BE621209A - - Google Patents

Description

       

   <Desc / Clms Page number 1>
      
 EMI1.1
 



  The present invention relates to a method for
 EMI1.2
 the production of highly cyanic cellulose and the improved products obtained by this process containing for use as a dielectric in electrical devices such as capacitors, panel-shaped electroluminescent lamps and the like.



   An electroluminescent device which is an example of a device in which the use of the new product is contemplated by the present intention, has basically a simple structure. In principle, such a device consists of two electrodes, at least one of them transmitting light. Between these electrodes, a luminescent substance is embedded in a suitable matrix.

   Among the various dielectric matrices previously proposed for electroluminescent substances, there may be mentioned certain cellulose ethers, as described for example.
 EMI1.3
 ple in U.S. Patents Nos. 2,111,100lu 2,792,447, 2,918,594 and 2,901,652. This latter patent suggests in particular the use of certain types of cyanoethylated cellulose.



   Such usage, however, inherently imposes certain physical limitations on the matter which forms the matrix. One of the critical requirements * and that this material must have an adequately high dielectric constant, as described by S. Roberts, in J. Opt. Soc. Am. 42, 850 (1952).



  This material should have as high a dielectric constant as possible in a product which has a sufficiently low dissipation factor; it must be sufficiently soluble in suitable solvents and it must be pourable
 EMI1.4
 from a solution, in films; rI3 "iftf.'lrstei. '* 1 6e' '*' # r .., i, y, a u ¯ Ii ...........

 <Desc / Clms Page number 2>

 more, a good dielectric material for 1 ', object of the present
 EMI2.1
 your invention, must not have its own color. SU, .-, 1.,: must be substantially transparent *
A satisfactory dielectric material must have
 EMI2.2
 a low dissi p ation factor to avoid electrical loss in the form of unwanted heat.

   In; gn3ra .; , '; a good dielectric for the purpose of the present invention should have a factor of less than 0.028.
 EMI2.3
 When trying to adapt these various e4genc, e. , - #, to cyanoethylated cellulose, other critical limitations are still imposed. Cellulose, whether natural or 'regenerated, reacted with' acrylonitrile, of
 EMI2.4
 different ways to produce a cyanoethyl derivative44 *, ',, The physical properties of the produced result vary according to
 EMI2.5
 the nature of the cellulose, ion molecular weight, 1 * method 'fft' 'treatment analogues.

   However, these properties) hY.4u.'nt: .. were most affected by the degree to which the cellulose was cyano-
 EMI2.6
 Ethylated "" ". ;
 EMI2.7
 cyanoethylation of .1, a can usually be defined by two different methods, either 4th the nitrogen content # expressed in% in poido distott or per year - decimal fraction ix'a8ntliit the nojj bp $ of the eyiÎtli groups Inthodults Per unit dtlyd , .xct3ati This fraction of liftai is hibituclltmônb called "degree of * 4botltvtton, Po4r dea, .. reasons for simplification the latter will be called 4" 0 "dahs i '# present memoir, Both terminology are used in the
 EMI2.8
 present brief.

   A complete lifetime oorsfeapofld e yiemthylation nitrogen content of about 13.1 xyz -and to a D8 dettoift A of low degrees of substitution, c'eat-è'-di a D3 up to about two cyanoethylation alters eta, however, the solubility or physical appearance of 'ceXI41' the fibrous characteristics being largely nailptelauea,

 <Desc / Clms Page number 3>

 
Most of the previous work on cyancethylation has been done in this area.

   However, as the DS gradually increases below about two, the loss of fiber characteristics and the resemblance of the product to a thermoplastic resin becomes more and more noticeable. In addition, the solubility of the product in certain organic solvent * develops. These latter characteristics become predominanta in products having a DS greater than about 2.3, which corresponds approximately to percentages of nitrogen content ranging from about 11.4 or 11.5 to just over 13. ,

   
In more recent research, it has been found that such products, particularly those having an SD greater than 2.5, possess characteristics which are useful for a number of applications; Among such characteristics, we can mention a relatively high dielectric constant and a relatively low dissipation factor. The present invention is particularly concerned with such products produced from highly cyanoethylated cellulose.

