US3231543A - Process for the formation of shaped trioxane structures and polymerization thereof - Google Patents

Description

United States Patent 3,231,543 PROCESS FOR THE FORMATION OF SHAPED TREOXANE STRUCTURES AND POLYMERI- ZATION THEREOF Saunders Eliot Jamison, Summit, N1, assignor to Celanese Corporation of America, New York, N.Y., a corporation of Delaware No Drawing. Filed Oct. 14, 1960, Ser. No. 62,534 3 Claims. (Cl. 260-67) This invention relates to shaped, self-supporting structures extended in no more than two dimensions and to processes for making such structures from solidifiable -mon0mers.

fibrous material or self-supporting films by a process which avoids thermal degradation of the fiber or film forming polymer. Other objects will appear hereafter.

The object of this invention is achieved by a process for the formation of shaped, self-supporting structures extended in no more than two dimensions which comprises polymerizing a solid phase monomer in the form -of said shaped, self-supporting structure in the presence of a fluid catalyst.

This invention is particularly applicable to the polymerization of trioxane and for convenience will be described with reference thereto.

In a preferred embodiment of this invention, trioxane is admixed uniformly with a resinous binder, extruded through a spinning orifice to form a stream and then polymerized in the presence of gasiform boron fluoride after solidification of the stream. solidification of the stream to a self-supporting structure makes the invention applicable to monomers which cannot be polymerized instantaneously.

The resinous binder serves the dual function of increasing the viscosity of the trioxane-to permit it to be extruded in a fine stream and of maintaining the trioxane in a fibrous structure while polymerization takes place.

In most cases, it is desired to eliminate the resinous binder after polymerization is complete so that the fibrous residue will have the character of the oxymethylene polymer. This may be achieved by the selection of a pears after lending its structure to the polymerization process.

When an oxymethylene polymer fiber is desired, the resinous binder is blended with trioxane in proportions between about 5 and 50 weight percent, based on the weight of trioxane. The binder is preferably dissolved in molten trioxane before extrusion thereof through the spinning orifice. If desired, both the trioxane and the binder may be dissolved in a common solvent to form a viscous solution and the solution may be extruded through the spinning orifice.

Solidification of the extruded stream is by cooling in the case where no solvent is used and usually by cooling and evaporation where a solvent is used. Volatile solvents and mild evaporative conditions are used with tri- "ice oxane to control the trioxane loss which would otherwise occur because of the high volatility of the trioxane.

In some cases wet spinning methods may be used wherein the solution is extruded into a non-solvent liquid, such as n-octane, as a coagulant. In such cases the filaments may be polymerized in the presence of a liquid phase catalyst, such as boron trifluoride in solution in the coagulant liquid. Alternatively, the filaments may be removed from their liquid coagulant environment before polymerization in the presence of a gasiform catalyst takes place.

Suitable resinous binders for trioxane include thermoplastic vinyl polymers such as polyvinyl acetate, polystyrene, polyvinyl chloride, polymethyl methacrylate, polyvinyl pyrrolidone, polyethyl acrylate and polyvinyl caprolactam; thermoplastic condensation polymers, such as relatively low melting polyamides and polyesters; and thermoplastic cellulosic derivatives, such as cellulose acetate and ethyl cellulose.

Polyacetaldehyde, prepared by acid-catalyzed polymerization of acetaldehyde at its freezing point and of the formula is a useful binder since it depolyrnerizes readily when exposed to a trioxane polymerization catalyst under polymerization conditions.

The nature of the common solvents used when dry spinning is desired is dependent on the nature of the resinous binder. For many binders trioxane solvents such as methylene chloride or acetone are suitable. Suitable spinning compositions of this type include from 10 to weight percent of binder and from 50 to 500 Weight percent of solvent per unit weight of trioxane.

Spinning conditions depend upon the nature and proportion of the resinous binder and the nature and proportion of solvent if any. The spinning orifice diameter may vary as desired according to the product desired. Spinning temperatures from about 0 C. to about 100 C. are suitable for most spinning compositions.

After the extrusion operation is completed, the extruded stream is solidified, preferably byvcooling or by cooling and evaporation. The atmosphere into which the spinning composition is extruded is preferably maintained at a temperature between about 50 C. and 50 C.

The preferred gasiform. catalyst is boron trifiuoride. It is preferably maintained in the atmosphere surrounding the solidified trioxane-binder filament at a concentration of from about 1 to 100 weight percent. Vaporizable acidic boron trifiuoride complexes may also be used. A suitable catalyst environment may be maintained by passing nitrogen through a normally liquid boron trifluoride complex and thereafter into the polymerization zone.

Suitable liquid phase catalysts include solutions of boron trifiuoride or of acidic complexes of boron trifiuori-de in liquids, which are non-solvents for the trioxane and resinous binder under the polymerization conditions.

