BE566481A - - Google Patents

Description

       

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     The present invention relates to a process for the polymerization of esters of methacrylic acid, particularly lower alkyl methaorylates, and other vinylidegen compounds having values of .2. are analogous, such as for example the alkyl acrylates, in order to obtain polymers having a reproducible molecular weight range and having a molecular size which is particularly favorable for particular applications, for example in molding or coating, applications where a particular combination of properties may be necessary for optimum use.



   The sodium and potassium salts which have been shown to be anionic polymerization initiators give polymers of methacrylates and acrylates which have a low molecular weight and which tend to vary somewhat from charge to charge. For example, if we treat meths

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 methyl oroxide with a sodium or potassium-based PQlymér1oation catalyst, it gives polymers which
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 have a molecular weight less than ao, oao, even when the optimum conditions are met with regard to the concentration of the catalyst, the solvent, the concentration of. mono-
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 mother, temperature and other environmental factors, ethyl faorylate,

   when polymerized under the influence of sodium and potassium salts acting as initiators, gives viscous liquids.
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 In opposition to these established methods, the applicant has just found a way to obtain polymers of acrylic and methacrylic esters having a mole or weight weight.
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 significantly higher than those ootained by catalysts based on sodium or potassium, the said molecular weights not being however high enough to cause difficulties in practical operations such as molding or molding. extrusion.



   It has been found that a mixture of sodium or potassium with lithium, calcium, strontium or barium in the form of salts of a Levais acid having a value of, pli, between about 16 and 36. and in the absence of a chain transfer agent, initiates polymerization.
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 Comparable polymerizable methacrylic acid esters and vinylidene aonposez esters yield polymers of moderately large molecular size.

   In addition, by adjusting the proportion (a) of sodium or potassium
 EMI2.7
 Sium with (b) lithium, calcium, strontium or barium in the catalyst, one can vary the molecular dimensions of. resulting polymer within the limits for which
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 obtains an optimum balance of polymer properties for applications such as molding, extrusion, coating or any other specialist application.

   The method of the present invention with a view to fora

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 mation of polymers having regular molecular weights and
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 between approx. 90,000 and approximately 1.0.7.OUU includes the. polymerization in an inert solvent, under anhydrous conditions and at a temperature below 0 C, of an ester of an acid selected from the class consisting of acrylic and methacrylic acids and of an alcohol having a residue.

   
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 from the class consisting of allyl groups having not more than eight carbon atoms, al- cuts
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 oexvle having from three to eighteen carbon atoms, benzyl groups, roupo3 phenyl and alicyclic hydrocarbon groups particularly those having up to 10 carbon atoms, by operating under the influence of a mixture of polymerization catalysts , the catalytic mdl., ar4,, e containing an alkali metal, acting as a catalyst, having an atomic weight at least equal to 2. and as a second cat, l, yseut in the salt form defined above;

   lithium, calcium, strontium or baruym, 1.1 proportion of said alkali metal acting as a catalyst to the second catalyst being adjusted so as to obtain polymers having molecular weights greater than those obtained
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 from catalysts consisting of sodium or metallic potdasium alone, The proportions of the two metallic catalysts (a) and (b) which give the molecular weights
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 desireas, which will be designated here under the name of intermediate malecular weights. vary somewhat with the type of ester to be polymerized and with the nature of the types of metal compounds used, if the metal salts of Lewis acids are taken or prepared in situ, the useful proportions expressed in atoms lying between 0.6:

  1 and 0.1: 1 (i.e. proportions of k or Na
 EMI3.6
 to 1.3., Cap Sr oa aa) when dealing with esters of methacrylic a- aid such as methyl methacrylate, of e-

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   thyl, propyl or. of butyl. When applying the mixture of Lewis acid salts to acrylic acid esters, the sodium or potassium should be in excess of lithium, calcium, strontium or lithium. In all cases the proportions, expressed in atoms, are between 10: 1 and 1: 1, the preferred proportions being between 6: 1 and 4: 1. this is in opposition to the proportions between 0.5: 1 and 0.2:

  1 which are preferred when there are methacrylates to be polymerized.



   Certain modifications of these various proportions occur when one of the metals is supplied by an anhydrous salt of a strong inorganic acid, for example hydrochloric acid. It can then be observed that more or less strong proportions are advantageous, this according to the whole system.



   A convenient way to prepare the initiator system is to disperse the two classes of metals in an inert solvent in which polymerization can be enhanced. The mixture is then treated with small increasing amounts of a Lewis acid until the coloring of the metal dispersion has disappeared.



   For example, 0.013 part by weight of metallic sodium and 0.011 part by weight of metallic lithium are mixed in 30 parts of liquid ammonia at a temperature of -70 ° C. The mixture is stirred. Small increasing amounts of methyl isobutyrate are added to the stirred mixture until the blue color has disappeared. This provides an initiator system which effectively polymerizes methacrylic esters and like vinylidene monomers to them. transforming into moderately high molecular weight polymers.



