CA1177190A - Polymer composition including polyacrylonitrile and a block copolymer with acrylonitrile and non-crystalline polymer sequences - Google Patents

Abstract

Abstract of the Disclosure There is disclosed a process for producing a novel polymer composition comprised of a polyacrylonitrile polymer and a block copolymer with acrylonitrile and non-crystalline polymer sequences wherein the polymer composition is formed by the removal of a solvent from a solution of a polyacrylonitrile polymer and a block copolymer with acrylonitrile and non-crystalline polymer sequences. -i-

Description

This invention relates to novel polymer compositions including polyacrylonitrile polymers and more particularly to novel polymer composi-tions including polyacrylonitrile polymers and block copolymers with an acrylonitrile sequence, and process for preparing same.
Crystalline polyacrylonitrile polymers have been produced Eor many years and are basically utilized in the production of acrylic and modacrylic textile fibers. Polyacrylonitrile polymers have several distinguishing structural features and physical properties including high degree of crystal-linity with little amorphous phase; orientable at temperatures of about 100C.; poor mechanical properties in an unoriented form and non-melting.
Notwithstanding low production costs and some desirable properties~ poly-acrylonitrile polymers have only found limited commercial usages primarily including thin-walled articles prepared directly from solution and exhibit-ing enhanced mechanical properties after orientation.
Block polymers of an acrylonitrile sequence with another polymer sequence, for example, acrylamide are a two phase structure separated into domains wherein the acrylonitrile domain has like crystalline structure to polyacrylonitrile polymer. Such a block copolymer may be readily formed by the controlled acid hydrolysis of polyacrylonitrile polymer and are highly swellable in water with a swelling capacity dependent on the ratio of both sequences and on the number of separate domains. Generally, such a block copolymer exhibits considerable strength in the swollen state caused by the two phase structure and crystallinity of the acrylonitrile domains. Such block copolymers have been shaped by pressure in the swollen state or from thermo-reversible gels (TRG), such as disclosed in United States Patents No.
4,053,422 and 4,173J606, respectively.
An object of the present invention is to provide a novel polymer composition.
Another object of the present invention is to provide a novel polymer composition comprised of a mixture of polyacrylonitrile polymers and block copolymers of acrylonitrile with a non-crystalline polymer sequence.
Still another object of the present lnvention is to provide a novel polymer composition comprised of a mixture of polyacrylonitrile polymers and block copolymers of acrylonitrile with a non-crystalline polymer sequence and exhibiting the more desirable properties of the respect-ive polymers.
A still further object of the present invention is to provide a novel polymer composition comprised of a mixture of polyacrylonitrile polymers and block copolymers of a acrylonitrile polymers with a non-crystal-line polymer sequence and capable of forming bulky articles.
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A further object of the pre.sent invention is to provide a novel polymer composition comprised of a mixture of . polyacrylonitrile polymers and block copolymers of acrylo-nitrile with a non-crystalline polymer sequence and capable of being stretched or oriented at room temperatures.
Still ano:ther object of the present invention is to provide a process for preparing such a novel polymer com-position.
A further object of the present invention is to provide a process for preparing such.a novel composition from polyacrylonitrile polymers and block copol.ymers of acrylonitrile with a non-cr~stalline polymer sequence.
A still further object of the present invention is to provide a process for preparing such novel composition from polyacrylonitrilep~lymers and block copolymers of acrylonitrile with a non-crystalline polymer sequence in a form for facile subsequent processing.

These and other objects of the present invention are achieved by forming in a solvent system a solution of poly-acrylonitrile polymers and block copolymers of acrylonitril.e with non-crystalline polymer sequence and subsequently . removing the solvunt system to form a novel polymer com- ¦
position. In one aspect of the present invention,the properties of the novel polymer composition are preselectable by varying the molecular weigh~ and/or weight percent of polyacrylonitrile polymer in the solution and by varying the . ~ 3 -:~ ~ 7~