Polymerization temperatures are suitably between about -50 and 60 C. and the period of reaction may vary from about 12 hours to 1 minute. In most cases the catalytic environment is maintained just beyond the spinning orifice so that polymerization proceeds as soon as the extruded stream is solidified to a self-supporting structure. It is possible that polymerization is initiated to a minor extent before solidification but by far the greater portion of the trioxane solidifies before being polymerized.

In some cases, it may be desirable to prepare filamentary material having characteristics intermediate between those of the oxymethylene polymer and those of the resinous binder. In such cases the resinous binder is not removed after polymerization and the amount used depends upon the desired characteristics of the final product.

In another advantageous aspect of this invention a cross-linked polymeric structure may be prepared by the copolymerization of trioxane with a polyfunctional comonomer and particularly a polycyclic ether, such as a polyepoxide. such cross-linked copolymers since a useful filamentary material is produced by the polymerization reaction and there is no necessity for further shaping of the intractable polymer.

Among the suitable polyepoxides which may be used are the diepoxides of hydrocarbon dienes, such as vinyl cyclohexene dioxide and dicyclopentadiene dioxide; and diepoxides of substituted hydrocarbon dienes, such as 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate. Polymeric epoxides, such as the epoxy resins produced by the reaction of epichlorohydrin with a bisphenol may also be copolymerized with trioxane by the method of this invention. Other polycyclic ethers include diketals and diacetals of pentaerythitol and dioxetanes formed from pentaerythitol and its derivatives. It may be noted that polyvinyl pyrrolidone and polyvinyl caprolactam, mentioned above as resinous binders are also polyfunctional comonomers capable of interaction with trioxane in a copolymerization.

The polycyclic ethers are suitably blended into the spinning compositions in proportions between about 10 and 50 weight percent, based on the weight of trioxane. Spinning and polymerization conditions are as described above.

In the copolymerization reaction, trioxane rings open to produce short chains of three oxymethylene units and the epoxy rings open to produce substituted oxyethylene units. These units link up to form a space polymer comprising chains of oxymethylene units interspersed with oxyethylene units said chain being cross linked across carbon atoms of said oxyethylene units.

While the invention has been described with respect to the polymerization of spun structures, it is to be understood that other fibrous structures may be polymerized. For example, filaments may be prepared by drawing the viscous mixture from a softened and sticky melt thereof. Fibrous trioxane strands may also be prepared by sublimation under carefully controlled conditions, as described below in Example I. While it is preferred to polymerize filamentary monomer other fibrous forms of monomer may be polymerized. Fibrous monomers having an extended dimension of at least 100 times the other two dimensions are suitable. Similarly monomers in film structures wherein each extended dimension is at least 100 times the thickness are suitable. 1 r

If desired, the trioxane may be copolymerized with from 0.4 to 40 weight percent of ethylene oxide or dioxolane. Such copolymers have greater thermal stability than homopolymers. Since the shaping of the polymer after its formation is not required, in accordance with this invention, high thermal stability is often not essential. But where it is desired such copolymers may be prepared by forming filaments from a mixture of trioxane, comonomer and binder and polymerizing as described above.

While the invention has been described with reference to the polymerization of trioxane, the general technique is also applicable to other normally solid or s-olidifiable monomers. The technique is particularly applicable to cationically catalyzed vinyl monomers and to cyclic compounds in which at least one ring bond is highly polarizable because of the presence of an electro-negative heteroatom. Examples of the cyclic compounds include other cyclic ethers, lactones, acetals, ketals, sulfides, imines and lactams. Examples of vinyl monomers include olefins, cycloefins, vinyl ethers and acrylic acid derivatives. It is preferred that the monomer have a molecular weight not higher than about 300.

This invention permits the utilization of V Example I A fibrous sublimate of trioxane was prepared by a sequence of two condensation operations. In the first, molten trioxane was heated in a vessel covered with a watch-glass in such a manner that the trioxane vaporized in the vessel and condensed as a closely packed snow on the under surface (convex) of the watch glass. The temperature of the watch glass could not rise above the melting point of trioxane (64 C.) for the condensation. The watch glass was cooled, by directing a cool air stream on the upper (concave) surface of the watch glass. Satisfactory rates of collection were maintained without boiling the trioxane (heating range -100 C.).

In the second condensation the watch glass with the trioxane snow attached to its lower (convex) surface was placed over another vessel which was kept cool (room emperature). A stream of warm air (55-60 C.) was directed at the upper (concave) surface of the watch glass so as to heat the trioxane without melting it. The trioxane then sublimed downward into the vessel where it formed a voluminous fibrous network.