   Another way to prepare an initiator system for application in the preparation of polymers according to the present invention is to mix sodium

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 or potassium with a soluble and dry salt of lithium, calcium, strontium or barium and a strong mineral acid or to mix lithium, calcium, strontium, or metallic barium with a soluble dry salt of sodium or potassium. The solubility criterion lies in the solubility of these mineral salts in water. the mixture is triturated with a Lewis acid having a PKa between 16 and 36 until the coloration from the free metal has disappeared.

   Mixing is accomplished in an anhydrous inert solvent in which polymerization can be accomplished.



   Perhaps the only way to combine its free particulate matter to prepare the initiator system is to mix one type of metal in a solvent, titrate with a Lewis acid, and then add a salt of the other class of. metals in order to obtain the desired ratio of the two classes of metals, at least one of the salts being a salt of a Levais acid.



   The Lewis acid which is used to form the initiator system must have a PKa whose value is between 16 and 36. The characteristic substances giving these values are listed by Hemmentt in the work "Physical Organie Chemistry" "Me Graw-Hill Back Co, New-
York, 1940. The basicity of Lewis acid salts increases as the Pka value increases, the initiation activity tending to increase with basioity.



   The Lewis acid salts can be prepared as indicated above, or they can be prepared independently of the solvent system in which they are to be used, provided that the amount of free Lewis acid present does not. act as a chain termination agent.

   It is therefore necessary, in the case of the preparation of the salts of the relatively strongest Lewis acids, to have recourse to

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 to preparation procedures which avoid giving a high concentration of Lewis acid binding acid, for example, to prepare an alkoxide, it is advantageous not to have recourse to a free alcohol, but to have recourse to
 EMI6.1
 an anhydrous alkyl caxbozylaze which then gives the alooxide by saponification with the metal.

   Obviously, water must be removed, as well as the free alkanol, since they can act as chain terminators. Methyl crotonate, methyl isobutyrate, n-butyl acetate, -butyl propionate or diethyl malonate can be used, for example, as esters serving: for the titration of the metal or metals, We can also
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 have recourse to aryl-metals, for example phdnyl-sodium or fluorinyl-lithium, to arallcyl-metals, to metal amides, to metal diphenylamides, to indenyl-metals, etc.
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  The preferred type of vinylidin compound includes the esters of nethacrylic acid and alcohols such as methyl, p-propyl, isopropyl, butyl, isobutyl, butyl (oo), butyl (tert) amyl alcohols, hexyl ootylique, nonyl or déeylique (as characteristic alcaaole), allyl alcohol, methallyl, undécényliqua, doddedrulique or octadéoényliquo (as characteristic aloénols), the oyclogentylique alcohols dioyclopentyliql1e, oycloh \ Jxyliql1e, méthyloycloexyliql1e, trimêthyloyolohexyliqueg batyloyolohexylique where tergénylique (as alicyclic alcohols characteristics), alcohols bonzjlique, methylphenyl, phenylethyl, dimethylbenzyliql1e (as characteristic araloanols), alcohols phenyl, ohlorophÓl \ yliql1e methylphenyl, t d1methylphenyl.e, bl1tyl (tert)

  phÓnyliql1e (as characteristic ester-generating phenols), tetra.hydrofurfuryliql1e or methoxyethyl, ethoxyethyl alcohols,

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 EMI7.1
 6-oxypropyl, butoxyethyl, ethoxyethoxyethyl, benzoxyethyl, phenoxyethyl, butylphenoxyethyl, oyolohexoxyethyl, or other alcohols which have residues other than hydrocarbon residues and which are free from reactive hydrogen. Alcohols having amino groups
 EMI7.2
 are also of interest, such as for example N, Nd; Lmethylamino6thanolp N-boetyl (tert) aminoethanol, N-octyl (tert) aminoethanol, 7-amlno-3,7-dimethyloctanol, beia-morpholinoethanol, beta-piperidinopropanol or N, i'T-di4thylaomopropaJ1ol.

   Mixtures of the methaorylates can be used.



   Instead of methacrylates, other vinylidene compounds can be used which have an e-value between about 1/10 and 1. The e-value is a parameter which depends on the polarity of the double bond of the mono-. mother. The greater the value of c, the more the double bond is polarized and polarized such that it becomes
 EMI7.3
 more prone to be fixed by nuclear-loving rÓaotifs; see page 91 of the work by ,, - 1frey, Bohrer and 1: 1 rk, entitled 'la ooolyàerisat ioii "Interaaience Fublishere, Inc, on4r- York, 1952.

   The higher the value of e, the more the double
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 polarized bond is willing to accept an anionic initiator and the less basic the initiator should be, on this scale of e methyl methacrylate has an e-value of +0.4 while methyl acrylate and the like have an e value of +0.6.
 EMI7.5
 vtnylidene compounds having an appropriate e-value therefore include esters of acrylic acid
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 and the list of alcohols given above also applies: to these esters.

   With the vinylidone o = .pos6a having values of .2. located outside the range indicated, the combination of the two metal aortas does not seem to give the interesting result described here for methacrylates

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 and acrylates.



