value of 2 can be produced.

EP-A-304792 describes the production of PPS with a narrow molecular weight distribution by extractive separation of oligomers from PPS with a broader molecular weight distribution. The extraction reduces the polydispersity of the PPS from 3.7 to 1.9.

EP-A-379014 describes a PPS with a polydispersity D of 2 to 5. The narrow molar mass distribution is achieved by washing the polymer with polar organic solvents at temperatures from 100 to 200 ° C.

The object was to obtain polyarylene sulfides which are simple to prepare and are superior to the prior art.

The invention relates to polyarylene sulfides with a narrow molar mass distribution, the value of the absolute polydispersity less than or equal to 1.8 being now preferably in the range from 1.3 to 1.8.

The present invention has made it possible to produce polyarylene sulfides with a narrow molar mass distribution from readily available starting materials in high yield without oligomers or low molecular weight constituents being present in the reaction product and having to be separated off. The polymers have sufficiently large molecular weights to be suitable for industrial applications.

It was surprising that the reaction of halogen-terminated prepolymers as starting components with sulfur compounds produces polyarylene sulfides in high yield, the polydispersity of the molar mass distribution being less than 1.8. The polymers are obtained in high yield and with a narrow molecular weight distribution without harmful or disruptive components must be separated. Finally, all molar masses of interest for technology can be set.

The absolute polydispersity of a polymer is obtained when M _w and M _n are measured using absolute molar mass determination methods (eg thermal field flow fractionation (FFF) in combination with a light scattering detector). In contrast, GPC provides relative polydispersities using polystyrene calibration.

Another object of the invention is a process for the preparation of said polyarylene sulfides.

Polyarylene sulfides are polymers that contain arylene sulfide units fAr-S), Ar = arylene. The arylene constituents of the arylene sulfide units contain mono- or polynuclear aromatics or linked aromatics. The aromatics can also contain heteroatoms. Such aromatics, which can be substituted or unsubstituted, are, for example, benzene, pyridine, biphenyl, naphthalene or phenanthrene. Substituents are, for example, C 1 -C 6 -alkyl, C 1 -C 6 -alkoxy, carboxyl, amino and sulfonic acid groups. Linked aromatics are, for example, biphenyl or aromatics linked by ether bridges (arylene ether). The preferred polyarylene sulfide is polyphenylene sulfide, in particular linear polyphenylene sulfide.

The polyarylene sulfides according to the invention generally have a molar mass M _n in the range from 2000 to 200000 g / mol, preferably 5000 to 50,000 g / mol. In a preferred embodiment of the invention, the polyarylene sulfides have a content of organic, low molecular weight impurities (organic compounds with M _w less than 500 g / mol) of less than 500 ppm together. In particular, the polyarylene sulfides according to the invention have a cumulative content of phenol, chlorophenol, thiophenol, chlorothiophenol, aniline and chlorine and / or methyl-substituted anilines less than 200 ppm. In addition, the polyarylene sulfides are pure white and practically do not change color under thermo-oxidative conditions. For example, storing the polyarylene sulfides at 200 ° C. in air for a period of 24 hours does not lead to any discernible discoloration. The polyarylene sulfides are preferably linear.

The term prepolymer comprises halogen-terminated oligomers or polymers which contain arylene sulfide units. These products usually have a molar mass, expressed as a number average molar mass M _n , in the range from 700 to 21000 g / mol, preferably 3000 to 10000 g / mol. They can be prepared by reacting a sulfur compound, in particular inorganic sulfides, with an excess, generally 5 to 200% by weight, preferably 10 to 100% by weight, of dihalogenated aromatic hydrocarbons.

The prepolymers generally have a halogen content of organically bound halogen in the range of more than 0.1% by weight, preferably 0.3 to 10% by weight and in particular 0.5 to 5% by weight, depending on the molecular weight. The presence of halogen-terminated oligomers or polymers is experimentally proven by the number average of their molecular weight and the halogen content and by their ¹ H-NMR spectra. Suitable halogen end groups are the halogens fluorine, chlorine, bromine and iodine, preferably chlorine and bromine, in particular chlorine. The preparation and characterization of these prepolymers is described in German patent application P 1 9513479.6 (title: Process for the preparation of polyarylene sulfide, filing date: April 13, 1995), to which reference is made. The polydispersity of the prepolymers is in the range from 1.3 to 2.5, preferably from 1.3 to 1.8.

