CA1082221A - Polysulfone resins - Google Patents

Abstract

Abstract of the Disclosure This invention is directed to the compound bibenzyl 4-sulfonyl chloride. This compound is used in the preparation of polymers which have good mechanical properties, toughness, flexibility, thermal and chemical stability and can be heat processed, extruded, drawn or otherwise formed into shaped articles having a high degree of strength and good dielectric properties.

Description

2~
B ground of the Invention The present invention is concerned with thermoplastic poly bibenzyl sulfone polymers and copolylners containing recurring biben7yl sulfone groups in the polymer molecule, said polymers and copolymers exhibiting high temperature stability and improved tensile properties as compared with conventional aromatic sulfone polymers .
There are a number of polymers available today which offer extremely good resistance to heat at te~nperatures in excess of 100C, good electrical properties and are relatively inert to attack by chemical solvents. Among these materials are the polyphenylene oxides, polysulfones, polysulfonates, polysulfone polyesters, polysulfonamides and like materials. These polymers are generally characterized by recurring phenyl or biphenyl groups joined together by sulfur, oxygen, sulfone, amide or bivalent hydrocarbon radicals.
One commercially available polysulfone is produced by the-reaction between the sodium salt of 2, 2 bis (4-hydroxy phenol) propane and 4, 4'-dichlorodiphenyl sulfone. This material is characterized as being stabie in alr at temperatures in excess of 300F and is fairly rigid, exhibiting a flcxural Inodulus of elasticity of nearly 400, 000 psi Z0 at room temperature. Another class of polysulone polymers are the polyaryl sulfones such as, for example, disclosed in British patent specification 1,122,192. These polymers are amorphous and consist mainly of phenyl and biphenyl groups linked by thermally stable ether and sulfone groups, and may be distinguished from polysulfones mentioned abo~e by the absence of aliphafic groups.
The moldillg grade polyaryl sulfones may be processed by injection , ~ .

:. . .. . , . ~ , . . . .

molding or extrusion techniques, but extremely high temperatures are required. For example, the cylinder and nozzle of an injection molding machine must normally be equipped to reach temperatures of 800F., and temperatures in the range of about 600F. to 750F. are required for extrusion. Other polyaryl sulfones exhibiting similar properties are taught in British patent specification 1,166,624 in which polymers having a diphenyl ether sulfone repeating unit in the polymer chain are prepared, and British patent specification 1,060,546 in which sulfone copolymers containing diphenyl ether sulfone and at least one other aromatic sulfone such as biphenyl, diphenyl methane or naphthalene are prepared.
Whereas the above and other sulfone polymers have filled a long felt need for thermoplastic materials which do not degrade at temperatures in excess of 100C. and in many cases at tempera-tures up to about 500C., their thermal characteristics are such that extremely high temperatures are required to process them.
This in turn may require the use of special or modified processing equipment adapted for high temperatures and the consumption of large amounts of energy.
Accordingly, it is an object of this invention to provide aromatic sulfone polymers which exhibit toughness, flexibility, high temperature stability, good tensile stress properties, a relatively high heat distortion temperature, and good dielectric properties.
Another object of this invention is to provide a novel monomer, ~anely bibenzyl 4-sulfonyl chloride, suitable for the preparation of sulfone polymers and copolymers.
Still another object is to provide aromatic sulfone homo-polymers and copolymers containing bibenzyl sulfone units which exhibit superior tensile stress and processing properties.

Sun~lnary oI the Invention This and other objects of the invention mi y be achievecl by preparing polysulfone homopolylners having the repeating bibenzyl sulfone unit of the formula:

~ CH2 CH2--~ so2 or copolymers having this unit chemically linked through the sulfone group to different aromatic units such as biphenyl, diphenyl ether, diphenyl sulfide and like aromatics. Polybibenzyl sulfone homopolymers may be most readily prepared by either forming the self condensation product of b;benzyl - 4 - sulfonyl chloride using a Lewis acid catalyst,or by ieacting approximately stiochiometric molar amounts of bibenzyl and bibenzyl - 4, 4' -disulfonyl chloride also employing a Lewis acid catalyst.
Copolymers may be prepared by the same method by copolymerizing the appropriate amounts of bibenzyl or its nlono or di sulfonyl chloride derivative with the selected comonomer or con~onomers or their mono or di sulfonyl chloride derivatives. Bibenzyl sulfone polymers prepared according to this invention exhibit good high tcnlperature stability, tensile strength, and flexibility. Also, polymers containing a major amount of ` 20 bibenzyl sulIone units may be processed using conventional molding or extrusion equipment. Shaped articles prepared fronl these polymers may be used in application where good high temperature stability and 1exibility are prerequisites such as heat generating appliance housings or parts, circuit components, automotive parts, medical appliances, and the like.