   One or more of these monomers having similar values of e are made to act on a solvent system which remains fluid at low temperature. Ammonia is a very important low temperature fluid and can be used as the sole solvent or as part of a mixture of solvents comprising, for example, a dry ether or a petroleum ether or an amine such as trimethylamines.



   The monomer concentration can advantageously be maintained at a value high enough to give a system capable of being worked and stirred, but dilute solutions are equally applicable, on a molar basis, in practice an amount of between approximately 0.05 and about five moles of monomer per liter of solvent. The concentration range between 0.05 and 0.5 volume of monomer per volume of solvent is preferred.



     The proportion of catalyst which is used can be varied between 0.01 and 0.2 moles of catalysts per mole of monomer or of monomers. Although a higher proportion of the metal relative to the monomer can be used, there is no obvious advantage in doing so.



   The polymerization is carried out at a temperature below 0 ° C., usually between -10 ° C. and -90 ° C. and preferably between approximately. -30 C and about -70 C.



   The polymer and the solvent are separated, for example by separating the polymer by filtration or by evaporating the solvent, leaving the polymer as a residue, or by causing precipitation by the addition of a non-solvent. The polymer is washed with water or alcohol to remove the initiator and dried. In some cases it may be beneficial to wash with an acid

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 in solution in water or alcohol, particularly with a view to removing mineral residues which may impart coloration.



   The polymer thus obtained is soluble in characteristic organic solvents, such as ethyl or butyl acetate, toluene, chlorinated hydrocarbons, or mixtures of solvents.



   The molecular weights of the polymethacrylates prepared with the mixed catalysts can be varied within a range of from about 90,000 to 1,000,000, depending on the particular ester and the combination of metals constituting the initiator system. The preferred range is between 100,000 and 400,000 since it is within this range that desirable properties are manifested for a large number of particular applications. In the case of polyacrylates, molecular weights are also obtained which are considerably higher than those obtained when the initiators consisting of sodium or potassium alone are used.

   The range will also usually be between about 100,000 and 400,000.



   An important consideration is that it becomes possible, by using the mixed catalyst systems of the present invention, to retranslate molecular weights with greater certainty than has heretofore been possible.



   Not only do the polymers have molecular weights which are in the range indicated above. but still they are characterized by the fact that they exhibit a very narrow distribution of molecular weight values.

   Polymores in the range of average molecular weights determined by viscosity which have been found to be of interest for a molding or coating composition will therefore combine the normal and valuable flow characteristics of these polymers with

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   The increased toughness caused by the increase in number average molecular weight. Alternatively, polymers can be prepared having a number average molecular weight equivalent to that which has been found to be of interest for a molding or coating composition.

   These latter polymers then have a lower mass and solution viscosity, which gives rise to a significant improvement as regards the ease of forming the material by molding, by injection, by extrusion or by application from a material. solution in a solvent. Bleating :, the polymers thus obtained have an exceptionally low monomer content.



   An example of this is given by a methyl methacrylate prepared by means of the present invention and having an intrinsic viscosity in benzene of 0.35 deciliter per gram which corresponds to an average molecular weight determined by the viscosity equal to 110,000. The molar weight measurements carried out osmotically on this sample give a number average molecular weight of 63,000. The ratio of the average molecular weight determined by the viscosity to the number average molecular weight is therefore 1.75 to 1.

   The percentage of unreacted monomer is equal to 0.5%. on the other hand, a polymer of methyl methacrylate prepared by a process using free radicals so as to obtain the mens
 EMI10.1
 determined utoyen'numncrig noleanle weight, ue of 55,000 and cut out the screw that the ratio will be 2, ü on 1.

   The p.rcentae of monocosity, will have a minimum weight that has not been reacted is then l ,;) 1.4 lecular-average 'Although with regard to polystyrene it has been indicated in the technical literature that the molar weight of the polymer is independent of the concentration of the alkali metal which is used as a catalyst, at least in the range studied there appears to be an increase

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   The molecular weights are well determined as the total concentration of the mixture of metals acts as initiators increases.



   Other details will be given in the examples which follow and which are presented by way of illustration and without limitation of the present invention.



  Example 1 -
A two-liter glass vessel is fitted with a view to carrying out tests under substantially anhydrous conditions by providing it with a stirrer, and several inlet tubes for alkali metals, dry nitrogen, amber. - moniac, the salt-generating co-catalyst and noromer.



  It is also equipped with a discharge port to the atmosphere through a drying tube lined with anhydrous silica gel. Before the operation, the container is swept with dry nitrogen for thirty minutes. then 0.633 grams of sodium and 0.545 grams of lithium are weighed out under benzene in order to minimize the formation thereof. Oxides and hydrolyses. This constitutes a molar ratio of sodium to lithium of 0.35 to 1. An autoar cooling bath is then placed in the vessel. The coolant consists of pieces of carbon dioxide snow in acetone, which gives a bath temperature of -78 °.

