Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
1999-02-10
2002-02-26
Wilson, Donald R. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S381000, C525S537000
Reexamination Certificate
active
06350852
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is filed pursuant to 35 U.S.C. §371 from PCT/EP97/02931, filed Jun. 6, 1997, which in turn claim priority to German application 196 23 706.8, filed Jun. 14, 1996.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for preparing linear or branched sulfur-containing polymers, such as polyarylene sulfides, in particular polyphenylene sulfide (PPS), in which the monomers are added to a polymerized, or partially polymerized, mixture.
2. Description of the Related Art
U.S. Pat. No. 4,910,294 describes a process for preparing PPS. The monomers used are dihalogenated aromatic hydrocarbons, in particular dichlorobenzene (DCB), and sodium sulfide, which are reacted in a high-boiling dipolar aprotic solvent, such as N-methylpyrrolidone (NMP). Substantial amounts of solvent must be employed in order to bring the reaction partners to reaction, since the metal sulfide and the aromatic dihalogen compound reaction components are not miscible with one another. At least 3.5 mole of NMP per mole of sulfide are typically employed.
EP-A1-536684 describes the preparation of polyphenylene sulfide in NMP in concentrations higher than 3.5 mol of NMP per mole of sulfide, by adding p-dichlorobenzene to a dehydrated mixture of sodium sulfide and NMP and then polymerizing the mixture. However, a reaction temperature of 280° C. is required, and reproducibly high molecular weights, characterized by the melt viscosity of the products, are not achieved.
DE-A1-237 110 describes a process for preparing low-molecular-weight polyarylene sulfide by precharging an alkali metal sulfide in a high boiling polar N-alkyl-2-pyrrolidone and then metering in an aromatic dihalide. Here, the molar ratio of solvent to the sulfide employed reaches at least 3.1. The reaction time is in total 12 h after the start of dihalide addition, at at least 255° C.
EP-B1-215 259 describes a process for preparing polyarylene sulfides from dihaloaromatic compounds and alkali metal sulfide in N-methylcaprolactam in which half of the reaction mixture is precharged under gentle reflux. The second half of the mixture, that is including the solvent, is then metered in. The minimum ratioachieved of solvent to the sulfide employed is 3.25. The mean reaction time in the stirred vessel cascade is 12.5 h.
EP 0 374 462 describes the preparation of polyarylene sulfides by continuous addition of sulfide to a mixture of dihaloaromatic compound and polar solvent. The molar ratio of polar solvent to sulfide is from about 1.1 to 1.8:1. The reaction times are from about 10 to 15 hours.
If less solvent is employed in the processes of the prior art, molecular weight and polymer yield are poor; at higher solvent concentrations, the space-time yield is unsatisfactory. To achieve satisfactory space-time yields, the reaction temperature is frequently raised, but this leads to an increase in side-reactions.
The object is therefore to prepare sulfur-containing polymers, in particular polyarylene sulfides, over a wide molecular weight range of molar mass (e.g. Mw=10,000-200,000 g/mol), with good space-time yield, using the mildest possible reaction conditions, and with the least possible contamination by by-products.
BRIEF SUMMARY OF THE INVENTION
It has been found that it is possible to prepare sulfur-containing polymers, in particular polyarylene sulfides, with high space-time yield, with a total solvent requirement of less than 300 g of solvent per mole of sulfide employed, at reaction temperatures not higher than 250° C., and with short reaction times (less than 5 hours), if a prepolymer is firstly formed from aromatic dihalogen compound and sulfide in a polar solvent, and is then converted, by addition of aromatic dihalogen compound and sulfide, to a polymer of higher molecular weight.
DETAILED DESCRIPTION OF THE INVENTION
The invention therefore relates to a process for preparing sulfur-containing polymers from at least one aromatic dihalogen compound and at least one sulfide, in a solvent, where a) a mixture of aromatic dihalogen compound and sulfide is polymerized, b) aromatic dihalogen compound and sulfide are added to the polymerized mixture and c) the reaction mixture is polymerized further.