molecular weight and/or weight percent of polyacrylonitrile polymer in the solution and by varying the molecular weight, weight percent and/or lengths of the acrylonitrile and non-crystalline polymer sequence of the block copolymers as well as by the functional groups of the non-crystalline polymer sequence.
In one aspect, the present invention relates to a novel polymer composition comprised of polyacrylonitrile polymer and a block copolymer with acrylonitrile and non-crystalline polymer sequences, said acrylonitrile sequence having a mean molecular weight of at least 500, said non-crystalline polymer sequence being comprised of at least about 10 units.
The polymer composition of the present invention is produced by forming in a solvent system a solution of poly-acrylonitrile polymer and a block copolymer with acrylonitrile and non-crystalline polymer sequences, and subsequently remov-ing the solvent system.
The term polyacrylonitrile polymer, as used herein, is defined as polymers and copolymers of acrylonitrile contain-ing more than 85 molar percent of acrylonitrile units being crystalline in the solid state and exhibiting a typical X-ray diffraction pattern of polyacrylonitrile (i.e. the main reflexion corresponding to a periodicity of 5.1A and lateral orientation under stress).
The term block copolymer with acrylonitrile and non-crystalline polymer sequences is a block copolymer having an acrylonitrile sequence and another polymer sequence, that is, a two phase structure with an acrylonitrile domain and a polymer domain of polar groups wherein the acrylonitrile domain exhibits like crystalline structure to polyacrylonitrile and the polymer doma.in exhibits an amorphous structure. The acrylonitrile sequence is a continuous sequence of acrylonitrile units of a mean molecular weight of at least about 500.

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The polar groups increase the moldulus of elasticity and slip limit of the polymer composition in the dry state. :
I Additlonally, the term block copolymer includes multibloc~
~ - copolymer~, i.e. two or more sequences each and generally p.referably at least three sequences with the sequence for ~he non-crystalline polymer se~uence for~e~ of at least . about 1~ units. The amount of the acrylonitrile sequence of the block copolymer LS from about 75 to about 1 weight percent, preferably of from about 50 to about 5 weight percent based on .the polymer composition.
. For one set of polymer composition, the amount o~
polyacrylonitrile polymer in~'such polymer:..composit~on is from 50 to 99 percent by weight, preferably 50 to 95 percent by weight of ~a molecular weight, of from 30,000 to 1,500,000, preferably 50,000 to I,000,000 with the non-crystalline polymer sequence amounting to f.rom 0.2 to 15 percent by weight., preferably 1.0 to 10 percent by weight of a molecular weight o-f from 3,000 to 1,500,000, preferably 10,000 to about 500,00. For a polymer composition exhibiting physical properties of increased tensile strength in both the dry . .and swelle~ state and of increased thermal stability in the swelled state, the amount of polyacrylonitrile polymers is . . from 0~5 to 40 weight percent, pre~erably 1.0 to 25.0 .
weight percent with the non-crystalline polymer sequence amounting to 30 to 99 weight percent, preferably 30 to 90 weigh~.percent.
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~ . , , ,.1 As herelnabove discussed, the amount o the block copolymer in the poLymer composition may vary between 0.2 to 99 weight percent with small concentrations improving the properties of the polymer composition since the non-S crystalline polymer sequence functions as a surface-active agent. The swellabili~y of the polymer composition in-creases with increasing concentrations o~ the non-crystalline polymer sequénce an~ thus end usage of the polymer composition determines the amount of non-crystalline polymer sequence.
It 1s noted that a polymer comp~si ~ n having an amount of the non-crystalline polymer sequence in e~cess of about 20 weight percent is significantly swellable in solvents of the non-crystalline polymer sequence.
The properties of the polymer composition are also depen~
dent on the molecular weight or polyacrylonitrile polymer and the block copolymer. Generally, the component present in minor amounts in the final composition can have a rather low molecular weight without loss of the mechanical properties of the polymer composition. The molecular weight of the ~0 minor component should be at least about 3,000 and prefer-ably more than about 10,000, while the molecular weight of the ma~Qr component should be at least a~out 30, obo and preferably at least 50,000. The upper values of molecular weight are limited by processability of the compositio~ The molecular welght of the minor component should not e.Yceed a~out 1,000,000, with a preferably upper limit of about 500,000. As a rule, the molecular weigh~ of ~he major component as high as l,500,000 are processable.
The processing properties of the solution also depend on the molecular weights of each polymer component as well as their w~ight ratios. For ease of processing, rather low molecular weights of both polymer components are pre.- .
. ferred ;.with a range o~ bet~een 40,000 and 25~,000 usually satisfying demands of both processing and properties of the final product.
The properties of the polymer composition are also dependent on the number of acrylonitrile and non-crystalline : polymer sequences per block in copolymer. Increased number of sequences per block copolymer chain increases the stabilitY
of the.adsorption of the acrylonitrile sequence on the polyacrylonitrile surface.
A preferred polymer compositi-o.n is obtained when the non-crystalline poLymer sequence of the block copolymer is formed by unlts of highly po~ar groups of a volume . .larger than the volume of a nitrile group. Such units include the acrylamide, N-substituted acrylamide, acrylic acid, salts of acrylic acid, esters of acrylic acid, hydrazides of acrylic acid, N-substituted hydrazides of acrylic acid and glutarimide. An advantage of such units is that they can formed by reactions of the cyano ~77 ~