   Anhydrous ammonia is then distilled from a bottle and it is condensed in the container until a volume of one and a half liters is obtained. A characteristic blue solution occurs. The total alkali metal concentration is 0.071 moles per liter. We start to agitate. Methyl isobutyrate is added slowly until the blue color disappears. This requires 5 ml. The resulting solution is clear with small pieces of suspended white solid material. 218 g of methacrylate (methyl eonomer.

   The mixture that is in the

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 container turns cloudy white, then chalky white, indicating rapid transformation into polymer. stirring is continued for half an hour. Add eight grams of
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 ohloraàe d t'atml0111W1l in order to neutralize any unused initiator. The ammonia and polymer slurry is poured into a sintered glass filter funnel and
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 the polymer is separated by filtration. the filter b.1teau is washed three times with water in order to separate the inorganic salts and it is dried in a vacuum oven. The product is a fluffy white powder.

   We dissolve a sample
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 Sample Q, 2 grams in 100 ml of ethyl 2ane dichloride and a determination of the reduced specific viscosity is made. This has a value of 0.058 liters per gram, which corresponds to a molecular weight of 150,000, as calculated using the equation of Baxendale, Bywater and Evans
 EMI12.4
 (Journal Polymer Soi. L, 237 (1946 modified for ethylene dichloride.

   In contrast, a methyl methacrylate polymer prepared in an analogous manner, except that metallic sodium alone is used as the salt-generating alkali metal, has a reduced specified viscosity of 0.017.
 EMI12.5
 liter per gram which corresponds to a molecular weight of 32,000.



    Example 2 -
 EMI12.6
 A methyl saethacrylace polymer is prepared by operating by a procedure identical to that of e-
 EMI12.7
 xample 1, except due, recourse is had to 0.11 of sodium and 0.557 grams of lithium. This represents a proportion
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 molar of sodium to lithium do 0, z o-ur 1. The total concentration of alkali metal is 0.071 molep per liter. The polymer has a reduced specific viscosity of 0.068 liter per gram, which corresponds to a molecular weight of 180,000.



    Example 3 -
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 A methyl methacrylate polymer is prepared

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 in a device and by a procedure identical to those of Example 1, except that 0.466 grams of sodium and 0.599 grams of lithium are used, this represents a molar ratio of sodium to lithium of 0.23 out of 1 The total alkali metal concentration is 0.071 moles per liter. 191 grams of polymer are obtained. The polymore has a reduced specific viscosity of 0.116 liters per gram, which corresponds to a molecular weight of 360,000.



    Example -
The device described in Example 1 is modified by replacing it with a larger container so that three liters of catalyst solution can be prepared. One gram of sodium and 1.5 grams of lithium are used. This represents a molar ratio of sodium to lithium of 0.201 to 1. The total concentration of alkali metal is 0.087 moles per liter. Methyl isobutyrate 9.5 ml is used to decolorize the alkali metal.



  540 grams of methyl methacrylate monomer are added and polymerization takes place. The polymer, after having been separated, washed and dried, represents 489 grams. It has a reduced specific viscosity of 0.157, which corresponds to a molecular weight of 530,000.



    Example 5 -
A "Pyrex" battery box with a capacity of nine liters is equipped with a "Plexiglas" cover. The necessary inlet and outlet orifices are added as described in Example 1. Six liters of catalyst solution are prepared by the same procedure as in Example 1. 2.80 grams are used. of sodium and 2.11 grams of lithium.

   This gave a molar ratio of sodium to lithium of 0.40 to 1, and a total alkali metal concentration of 0.071 moles per liter, methyl isobutyrate was added until the color changed from dark blue to dark blue. naance limpid pale blue, there

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 EMI14.1
 a, add 8 × 3 6 ràmmee of methyl methacrylate monomer which is then p × 3, se, The polymer is washed three times -r 31, with deionized water and dried in a vacuum oven. The polymer has a reduced specific viscosity of 0.044 liters per gram which corresponds to a molecular weight of 111,000.
 EMI14.2
 



  E: oen'ol e 6 We equip with a cover of ".lexi,; 3.as" a battery box "in 2yret having approximately a winter capacity of nine free, we adjusted the orifices df, .al3. F3.OI7. Or evacua-% ion necessary as described in Example 1 <Prepare liters of ca'talpyseu: r by operating by the same operating mode as in Example 1. We use 3 , 27 grams of sodium and 2.46 grams of lithium, This gives a molar ratio of sodium to lithium of 0.400 to 1. The alkali metal concentration is 0.071 soles per liter.



  Oven to form the alkali metal salts, use is made of
 EMI14.3
 20 ml of methyl isobatyra-ce and 83 x'ammea of methyl methMrylate monomer is polymerized. Separate, wash and dry 707 grams of polymer. The polymer has a reduced specific viscosity of 0.042, which corresponds to a molecular weight of 99,000.
 EMI14.4
 



  The properties of rthc, crylate to nothyl a; an id
 EMI14.5
 Molecular molecular weights are 1.01100 that it cu.wti; u.e a high powder with an interesting molding polymer. A certain purity of the low viscosity ketanionic material in the form of rods or frills is half-done and physical tests are carried out. Ji. As a complaisant, the same physical tests were carried out on a molding powder consisting of conventional commercial methyl methacrylate
 EMI14.6
 and also on a blend of u.nion.iqu.e molecular weight polymer.