Suitable dihalogenated aromatic hydrocarbons include dihalobenzenes such as o-, m- and p-dichlorobenzene, substituted dihalobenzenes such as 2,5-dichlorotoluene, 3,5-dichlorobenzoic acid or 2,5- Dichlorobenzenesulfonic acid (or its salts). However, dihalonaphthalenes such as 1,4-dibromonaphthalene or dihalodiphenyl ether such as 4,4'-dichlorodiphenyl ether can also be used. Mixtures of dihalogenated aromatic hydrocarbons can also be used in the same way in order to obtain copolymers. It is also possible to prepare substituted prepolymers by using substituted dihaloaryl compounds (for example 2,5-dichlorotoluene).

Inorganic sulfides of alkali and alkaline earth metals, such as lithium sulfide, potassium sulfide, calcium sulfide and preferably sodium sulfide, are suitable as sulfur compounds for the preparation of the prepolymers. The salts can be added as such or generated in situ. B. the preferred sodium sulfide from sodium hydrogen sulfide and sodium hydroxide. The sulfides can also be used with water of crystallization. It has been shown that about 1 mol of water per mol of sulfide is advantageous for the preparation of the prepolymers. The sulfur compounds are also suitable for converting the prepolymers into higher molecular weight polymers. The hydrate content is typically around 9 mol water per mol sulfide.

Dipolar aprotic amide-type solvents such as dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylcaprolactam or N-alkylated pyrrolidones or mixtures thereof are suitable as solvents both for the preparation of the prepolymers and for their conversion into polymers with a higher molecular weight. N-Methylpyrrolidone (NMP) is particularly preferred.

For example, to produce the halogen-terminated prepolymers, sodium sulfide is reacted with excess p-dichlorobenzene in NMP up to about 80 to 95%. The prepolymer is filtered off together with the sodium chloride and the salt is removed by dissolving in water. The prepolymer is then dried at 90 ° C. The reaction takes place in closed vessels (autoclaves), preferably a titanium reactor. To produce high molecular weight PPS, the prepolymer, preferably with a narrow molar mass distribution, is dissolved in NMP under pressure at temperatures of 230 ° C. and reacted with sodium sulfide. The concentration of the prepolymer in the solvent is advantageously as high as possible. It can be in the range from 15 to 90% by weight, preferably from 25 to 60% by weight. The amount of sodium sulfide added determines the halogen content, ie the molecular weight of the prepolymer. If the molar mass is plotted as a function of the mass ratio of sodium sulfide / prepolymer, the result is a graph with a pronounced maximum at a ratio of sodium sulfide / prepolymer, which satisfies the following formula:

m (Na ₂ S) = m (PP) x P _cι

Here: m (Na ₂ S): mass of the added sodium sulfide (anhydrous) m (PP): mass of the prepolymer used

PQ ,: percentage by weight of organically bound chlorine in the prepolymer

(e.g.: 2 percent by weight = 0.02)

The reaction temperatures are generally 220 to 270 ° C, preferably 230 to 260 ° C and the reaction times are 30 min to 5 h, preferably 1 to 3 h. At the end of the reaction, the polymer is in the form of an almost clear, viscous solution, from which it crystallizes on cooling. It can be easily isolated by simple filtration. By washing with a little NMP it can be freed from mother liquor residues. After washing with warm water, the polymer is dried.

The melting points of the polyphenylene sulfides obtained in this way are in the range from 270 ° C. to 305 ° C., typically 280 to 295 ° C. The melt viscosity is in the range of 5000 to 500000 mPas (centiPoise), typically 50,000 to 250,000 mPas (centiPoise). The melt viscosity is stable without additives: At 300 ° C it changes by less than 10% over a period of 1 h.

The polyphenylene sulfides can be processed into moldings by melt extrusion. Films and fibers with good mechanical properties can also be produced.