A portion of the above-described fibrous mass was inserted into a stoppered test tube and sufficient boron tri fiuoride to provide a concentration in the test tube of 3 volume percent was thereafter introduced. The tube was maintained at 25 C. for a period of 150 minutes. The contents of the tube were then washed with acetone to remove unreacted trioxane and boron trifiuoride. The polyoxymethylene fibers corresponded in weight to 71% of the trioxane starting material.

Example II 25% solution of polyvinyl acetate in trioxane was extruded at C. through a 2.0 mm. orifice into a chamber held at 50 C. from which it was taken up at room temperature on glass tube. The filaments thus prepared were exposed for 30 minutes in a test tube at room tempera= ture to an atmosphere of dry nitrogen containing about 20 volume percent of boron trifiuoride. After exposure the filament was washed extensively with warm water to remove unreacted trioxane. Analysis showed that the filament had a composition of 47% polyoxymethylene and 53% polyvinyl acetate.

Example III Polyacetaldehyde was obtained by polymerizing acetaldehyde at its freezing point (123.5 C.). Acetaldehyde 392 parts by weight) was distilled into a cold trap maintained at its freezing point and containing 0.22 part of boric acid. Upon completion of the distillation, 1.45 parts of polymer was recovered having an inherent viscosity of 3.0 (0.1% solution in acetone at 25 C.).

Strands were drawn with a glass rod from a 10% solu tion of this polyacetaldehyde in trioxane. The strands were exposed at room temperature for 30 minutes to an atmosphere of volume percent of boron trifluoride. After washing with water, analysis showed that the polymer filaments were pure polyoxymethylene.

Example IV Strands were drawn with a glass rod from a solution (at 75-80" C.) consisting of 10 parts of trioxane, 2.5 parts of' polyvinyl acetate and 1 part of a diepoxide of the group listed below. The strands were exposed at: room temperature to boron trifluoride in concentrations: ranging from 13% to 100% by volume (in nitrogen) for riods of two hours at room temperature. The mate-- rial was then Washed with boiling dimethylformarnide to remove all material other than the crosslinked polymer- The results are shown in Table 1, below.

e 3,4-epoxy-6-methyl-cyclohexylenethyl-Ii,4-epoxy-6-methyl-cyclohoxanecarboxylate.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention, what I desire to secure by Letters Patent is:

1. A process for the formation of a shaped, self-supporting structure selected from the group consisting of filaments and films which comprises forming a solid phase monomer comprising at least 50% of trioxane into said shaped, self-supporting structure, and polymerizing said monomer in the presence of a fluid trioxane polymerization catalyst.

2. A process for the formation of fibrous material from a monomer comprising at least 50% of trioxane which comprises forming said monomer into a solid structure in filamentary form and polymerizing said monomer in said structure in the presence of a gasiform trioxane polymerization catalyst.

3. A process for the formation of fibrous material from trioxane which comprises forming trioxane into a solid 6 trioxane in said structure in the presence of gaseous boron trifluoride.

References Cited by the Examiner UNITED STATES PATENTS 2,170,439 8/ 1939 Wiezevich 18--57 XR 2,519,550 8/1950 Craven 260-340 2,806,015 9/1957 Kern.

2,822,237 2/ 1958 Iwamae 1854 2,840,447 6/ 1958 Green 1854 2,864,827 12/1958 Baer et a1 260--340 2,883,361 4/1959 Handy et a1.

2,890,191 6/ 1959 Edmonds 260-30.4 2,891,837 6/1959 Campbell 1854 2,913,430 11/1959 Roeser 26030.4 2,934,528 4/ 1960 Lundberg 26088.3 2,947,727 8/1960 Bartz 26067 2,947,728 8/1960 Bartz 260 -67 2,947,736 8/1960 Lundberg 26088.3 2,989,506 6/ 1961 Hudgin et al 26067 2,989,510 6/1961 Bruni 26034 XR 2,989,511 6/1961 Schnizzer 260-67 OTHER REFERENCES DAlelio: Fundamental Principles of Polymerization, John Wiley & Sons, Inc., New York (1952), and Chapman & Hall, Ltd., London, p. 192.

WILLIAM H. SHORT, Primary Examiner.

WILLIAM J. STEPHENSON, NICHOLAS S. RIZZO,

Examiners.

J. W. GERIAK, A. B. ENGELBERG, C. B. HAM- BURG, I. TOVAR, E. M. WOODBERRY,

Assistant Examiners.

Claims (1)

1. A PROCESS FOR THE FORMATION OF A SHAPED, SELF-SUPPORTING STRUCTURE SELECTED FROM THE GROUP CONSISTING OF FILAMENTS AND FILMS WHICH COMPRISES FORMING A SOLID PHASE MONOMER COMPRISING AT LEAST 50% OF TRIOXANE INTO SAID SHAPED, SELF-SUPPORTING STRUCTURE, AND POLYMERIZING SAID MONOMER IN THE PRESENCE OF A FLUID TRIOXANE POLYMERIZATION CATALYST.