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Detailed Description oI the Invention The polysulfones disclosed herein employ bibenzyl (diphenylethane) as the basic recurring structural moiety in the polyme r backbone. Bibenzyl is a white crystalline compound which is insoluble in water and may be synthesized by treatin~ benzyl chlor~de with metallic sodium or by the action of benzyl chloride on benzylmagnesium chloride.
It may also be prepared by hydrogenating stilbene which, in turn, is manufactured as a by-product in the dehydrogenation of ethyl benzene during the manufacture of styrene. Stilbene may also be synthesized by passing toluène over hot lead oxide.
Polybibenzyl sulfone homopolymers are prepared by heating bibenzyl - 4 - sulfonyl chloride in the presence of a catalytic amount of an anhydrous Lewis acid, or by using a stoichiometric mixture of bibenzyl and bibenzyl - 4, 4' - disulfonyl chloride as hereinafter described.
The preparation of the homopolymer first necessitates the synthesis of either the mono or di sulfonyl chloride derivative of bibenzyl.
Bibenzyl - 4 - sulfonyl chloride may be prepared by a three step procedure by treating bibenzyl in solution with approxil~ately equi molar quantities of chlorosulfonic acid to form bibenzyl - 4 - sulfonic acid followed by neutralization in an aqueous mediurn using sodium or barium hydroxide to yield the sodium or barium salt which is in turn treated in a solvent with an acid halide such as thionyl chloride to yield bibenzyl - 4 - sulfonyl chloride. Another suitable technique for the preparation of the mono-sulfonyl chloride derivative involves the treatment of lhe free sulfonic acid derivative of bibenzyl in a solvent with a complex of phosgene and a tertiary organic anlide.

... . _ ~zz;~

Bibenzyl 4, 4'-disulfonyl chloride n~ay be prepared by a three step procedure by sulonation of bibenzyl USillg a molar excess of sulfuric acid to form bibenzyl 4, 4-disulfonic acid, followed by neutralization and treatment with tlhionyl chloride as discussed above.
It may also be prepared directly from bibenzyl by chlorosulfonation in chloroform using at least a two molar excess of chlorosulfonic acid.
It has also been reportedly prepared by treahnent of the sodium salt of bibenzyl disulfonic acid with phosphorous pentachloride and phosphorous oxychloride- - Polymer Science, U.S.S.R.,A-14, No. 9, 2102-2105, 1972.
The following Examples illustrate the preparation of bibenzyl-4-sulfonyl chloride and bibenzyl 4, 4' - disulfonyl chloride respectively.

EXAMPLE I

To a solution of 54. 6 g. (0. 30 mole) of bibenzyl in 100 ml. of chloroform was added dropwise 24 ml! (o. 372 mole) of chlorosulfonic acid in 40 ml. of chloroform. After stirring for two hours, the nlixture was concentrated on a rotary evaporator and the solids washed with lOO ml. of hexane. There was obtained 78. 7 g. of bibenzyl 4-sulfonic acid.
The above product was dissolved in 1600 ml. of water and filtered, yielding 71.1 g. of soluble product. This filtrate was further diluted with 800 ml. . of water and treated with barium hydroxide until the solution was basic. The solids were filtered and dried resulting in a 78.1% yield of the barium salt of bibenzyl 4-sulfonic acid.
To 66. 0 g. (0.10 n~ole) of the above salt in 500 ml. of DMF at o 10 C was added dropwise 44 ml. (0.60 nlole) of thionyl chloride. After one hour the mi.Yture was gradually warmed to room temperature while stirring.