   For reasons of simplification, such products will be referred to as debt hereafter by the abbreviation "HOC".



   To meet the aims of the present invention, an HCC product must have a *! as mentioned above a dielectric constant between about 11 and 14.



   Achieving this value in HCC usually requires producing a DS of about 2.3 or more, which corresponds to a nitrogen content of at least about 12.5%. This is a strict limitation *
It has long been known that HCC having such a nitrogen content can be produced. This is described, for example, in US Pat. No. 2,375,847.



   Further, it is possible, by such known methods, to produce HCC having a dielectric constant of about.

 <Desc / Clms Page number 4>

 9-10. Therefore, HCC products have previously been obtained which met, for certain electrical purposes, the dielectric requirements. However, these products did not meet the dielectric constant limits of 11 to 14 required for many other applications,
Unfortunately, the industrial use of HCC in this growing field has been hampered by the fact that in the previously obtainable HCC,

   the dissipation factor was much too high. In addition * the color of such products was much too dark. Ultimately, it was not possible to take up such products in a solvent useful for casting a suitable film having the desired color absence.



   For this reason, the main object of the present invention is the production of an HCC product which is not subject to these limitations of too low a dissipation factor and too high coloring.



   During the development of the present invention, it has been found that these two undesirable properties appear to be interrelated. This at least results from the fact that these properties appear to be due to excessive residues of various types in the final product. It has been found that the desired dielectric constant can be obtained if the electrolyte content can be lowered adequately.



   Unfortunately, the residual electrolyte content inherently present is due to the process by which HCC is produced. In the best previously obtainable products this residual electrolyte content has re-mixed to be about 200-500 ppm (parts per million).



  To meet the requirements of the dissipation factors, this content should be reduced to no more than 100 ppm and preferably to no more than 50 ppm. This imposes a new restriction. ,

 <Desc / Clms Page number 5>

 
In a similar situation in other fields, excessive electrolyte content as well as much of any excessive coloring can often be reduced by adequate washing. In the case of HCC, which could previously be obtained, this reduction by

    washing can be done eventually but growl after long and repeated treatments. For the production of material for industrial use, these treatments are economically impossible to do away with, for known HCC products of a nitrogen content and an appropriate dielectric constant *
The other physical properties of these products are such that they make ordinary washing and their handling extremely difficult.



   It is therefore another object of the present invention to provide a suitable process for producing HCC which is not subject to these limitations or restrictions whether it is the process per se or the New HCC Product. Such a process should be capable of producing HCC having a D3 of at least 2.5, that is, a nitrogen content of 12.1% or more. The product should have a non-dielectric constant. less than about 10 and preferably between about 11 and about 14, a dissipation factor of no greater than * 0.028, preferably within 1 about 0.025 and a dissolved electrolyte content of not more than 100 ppm, preferably,

   not exceeding 50 ppm. In addition, the product should be substantially colorless.



     Surprisingly, this goal has been achieved with considerable success. This has been accomplished by probing the well-known method which finds cellulose and acylonitrile to react in the presence of caustic soda, as described, for example, in United States Patent No. * 2,375,847 cited above.



   In short, the method according to the present invention, which

 <Desc / Clms Page number 6>

 
 EMI6.1
 differs from the previously known methods, by various aapecs, # "- \ can be schematized in a simple way The first pack" crm "ends in reaction of cellulose. d9act-eoiitriie jet of soda 'V' * caustic At a temperature contrileob usually lGrrmpr:

   between about 35 and about 65, in the presence of a controlled amount of water. In a second stage, the reaction mass is then neutralized using an appropriate acid. In the third stage, the neutralized mixture is uniformly dispersed - '' holds in a large volume of hot water at a temperature contrê-
 EMI6.2
 Even though the acrylonitrile has not reacted and a ferk., so much water is flushed out instantly.

