Abstract:
The process enables the simultaneous production of hydroxytelechelic polymers and oligomers by the radical route. At least one ethylenically unsaturated monomer is polymerized in the presence of hydrogen peroxide under the effect of ultra-violet radiation. The polymerization is carried out in a diluent medium comprising essentially an alcohol. The process can be operated to produce polymers having average molecular weights between one hundred and one million and to produce selectively unimodal, bi-modal or multi-modal distributions of molecular weights.

Description:
This is a continuation, of application Ser. No. 672,917, filed Apr. 2, 1976, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of polymerization by the radical route in the presence of hydrogen peroxide under the effect of ultra-violet radiation. 
     More particularly it relates to a process for obtaining hydroxytetechelic polymers and oligomers by the polymerization of monomers in the presence of hydrogen peroxide. 
     DESCRIPTION OF THE PRIOR ART 
     It is known to be possible to split perhydrol, the active component of hydrogen peroxide, by ultra-violet rays of wave length equal to 2537 A, into two hydroxyl radicals. 
     This action of UV radiation has already been used for the copolymerization by the radical route of tetrafluoroethylene with propylene in the presence of hydrogen peroxide. 
     According to this method, described in &#34;Polymer Letters Edition&#34; vol. 12, pages 95-99 (1974) and &#34;Journal of Polymer Science&#34; vol. 12, pages 911-920 (1974), the copolymerizations are always carried out in emulsion under the effect of UV or γ rays. The medium in which the polymerization is carried out in micellae is constituted by water and contains mostly an emulsifier. The one or more monomers used are hence insoluble in the medium and the polymerization is carried out in a binary system with very small amounts of initiator (10 -3  to 10 -2  M/l H 2  O 2 ). 
     The polymers or copolymers obtained according to this known process are insoluble in the medium and have a high number average degree of polymerization (DPn), the average weights of these macromolecular components being comprised between 13,000 and 190,000. 
     The GPC shows a unimodal distribution of these polymers or copolymers which occur in the form of an aqueous emulsion of these solid compounds, that is to say a latex. 
     It would be interesting to obtain hydroxytelechelic oligomers, that is to say polymers of smaller weight, of the order of 100 to 20,000 for example. In fact, these polymers, generally liquid, have found numerous applications. In particular, polyisopropylenes, polybutadienes, polybutenes of low molecular weight and possessing at the chain ends functional groups such as --OH, --Br, --Cl, --CN, --COOH, --SO 3  H, etc . . . are used as additives of lubricants or of certain fuels and essences, as adhesives, binders, propergol binders, etc . . . They can also be incorporated in natural or synthetic elastomers and their derivatives, in synthetic gums and the like. They can also be used to obtain alveolar masses of greater or less density by reaction with multifunctional molecules. These and other applications have been described by J. Brussas in &#34;Information Chimie&#34;n°128 of January 1974. 
     Such oligomers have already been obtained in the prior art by polymerizing monomers in the presence of hydrogen peroxide under the effect of heat. Such a process is described in French Patent Application 73, 24 392 filed by Applicants on July 3, 1973 for: &#34;Preparation of telechelic polymers and products obtained thereby&#34;, and in U.S. Pat. No. 3,673,168. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved process for the preparation of hydroxytelechelic polymers and oligomers by the radical route. 
     It is another object of the invention to provide a process for the simultaneous production of hydroxytelechelic polymers and oligomers by the radical route, of molecular weights of the order of 100 to 20,000. 
     Other objects and advantages of the process of the present invention will be apparent from the description which follows. 
     According to the present invention there is provided a process for the simultaneous production of hydroxytelechelic polymers and oligomers by the radical route by the polymerization of at least one ethylenically unsaturated monomer in the presence of hydrogen peroxide under the effect of ultraviolet radiation, characterized in that said polymerization is carried out in a diluent medium comprising essentially an alcohol. 
     DESCRIPTION OF THE INVENTION 
     The reaction system according to the invention always comprises at least the following four elements: 
     one ethylenically unsaturated monomer 
     hydrogen peroxide 
     a diluent such as an alcohol 
     ultra-violet radiation. 
