Process for the preparation of copolyarylene sulphides with reduced crystallization temperature

This invention relates to a process for the preparation of polyarylene sulphides with reduced crystallization temperature.

This invention relates to a process for the preparation of polyarylene 
sulphides with reduced crystallisation temperature. Polyarylene sulphides 
and methods for their preparation are known (e.g. U.S. Pat. No. 
2,513,188). 
Polyarylene sulphides are partially crystalline polymers which can be 
processed thermoplastically and have a high dimensional stability under 
heat. They are also very resistant to chemicals. 
Delayed onset of crystallisation of the molten polymer is advantageous for 
certain purposes, for example when premature solidification of the flow 
front of the molten polymer is to be avoided when the polymer is being 
injection moulded into complicated molds. 
The present invention therefore relates to a process for the preparation of 
highly crystalline, optionally branched polyarylene sulphides with reduced 
crystallisation temperature, by the reaction of 
(a) 75-99.5 mol-% of dihalogenated aromatic compounds corresponding to the 
formula 
##STR1## 
wherein X denotes halogen atoms such as chlorine or bromine in the 
para-position to one another and the 
R.sup.1 s may be identical or different and denote hydrogen, C.sub.1 
-C.sub.4 -alkyl, C.sub.5 -C.sub.10 -cycloalkyl, C.sub.6 -C.sub.10 -aryl, 
C.sub.7 -C.sub.14 -alkylaryl or C.sub.7 -C.sub.14 -arylalkyl, where any 
two R.sup.1 s which are in the orthoposition to one another, together with 
the carbon atoms in a ring to which they are attached, may be linked 
together to form an aromatic or heterocyclic ring having 5 or 6 ring 
atoms, and up to 3 ring carbon atoms may be replaced by O, S or N, 
(b) from 0 to 5 mol-%, preferably from 0 to 1.25 mol-%, based on the 
dihalogenated aromatic compounds of formula I, of a tri- or 
tetra-halogenated aromatic compound corresponding to the formula 
EQU ArX.sub.n (II) 
wherein 
Ar denotes an aromatic group having 6 to 14 carbon atoms or a heterocyclic 
group having 6 to 14 carbon atoms and up to 4 ring carbon atoms may be 
replaced by hetero atoms such as N, O or S, 
X denotes halogen such as chlorine or bromine and 
n represents the number 3 or 4, 
(c) conventional chain terminating agents, 
(d) alkali metal sulphides, preferably sodium or potassium sulphide or 
mixtures thereof, together with alkali metal hydrogen sulphides, 
preferably sodium or potassium hydrogen sulphide or mixtures thereof, in 
the form of their hydrates or aqueous mixtures, optionally together with 
catalysts or other auxiliary agents in a solvent, and 
(e) from 0.5 to 25 mol-%, preferably from 0.5 to 10, most preferably from 1 
to 7.5 mol-% of a comonomer or a mixture of different comonomers at a 
pressure of from 1 to 50 bar, characterised in that the comonomers are 
selected from 3,4-dichlorodiphenylsulphone, 3,4-dichlorobenzophenone, 
N-(3,4-dichlorophenyl)-phthalimide, 4,4'-dichlorotriphenylamine, 
N-phenyl-4,5-dichlorophthalimide, 
N-(3,4-dichlorophenyl)-hexahydrophthalimide, 
2,4-dichloro-6-phenyltriazine-(1,3,5), 2,3-dichloroquinoxaline, 
2,3-dichloro-6-methyl-quinoxaline, 
N-(3,4-dichlorophenyl)-3,4-diphenyldicarboxylimide and/or 
2,6-dichlorobenzothiazole.

The following are examples of dihalogenated aromatic compounds of formula 
(I) to be used according to the invention: 1,4-Dichlorobenzene, 
1,4-dibromobenzene, 1-bromo-4-chlorobenzene, 2,5-dichlorotoluene, 
2,5-dichloroxylene, 1,4-dichloro-2-ethylbenzene, 
1,4-dibromo-2-ethylbenzene, 1-bromo-4-chloroethylbenzene, 
1,4-dichloro-2,3,5,6-tetramethylbenzene, 1,4-dichloro-2-cyclohexylbenzene, 
1,4-dichloro-2-hexylbenzene, 2,5-dichlorodiphenyl, 
2-benzyl-1,4-dichlorobenzene, 2,5-dibromodiphenyl, 
2,5-dichloro-4'-methyl-diphenyl, and 2,4-dibromo-4'-methyl-diphenyl. They 
may be used separately or as mixtures with one another. 
1,4-Dichlorobenzene and/or 1,4-dibromobenzene are particularly preferred. 
Polar organic solvents may suitably be used, e.g. lactams such as 
N-alkyllactam, for example, N-methylpyrrolidone, N-ethylpyrrolidone, 
N-isopropylpyrrolidone, N-methylpiperidone, N-methylcaprolactam, 
N-ethylcaprolactam, N,N'-dimethylimidazolidinone and 
1-methyl-1-oxophospholan or mixtures thereof. 