   Cyanoethyl cellulose is, in this way, precipitated in the form of a; fine and fluffy product having the desired characteristics
 EMI6.3
 This cyanoetylated cellulose is easily washed until obtained.
 EMI6.4
 electrolyte level below the critical ctrolyte level 4! 61 and is readily collected.



   This result is very well illustrated by the attached drawings '- #' in which:
 EMI6.5
 - Figure 1 is a photograph of a produtt, -Ot4 ;. naked according to the practice previously considered to be best, and
 EMI6.6
 - Figure 2 is a piotcgraPhi, ara7, opue of a; iobfcenue material according to the present invention. f.



  The two figures are * photomicrographs taken * 'at an enlargement of ten diameters. * *% As desired, the simplicity of the procedure is' #'% perhaps more apparent than real. Cosme notes and "desua, il * -," there are a number of critical limitations. Although the process is flexible enough to be able to draw easily.
 EMI6.7
 However, there are practical limits to each,, control. In addition, all stages must be maintained in:

 <Desc / Clms Page number 7>

 the operating limits for each particular operation carried out.



   An advantage of the present invention is that substantially any cellulosic material can be processed by the method described in this specification. Thus, cellulose and certain chemically apparent compounds. to cellulose are anhydroglucose polymers. Different polymers are usually classified by the number of anhydroglucose units existing in a molecule. Chemically, an anhydro-glucose unit is a trihydric alcohol. One of the hydroxyl groups is a primary alcoholic hydroxyl group, the other two being secondary alcoholic groups.

   Celluloses are predominantly 1-4 polymers, the number of polymerized units being ordinarily referred to as abbreviated degree of polymerization, in the remainder of this specification, as "DP", Copme in other polymers, each cellulose polymer is a mixture of polymers * of different molecular weights. It is the average DP that determines the classification of a specific product. In general, celluloses suitable for use in the present invention have an average DP ranging from greater than about 200 to greater than 1000.

   Various cellulosic materials available fall within these limits, for example, viscose rayon with a DP ranging from about 250 to about 350, natural cotton with an average DP of about 850 to 1000 and some pulp derivatives of. wood with a DP greater than 1000.



   Although the invention is not limited to it, radiated it. viscose may be preferred. It gives a final product which, due to its low viscosity and excellent handling characteristics, is in most cases perfectly suitable for the applications of the present invention.

 <Desc / Clms Page number 8>

 



     Therefore, viscose rayon and celluloses $
 EMI8.1
 Regenerated cells, although possessing a relatively low degree of polymerization, constitute a preferred embodiment. '! For, 1 any cellulose chosen names the starting material,
 EMI8.2
 there is a '.11ulol weight ratio. 1 .cq1ontril. opti u% for the reaction * From this point of view, the DP of the starting cellulosic material must be taken into account. Co DP influences, ounce the amount of excess acryloniti'ile needed.

   This checkerboard does not only serve as an essential reagent but the excess of acrylodi4rile with respect to the .toichiometric conditions that .. serves as a clearing of solvent for the HOC yant W1 # ', .El) lirleur, about 2, i # In generated celluloaeo of' a high DP form more viscous solutions and thus necessitate the use of a larger, xc of acrylonitrile.

   For this reason, it is advisable to use cellulosic starting materials of lower molecular weights within the limits. cited above,
Flaky viscose rayon being of low viscosity and readily obtainable at a moderate cost, is a preferred raw material. cotton tinta and some wood pulp based celluloses are of course chemically equivalent and somewhat expensive than fluffy viscose.

   However, the necessary use of a
 EMI8.3
 additional amount of acrylonitrile and other problems resulting from a higher viscosity of the final product may
 EMI8.4
 , frequently more than offsetting the initial saving.



   It has been found that the temperature of the reaction mixture during cyanoethylation can vary within limits of between about 35 and about 65 ° C.
 EMI8.5
 however advantageous, to maintain the average temperature ...: near about 50 * C as the equipment allows.

 <Desc / Clms Page number 9>

 
 EMI9.1
 Cynoethylation, in the reagent according to. , tt invention, requires the presence of a quantity of acryi, iiril9 largely in excess. Usually, this exoea is between about ten and twenty times the weight of cellulose. The go large excess serves to maintain contblea rh4ott-omollos rai "rates and to form a reaction medium in which the cyano4thylated cell formed is soluble.