Sulfur-containing polymers are polymers which contain arylene sulfide units. The arylene constituents of the arylene sulfide units contain mono- or polynuclear aromatics or compound aromatics. The aromatic compounds may also contain heteroatoms. Examples of such aromatic compounds, which may be substituted or unsubstituted, are benzene, pyridine, biphenyl, naphthalene and phenanthrene. Examples of substituents are C
1
-C
6
-alkyl, C
1
-C
6
-alkoxy, carboxyl, amino and sulfonic acid groups. Examples of compound aromatics are biphenyl and aromatics bonded by ether bridges (arylene ethers).
Preferred sulfur-containing polymers are polyarylene sulfides, in particular polyphenylene sulfide.
Both inorganic and organic sulfides are suitable as sulfide for preparing the polymers. Inorganic sulfides are sulfides of alkali metals and alkaline earth metals, such as lithium sulfide, potassium sulfide, calcium sulfide, and preferably sodium sulfide. The corresponding bisulfides, or hydrogen sulfide, may also be employed, if desired together with alkali metal hydroxides. Suitable organic sulfides are salt-like sulfides with organic cations. For the purpose of the invention, organic sulfides are also those organic sulfur compounds which liberate sulfide anions or bisulfide anions under the conditions of the reaction, for example thioacetamide and thio-N-methylpyrrolidone. Sulfides may also be employed with water of crystallization.
Suitable aromatic dihalogen compounds are dihalogenated aromatic hydrocarbons, inter alia dihalobenzenes, such as o-, m- and p-dichiorobenzene, substituted dihalobenzenes, such as 2,5-dichlorotoluene, 3,5-dichlorobenzoic acid, 2,5-dichlorobenzenesulfonic acid and 3,5-dichlorobenzenesulfonic acid and their salts. Dihalonaphthalenes, such as 1,4-dibromonaphthalene and dihalodiphenyl ethers, such as 4,4′-dichlorodiphenyl ether, may, however, also be employed. Mixtures of different arylene dihalides may likewise be employed. Small amounts (from 0.2 to 5 mol percent based on dihaloaromatic compound) of polyhalogenated aromatic hydrocarbons may also be employed in order to obtain branched or crosslinked sulfur-containing polymers.
Dihaloaromatic compounds and sulfide are also referred to as monomers.
Suitable solvents for preparing the polymer are dipolar aprotic solvents of the amide type, such as dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylcaprolactam and N-alkylated pyrrolidones, such as N-methylpyrrolidone (NMP), or mixtures thereof. NMP is particularly preferred.
The term prepolymers includes oligomers and polymers containing arylene sulfide units. These products usually have a molar mass, expressed as number average molar mass M
n
, in the range from 500 to 20,000 g/mol. They may be linear or branched. It is also possible, by employing substituted dihaloaryl compounds (e.g. 2,5-dichlorotoluene) to prepare substituted prepolymers. Prepolymers with halogen end groups, in particular chlorine end groups, are preferably prepared.
The preparation of the prepolymer in step a) is generally carried out by reacting sulfide with dihalogen compounds in polar solvents, such as dimethyl sulfoxide, dimethylformamide (DMF), dimethyl acetamide (DMAc), N-alkylated lactams, such as N-alkylcaprolactams, e.g. N-methyl caprolactam (NMC), N-alkylpyrrolidones, e.g. N-methylpyrrolidone (NMP) or mixtures of these, under mild reaction conditions, i.e. at temperatures not above 250° C. The weight of solvent employed per mole of sulfide here is from 150 g to 1000 g, preferably from 250 g to 600 g. If NMP is employed as solvent, this is from 1.5 to 10 mol of NMP per mole of sulfide, preferably from 2.5 to 6 mol of NMP per mole of sulfide. From 0.9 to 1.5 mol of dihaloaromatic compound i
Haubs Michael
Wagener Reinhard
Frommer & Lawrence & Haug LLP
Ticona GmbH
Wilson Donald R.
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