The molecular weight distribution of the polyphenylene sulfides is characterized by size exclusion chromatography

(Gel permeation chromatography, GPC) as well as by field flow fractionation. To be able to use these methods, the polymer must be dissolved. For example, chloronaphthalene at a high temperature (220 ° C) is suitable. On the other hand, the polymer can also be converted into a soluble form by a polymer-analogous reaction. This is done by selective and mild oxidation of the polymer to polyphenylene sulfoxide (PPSO). In order to obtain organically soluble polyphenylene sulfoxides, two ways can be labeled: the complete oxidation to PPSO or the partial oxidation of PPS to polyphenylene sulfide sulfoxide (PPSO _x ).

Complete oxidation to PPSO is achieved using nitric acid as the oxidizing agent. For this purpose, the polymer is dissolved at room temperature in 85% (weight percent) nitric acid with the development of nitrous gases and the PPSO formed is precipitated in water. This gives polymers which dissolve in strong acids such as trifluoroacetic acid or dichloroacetic acid at room temperature. The partial oxidation of PPS can be achieved with a dilute solution of dinitrogen tetroxide (N ₂ O ₄ ) in dichloroacetic acid. The PPS is dispersed in dichloroacetic acid and a 20% strength (by weight) solution of N ₂ O ₄ in dichloroacetic acid is metered in at room temperature over a period of 1 to 2 hours. As soon as the entire polymer has gone into solution, the supply of oxidizing agent is stopped, the mixture is left to react for 10 minutes and the polymer is precipitated in water. Polymers are obtained which, for example, dissolve in NMP at room temperature. The polydispersity is not changed in this polymer-analogous partial oxidation. In thermal field flow fractionation, the polymer is first dissolved and roughly filtered through a 5 μm filter. The solution obtained is injected into the field flow channel. There a temperature gradient acts perpendicular to the laminar flow of the solvent. It causes macromolecules to be deflected in the temperature gradient differently depending on their size and therefore leave the channel at different times. The fractions are analyzed analogously by multi-angle light scattering and UV detection. This method known as TFFF is described in detail in the literature [JC Giddings, Science vol.260, pp. 1456-1465 (1993)] and provides absolute molar mass distributions and in particular absolute polydispersities.

Molecular weight distributions were also determined using GPC. In this widely used method known to those skilled in the art, molecules are sorted according to their size, i.e. according to their hydrodynamic volume, separated. However, the GPC only provides relative molar mass distributions and relative polydispersities based on the polymer standard used.

Examples

1) Preparation of the prepolymer PP1

850 ml of NMP, 30 ml of water, 256 g of sodium sulfide-2,8-hydrate were placed in a 2 l autoclave. The mixture was heated to T = 190 ° C. with stirring and then 145 ml of NMP-containing water were distilled off. 370 g of p-dichlorobenzene and 50 ml of NMP were added to the mixture which had cooled to T = 1 70 ° C. The contents of the autoclave were heated to T = 230 ° C. with stirring and held there for 2 hours. 55 ml of a water / NMP mixture and 18 ml of p-dichlorobenzene were then distilled off. The temperature was lowered to T = 150 ° C., held there for 90 min, the mixture was filtered and the remaining filter cake was boiled twice with water. The prepolymer obtained was dried at 110 ° C. The elemental analytically determined chlorine content of the prepolymer was 1.2% by weight. 2) Preparation of the prepolymer PP2

In a 2 l autoclave, a mixture of 300 ml of NMP, 79.2 g of Na ₂ S x 3 H ₂ O, 132.3 g of p-dichlorobenzene and 49.2 g of sodium acetate is first stirred at 220 ° C. for 30 minutes and then heated to 245 ° C for 30 min. The cooled reactor contents were then added to 2.5 l of water, which had previously been mixed with 1 5 ml of HCl cone. had been transferred. The precipitate was filtered off, washed with 2 l of water and then with 700 ml of acetone. It was then extracted with THF overnight. The yield of predominantly chlorine-terminated oligomers was 55%. The Cl content (organically bound chlorine) of the sample was 3.8 percent by weight. This corresponds to a molar mass M _n of 1870 g / mol.