   When using a. too low a quantity of acrylonitrile, the relationship mixture
 EMI9.2
 becomes Inagitable and non-uniform. your upper limit is' a cowppomy. Sufficient acrylonPrI, 16 is used to handle the product, use of a large amount of acrylonitrile is undesirable because it reduces the capacity of a given container to produce HCC.



   The particular caustic alkali used is not critical. However, as there is no particular advantage
 EMI9.3
 In using more potassium hydroxide, Pn generally prefers to use acirt hydroxide: The optimum aqueous alkali concentration will vary somewhat with the particular cellulosic starting craft chosen and with the reaction temperature used.

   It is general good practice to use an amount of alkali of between about 2.5 and about 7% by weight of the weight of the cellulose. The concentration of aqueous alkali in the added ablution is not not critical. On the contrary, the critical factor is constituted by the weight ratio of alkali to water in the entire reaction mixture.
 EMI9.4
 This report is described below in p.ua. ample detail.



   Another factor that must be taken into consideration is the risk of dangerous thermal runaway. 31 leerap-
 EMI9.5
 caustic material / water port becomes too high, unreacted acrylonitrile can polyiterate and polymerize, giving off a large amount of heat.

 <Desc / Clms Page number 10>

 
 EMI10.1
 aeuiant by a per <m d9acrylonitrile 'Intrg'dt4lt 4010% * t a serious' danger! r. explosion. ; ## # "# ','; # # * l / th Aï # pl9 addition of a large quantity of artu ,. fYy. Y <'¯' Worse this problem,.! .. irCra, auntiqut-ni ' t4t, ao, '2 together with tray-er3,1 & ma rëatine ..s pendatft 4xt'f; #' l {\ the duration of Ha reaction.

   At some eade ,. ela mafel | i; #> aUsPr / 'tique o pts pàk, example # ooudainem nt released atns # at * 4 surrounding reaction containing a large acsd'aclonjt :. i trile. This initiates a side reaction of srr.ï.t, rlr., .. 1 le and water to force the oxy, dii3ropio itrit if J5 * ttj r reaction. r can remain entirely localized in aiâit, caa. C3atf 't oxidiproplonltrile molecule formed eliminates f, l Y ^ o,. reaotjL6nnel medium. As a result, the alkali bzz continues to rise. If a quantity of d-1 e-aau & iéhfeW- '#t. nHat pàa available, conientration eh alèll jfeut '<téî? 4srB <a K
 EMI10.2
 the critical limit and cause a danger = d'te: * p3LQa; i ± n * -V, rJ limit concentration ihgii'èsré rc & uçtitâuè ** L * A i, '' "# '#' ', *' '; fli critical also depends on the temperature; at which 1 ve / 1 ± \ the toe action performed.

   Typically, P1U: '.p: ur. , summer- . , véi # pqinl forte is the concentration of .de wâtijèçf caustAq *;. ; i? # that can cause a runaway. heici./',oet1ât: l'es teit je. rature,, lower between, timl'tdcmn6e. <:, iL-de. <! $ t, give a slow p198 Traction. In practice, it is: W \, 1r èt4 \: more desirable reason to perform the .re'eii to the lifts mentioned above.

   A cea teMpra.tm * 6 <tt ie, PQ; t "'mj: i 21 caustic: water, that is to say, the critical concentration of," * 1 cauatic material may be ageat weak u.,. 1i1, .to.1 .. ptl requires an initial quantity of water re it'l 'i:' 1 - '## /' # '1 .. "- / ï: create a safety factor. \, * ;,: # -, * 'However, a large q, uant1é',. Xdn.a + 'if1t1.l:,.': '\'. I # ': i',, '' '* i d' water causes another problem: tn; 'su1; t "+ a. aad '<total formation dtoXY - 1'ropion1trile 1 "Cê njun, ± rou'

 <Desc / Clms Page number 11>

 
 EMI11.1
 that the product is formed by a reaction which M takes place at uni vites ** only slightly less than the cube of the water content.