The boiling point of the solvent should be from 200.degree. to 350.degree. 
C. 
The usual chain terminating agents may be used: 
(1) aromatic monohalogen compounds, e.g. chlorobenzene, bromobenzene, 
4-chlorotoluene, 4-bromotoluene, 4-chlorobiphenyl, 
4-chlorodiphenylsulphone, etc., 
(2) phenols, e.g. phenol, para-cresol, ortho-cresol, m-cresol, etc., 
(3) thiophenol, e.g. thiophenol, n-methylthiophenol, 3-methylthiophenol, 
4-mercaptobiphenyl, etc. 
Alkali metal fluorides, alkali metal sulphates, alkali metal phosphonates, 
alkali metal sulphites, alkali metal acetates, etc. may be used as 
catalysts. 
The reaction may be carried out by various methods: 
The alkali metal sulphides and/or alkali metal hydrogen sulphides are 
preferably used in the form of their hydrates and aqueous mixtures or 
aqueous solutions. The reaction mixture is partially or, preferably, 
completely dehydrated. Anhydrous sulphides may also be used. The water 
present in the reaction mixture may be distilled off either directly or 
with the aid of substances which form azeotropic mixtures with water, 
preferably the dihalogenated aromatic compounds of formula (I). For 
dehydration, all the reactants may be mixed together and the whole mixture 
may then be dehydrated. Alternatively, the alkali metal sulphide and/or 
alkali metal hydrogen sulphide may be dehydrated separately with a portion 
of the reactants or on its own. 
In one embodiment of the reaction, the reactants are continuously brought 
together in the presence of the polar solvent, optionally together with a 
reaction accelerator or a mixture of reaction accelerators, and water is 
removed at the same time. With this procedure, any reaction setting in may 
be controlled by the rate at which the reactants are introduced. The 
procedure also allows the prolonged presence of water in the system to be 
avoided. 
If the reaction mixture is completely dehydrated, the reaction may be 
carried out pressure-free down to a pressure of about 10 bar, preferably 3 
bar. Higher pressures, up to 50 bar, may be employed for the purpose of 
obtaining higher reaction temperatures, above the boiling point of the 
solvent or of the mixture of solvent and dihalogenated and polyhalogenated 
aromatic compounds. 
The reaction may be carried out continuously or discontinuously. The 
reaction time may vary over a wide range. It may extend over 1 to 48 
hours, preferably 1 to 18 hours. The reaction temperatures range from 
150.degree. C. to 300.degree. C., preferably from 170.degree. C. to 
280.degree. C. 
The comonomers and chain terminating agents may be added before or during 
the process of dehydration or after dehydration has been completed. These 
substances may be added portionwise at certain times during the reaction 
over a certain period of time, e.g. within the first three hours of the 
reaction, or the total calculated quantity may be added directly at a 
specified time during the reaction. 
Working up of the reaction mixture and isolation of the polyarylene 
sulphides may be carried out in known manner. 
The polyarylene sulphide may be separated from the reaction solution by the 
usual procedures, for example by filtration or centrifuging, either 
directly or, for example, after the addition of water and/or dilute acids. 
After the polyarylene sulphide has been separated, it is generally washed 
with water although washing or extraction with other washing liquids may 
also be carried out in addition or subsequently to this washing with 
water. 
The polyarylene sulphide may also be obtained by, for example, removal of 
the solvent by distillation followed by the process of washing described 
above. 
The polyarylene sulphide may also be precipitated by its introduction into 
organic solvents, for example into alcohols such as ethanol, methanol, 
1-propanol or 2-propanol or into ketones such as acetone or methyl ethyl 
ketone, and may then be freed from impurities. 
Work up of the product may be carried out continuously or batchwise. 
The polyarylene sulphides prepared by the process according to the 
invention are distinguished by the fact that their crystallisation sets in 
at a lower temperature (about 150.degree. to 250.degree. C.) although 
their crystallinity is substantially the same and their melting 
characteristics virtually unchanged. These polyarylene sulphides are 
therefore more easily manufactured, for example into foils and films, 
fibres and injection moulded parts with long flow lengths or small 
cross-sections. 
The polyarylene sulphides prepared according to the invention may be mixed 
with other polymers and with pigments and fillers such as graphite, metal 
powders, glass powder, quartz powder, fused quartz, glass fibres and 
carbon fibres or with mould release agents or stabilisers conventionally 
used for polyarylene sulphides. 
The melt flow properties of the polyarylene sulphides are generally 
determined according to ASTM 1238-70 at 316.degree. C. using a 5 kg weight 
and given in terms of g/10 min. 
If the melt flow values are high, however, this method of measurement may 
give rise to difficulties owing to the high outflow rate of the polymer 
melt. 