   The high molecular weight polymer is prepared having a reduced viscosity of J'1.0 (corxeopond, .sn at a molecular weight of ° 6J.OOJ) by a pracesouj anioniiiae ana-

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 EMI15.1
 Lvgue CelUi described above except that the catalyst is, formed from. u.3 ... a lithium salt with methy- iaobutyrate, 16 * The low molecular weight polymer (reduced specific viscosity of OoOI7 # corresponding to a weight mgléoula: L- re of 32,000) is obtained by a process analogous to that described above except that the catalyst is formed from the uni
 EMI15.2
 than sodium salt with methyl isobatyrate
 EMI15.3
 1 'T ". 1 - -1 Polymer Mixture of iaworoé with 4 polymer polymers;

   average molecular weight 1 olassic 1 mixture fo.i- 1. of wheat and high salts (r-100i i "" ,, - ,,, "" - 1 -... "'.. ¯-A¯ -" ---; ----- V1soo & specificity d- 1
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 me 0.042 1 OsO43 09043
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 bar 12.5xyz mm 0.67 '0.07' "o, 45
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 Heat diatorsion, 0.5 per minute, soue t 1ü, 5 kg / cm2 0. 92 0, 65 0.
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 thousandth of a cm per cm 8 2.4 1.4 1 1.4
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 ? 4sistanoo flexion. 1 in k.g / cm2 9 .1.260 8 427 1.420
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 monomer 1 0.15 1.0 2 -? t!> .- c #. "'Ir' -4--1
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 example y - a series of tests are carried out using. device described in Example 1. the salts of
 EMI15.17
 sodium and lithium by bubbling oxygen through the solution of the salts until the blue solution becomes clear.

   The total concentration of an alkali metal is kept constant at a value of 0.071 mol per liter.



  The proportion of sodium to lithium is varied as an indication.
 EMI15.18
 than. The monomeric methaorylate is polymerized and the polymer is treated as in Example 1. The values obtained for

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 EMI16.1
 the qieoosized, bp40ific reduced are those indicated in leta.blea.u. The molecular weights are calculated as in Example 1,
 EMI16.2
 xunero i 1 hoids noléeulaire i 1 Rappork a polynero 'Molecular weight number IV.8.R ratio of the polymer of 8 calculated from: molars in liters by the test t polymer i Na / t1 9 gram "' fll" W-. . 1 sr-.8I r ..........---- ¯ -..-. - ...--: ----.... per ....-- .-- .. '-¯bl..A - 4Nl .-- w .... "P" ir ""' - 9 HW 5-.? a 100,000 a 0.5 $ 4 0.043
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 HW 3-4.3 fi 130 * 000 r o, 494 /.

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 Ew 3-su 180,000 1 0.100 / 1 oao68
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 HW 4-26 3,100,000 a û, 3 ?. 09104 MY 5-16 740.000: a, 26s //. 4 z21 1. 1 t
 EMI16.9
 Example 8 -
 EMI16.10
 This is a series of tests analogous to those of Example 79 except that the total alkali metal concentration is maintained at z214. mole per liter. The values of the reduced specific viscosity (V.3.R) of the polymers vary
 EMI16.11
 . as shown below.

   The molecular weights are
 EMI16.12
 calculated coma in Example 1 ..
 EMI16.13
 a t number molecular weight proportion iV. 8.R of the polymer of 1 .calcula of the 8 molar g in liters "the polymer test 1 Na / 11 4 gram -....-.-. * ---. --------- TWill WI: f8J¯ ...... 'WI ..... II, ¯-. 1I "R"' PV9f & "" '- "" "" U -.-- .Jl -
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 IIW 5-18 1 71,000 1 0.590 / 1 0 # 032 III HW 3-a5 85,000 1 0 # 493/1 0.0; 7
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 HW 4-6 150,000 1 0, '9711 0.059 EW 53 ° 1,100,000 09260A 0029 1. 'r.
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  '' XA $ 9 On> o1-me: r1se methyl methacrylate in ua d1a> oai tU '-: LdentiQ.l1elQell.1i which was used in example 1. We said 2 <46 grams of sodia @ in a liter and a half of fammon1ag anhflra. Oxygen is bubbled through the ablution until the blue color is dieparalose, 1.89 grams of lithium chlorine are added and

 <Desc / Clms Page number 17>

 stir the solution for 15 minutes. 218 grams of methyl methacrylate monomer are added. The polymer is formed. Stirring is continued for one hour.

   Two grams of ammonium chloride are added to neutralize the excess initiatour and the ammonia is allowed to evaporate for sixteen hours. The polymer is washed three times with water in order to remove inorganic salts and dried in a vacuum oven. The polymer weighs 205 grams and has a reduced specific viscosity of 0.044 liters per gram, which corresponds to a molecular weight of 110,000.