The mixture was then mixed with 1 kg. of ice water and stirred for fifteen minutes. The solids were filtered, water washed and dried under vacuum yielding 52. 1 g. of bibenzyl 4-sulIonyl chloride, mp. 83-86C.
The above solids were purified by refluxing in ligroin S at a concentration of 5% by weight and by filtering out the resultant insolubles. The filtrate was concentrated and dried, yielding greater than 80% yield of purified bibenzyl 4-sulfonyl chloride, mp. 90 to 95 C.
Analysis: calculated: C, 59. 8; H, 4. 6; Cl, 12. 6; S, 11. 5.
Found: C, 60. 0; H, 4. 8; Cl, 12.~5; S, 11. 4.

EXAMPLE II

To a solution of 36. 4 g. (0. 20 mole) of bibenzyl in 400 ml.
of chloroform at 0 C. was added dropwise a solution of 105 ml.
(1. 60 mole) of chlorosulfonic acid in 100 ml. of chloroform. The cooling medium was removed and after one hour of stirring, the mixture was poured into 1 kg. of ice. The mixture was filtered and dried, yielding 50. 7 g. of bibenzyl 4, 4'-disulfonyl chloride, mp. 166-185C.
A 10 g. sample in a soxhlet tube was extracted overnight with 200 ml. of methanol. There was recovered ater drying ~. 8 g.
of white solids, mp. 199-20S C. Analysis: calculated: C, 44. 3;
H, 3. 2; Cl, 18. 7; S, 16. 9. Found: C, 43. 6; H, 3. 4; Cl, 18. 2; S, 16. 7.
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As previously suggested, bibenzyl sulfone hol~opolymers and copolylners of the present invention may be effectively prepared by melt or solution polymerization tec~mique. Polybibenzyl sulfone may be prepared using the self condensable bibenzyl 4-sulIonyl chloride monomer such as prepared in Example I, or by condenslng equi molar _6-;z~

quantitie~s of bibenzyl and bibenzyl 4, 4'-disulIonyl chloride such as prepared in ~xample II. Copolymers containing the bibenzyl moiety and one or more other aromatic moieties such as diphenyl ether, naphthalene, diphenyl sullide and like arolnatics rnay be prepared by copolymerizing an appropriate mixture of bibenzyl mono sulfonyl chloride with at least one other aromatic n~onosulfonyl chloride, or by copolymerizing a mixture colnprising an aromatic disulfonyl chloride and unsubstituted aromatic.
The above lnonomers or comonomers may be substituted with non-reactive substituent groups on the aromatic nuclei. Such substitueNt groups include alkyl or perfluoroalkyl groups containing from about l - 5 carbon atoms, halogens such as bromine or chlorine and other substituents which are inert under the conditions of polymerization.
The polymerlzation process may be carried out using n~elt or solution condensation procedures involving a repeating reaction between an aromatic sulfonylchloride group and an aromatic hydrogen atom by heating the monomers to a temperature of about 80 to 250 C
in the presence of a Friedel Crafts catalyst.
Suitable Friedel Crafts catalysts include metal salts or oxides - such as ferric chloride, ferric bromide, ferric oxide, aluminum chloride, ~inc chloride and antilnony chloride. Anhydrous hydrofluoric acid or trifluoromethane sulfonic acid may also be used. These catalysts are generally effective in an amount of from 0. 05 to 0. 5 Inole per cent based on monomer amount.
Suitable inert solvents useful for solution polymerization include nitrobenzene and halogen containing aromatic or aliphatic solvents such as tetrachloro ethane, methylene chloride, chlorinated biphenyl and diphen~-l ether, and like materials.
- The general proceduresfor polylnerization involves first heating the . ,, ~ ~ . ~ . ... . . .

mono]ners or a solution oL monolne:rs to a tcmperature above the n~elting point to obtain a uniform mclt. Then, an appropriate quantity of catalyst is added and the mixture is rnaintained at a polymerization temperature usually within the range o about . 5 100 to 250C lor about 1 to 20 hours until polymerization is complete, The polymer n~ay then be recovered by conventional techniques.
Polymers prepared according to the present invention will in general have an inherent viscosity in the range of about 0. 2 to about 1. 0 when determined as a 1% solution at 25 C in N-methyl-2-pyrrolidinone and may comprise the so-called AB type of polynaers prepared by condensation reaction of biben~yl monosulonyl chloride or a mixture of bibenzyl monosulfonyl chloride with one or nlore different aromatic monosulIonyl chlorides, as represented by the following formulae:

1 {~ ~--CH2---- CH2 ~3 ~
wherein~,is a positive ~,vhole number equaling the degree of polymeri~ation and is such that the inherent viscocity of the polymer is within the range of about 0. 2 to about 1. 0 when determined as a 1% solution at 25C in N-methyl-2-pyrrolidinone.