groups in the polyacrylonitrile polymer. Alsc advantageously significant is the use of a block copolymer where the non-crystalline polymer sequence are formed by two or more different groups, e.g., copolymers of acrylamide with acrylic acid or with N-substi~uted acrylamide or with an ester of acrylic acid,et~ :
Generally, the solvent system includes at least a solvent for polyacrylonitrile polymer , such as dlmethylsulfoxide, dimethylformamide, demethyl acetamide, dimethyl metho~yacetamide, N-formyl morpholine, N-formylhexamethylene imine, cyclic hexamethylene sulfone, 1,2,3-trithiocyano propane, gamma-thiocyanobutyronitrile; some dyclic lactones and lactames;
carboxylic acids, such as formic acid and halogenacetic acids, nitric acid with a concentration higher than 50%, 70 to 85%
sulphuric acid, hydrofluoric acid, phosphoric acid, cyclic 15- ethylene carbonate, aqueous solutions of zinc chloride, lithium, potassium, sodium or calcium rhodanide, alkali metal perchloratesl, lithium bromide, etc. Another suitable solvent systems are solutions of the above solvents with minor amounts of solvents capable of solvating the non-crystalline polymer sequence, e.g. water, glycols or glycerols, if the non-crystalline polymer sequence consists of the highly polar groups, such as acrylamide.
The range of concentration of the polymer components i.e. polyacrylonitrile polymer and bloc~ copoly~er in the solution is from about 5 to abou~ 80 percent by weight, advantageously from 15 to about 70 percent by weight. At concentrations ab o ve abou_ 35 percent by weight, the solution may be processed by heavy . , . '.

equipment such as extruders, calanders,kneaders, presses and the like because highly concentrated solutions kehave more as . a gel or a rubber than as a solution. Such highly concentrated l solution yield very compact products with ~mall amounts of 5 1 solvents to be recovered with processing advantageously effected at elevated temperatures, which as a rule, is limited tc the boiling point of the solvent.
At a concentration range of from about 15 to about 30 pe.rcent by weight of the solution, the polymer composition may be processed from the solution or by the TRG method to produce membranes, tubings, f~bers, layers on substrates, etc.
A polymer composition with high concentration of the non-crystalline polymer sequence is.thus substantially swellable with solvents therefor, and can be advantageously processed by 1~ these methods since swelling of the final article diminishes the contraction caused by the solution-solid transition. The TRG method for processing a polymer ~osition. differs from the same method used for processing the polyacrylonitrile of the ~ multiblock .copolymers, Since hiyher concentration of the polymer 20 ~ components can be used yielding stronger, tougher and mcre stable products.
Formation of the polymer solution of the polymer components .. m a solvent system may be effected in a plurality of methods.
.In one method, the polymer components are dissolved in the commor .
solvent using stirring, kneading and homoyenization equipmen~.
Tile concentration of the polymer components in the mixture is limited by the viscosity which allows homogenization. Such method s pFeferred fo~ the ~reparation of lo~ concentrate 9 _ , 7~
.1 . ' '. ., solutions, and permits the use of heavy homogenization ' equipment to prepare solutio~s containing as much as 50 percent I by weight of the polymer components. Additionally the use of inert solvents, in such a solution permits operation at elevated temperatures thereby facilitating homogenization.
Another method involves the polymerization of acrylonitrile in a block copolymer solution and is advantageous in the preparation of very viscous mixtures without resort to homo-gènization equipment. One preferred solvent for such method is a zinc chloride solution permitting of the preparation of the mixture without isolating~any intermediate product. This method is suitable for the preparation of a product of the polymer composition with fibers and fillers, slnce the fibers and/or fillers may be added to the solution before completion of the polymerization of the acrylonitrile, i.e. at low vis- ¦
cosities of the solution. -Still another method comprises the formation of the block copolymer in a polyacrylonitrile solution, preferably preparing the block copolymer of acrylonitrile with the non-crystalline polymer sequence from the polyacrylonitrile units,e.g~ by the hydrolysis of polyacrylonitrile polymer in the presence of 50 to 72 weight percent nitric acid to yield a multiblock copoly~er having acrylonitrile and acrylamide sequences. The hydrolysis of polyacrylonitrile polymer is an accelerating reaction with the rate strongly decreasing with increasing concentration of the polyacrylonitrile polymer in solution.It is also known that the monomeric acrylonitrile acts as a precit-tant for polyacrylonitrile polymer.