     The polymer obtained under the same conditions, but using sodium as the only metal, has a molecular weight of about 30,000. example 10 -
The methyl methacrylate is polymerized in a device identical to that used in the e-
 EMI17.1
 / Etô; 6is xample 1. one dissolves c, 68z gram of7lith1Wll in one gram of liters and a half of anhydrous ammonia. This corresponds to a molar ratio of 0.20 to 1 and a total alkali metal concentration of 0.071 mol per liter. Mixed salts are formed by adding oxygen gas to the solution until the blue color disappears.

   94 ranges of methyl methacrylate monomer are added.



  The polymer is formed. ' The reaction mass is stirred for thirty minutes, after which ammonium chloride is added, The polymer is separated by filtration, washed with water and dried in a vacuum oven, It has a reduced specific viscosity. of 0.26 liter pure gram in ethylene dichloride, which corresponds to a molecular weight of 930,000.



   On the contrary, a methyl methacrylate polymer prepared in an analogous manner, but with the use of metallic potassium alone as the alkali metal salt generator, has a reduced specific viscosity of 0.021, corresponding to

 <Desc / Clms Page number 18>

 
 EMI18.1
 having a molecular po38.e of 40,000. emllIe, 11., - If we repeat the procedure of Example 11 using 'to. 137 grams of potassium, at 00489 grams of iithî = - (i.e. a molar proportion of 0.5 to 1) and 218 grams of methyl methacrylate, a poly-
 EMI18.2
 mother having a reduced viscosity of 0.030 liters per gram in ethylene dichloride. which corresponds to a molecular weight of 55. 00 0.



  Example 12 - methacrylate is polymerized. te of IJÓt.l1le in a device identical to that used in Example 1., We d3.a or 0.421 gram of sodium and 11 ′ gram of calcium in one and a half liters of anhydrous anmoniao. Mixed salts are formed by the addition of oxygen gas to the metal solution until the color changes and passes.
 EMI18.3
 from dark blue to bluish white. then 213 g of monomeric methyl methacrylate are added. The polymer forms. Stirring is continued for half an hour.
 EMI18.4
 The polymer was filtered off with water and dried in a vacuum oven to give 210 grams of product.

   This has a reduced specific viscosity of
 EMI18.5
 0.25, corresponding to a, c3.c: dJ1Sctù. <Ir.} Dc3: J4; "ÙOÙ.



  On the contrary, a polymer of m.ôL, cry., Atc methyl prepared in an analogous manner, but using a single alkali metal, has a reduced specific viscosity of 0.024 when sodium alone is used as a catalyst and 0.80 when calcium alone is used as a catalyst.
 EMI18.6
 xsmple 13 The methyl methaorylate is polymerized in a device identical to that used in Example 1 with the aid of 0.513 grams of sodium and 1.68 grams of calcium dissolved in one and a half liters of anhydrous ammonia,
 EMI18.7
 The mixed salts are formed by the addition of oxy, to a gas

 <Desc / Clms Page number 19>

 until the coloring changes from dark blue to bluish white.

   Then 218 grams of methyl methacrylate monomer are added. A polymer is formed. The mixture is stirred for 20 minutes. The ammonia is allowed to evaporate for sixteen hours. The polymer is washed three times with water and dried in a vacuum oven. The polymer has a reduced specific viscosity of 0.083 liters per gram in ethylene dichloride, which corresponds to a molecular weight of 230,000. example 14 - *
The methyl methacrylate is polymerized in a device identical to that used in Example 1 using 2.44 grams of sodium diseous in one and a half liters of anhydrous ammonia.

   Ethyl acetate is added in small increasing amounts until the solution turns from blue to colorless. At this point 4.09 grams of lithium chloride is added and the solution is stirred. for seventeen minutes. Then 218 grams of monomeric methyl methanolate are added. The polymer is formed. The mass becomes too viscous to be stirred after five minutes. The ammonia is allowed to evaporate for sixteen hours, the polymer is washed with water three times and dried in a vacuum oven. The polymer has a reduced specific viscosity of 0.042 liters per gram in ethylene dichloride.

   This corresponds to a molecular weight of 99,000.



     . 1% contrast, a polymer of methyl methacrylate prepared in an analogous manner but without adding lithium chloride, has a reduced viscosity of 0.016, corresponding to a molecular weight of 30,000. example JL 5 -
Methyl methacrylate is polymerized in a device identical to that used in the e

 <Desc / Clms Page number 20>

 ample 1 using 2.44 grams of sodium dissolved in a liter and a half of anhydrous ammonia, Methyl isobutyrate is added in small increasing amounts until the solution turns from blue to clear, A at this stage, we add
4,

  4 grams of anhydrous aluminum chloride and the solution was stirred for thirty minutes, then 94 grams of methyl methacrylate monomer was added. The polymer is formed, the reaction mass is stirred for thirty minutes, then two grams of ammonium chloride are added in order to neutralize the remaining initiator, the polymer is separated from the ammonia by filtration. The polymer was washed with water and dried in a vacuum oven to give 57 grams of dry polymer having a reduced specific viscosity of
0.097 liter per gram in ethylene dichloride. This corresponds to a molecular weight of 290,000.