II. {~3--CH2---CH2 ~3--so~ Z--~3~S

whereill 0. 01~ X C 0. 99, and x equals the molar ratio of biben~yl 4-sulfone units present in the total polymer weight, r~ is as defined ab~ve, and 5 Z is selected from the group consisting of a direct link, oxygen, sulfur, lower alkylide1le, or lower alkyl other than ethylene having from about 1 to 5 carbon atolns.

III. _ ~ _CHz_CH~_ <~ SO~ Z {~_ SO~

~ Z~ 50~

wherein: 0. 01 ~ x ~ x + y C 0. 99, and x, Z andh_are as defined above y equals the molar ratio of -~Z ¢3 S0 units present in the total polymer weight, and Z is a member of Z different than the specific Z group present in the polymer.

Typical AB polymers corresponding to the above formulas include polybibenzyl sulfone (formula I); copolymers of bibenzyl sulfone copolymerized with biphenyl sulfone (Z is a direct link) or diphenyl ether sulfone ( Zis oxygen), said copolymers containing at least 1 mole per cent of bibenzyl sulfone units (formula II); and terpolymers of bibenzyl sulfone copolymerized with two different aromatic sulone units such as biphenyl sulfone (Z is a dlrect link) and diphenyl ether sulfone (Zl is oxygen),said terpolymers also containing at least 1 mole percent of bibenzyl sulfone units (formula III). It should be evident that suitable copolymers containing more-than three different aron~atic sulIone units would also be within the scope of this invention.
It is also possible to prepare so called AABB type polymers by the condensation reaction of approxinlately stoichiometric quantities of one of the 4, 4~-disulfonyl chloride derivatives of any of the above recited mononlers ~vith one or lnore unsubstituted monomers. For example, polybibenzyl sulfone having repeating units as sho~,vn in formula I, can be prepared by reacting approximately equi molar a~nounts of bibenzyl and _9_ bibcnzyl 4, 41 disulfonyl chloride. Copoly~ners may be prepared by reacting approximately equi Inolar quantities of an unsubstituted monomer containing arornatic groups and the 4, 41_ disulfonyl chlor;de derivative of another different monomer containing aromatic . 5 groups which copolymers may be represented by the formula:
[v t~--CH2--CH2- ~ S 2r~ ~ ~

wherein Z and~_are as defined above.

In a similar manner, terpolymers may be prepared by reacting approximately equi. molar quantities of a 4, 41 _ disulfonyl chloride monomer derivative and a mixture of unsubstituted monomers, or a mixture of different 4, 41 _ disulfonyl chloride monomer derivatives with an approximately equi molar alnount of an unsubstituted monomer, The structure of such polymers would be similar to that of formula III with the proviso that the polymer lnust contain about 50 mole per cent of units derived from 4, 41 _ disulfonyl chloride monomer or rnonolner mixture as represented by the following formula:

Z~ V, ~ CHz- CH2 ~(~ ~ 52~ \ (~

-~ ~ Z 1~ 52 ~ Z ~ )_ wherein a and b are positive whole numbers equal to 1 or greater but not necessarily equal to each other, and~,, Z and Z' are as d ef ine d ab ove .

A typical polymer species represented by formula V would be the stoichiometric reaction product of diphenyl ether 4, 4'-disulfonyl chloride (Z is oxygen) with an approximately equi molar .

-10_ ;z~

alnount of bibenzyl al~d biphenyl (Z' is a direct lin]c).

The advantages of polymers prepared according to the present invention in terms of thèir low temperature processability are best realized in the polybibenzyl sulfone homopoly1ners or in copolymers containing at least about 25 mole per cent of the bibenzyl sulIone moiety, more preerably in the order of at least about 50 n~ole per cent. Such polymers generally exhibit melting point ranges in the order of 200 to 260C as opposed to higher melting point ranges possessed by certain of the commercially available polysulfones.
The following Examples illustrate the preparation of the bibenzyl sulfone homopolymers and copolymers in accordance with the presen-t invention.