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, '' It has been found that the polymerization of acrylonitrile in nitric acid is accompanied by the precipitation of solid polyacrylonitrile polymer, if the initial concentration of acrylonitrile is sufficLently high and/or the temperature is sufficiently low. As the polymerization proceeds and the concentration of acrylonitrile decreases, the precipitated polyacrylonitrile polymer slowly dissolves into solution and the dissolved portion initiates hydrolysis at a low ,concentration of polyacrylonitrile polymer in solution while the remaining precipated portion is protected ~gainst hydro~lysis. The dis-solved portion of the polyacr~!lonitrile polymer has a considerabl e start before hydrolysis of the precipatated portion thereof which time difference leads to a considerable difference in the hydrolysls conversion whereby multiblock copolymers ~rP always simultaneously present in the mi~ture ~ith intact polyacrylo-nitrile chains. The resulting distribution of the hydro'lysis converslon per polyacrylonitrile polymer chain is considerably broadened with a result similar to a mixture prepared by dis solving polyacrylonitrile polymer and the respective bloc~ copolyrers~
Moreover, there are considerable local fluctuations in the hydrolysis conversion, i.e. the chains are concentrated in some !
locations and the intact polyacrylonitrile chains in other locations and improves the conditions of the,separation of the phases.
This last method of solution formulation is technologically a~vantageous since concentrated solutions may be prepared in one step.