   If the above procedure is repeated, replacing the above-mentioned calcium chloride with strontium chloride or anhydrous barium chloride, a very similar polymer is obtained. It is therefore obvious that these alkali = earth metals have the same action in the initiator system.



    Example 16 -
The methyl methacrylate is polymerized in a device analogous to that used in Example 1, using 0.594 grams of sodium and 0.564 grams of lithium dissolved in one and a half liters of anhydrous ammonia. This corresponds to a molar ratio of 0.32 to 1. Methyl isobutyrate is added in small and increasing amounts until the solution turns from blue to colorless. the bath surrounding the reaction mixture is brought to a temperature of -40 ° C. The reaction mixture is stirred for twenty-seven minutes. Then 218 grams of methyl methacrylate monomer are added.

   The polymer is formed. stirring is continued for thirty minutes.

 <Desc / Clms Page number 21>

 two sums of ammonium chloride. the polymer is washed with water, and dried in a vacuum oven. The product obtained poses 195 g and has a reduced specific viscosity of
 EMI21.1
 A 4ri. liter p .. # gram in ethylene dichloride. This corresponds to a molecular weight of 220,000.
 EMI21.2
 xeGlla 1.1 -
Methyl methacrylate is polymerized in a device identical to that which was used, used in
 EMI21.3
 example 1 using 09633 gram of sodium and a, I gram of lithium dissolved in a liter and a half of ammonia
 EMI21.4
 anhydrous. This corresponds to an ILol1re proportion of 09345 to 1.

   Acetonitrile is added in small, increasing amounts until the color turns bluish white. Then 218 grams of methyl methacrylate monomer are added. The polymer is formed. We shake the masae reaotion-
 EMI21.5
 nelle for thirty minutes. two giaaMea of ammonium chloride are added to neutralize the remaining initiator.



  The ammonia is allowed to evaporate for sixteen hours, the polymer is pudded with water, and dried in a vacuum oven. The product weighed 203 grams and had a reduced specific viscosity of 0.040 liters per
 EMI21.6
 gram in ethyl bichloride. Ce01 corresponds to a molecular weight of 93-000o On the contrary: re a polymer of metb.acr'ylate of netuy10 - prepared in an analogous manner, but using only metallic sodium as the alkali metal which generates salt, has a specific viscosity reduced by 0.012 liters per
 EMI21.7
 gram in ethylenep dichloride, which corresponds to a molecular weight of 21,000.



  Txemn 'the 18¯ ¯ We equip a one liter glass container in sight
 EMI21.8
 to carry out the eaoa10 in appreciably anhydrous conditions, by providing it with inlet and outlet tubes

 <Desc / Clms Page number 22>

 
 EMI22.1
 Iden% iqaes To those used in Example 1. Prior to operation the vessel is swept with dry nitrogen and 2.0 grams of sodium chloride and 0.138 grams of lithium are added. a cooling bath is then placed around the container. 'The refrigerant consists of pieces
 EMI22.2
 of carbon dioxide snow in aoetone. huia, 200 grams of anhydrous ammonia are condensed in the container. The cooling bath and the solution of the metal and the salt reached are removed.
 EMI22.3
 an emp ure of -33 µ 0.

   Gaseous oxygen is added until the blue solution has disappeared. Then 40 grams of methyl methacrylate monomer are added. The polymer is formed. After twenty minutes of stirring, 0.2 gram of NH4Cl is added. The polymer is separated from the ammonia by filtration. The polymer is washed with water and dried in a vacuum oven.

   The polymer has a reduced specific viscosity of 0.389 in ethylene dichloride, which corresponds to a molecular weight of 1,500,000. On the contrary, a polymer obtained in an analogous manner, but without adding sodium chloride, has a reduced specific viscosity of 0.500, corresponding to a molecular weight of 2,000,000 *
If the above procedure is repeated in
 EMI22.4
 replacing the sodium chloride used s: .ie; scs pclr potassium chloride, a polymer is obtained r4: n ... 3.oQua, The aus-mentioned procedures applied to allyl, dundée6ayle or o3 methacrylates Eyl, as typical alkenyl methacrylates, give quite comparable results for the formation of polymers.
 EMI22.5
 qant intermediate molecular weights.

   This is also true for alicyolic esters such as ayaloa3ryl or dtinobornyl methaarylate and also for benzflic and phenylic methacrylic acid. Example 19 Methyl aorylate is polymerized in a device.

 <Desc / Clms Page number 23>

 identical to that which was used in Example 1.



  0.577 grams of sodium and 0.202 grams of calcium are added to the flask. This corresponds to a molar ratio of sodium to calcium of 5 to 1. One and a half liters of the anhydrous liquid ammonia are condensed in the flask. The mixed salts are formed by adding oxygen gas to the solution until the solution turns from blue to white. When 107 grams of ethyl acrylate are added, the polymer is observed to form. The ammonia is separated by decantation. The weight of the polymer is 74 grams. It is purified by dissolving in benzene, filtration and freeze drying. The polymer has a reduced specific viscosity of 0.039 liter per gram in ethylene dichloride, at a concentration of two grams per liter.

