Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From sulfur-containing reactant
Reexamination Certificate
2000-04-12
2001-07-17
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From sulfur-containing reactant
C528S373000, C528S480000, C528S486000, C528S50200C, C528S503000
Reexamination Certificate
active
06262224
ABSTRACT:
This invention relates to a process for producing polyarylene sulfone fiber material by oxidizing polyarylene sulfide fiber material with a peracid/acid mixture of an organic acid.
Polyarylene sulfones are particularly notable for their chemical resistance and thermal and mechanical stability. They are therefore predominantly used as thermally stable filling and reinforcing materials in other engineering plastics. It is even possible to sinter polyarylene sulfones to obtain high temperature resistant products.
Polyarylene sulfones are obtained by oxidation of polyarylene sulfides. The product obtained is generally not further processable thermoplastically. This means that the physical form (powder, fiber, molding, etc.) of the oxidized product essentially depends on the physical form of the polyarylene sulfide used for oxidation. To produce polyarylene sulfone fiber material it is thus necessary to oxidize polyarylene sulfide fiber material.
EP-B-0283520 discloses polyphenylene sulfone fibers and a process for producing them by oxidizing polyarylene sulfide fibers. The polyphenylene sulfide fibers treated have a degree of orientation of not less than 60% and at least 90 mol % of their structural units are phenylene sulfide units and they are treated with an organic peroxide, for example peracetic acid. The disadvantage with this process is that only substantially oriented fibers having a high crystalline fraction can be oxidized.
EP-B-0283520 discloses in particular the oxidation of composite fibers from poly(p-phenylene sulfide) (PPPS) and polystyrene including the oxidation of fiber webs. This oxidation is carried out at 30° C. (room temperature) or 50° C. for 1 to 3 hours. Pure PPPS fibers were oxidized at 30° C. for two weeks to obtain fibers containing 75 mol % of sulfone groups, 16 mol % of sulfoxide groups and 9 mol % of remaining sulfide groups. The long reaction times are a disadvantage here.
The use of a hydrogen peroxide/acetic acid mixture for oxidizing aromatic polythioethers containing sulfone groups is described in Chimia 28, 567 (1974). However, this method presupposes the use of large amounts of suspension medium and of high temperatures. This method too has the disadvantage of long reaction times of up to 24 hours.
EP-A-0 623 641 discloses oxidizing PPS powder with peracetic acid (acetic acid+H
2
O
2
)—selectively in the presence of catalytic amounts of sulfuric acid—to obtain a pure polyarylene sulfone or a polyarylene sulfoxide sulfone copolymer where the sulfone units predominate in number. The long reaction times of 1-3 hours are a disadvantage.
A process for producing polyarylene sulfones by oxidizing polyarylene sulfides in acetic acid with hydrogen peroxide in the presence of catalytic amounts of sulfuric acid or organic equilibrium peracid is also described in DE-A-43 14 738. This process has the disadvantage that the reaction temperature fluctuates wildly during the addition of the hydrogen peroxide.
EP A 0 827 977 discloses that the temperature in the reaction mixture of the production of polyarylene sulfones by oxidation of polyarylene sulfides with hydrogen peroxide or peracids can easily be kept constant under reduced pressure, so that the liquid reaction medium, for example the solvent, boils. The disadvantage here is the fact that this process can only be carried out in a sealed vessel and hence not continuously.
It is an object of the present invention to develop a process whereby polyarylene sulfide fiber material can be oxidized economically and without technical problems.
It was found that, surprisingly, oxidation of polyarylene sulfide fiber material with an organic peracid/acid mixture at 60 to 100° C. will provide a very high degree of oxidation after just a very short reaction time.
The invention accordingly provides a process for producing polyarylene sulfone fiber material by oxidizing polyarylene sulfide fiber material with a peracid/acid mixture of an organic acid, which comprises effecting said oxidizing at 60 to 100° C. for 10 seconds to 45 minutes.
The particular advantage of the process of the invention is that the rapidity of the oxidation renders continuous processes for oxidizing polyarylene sulfide fibers economical.