The molar mass M _n (number average) was calculated from the elementally determined content of organically bound chlorine using the following formula:

^M n = < ⁷¹ / P _C ι> 9 / mol

Here mean:

M _n : number average of the molar mass

P _C) : Weight fraction of organically bound chlorine in the prepolymer

3) Production of high molecular weight PPS

31.2 g of prepolymer PP1, prepared according to Example 1, were suspended in 60 ml of NMP in a 250 ml glass autoclave with stirring, and 1.5 g of Na ₂ S and 0.5 ml of H ₂ O were added with the exclusion of air. The mixture was then heated to 245 ° C. with stirring for 2 h. The largely homogeneous viscous solution was cooled and diluted with 40 ml of NMP. The crystalline precipitate was filtered off, washed with NMP and briefly boiled in water. After suction, the polymer was dried. Yield: 95%. The polyphenylene sulfide obtained had a melt viscosity of 1 77000 mPas at 300 ° C and a shear rate of 10 min ^"1. After one hour at 300 ° C it was 1 72000 mPas. The melting point at the first heating was 293 ° C, the recrystallization temperature at Cooling from the melt at 246 ° C and the melting point during the second heating at 285 ° C.

4) Characterization of the molecular weight distribution by field flow fractionation: A Model T-100 ThFFF polymer fractionator from FFFractionation Ltd. was used. (Salt Lake City, Utah, USA) in connection with a light scattering detector DAWN F from Wyatt Technology Deutschland GmbH (D-65388 Schlangenbad) and a UV detector UV2000 from Spectra Physics, D-6100 Darmstadt, which was operated at 330 nm , used. As a running medium and solvent, NMP was used with a flow of 0.2 ml / min. It was operated in the so-called power mode (see e.g. P.Stephen Williams and J.Calvin Giddings: Anal. Chem. 1987, 59, 2038) under the following conditions. The temperature difference ΔT between the upper and lower temperature block is changed as a function of time t as follows:

ΔT (t) = ΔT ₀ [(t1 -ta) / (t - ta)] -Ita / t1 | With

ΔT ₀ = 100 ° C t1 = 8 min ta = - 1 6 min

The ASTRA 4.0 software from Wyatt was used for the evaluation. Narrowly distributed polystyrene standards were used to standardize the scattering angles. The measurement method used allows the determination of absolute molar mass distributions and in particular absolute polydispersities.

Part of the high molecular weight polymer prepared according to Example 3 was partially oxidized with N ₂ O ₄ in dichloroacetic acid, dissolved in NMP and after this Analysis method examined. The following results were obtained:

Mass average M _w : 38000 g / mol number average M _n : 28000 g / mol polydispersity D: 1.36

The absolute molar mass distribution is shown in Fig. 1.

5 (comparative example)

Commercially available PPS samples, Fortron 0214 B1 (Fortron Industries, USA) and Ryton GR 06 (Phillips Petroleum, USA) were oxidized to PPSO by exhaustive oxidation with excess N ₂ O ₄ in dichloroacetic acid at room temperature. The isolated samples were dissolved in dichloroacetic acid and their molar mass distribution was determined by light scattering. The weight average molecular weight was 41,000 and 32,000 g / mol, respectively.

Both PPS samples were also partially oxidized with N ₂ O ₄ and thus NMP-soluble PPSO _x ^" polymers were obtained. They were characterized by field flow fractionation. Absolute polydispersities of> 1.8 were obtained for both polymers. A more precise quantitative determination of the polydispersity was not possible because there were too many components in the samples that were below the resolution limit of the FFF apparatus.

6) Polymer characterization using GPC

A Waters 510 pump from Waters and a UV detector UV2000 from Spectra Physics, D-6100 Darmstadt, which was operated at 330 nm, were used. NMP with 0.05% LiCl and 0.02% ammonium acetate was used as eluent and solvent with a flow of 1 ml / min. Styragel columns from Polymer Standards Service GmbH, D-55023 Mainz (100, 1000, 100000, 1000000 Angstrom, series connection, 65 ° C) were used as columns. A polystyrene calibration was used to evaluate the measured data. The following results were obtained for the prepolymer from Example 1:

M _n : 6300 g / mol M _w : 1 1200 g / mol polydispersity D: 1.78

The chlorine content determined by elemental analysis is 1.2% by weight of organically bound chlorine.