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After formulation of the solution of the polyacrylo~itrile polymer and the block copolymer, removal of the solvent system is effected to form the polymer compcsition as a- result of ~ polymer phase separation. The conditions of solvent removal S directly influence the size of the crystalline domains and thus the properties of the resulting polymer composition.
The higher the viscosity of the solution at the moment of the polymer phase separation, the larger is the number of crystalline domains, and the~efore, the larger is the apparent crosslinking density of the final polymer composition.
Consequently, the modulus of ~!lasticity increases as the swellins capacity decreases with increasing concentration of the polymer components in the solution at the moment of polymer phase separation.
Essentially, there are two methods of solvent removal, i.e. evaporation and extraction-. The evaporation method dictates the need of a solvent system of required volatility (e.g. dimethysulfoxLde~,and yields a polymer composition of high apparent crosslinking density since polymer phase separation ¦ is effected by high concentrations of the polymer components, i.e. at high viscosities. Evaporation techniques produce a polymer compositio~ which may be shaped into membranes, fibers, layers on textile substrates, etc.
Extracting techniques utilize a suitable solvent to extract the solvent system to coagulate the polymer composition. The extraction solvent is at least miscible with the polyacrylo-nitrile polymer solvent of the solvent system, let alone . ' ', .
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. ' . i totally miscible with the solvent system, per se. Preferably such an extraction solvent is water or dilute aqueous solu-tions of the polyacrylonitrile solvents, such as the lower aliphatic alcohols (methanol, et~hanol, isopropaniol and the like), S glycerol, glycols and mixtures thereof. The extraction solvent should be miscible w1th polyacrylonitrile polymer solvents while simultaneously capable of precipatating polyacrylonitrile polymer.
As hereinabove mentioned, the properties of the polymer composition depend upon the viscosity of the solution at the moment of separation of the polymer phases. The viscosity of the solution may be selected withln broad limits depending mainly upon the concentration of each polymer components in the solution. Highly sweLlable (that is, physically sparingly crosslinked) polymer compositions are preferably produced by coagulating diluted solutions (e.g. 10-25 percent by weight of the polymer components) whereas the non-swellable or slightly swellable polymer ~x~ositions are prepared by the coagulation or precipatation of highly concentrated, gelatinous or rubber-like solutions or mixtures.
~ he methods of solvent removal may be combined. If themixture contains both a solvent and an extraction solvent, the resulting mixture forms a physical gel at a certain temperature and a solution above such temperature. Mixing a more volatile solvent, such as dimethylsulfoxide, with a less volatile extraction solvent, such as glycerol and evaporating a portion - ~ 13 -~7~7 of the solvent a~ove the gelling temperature, a separation of the polymer phases begins by cooling the solution to yield a tough gel which can be easily processed. The remaining portion of solvent and the extraction solvent may be separated by a more volatile liquid, such as water or methanol.
While the mechanism of formation o the polymer composition is not fully understood, it is believed that the crystalline domains of the acrylonitrlle sequence of the block copolymer orient themselves with the polyacrylonitrile polymers with the non-crystalline polymer sequence congregating with themselves thereby forming ordered regions of crystalline domains or phases embedded in ~morr ~ ~matrix or vice versa, i.e.
~ oh D VJ' ~eD~*0~us domains or phases embedded in a crystalline matrix.
It will be appreciated that the solution may be shaped before polymer phase separation. Dilute, low-viscosity solutio~s may be shaped b~ extrusion through a nozzle into a coagulation bath or by spreading onto a textile support or substrate, etc. ~n-y shaping technology is available for pro-cessing the polymer component solutions.
Highly concentrated solutions, which are more or less tough physical gels, may be shaped by methods used for soft plastics or polymer melts, e.g. pressing, punching, extrusion, calendaring, in3ection-molding, etc. Shaping is followed by evaporation or extractio~ of the solvents system. Shaping may also be effected during coagulation and/or during subsequent washing o the solvent residues in which case, shaping is accompanied by orientation.
The polymer compositlon may be shaped after all the polyacrylonitrile polymer solvents are removed, preferably by applying pressure a~ a tempera~ure above 75C. and .

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advantageously above 120C. Such shaping is accompanied by .~ .orientation of the crystalline domains of the polymer com-position and thereby improving its mechanical properties.
Shaping may be effected while the polymer comp~ition containS
some extraction solvent such as water or glycerol.

Water can be present in two forms, i.e. as true swelling water if the pclymer composition is water-swellable, or as so called "aquagel water'.', if the polymer compcsition is essentially not water-swellable. Since aquagel water is not equilibrial, a polymer composition cannot again swell once such polymer composition is dried.
The aquagel water content in a polymer composition is about .
50 percent by weight, and similar to polyacrylonitrile po~ymer coagulates under similar conditions.
The aquagel water in a polymer composition in an "aquagelous state" can readily be replaced by glycerol or the like. A
polymer composition in an glycogelous state is more stable than a polymer composition in the aquagelous state. It has been found that the polymer composition of either an aquagelous or glycogelous states are very suitable for shaping at room temperature or at sLightly elevated temperatures.. The polymer composition even if completely dry can be shaped at temperatures between 10 to 210C., preferably between.llO and 180C.
Shaping of the polymer composition in a dry state is especially useful for final shaping and orientation of an article of t~e polymer.composition.