   Air doors of matter, can o 'r4oul.
 EMI11.2
 ter and the overall cost of the process increases proportionally
 EMI11.3
 Thus, according to the present invention, critical control and maintenance of the total water content throughout the reaction at a level such that the ratio of weight to atatic material to water is from about 1 d z0 to about 1 t 40. U. hold
 EMI11.4
 continuous optimum water content is a characteristic
 EMI11.5
 particular of the process according to praente.invention. H peraeV #
 EMI11.6
 also another substantial saving! manufacturing * Water
 EMI11.7
 is soluble in acrylonitrile to a value of about 300% by weight. For this raioonf the nepiaary excess of acry-; lonitrile is not water.

   An advantage. of the present invention lies in that this oatur4 product is suitable -à from the end of recycling *.



  When the cyanoothylation has proceeded to the desired degree usually after about 3–3% hegréo.-a., It is necessary to stop the reaction. This is usually done by neutralizing the appropriate acidic caustic material 6 1 # 'fido.dtttiw. A liver primed at this neutralization should be done as quickly as possible. Tour this f r ,,,,
 EMI11.8
 good agitation should be maintained throughout *, the acidification stage.
 EMI11.9
 Chemically, the nature of the acid does not exist:
 EMI11.10
 However, the way of adding the acid is criticized and it
 EMI11.11
 It is a further feature of the present invention. For this reason, an organic acid, which contains acetic acid, is preferred.

   If the acid of neutralization is not substantially anhydrous, or api the concentration of acid in the
 EMI11.12
 reaction mixture becomes too large, - even when using
 EMI11.13
 of anhydrous acid, cellulose cyanoethyléô est. precipitated knots the shape of a * gel * of particles or. "Agrafa? .. these particles contain acrylonitrile and alkali, too

 <Desc / Clms Page number 12>

 
 EMI12.1
 well qM y., .. ü tel, fonMtio * fast 6ç $ lmmP upe r j, penetration ± ticld * fast, t. lpiet. <# * # 3.! 7..¯ n a '' '##! mmédtàténfent neutp4liodp hr, 'n.', a3. er by the particle * rules with Xf at \ àiepdnilpi> .p <tttjr, ibrtwir <* # 1 toxydipropionttril ..

   This results - to no? 0 !! ' ttne gradual increase! in the concentration of alkali tazel 'i p ".t z asses, SI Ji * n. allows it anaen.trtian 'd'.i. praised real * '! aunt der d'avenir bufflfamnient 41, eevee 11 occurs' une poly ', Piaati-on anionique * de L'aryloftitrU,' q, ui translates p * J!! i satitii anioniqu't de "serylonitrilet, from qMl has 0 translates plke ,, a subsequent loss of acrylanitri.1,, n UaRt that ntntaritr8s k; Desirable of the product, a special feature of the present invention is the elimination of this difficulty.

   This water., Obt * nt4-eii solvent of, IacidwaGtiug.aia o a chemically equivalent anhydrous apid! in 1 xa'rrnitr3 .., the ratio prefers acid t acry | onit; ri4.e, at cotoprta t1 approximately- 1 ri and approximately 18 10 golutior resulting is
 EMI12.2
 used for the addition of acid to. reaction mixture.
 EMI12.3
 



  In this volume, the acid and the gas flow through the reaction mixture. From this basket, we avoided .0en-
 EMI12.4
 targeted the formation of a gel ...



  When strongly poiyaterif ## * forms of eellu "'; #'" 'j lobe! Are. used, function power '4., gel tends usually to be somewhat longer, xand.Sfbua some # 4e this ca' i
 EMI12.5
 a little heat produetiop, p1.us scolded p-8. \ 1t between pei88ible and fl is possible dtut11! run ardsi, acid dr ### '-' #. # such, qu (1 'nhydr! from acetic to: instead of 4'td '; glacial acetic Ceei again reduces the amount. q, t'ea \ Í. "lltbr .. pjt4: ent ..