   This corresponds approximately to a molecular weight of 110,000.



   On the contrary, an ethyl acrylate polymer prepared in an analogous manner but using only sodium as the metal, is a viscous liquid having a molecular weight of 5,000. Also, for comparison, an ethyl acetate polymer prepared in an analogous manner, but using calcium only as the metal, is a polymer having a reduced specific viscosity of 0.10. corresponding approximately to a molecular weight of 370,000.



  Example 20 -
Butyl methacrylate is polymerized in a device identical to that which was used in Example 1. 0.40 gram of sodium and 0.40 gram of lithium are added to the flask. this corresponds to a molar ratio of sodium to lithium of 0.3 to 1.

   One and a half liters of liquid anhydrous ammonia is condensed in the flask. Mixed salts are obtained by adding small increasing amounts of methyl isobutyrate until the solution

 <Desc / Clms Page number 24>

 
 EMI24.1
 change alitide blue * This detains 2 ml of M iaobutyrate, 6thyloi laimelor, adds 69 grams of m4% haooeyla% e butrley, the formation of the polymer is observed * The aNxaam3ac gar .daa, n.ta, tio is observed .. the weight of the polymer is 64 grams * mea.

   It is pacified or dissolved in benzine by filtering, conµelan% and sublimating the frozen benefit. The specific aw viaooaite polymer reduced by 0.058 liters per gxanne results in a concentration of two grams per liter in the dichloride of 4% hylene. This corresponds apparently to a molecular polish of 2fi, C00, Example 21 Butyl aozylate is polymerized in a d9.apo. t aitive identical to. oei which we have or resort to in 1 example 11 '? 0.58 grams of sodium and 0.20 grams of calcium are added to the flask. This corresponds to a molar ratio of sodium to lithium of 5 on the flask.

 <Desc / Clms Page number 25>

 anhydrous niao in the flask. The mixed salts are obtained by adding gaseous oxygen to. the solution until the solution turns from blue to white.

   When 69 grams of butyl aorylate are added, the formation of the polymer is observed.
We. separates the ammonia by decantation. The polymer weighs 55 fat. It is purified by dissolving it in benzene, filtering and drying by freezing. The polymer has a reduced specific viscosity of 0.042 liters per gram at a concentration of two grams per liter in ethylene dichloride. This corresponds approximately to a molecular weight of 120,000.



   Application of the above process to other esters of acrylic acid proves that polymers of intermediate molecular weight are consistently obtained with the intended mixture of catalysts. Thus, it can be applied with a result analogous to alkenyl aorylates such as allyl, crotyl or oleyl acrylates, to phenyl or benzyl aorylates or to alicyclic acrylates, including in part sheet metal. dicyolopentenyl, cyclohexyl and isobornyl acrylates.


    

Claims (1)

-R E S U ME - .Process for the preparation of polymers having molecular weights between about 90,000 and about 1, 000, characterized by the following points, separately or in combinations: 1) polymerizing in an inert solvent and under anhydrous conditions, at a temperature below 0 ° C., an ester of an acid chosen from the class consisting of acrylic and methacrylic acids and of an alcohol having a residue belonging to the dusse consisting of the alkyl groups having not more than eight carbon atoms, the alkenyl groups having from three to eighteen cubone atoms, the benzyl and phenyl groups and the alkyl hydrocarbon groups. <Desc / Clms Page number 26> cliques' having up to ten carbon atoms, under the influence of a mixture of polymerization catalysts, said mixture containing an alkali metal serving as a catalyst having an atomic weight of at least 23 and a second catalyst based on a metal selected from the class formed by lithium, calcium, strontium and barium, one to. less of these catalysts being a salt of an acid having a PKa between 16 'and 36, the proportion of said alkali metal acting as a catalyst to said second catalyst, expressed on the basis of the metal atoms, being between approximately 0.6: 1 and 0.1: 1 when polymerizing methacrylic acid esters and between about 10: 1 and 1: 1 when polymerizing acrylic acid esters. 2) When the ester which is polymerized is an alkyl methacrylate or an alkyl acrylate, the operation is carried out at a temperature of between -la and -90 0. 3) Methyl methacrylate or butyl methacrylate is polymerized by operating at a temperature between -30 and -70 ° C., the molar proportion of said alkali metal acting as a catalyst for said second catalyst, expressed on the base of the metal ions, being between about 0.5: 1 and 0.2: 1, resulting in poly (methyl methacrylate) or poly (butyl methacrylate) having a molecular weight of between 90 . 000 and 1,000,000 .. 4) Ethyl aorylate is polymerized at a temperature between -30 and -70 ° C., the molar proportion of said alkali metal acting as a catalyst for said second catalyst, on the basis of metal ions, being between approx. -, 6: 1 and 4: 1.