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Polymer composition may be produced e~hibiting many desirable physical properties depending on intended end use.
For e~ample, water-swellable polymer compositions may be l utilized as very strong hydrogels for prosthetic medicine 5 ¦ in the production of permeable membranes, hydrophillic fibers, etc.
Non water-swellable polymer compositions may be utilized as a replacement fox plastic or metallic structural components where physical properties, such as low weight, high s-trength, high impact resistance, low flammability, corrosion resistance, etc. are important design con~iderations. Thus, such polymer compositions can be used as tubes, containers or the like in contact with h~drocarbons, such as gasolene ! since such ~ polymer compositions are comp.letely impermeable for non-polar 15. 1 compounds. The polymer compositions may be combined with electro _ conductive compounds to eliminate static charges. The property of low heat:conductivity renders the polymer compositions a .
¦ compatible outer laminate sheets with a foamed inner layer.
The water-swellable and non water-swellable polymer compo-sitions may be readily combined to form laminates o.f mechan-ically strong layers with intermediate hydrogel layers. It is known that hydrogel-coated surfaces exhibit lower hydrodynamic resistance. then untreated hydrophobic. surfaces. Such decrease in hydrodynamic resistance is advantageously utilized either for transport of water, or for transport.of a solid body through w~ter. Therefore, hydrogel layers on ships, inner surfaces of pipes, centrifugal pumps, propeller blades and the like would increase the efficiency o~ the respective cevice.

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Non water-swellable polymer compositions can be readily provided with a hydr~gel layer, either from the hydrogel~like species of the polymer compositions or from the h~drogelous block co-polymer to achieve a strong and desirable connection with a hydrogel and a hydrophobic solid surface, e.g. a metal, a plastic or a hydrophobic plastic.
Such a connection may be effected in any one of a plurality of methods. Thus, by one method, an article formed of the polymer composition is covered with a solution of a block copolvmer of acrylonitrile of an appropriate viscosity in a solvent system. Removal of th~e solvent system causes an integral hydrogel layer to be formed on the article. Another method includes the steps of overlaying such a preformed article with a polymer components solution with subsequent solvent removal. Still another method includes the casting of a two polymer component solution followed by solvent removal using extraction techni~ues to form connected layers of different properties. ~ further method would include contact between a~ preformed article of non water-swellable polymlr composition and a solution including a swelling and a hydrolyzin~
agent to form insitu a superficial layer of a hydrogel.

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E.Yamples of the Invention _ _ The following e.~amples are illustrative of conditions for the process of the present invention and it is to be under-l stood that -che scope of the invention is not to be limited thereby.
EXAMPLE I
Fifteen (15) parts by weight of polyacrylonitrile polymer (M.W. - 175,000) are dissolved in 85 parts by weight of 65Q~
nitric acid and the solution maintained at 10~C. until about 75 moIar ~ of the cyano groups are hydrolyzed. To the solution cooled to -5~C., there is add~d 3.75 parts by weight of poly-acrylonitrile polymer (M.W. - 25,000). The solution is stirred to dissolve the polyacrylonitrile polymer with the --resulting solution being extruded through an annular orifice into a water coagulation bath. The thus formed hydrogel membrane exhibited improved properties of increased tensile strength and reduced increase of the swelling capacity with increasing temperature, as compared to a hydrogel prepared without the subsequent introduction of a non-hydrolyzed polyacrylonitrile polymer.
EXA~LE II
Ten (10) parts by weight of polyacrylonitrile polymer (M.W. - 350,000) are dissolved in 70 parts by weight of aqueous 60 percent by weight solution of NaSCN to which is added 5 parts by weight of NaOH dissolved in 15 parts by weight of 60 percent by weight NaSCN solution. The resulting solution is heated to 75C. for several hours and the hydrolyzed ' . I
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- ! i. 1 77 ~9 polyacrylonitrile coagulated with water and acidified with diluted acetic acid. The resulting block copolymer containing a~out 45 molar % of cyano groups and both carboxilic and amidic groups, is dried and milled to a powder. Fortyfive (45) parts by weight of powdered polyacrylonitrile polymer, 5 parts by weight of the powdered block copolymer and 30 parts ~y weight of a very finely crystalline NaSCN are thoroughly mixed and evenly spread on a glass dish for subsequent steam exposure. The mixture gelatinated yielding a homogeneous rubber-like mixture which is then extruded into a 10 percent by weight solution of NaSCN, washed with water an~ pressed into the shape of a sheet.
EXAMPLE III
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Twenty (20) parts by weight of polyacrylonitrile polymer l (M.W. - 550,000) are dispersed into a mixture of twenty (20) parts by weight of dimethyl sulfo~ide (DMSO) and 80 parts by weight of isopropanol. One ~1) part by weight of a diblock copolymer containing 70~ mol. of AN and 30~ mol. of styrene is added, with the dispersion being spread onto a tray having crimped polyester fibers arranged in a criss-cross fashion.
Alcohol is evaporated into an oven, so that the residual DMSO dLssolved the polymers components forming a reinforced rubber-like sheet. The sheet is stretched onto a positive mold and put into the oven until the DMSO is evaporated to produce a pre-formed sheet which is pressed and simultaneously oriented at 175C.