   Usually, however, using e * 'tys, PFtSt ,. of materials
 EMI12.6
 cellulosic, tele that radiates in flakes, acetic acid
 EMI12.7
 commercially available ice cream is fully satlsfal- '*' before and after pt6fé practice. ' As soon as the reaction is stopped by acidification,;

  cellulose cyanoethyKt dojib tr f% a * vµ # of the mm <* a

 <Desc / Clms Page number 13>

 
 EMI13.1
 hot tional containing the. glu grand at. "d, tlrki, 7oi '! ,,' - the non-pae reacts Dma the patsé, we have t ltd <* f -'tà-ftli1 by adding a mixture t4 * Ql4 of partiisa env .r 1.. alcohol and water, in order to cool me '19 MAY "made of tp the cyano-ethyl cellulose <te, nultanaaat .. The precipitate thus obtained, present themselves to the Éumè 4 ** gi! * g ti" PaiuilfT . #Xl ent partially jellied you figure 1 n-trr X'apiyaï'eijS "! wu rope tol.s precipitated * as described below, of such # gt4'r ,, -gâta not aont paa fully aatiafaiaantt p.0 r; X # ipfêp v m 1 tion of panels 61 * ctrçlumintéconte.

   In addition>, unreacted trill must be corrected having dttt; *,
 EMI13.2
 reuse ..,. According to the present invention, 4P * al has been found to be the reaction mixture, preferably while hot and hot, is gradually introduced into the very hot water. '(eg water and finding a temperature up to tanint 90 * C and ci * preferably at a fire temperature between about 9500 and the point of fb11tli'. H $ e. produces elimination instant of an azdûtropt dtciftr 'nitrile and water.

   This advantageously results in a quick and easy recovery of 11q'o by 1mpl (J) nd 18at10: - nitrile suitable for reuse. In addition, ia 6eH! ' los * cyanoethyl precipitated by this distillstlog process
 EMI13.3
 tnn
 EMI13.4
 4 instatui "is very different from the point of view of., Caractr1 ... '
 EMI13.5
 physical ticks of the product obtained by the previous practice of immersion in water or alcohol * water mixtures. Instead
 EMI13.6
 to be aggregates. combined 4 small quantity)! ' 4 .tt ,,. 1! gelatinous, the product is obtained in a finely divided paruculary forae, of granular appearance to; fluffy shown in Fig. 2. This product is easily eaten hot and collected by filtration.

   More importantly, depending on the physical condition of the parts, it is easily washed using any available U <#, vag .. up to an electrplytç Oftpejff .1 content.

 <Desc / Clms Page number 14>

 
 EMI14.1
 decent low. Such a low content could previously only be achieved on a small scale using methods not practiced and according to the present invention. The preferred embodiment had precipitated the cellulose-glycol eyanoethylated in high-grade cells. 'water as close as' Possible of the po.ni d a'bt., t.i1 and tacual, then the precipitate. This: can be carried out using a filter. Preferably , we prefer to use a
 EMI14.2
 centrofugeuae.

   This facilitates the rotary rinsing stage,. of the cake collected. This cake is then resuspended in water, centrifuged again and again rinsed by rotation. nothing other than these washing and rinsing steps is needed to reduce the residual electrolyte content to below the limit of 50 ppm mentioned above,
 EMI14.3
 this two-stage collector and scrubber process is economical.



  , This results in the production of a product of properties $ UP.6. for use in boards or light panels.
 EMI14.4
 neacenta ... - 1, the water used in the process according to the present invention must be filtered, it must be low water
 EMI14.5
 tone content or water which has been deionized or released.



  If necessary, filtered tap water can be used in the r6e <tioR itself and in some cases, if it, slow 1 possible to do otherwise, leads into the first cycle of
 EMI14.6
 rotary rinsing. If possible, however, such a practice should be avoided. In any case, during the last rotary rinsing cycle, deaipnia water should be used.
The following examples are given purely by way of illustration and without limitation of the present invention. '
 EMI14.7
 KXflviPLE 1 ##,. '; #' 4.