7) Characterization of the organ. Contamination by GC-MS A sample of the polyphenylene sulfide prepared in Example 3 was baked out at T = 320 ° C. in a stream of helium. After the helium stream had passed the sample, it was passed through a trap cooled with liquid nitrogen to collect the volatile components of the sample at 320 ° C. After a test period of 16 hours, the trap was removed from the cooling bath, warmed to room temperature and the collected substances were dissolved out with a mixture of dichloromethane and methanol. The resulting solution was analyzed using a combination of a gas chromatograph and mass spectrometer (GC / MS). Based on the weighed mass of the polymer, the following amounts of low molecular weight impurities were detected:

1.) Substituted mononuclear aromatics (benzene derivatives):

Phenol: 25 ppm

Bis-tert. butyl phenol: 30 ppm

Thiophenol: 30 ppm

2.) Heterocyclic decomposition products of the NMP: dihydrofuranone: 10 ppm Tetrahydrothiophenone: 10 ppm

Chlorophenol, chlorothiophenol, chloraniline or other chlorinated benzene derivatives could not be detected. Aniline and chlorine and / or methyl substituted anilines were also below the detection limit.

8) (comparative example)

Characterization of organic contaminants by GC / MS

Samples of commercially available polyphenylene sulfide products were treated in the same way as described in Example 7 at 320 ° C. in a stream of helium and by means of

Characterized GC / MS. The details were as follows

Products:

1 . Fortron 0205 X49 G24EO (Hoechst Celanese, USA)

2. Tohpren T1 / 1 N1 XO41 (Tohpren, Japan)

Almost twenty different organic compounds were detected for both samples. In the group of substituted benzenes, the following compounds were detected in both samples: phenol, thiophenol, chlorothiophenol, aniline, N-methylaniline, N, N-dimethylaniline, N-methylchloraniline. The heterocyclic compounds dihydrofuranone and tetrahydrothiophenone derived from the thermal decomposition of NMP were also present in significantly larger amounts than in the polyphenylene sulfide sample according to the invention in Example 7. The table shows the results in detail:

Claims

Claims:

1 . Polyarylene sulfide with an absolute polydispersity D less than or equal to 1.8.

2. Polyarylene sulfide according to claim 1, characterized in that the polydispersity is in the range of 1.3 to 1.8.

3. polyarylene sulfide according to claim 1 or 2, characterized in that the polyarylene sulfide has an organic impurity content of less than 500 ppm.

4. Polyarylene sulfide according to one or more of claims 1 to 3, characterized in that the polyarylene sulfide contains a total of the compounds phenol, chlorophenol, thiophenol, chlorothiophenol, aniline, chloroaniline, N-methylaniline, N-methylchloraniline and N, N-dimethylaniline has less than 200 ppm.

5. polyarylene sulfide according to one or more of claims 1 to 4, characterized in that the polyarylene sulfide is polyphenylene sulfide, preferably linear polyphenylene sulfide.

6. A process for the preparation of a polyarylene sulfide, characterized in that A) is a halogen-terminated prepolymer with a halogen content of greater than 0.1% by weight and a polydispersity in the range from 1.3 to 2.5 with B) at least one inorganic sulfide is reacted at elevated temperature in a solvent, the amount of sulfide being determined by the halogen content of the prepolymer.

7. The method according to claim 6, characterized in that prepolymers with narrow molecular weight distribution are used.

8. A process for the preparation of a polyarylene sulfide, characterized in that a halogen-terminated prepolymer with a halogen content of greater than 0.1% is produced by reaction in a solvent of a) at least one dihalogenated aromatic hydrocarbon in excess with b) at least one inorganic sulfide, wherein the conversion takes place at about 80% to 95% and the prepolymer obtained has a polydispersity in the range from 1.3 to 2.5, the prepolymer is separated off, and then with at least one inorganic sulfide at elevated temperature in a solvent to give the polyarylene sulfide is implemented, the amount of sulfide being determined by the molecular weight of the polymers.

9. The method according to one or more of claims 6 to 8, characterized in that the halogen content of the prepolymer is in the range from 0.3 to 10 wt .-%, preferably from 0.5 to 5 wt .-%.

10. The method according to one or more of claims 6 to 9, characterized in that the number average molecular weight M _{n of} the prepolymer is in the range from 700 g / mol to 21000 g / mol.

1 1. Method according to one or more of claims 6 to 10, characterized in that a polyarylene sulfide with an absolute polydispersity D less than or equal to 1.8, preferably in the range from 1.3 to 1.8, is obtained.