EXAMPLE III

Solution homopolymerization of bibenzyl 4-sulfonyl chloride.
To a flamed out flask under nitrogen was added 5. 6 g. (0. 020 mole) of bibenzyl 4-sulfonyl chloride in 10 ml. of nitrobenzene. The mixture was warmed to 80 C. and 2. 0 ml. of a 10% catalyst solution of ferric chloride in nitrobenzene was added. -After a few minutes copious arnounts of hydrochloric acld were liberated. The off gas was passed through water and then neutralized with lN sodium hydroxide. After heating overnight at 120C. a total of 39 ml. of base was needed to neutralize the off gases or 97. 5% of the theorical alnount of HCl was liberated during the condensation polymerization. A total of 80 ml. of dlmethyl formamide (DMF) ~.vas added and the solution heated for 10 minutes at 100C.
After filtration the mixture was slowly added to 500 ml. of methanol in a blender. The polymer was filtered and oven dried. There was obtained .- : . . - - . ::
... .. : - . , - . , - . : - :
:, :

Z;~l 4. 5 g. (91. 4% yield) oI polybibenzylsulfone, mp. 203-205C. The infrared spectra showed intcnse bands at 1300 andll50 cm~l characteristic of sulfone absorption. The inherent viscosity as determined at 25C as a 1% solution in N-n~ethyl pyrrolidinone was 0.16.

EXAMPLE IV

Melt homopolymerization of bibenzyl 4-sulfonyl chloride.
To a flamed out polymer tube flushed with nitrogen was added 5. 6 g, (0. 02 mole) of bibenzyl 4-sulfonyl chloride. The tube was heated to lZ0 C in a tube furnace and then 0.1 g. of anhydrous ferric chloride was added. After one minute hydrochloric acid was liberated. Thetube was heated to 250C for two hours and attached to a vacuunn pump for one hour.
To the cooled tube was added 50 ml. of DMF and 1/2 ml.
of 2,4-pentanedione. The contents were heated for ten minutes at 100 C and some particles were filtered. The filtrate was added dropwise to 500 ml. of methanol in a blender. The polymer was washed with methanol and then dried in the oven. There was obtained 4. 4 g., 89. 5% yield of gray solids of polybibenzyl sulfone, mp. 200 - 210C.
The infrared spectra showed intense bands at 1300 and 1150 cm 1 - characteristic of sulfone groups. The inherent viscosity as determined at 25 C. as a 1 % solution in N-methyl pyrrolidinone was 0. 22.

EXAMPLE V

This Example illustrates the preparation of polybibenzyl sulone diphenylether sulfone copolymer containing approximately equi molar amounts of diphenyl ether and bibenzyl moieties. Under nitrogen was added 14. 56 g.
(0. 08 mole) of bibenzyl, 29. 96 g. (0. 0816 rnole) oI diphenyl ether -12_ 2~

4, 4' -disulIonyl chloride and 30 ml. of nitrobenzene. The mixture was warmed to l 20C. and 0. 20 g. of ferric chloride was added.
After twelve hours at 120C, the polymerization was terminated by the addition of 50 ml. of DMF, 1 ml. of aniline and 1/2 ml. of 2, 4-pentanedione. The warm solution was added dropwise to 500 ml.
of methanol in a blender. The polymer was filtered and extracted overnight with methanol and dried in an oven. There was obtained 27. 4 g., 71. 9% yield of polymer, mp. range 220 - 250C.

EXAI\/IPLE VI
This Example illustrates the preparation of polybibenzyl sulfone diphenyl sulfone copolymer containing approximately equi molar amounts of diphenyl and bibenzyl moieties, Under nitrogen was added 5. 61 g. (0. 02 mole) of bibenzyl 4-sulfonyl chloride, 5. 06 g. (0. 02 mole) of biphenyl 4-sulfonyl chloride and 40 ml, of nitrobenzene, The mixture was warmed to 120C and then 0, 10 g, of ferric chloride was added. After stirring overnight at 120C, 50 ml, of dimethyl formamide, 1 ml. of aniline and 0. 5 ml. of 2, 4-pentanedione was added to the polymerization reaction. The hot mixture was added slowly to 500 ml, of methanol in a blender, The filtered polymer was washed numerous times with methanol and oven dried at 50C. There was obtained 9.1 g., 98. 7% yield of polymer having a melting point range of 270 - 293C. and an inherent viscosity of 0, 22 as determined as a 1% solution in N-methyl-2-pyrrolidinone, EXAMPLE VII