   In a receptacle with chimney <nis #, made of inrcyçti steel, e. ,, e, ', 1000 gallons, capable of efficient stirring means, one inter-

 <Desc / Clms Page number 15>

 produced 120 lbs of rayon in 1.5 denier bottle and 2,400 booklet of wet acrylonitrile (approx 97% actual). Agitation is initiated and is maintained throughout the process.



     As soon as the acrylonitrile etaa radiates are vigorously mixed, an aqueous solution of sodium hydroxide containing 6 pounds of sodium hydroxide and sufficient water to give a total water content / taking into account. water in acrylonitrile and rayon, delivered 94 or about 3.5% by weight, Hot water * and then introduced into the jacket and run for a period of one hour, the temperature is raised to about 45-50 C and is then maintained at this value * Every 30 minutes,

   a sample is taken and immediately analyzed for water content. Then, over the next 30 minutes, enough water is gradually added to maintain the alkali concentration uniform, for example, approximately 3.5%. The reaction is continued for about 6 hours, after which it is substantially complete.



   Thirty-six frees of glacial acetic acid were dissolved in an equal weight of acrylonitrile and were introduced at a moderate rate until the reaction mass was neutralized. E14PtE EXAMPLE 2
A sample of the neutralized reaction mixture obtained in Example 1 is slowly added to about 1 liter of a mixture of equal parts of ethanol and water until the precipitation has ceased,

   The precipitate is collected with difficulty on a suction filter. The filter cake is redispersed twice in deionized water and is again collected on a suction filter. The washed final cake is dried. A photomicrograph of the product at ten-diameter magnification is shown as phlegm 1. This product had a dissolved residual electrolyte content of about.
255 ppm.

 <Desc / Clms Page number 16>

 
 EMI16.1
 



  EXAMPLE}: In a second container fitted with a condenser and
 EMI16.2
 from a collector rn adds liquid to about an amount of about 35 times the weight of the solids contained.
 EMI16.3
 the rest of the reaction mass! * nltr'1 & 6..d. Example It This mass is then pumped daHe.d 1'ea hot through a series of nozzles in order to finely disperse the mixture to obtain initial contact with the maximum possible surface area
 EMI16.4
 of water The acrylonitrile is instantly removed in the vapor phase, Pumping of the reaction mixture is continued while the vessel is heated to maintain the temperature.
 EMI16.5
 of the eu above 90 # C.

   The cyanô4ethylé cellulose precedes in the form of fine, flaky and discrete particles.
 EMI16.6
 Acry'on: 1trile condensed forms two layer one layer
 EMI16.7
 the saturated acrylonitrile layer and a lower layer of water * The t (lU (; U 5l! is. decanted and / or discarded. The wetted acrylonitrile layer is retained for reuse * in the next reaction process, '
 EMI16.8
 The precipitated CYGthyl "cellulose slurry is transferred from the precipitation vessel to a centrifuge where it is very quickly collected and rotated.

   Cyano4thyl & coliulosis. rocustll'îê is then resuspended in water and the rotary rinse is repeated * The rotary rinse cycle of the suspension is repeated until
 EMI16.9
 that the cyonoethylated cellulose contains Less than 50 ppw of electrolyte A photomicrograph of the product 8granQi. at 10 diameters is shown in Figure 2. A summary of the properties of the products obtained during five tests is shown in the following table.



  From this table it follows that a superior quality product
 EMI16.10
 has been produced.

 <Desc / Clms Page number 17>

 



  BOARD
 EMI17.1
 Xe of the test <rjL ,, ..., 2 .. 4,;.,!, #,% Dtatote 12.4 12.4 2 | 2 12018 Sodium acetate (ppm) 2 to 30 39. 39 Dielectric constant 1008 1006 12 ,,; 16.4 Dissipation factor OeOl5 0.01 '0 $ 019 0.019 If desired *, the cake of product collected
 EMI17.2
 can be dried, after washing and pulling twice, and then again in an organic solvent, such as the example of 1t.cetonl- tril.a. The resulting solution is filtered through a tl ... sufficiently dense to retain all the particles. particles larger than about 5 microns.