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EXAMPLE IV
The rubber-like sheet prepared in accordance with I Example III is cut into strips and introduced into a scréw extruder together with finely pow~ered ammonium carbonate. The S barrel of the extruder is heated to 70C. with iks annular head heated to 150C. An extruded foamed tube is withdrawn from the head and washed with hot water. The wet tube is filled with a solution of 7.5 percent hy ~eight of~laOH and a2.5 percen~ by weight of NaSCN
in water at 50C. ~ntil a hydrogel layer is formed. The tube is then washed with water and dried. The resulting porous tube having an inner hydrogel lin~ng exhibited excellent thermal-insulating capability and xeduced hydrostatic resistance to water .
EXAMPLE V
An amount of 0.1 parts by welght of ammonium persulphate lS is dissolved in 50 parts by weight of 65~ nitric acid, and 50 parts by weight of distilled acrylonitrile added to the solution.
Thesolution is then p~ured into a polypropylene mold filled wlth a mat of 2.5cm. long crimped polyacrylonitrile fibers (Orlon).
The mold is placed into a water bath maintained at a temperature of 50C. and is stored therein for 55 hours. The mold is there-after opened and a sheet of rubber-like, turbid, reinforced composition is washed with water. A 10 mm. thick tough, china-lLke sheet is then rolle~ between crossed rollers heated to 110C. to form a pre-formed sheet having a thickness of 3 mm.
The sheet is pressed into a mold to form one half of a rectangulc r vessel of a final wall thickness of lmm. A vessel made of two such parts is tested as a gas tank.

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E~A~I~LE VI
The polymer composition prepared in accordance with ll EYample I is dried, milled and dissolved in D~ISO to yield I a 20 percent by weight solution. The solution is heated to 120C. with a 10 percent by wei-ght of glycerol thereafter added. The xesulting solution is poured onto a preformed sheet of the polymer composition prepared in accordance with Example V and slowly cooled to effect gelatination. The re-sulting laminate is washed with water, soaked with 10~
aqueous glycerol and dried. The thus formed two layer laminate is shaped in a press to provi,de a panel for ship hull constructi n The thickness of the laminate is about 6 mm. when the hydrogel is swelled with water.
While the i~vention has been described in connection with several e~emplary embodiments thereof, it will be understood that many modifications will be apparent to those of ordinary skill in the art; and that this application is intended to cover any adaptations or variations thereof. Therefore, it is manifestly intended that this invention be only limited by the claims and the equivalents thereof.

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Claims (26)