Polyarylene sulfides in the broadest sense are linear, branched or crosslinked polymers that contain arylene sulfide units. Polyarylene sulfides and their synthesis are described, for example in “Ullmann's Encyclopedia of Industrial Chemistry”, Volume A21, B. Eivers, S. Hawkins and G. Schulz (Eds.), VCH, Weinheim-New York 1992, p. 463-472, incorporated herein by reference. Preferred polyaryiene sulfides are polyarylene thioethers containing repeat units of the formula
—[(Ar
1
)
n
—X]
m
—[(Ar
2
)
i
—Y]
j
—[(Ar
3
)
k
—Z]
l
-[(Ar
4
)
o
—W]
p
— (I)
where Ar
1
, Ar
2
, Ar
3
, Ar
4
on the one hand and W, X, Y and Z on the other are independently identical or different, the indices n, m, i, j, k, l, o and p are independently zero or 1, 2, 3 or 4, subject to the proviso that their sum total is not less than 2, Ar
1
, Ar
2
, Ar
3
and Ar
4
are arylene units of 6 to 18 carbon atoms, W, X, Y and Z are bivalent linking groups selected from —SO
2
—, —S—, —SO—, —CO, —O—, —COO— or alkylene or alkylidene groups of 1 to 6 carbon atoms, and at least one of the linking groups W, X, Y or Z is —S—. The arylene units Ar
1
, Ar
2
, Ar
3
and Ar
4
may be selectively substituted or unsubstituted.
Preferred arylene systems are phenylene, biphenylene, naphthylene, anthracene and phenanthrene. The polyarylene sulfide advantageously contains at least 30 mol %, preferably at least 50 mol %, particularly at least 70 mol %, of arylene sulfide units. The preferred polyarylene sulfide is polyphenylene sulfide. This generally contains at least 50 mol %, especially at least 70 mol %, of phenylene sulfide units and is known for example under the names of ®Fortron and ®Ryton.
By fiber material are generally meant all possible and conceivable materials that are fibrous or composed of fibers, for example individual fibers, fiber strands, networks, wovens, needlefelts, nonwovens, etc.
The process of the invention is particularly useful for fiber materials whose fibers have a filament diameter of 1 to 20 &mgr;m, preferably 2 to 10 &mgr;m, especially 3 to 6 &mgr;m. These fibers may have been produced, for example, in the melt-blown process. Other advantages are a fiber BET specific surface area of ≦0.3 m
2
/g and a polyarylene sulfide crystallinity of less than 40%, especially within the range from 5 to 20%. Whereas the specific surface area of the oxidized product is substantially unchanged, the crystallinity is increased by the oxidation.
The advantages of the process of the invention are particularly apparent in the case of the oxidation of polyarylene sulfide fiber material produced by the process described in EP-A 0 709 499, wherein polyarylene sulfide is extruded together with specific organic phosphites or phosphonites and formed into microfibers by the melt-blown process. The disclosure content of EP-A 0 709 499 and its priorities U.S. Pat. No. 324,946 and U.S. Pat. No. 517,494 is hereby incorporated herein by reference.
The polyarylene sulfide fiber material may be oxidized according to the invention using, in general, mixtures of organic peracids and concentrated organic acids. The peracid may be formed in advance by mixing hydrogen peroxide and an acid or in situ by addition of hydrogen peroxide to concentrated organic acid. Organic acids are aromatic or aliphatic carboxylic acids, for example benzoic acid and acetic acid. If the acid is a liquid, it may be used as reaction medium. The acids may include water or be dissolved in water. An example of an organic peracid is peracetic acid.
Sulfuric acid is advantageously added to the organic acids to catalyze the reaction with hydrogen peroxide to form peracid. An exception is the reaction in formic acid. It does not require further activation by mineral acid.
The preferred oxidizing agent according to the invention is hydrogen p
Bruck Martin
Scheckenbach Helmut
Zierer Dirk
Connolly Bove & Lodge & Hutz LLP
Ticona GmbH
Truong Duc
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