   Although this parentage does not significantly increase purity, it usually eliminates
 EMI17.3
 also a certain small amount of oontaminanta Solids which are undesirable when the product is to be used for luminescent panels or boards
Alternatively, the last step can be carried out by dissolving the washed filter cake, in the solvent which is to be used to deposit the product on the panels.
 EMI17.4
 luminescent, "by filtering this solution and using the HCC outside in this solution.

   The final quality of the product is the same in each case. The particular operation chosen is dictated only by reasons of convenience and other considerations
 EMI17.5
 MVENSICATICN9.



  1.- Strong cyanc4thylated cellulose, characterized in that it has a sot * content greater than 11 # 5% and in that it is substantially colorless, in that it has a dielectric constant greater than about 11, in that it has a dissipation factor of less than about 0.028 and in that it has an electrolyte content of less than about 100 ppm.

 <Desc / Clms Page number 18>

 
 EMI18.1
 



  2.- Strongly cyaaityl cellulose, 8th according to Telren; <,. The 1-carat dication is that the nitrogen percentage is at least 12 and the electrolyte content is less than about 50 ppm.
 EMI18.2
 



  3. Highly cyanoethylated cellulose according to claim 2, characterized in that the cellulose has a degree of polymerization corresponding to an average of about 250 to 350.
 EMI18.3
 anhydroglucese units per molecule.



  4. A finely divided, low density, highly cyanoethylated cellulose material characterized in that it has a granular to flaky consistency, in that its nitrogen content is at least about 11.5% by weight. and in'. that its electrolyte content is less than 50 ppm, the
 EMI18.4
 said material, when dissolved in 4-etonitril and poured onto a glass surface, forms a film having a dielectric constant of at least about 11 and a dissipation factor of less than about 0.028.



   5.- Process for the production of strongly cyanoethylated cellulose characterized in that it is combined at a temperature '
 EMI18.5
 from about 35 ° to about 650 ° C, a discrete mass of cella loae particles with a large excess of amlonitrles in that the reaction of the mixture is initiated in the presence of '(*) about 2.5 to about 7% by weight of the cellulose of a caustic material .. and (b) from about 20 to about 40 parts of water for each part.
 EMI18.6
 tie of 7.a.d.t caustic matter, in that we maürrit, * nt the # - *.

   reaction temperature and periodically adding sufficient water to maintain the caustic material: water ratio between about 1:20 and about 40 until a cyanoethylated cellulose product having a higher nitrogen content
 EMI18.7
 to 11.5 is obtained. #; . 'r: - 6.- The method of claim 5, charatèi-ized -'
 EMI18.8
 that the cellulosic material is fine divided viscose rayon.

 <Desc / Clms Page number 19>

 



   7. A method according to claim 6, characterized in and that the caustic material is sodium hydroxide ,.



  8. A process according to claim 7, characterized in that the reaction temperature is maintained between approximately 45 and approximately 55 ° C. throughout the duration of the reaction.



   9. A process according to any of claims 5 to 8, characterized in that the strongly cyanoethylated cellulose is recovered by contacting the reaction mixture, in a finely divided form, with a large mass of. water heated to a temperature between about 90 ° C and its boiling point, whereby unreacted acrylonitrile is instantaneously distilled off and cyanoethylated cellulose is precipitated.



   10. - Process for recovering highly cyanoetylated cellulose having a nitrogen content greater than 11.5% by weight, from a reaction mixture containing a substantial amount of unreacted acryionitrile, characterized in that one puts This contact mixture in finely divided form entered with a large mass of water heated to a temperature of about 90 ° C and about its boiling point whereby the unreacted acryhenitrile is instantaneously distilled off and cyanoethylated cellulose is precipitated.



   II. The method of claim 10, characterized in that the precipitated strongly cyahoethylated cellulose is collected and washed repeatedly until its electrolyte content does not exceed 50 ppm.



   12. A method according to claim 11, characterized -in that at least the last stage of washing is carried out with deionized water.