1. What is Claimed l. A navel polymer composition comprised of polyacrylonitrile polymer and a block copolymer with acrylonitrile and non-crystalline polymer sequences, said acrylonitrile sequence having a mean molecular weight of at least 500, said non-crystalline polymer sequence being comprised of at least about 10 units.
2. 2. The polymer composition as defined in Claim 1 wherein an average number of said sequences per copolymer chain is equal and at least 2.
3. 3. The polymer composition as defined in Claim 1 wherein said non-crystalline polymer sequence is formed of one or more highly polar units selected form the group consisting of acrylamide, N-substituted acrylamide, acrylic acid, esters of acrylic acid, salts of acrylic acid, hydrazides of acrylic acid, N-substituted hydrazides of acrylic acid and glutarimide.
4. 4. The polymer composition as defined in Claim 1 wherein said polyacrylonitrile polymer comprises of from 50 to 99 percent by weight of said polymer composition and has a molecular weight of from 30,000 to 1,500,000.
5. 5. The polymer composition as defined in Claim 4 wherein said polyacrylonitrile preferably comprises of from 50 to 95 percent by weight of said polymer composition and said molecular weight is from 50,000 to 1,000,000.
6. 6. The polymer composition as defined in Claim 4 or 5 wherein said non-crystalline polymer sequence comprises from 0.2 to 15 percent by weight of said polymer composition and salt lock copolymer has a molecular weight of from 3,000 to 1,500,000.
7. 7. The polymer composition is defined in Claim 4 or 5 wherein said non-crystalline polymer sequence comprises from 1 to 10 percent by weight of said polymer composition and said block copolymer has a molecular weight of from 10,000 to about 500,000.
8. 8. The polymer composition as defined in Claim 1 or 3 wherein said polyacrylonitrile polymer comprises 0.5 to 40 percent by weight and said non--crystalline polymer sequence comprises 30 to 99 percent by weight of said polymer composition.
9. 9. The polymer composition as defined in Claim 1 or 3 wherein said polyacrylonitrile polymer comprises 1 to 25 percent by weight and said non--crystalline polymer sequence comprises 50 to 90 percent by weight of said polymer composition.
10. 10. The polymer composition as defined in Claim 1 or 3 wherein said polyacrylonitrile polymer comprises 0.5 to 40 percent by weight and said non--crystalline polymer sequence comprises 30 to 99 percent by weight of said polymer composition, said polyacrylonitrile polymer has a molecular weight of from 30,000 to 1,500,000 and said block copolymer has a molecular weight of from 10,000 to about 500,000.
11. 11. The polymer composition as defined in Claims 1 and 3 and including 0.5 to 90 weight percent of a material selected from the group consisting of water, glycerol, alkylene glycols, and sugar.
12. 12. The polymer composition as defined in Claims 1 or 3 and including from 2 to 55 weight percent of a material selected from the groups consisting of water, glycerol, alkylene glycols, and sugar.
13. 13. A process for producing a polymer composition which comprises:
    
    a) forming a solution of polyacrylonitrile polymer and a block copolymer with acrylonitrile and non-crystalline polymer sequences in a solvent system; and b) separating said solvent system from said solution to form a polymer composition.
14. 14. The process as defined in Claim 13 wherein said polyacrylonitrile polymer and said block copolymer are introduced into said solvent system in an amount to form a solution of less than 50 percent by weight of the solution.
15. 15. The process as defined in Claim 14 wherein said solution is formed by homogenization techniques.
16. 16. The process as defined in Claim 13 wherein polyacrylonitrile is formed by the polymerization of acrylonitrile in a block copolymer solution.
17. 17. The process as defined in Claim 16 wherein said solvent system in-cludes a zinc chloride solution.
18. 18. The process as defined in Claim 17 wherein a material selected from the group consisting of fibers and fillers is added prior to step b).
19. 19. The process as defined in Claim 13 wherein said block copolymer is formed by reacting in situ polyacrylonitrile under conditions to form non--crystalline polymer sequences.
20. 20. The process as defined in Claim 16 wherein said polyacrylonitrile is hydrolyzed in the presence of 50 to 72 weight percent nitric acid.
21. 21. The process as defined in Claim 13 wherein step b) is effected by evaporation of the solvent.
22. 22. The process as defined in Claim 13 wherein step b) is effected by extraction of the solvent.
23. 23. The process as defined in Claim 13 wherein said polyacrylonitrile polymer is added in an amount to form of from 50 to 99 percent by weight of said polymer composition and said polyacrylonitrile has a molecular weight of from 30,000 to 1,500,000.
24. 24. The process as defined in Claim 23 wherein said block copolymer is added in an amount to comprise of from 0.2 to 15 percent by weight of said polymer composition.
25. 25. The process as defined in Claim 23 wherein said polyacrylo-nitrile polymer is added in an amount to comprise of from 0.5 to 40 percent by weight of said polymer composition.
26. 26. The process as defined in Claim 23 wherein said block copolymer is added in an amount to comprise of from 30 to 99 percent by weight of said polymer composition.