A cooolylner com~rising polybibenzyl sulfone, diphenyl ethe,r sulfone, co-~olybi~henyl diphenyl ether sulfone units was prepared according to the metllod of Example V using as monomers 29, 96 g. (0, 0808 mole) of .
.: .
: , , diphenyl ether 4, 4'- disulfonyl chloride, 3. 65 g. (0. 0~ mole) of biben~yl, 9. ~5 g. (0. 06 mole) of biphenyl, and 30 ml. of nitrobenzene.
At 110C, 0 20 g. of ferric chloride catalyst was added and the mixture heated overnight at 1 Z0C. There was obtaine~ 34, 7 g., 94. 8% yield of dried polymer, mp. range of 280 - 290C

EXAMPLE VIII

A copolymer of polybibenzyl sulfone, diphenyl ether sulfone copolybiphenyl diphenyl ether sulfone was prepared according to the method of Example V using as monomers 1~. 68 g. (0. 04 1nole) of diphenyl ether 4, 4'- disulfonyl chloride, 3. 64 g. (0. 02 mole) of bibenzyl, 3. 08 g. (0. 02 mole) of biphenyl, and 20 ml. of nitrobenzene and 4 ml. of ferric chloride catalyst solution.
The re was obtained 16. 8 g., 90. 0% yield, of dried polymer mp.
range of 255 - 260C., vicat softening point of greater than 175C. and inherent viscosity of 0.17.
Tensile and elongation properties of the polymers p~epared 1n accordance with Exal~ples V and VII, which exhibited good film ~
forming properties, were evaluated by preparing films of these polyrners in accor~lance with the following procedure:
To a 5. 0 g. sample of polymer in a flask was added 12. 5 ml of N-methyl-2-pyrrolidinone. The mixture was placed on a shaker overnight or longer to give a 40% solution.
Part o the 40% solution was placed on a photographic plate and the VISCOUS material was drawn across the plate using a Gardner Film Casting KniIe having an adjustable clearance controlled by micrometrics which was set for approximately 0. 10 inches.
The plate with the cast filln was dried overnight at 70C
in an air circulating oven. The filn~ was either peeled off manually or chilled with dry ice to help ren~ove it froln the glass surface.
Films were also prepared under identical conditions with three samples of commercially available sulfone polymers designated as follows:
A - Copolymer of diphenyl ether sulfone and diphenyl sulfone (Imperial Chemical Ind. - 7Z0 P) having the structure:
'10 50~ 0_~_50~

B - Polyethersulfone (Imperial Chemical Ind. 200 P) having the structure:
~ _ _ --[~-O~ SO2-- -C - Polysulfone (Union Carbide - Udel 1700) having the structure:

Comparative properties of these materials are recited in Table 1.

~. _ .. .. _ ' . .

.. .. . .

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Inherent viSCoSity ~ensi]e Str~ ss PcJc~nt_ Polysul~one M.P.Range C (NMP ) ~ai] psi; - _ fail E~si -E};ample V 229-250 0. 54 59g5 Z.17 S E~;an~ple VII Z80-790 0. 54 5328 2. 03 A 258-~93 0. 43 ~676 2. 90 B 235-273 0. 51 3989 4. 63 C 213-Z39 0. 57 5095 2. 27 * - Determined as a I % solution at 25C in N-methyl-2-pyrrolidinone 1~
r _ ASTM Test - D-882-73 Therlnoplastic polymers prepared in accordance with the present invention n~ay be characterized by a high degree o~ thel mal and chemical stability and are ideally suited for use in the Iabrication 1 5 o shaped articles such as by molding or extrusion. They may also be processed into fibers or films or used as a component in adhesive cornpositions. Conapositions based on the present poly1ners may also contain ~ngredients as are known in the polymer art such as pigments, fil1ers, lubricants, nucleating agents, stabilizers, plasticizers and lil;e additives.
Although the invention has been described with pàrticular reference to speciic e.~;anlple, it should be understood that the invention should not be so limited but l;mited only by the scope of the appended clain~s.

This application is a division o$ Canadian Application Serial No. 268,276, filed December 20, 1976.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Bibenzyl 4-sulfonyl chloride.