The melt viscosity n.sub.m of the polymer melt (in Pa.s) in dependence upon 
the shearing strain (in Pa) at 306.degree. C. was therefore determined by 
means of an Instron Rotation viscosimeter. 
This enables the melt viscosity to be determined over a very wide range of 
from 10.sup.1 to 10.sup.7 Pa.s. In the Instron Rheometer, the polymer is 
melted between a fixed plate and a rotatable cone and the torque of the 
cone is determined. The melt viscosity in dependence on the shearing 
strain can be calculated from the torque, the angular velocity and the 
constants of the apparatus. The Rheometer Model 3250 of Instron was used. 
The value given for the melt viscosity was that which was determined at a 
shearing strain of .tau.=10.sup.2 Pa. 
The melting and crystallisation points [.degree.C.] were determined by DSC 
(="differential scanning calorimetry") on a commercially available 
measuring apparatus at heating and cooling rates of 20 k/min. 
The polyarylene sulphides according to the invention generally have melt 
viscosities of from 0.1.times.10.sup.1 to 5.times.10.sup.4 Pa.s, 
preferably from 0.1.times.10.sup.1 to 1.5.times.10.sup.3 Pa.s immediately 
after their isolation from the reaction mixture. They can be directly 
manufactured into films, fibres or moulded bodies by extrusion, extrusion 
blowing, injection moulding or other conventional processing techniques. 
These products may be employed for the conventional purposes, e.g. as 
motor vehicle parts, mountings and fittings and parts of electrical 
equipment, e.g. switches, electronic panels and electronic parts, 
chemically resistant and weathering resistant parts and apparatus such as 
pump housings and pump impellors, etching batch containers, sealing rings, 
parts of office machinery and telecommunication equipment, domestic 
appliances, etc. 
EXAMPLE 1 
Comparison example 
2693.0 g of N-methylcaprolactam, 608.7 g of 1,4-dichlorobenzene and 27.3 g 
of phenol are introduced into a 5-liter reaction vessel equipped with a 
thermometer, stirrer, coolable column, distillate divider, reflux 
condenser and two dropping funnels and heated to reflux. A solution of 
1147.5 g of sodium sulphide hydrate, 4.4 g of sodium hydroxide and 141.1 g 
of caprolactam is added dropwise at such a rate that the water can distil 
off azeotropically with the 1,4-dichlorobenzene. At the same time, a 
further 608.7 g of 1,4-dichlorobenzene are continuously added to the 
reaction mixture. The 1,4-dichlorobenzene distilled off is returned to the 
reaction mixture after removal of the water in order to maintain the 
stoichiometric proportions. When all the components have been added and 
dehydration has been completed, the column is adjusted to reflux, the 
reaction mixture is heated under reflux for a further 10 hours and the 
product is finally isolated in the conventional manner (for values of DSC 
measurements see Table). 
EXAMPLE 2 
The same as Example 1 but without phenol. Furthermore, only 566.1 g of 
1,4-dichlorobenzene are introduced into the reaction vessel. In addition, 
47.7 g of 3,4-dichlorodiphenylsulphone and 63.0 g of 
4-chloro-diphenylsulphone are introduced. 
EXAMPLE 3 
The same as Example 2 but using 35.1 g of phenol instead of 
4-chloro-diphenylsulphone. 
EXAMPLE 4 
The same as Example 3 but with the addition of 48.5 g of 
N-(3,4-dichlorophenyl)-phthalimide after dehydration instead of 
3,4-dichlorodiphenylsulphone. 
EXAMPLE 5 
The same as Example 1 but without phenol and with the addition of 52.0 g of 
4,4'-dichlorotriphenylamine. In addition, 584.4 g of 1,4-dichlorobenzene 
were introduced. 
EXAMPLE 6 
The same as Example 5 but with the introduction of 41.9 g of 
2,6-dichloro-benzothiazole into the reaction vessel instead of 
4,4'-dichlorotriphenylamine. 
EXAMPLE 7 
The same as Example 5 but with 37.5 g of 2,4-dichloro-6-phenyl-triazine 
instead of 4,4'-dichlorotriphenylamine. 
EXAMPLE 8 
The same as Example 5 but with 35.3 g of 2,3-dichloro-6-methyl-quinoxaline 
instead of 4,4'-dichlorotriphenylamine. 
Table 1 below shows the melting points (Tm) determined by DSC measurement 
and the crystallization points (Tk) appearing in the cooling curve, all 
measured at a rate of 20 K/min. 
TABLE 1 
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Example Tm [.degree.C.] 
Tk [.degree.C.] 
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1 285.2 234.7 
2 278.8 192.2 
3 281.0 209.0 
4 269.8 187.1 
5 270.7 208.2 
6 268.4 201.1 
7 281.3 192.0 
8 281.9 200.5 
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