     The monomers which are capable of polymerization according to the process of the invention are compounds containing at least one ethylenic linkage, such as notably butene-2, isobutene, butadiene, isoprene, dimethyl-2,3 butadiene, methyl and ethyl acrylates, acrylic and methacrylic acids, methyl methacrylate, acrylonitrile, methacrylonitrile, vinyl acetate and chloride, styrene, α-methyl-styrene, vinyl pyrrolidone, acrylamide, piperylene, or compatible mixtures of such monomers. 
     The wave length of the UV radiation used is, for reasons explained above, equal to 2537 A. However, within the range of ultra-violet radiation (1800 to 4000 A), any wave length capable of causing the homolytic splitting of perhydrol into hydroxyl radicals may be used. 
     By the present process, the polymerisations are carried out in an original manner, always in solution and if necessary in a precipitated phase, without any surfactant. 
     The concentrations of hydrogen peroxide are always superior to quantities usually used in catalytic systems and are from about 1% to about 20% or more by weight of the polymerization mixture; the reaction system is hence ternary. 
     The use of photolysis for obtaining hydroxytelechelic polymers according to the invention allows the high concentrations in H 2  O 2  ; these concentrations were not possible in the polymerization processes by the thermic route owing to the instability of H 2  O 2 . 
     The polymers obtained are soluble or insoluble in the reaction mixture, according to the nature of the monomer, the composition of the reaction mixture and the amount of polymers in the mixture. When the polymer is soluble in its monomer and in alcohol, the GPC shows a unimodal distribution of molecular weights. When the polymer is not soluble in alcohol, the molecular weight distribution may be multimodal. 
     Without wishing to be bound to a particular theory, it is probable that this multimodal distribution of the macromolecules obtained is due on the one hand to a non-solvent effect exerted by the medium on the polymeric chains, favoring high molecular weights, and on the other hand, to the presence of zones of local over-concentration in solution, respectively of the monomer and of the hydrogen peroxide, favoring the formation of macromolecular chains of average and low DPn. 
     It has now been discovered that it is possible through an appropriate choice of the alcoholic diluent to influence the unior multimodal repartition of the obtained polymers. 
     Thus, the composition and DPn of the polymers obtained by the process of the invention are different as on the one hand the monomer is polymerized in the presence of hydrogen peroxide and of an alcohol, said alcohol being a bad solvent of hydrogen peroxide but a good solvent of the monomer and polymer, or on the other hand the polymer is polymerized in the presence of hydrogen peroxide and of an alcohol, said alcohol being a good solvent of hydrogen peroxide and monomer but bad solvent of the polymer. 
     When the alcoholic diluent is a good solvent of hydrogen peroxide and monomer but a bad solvent of polymer, the GPC shows the existence, in the case of polymethylmethacrylate, of two, sometimes three or even four types of products clearly characterized by the length of chain: a fraction of low average molecular weight comprised between about 500 and about 2000, according to the quantity of the ingredients in the original reaction mixture, these products are called &#34;oligomers&#34;; a fraction of higher average molecular weight comprised between about 1000 and about 50,000, called polymers; moreover, it has sometimes been put in evidence the production of &#34;High Polymers&#34; of about 340,000 average molecular weight or &#34;low oligomers&#34; of about 400 average molecular weight. 
     On the contrary, when the alcoholic diluent is a bad solvant of hydrogen peroxide, but a good solvent of monomer and polymer, a bi- or unimodal repartition may be reached, the average molecular weight of the obtained polymers being increased. 
     Thus it will be possible for a man skilled in the art to obtain the required oligomers or polymers by using the process of the invention and by selecting a suitable alcohol diluent. 
     As a diluent, it is possible to use any alcohol, aliphatic or cyclic, which is liquid under the conditions of the experiment, such as, for example, methanol, ethanol, isopropanol, tertiary amyl alcohol, ter-butyl alcohol, cyclo hexanol, n-butanol, hexanol and the like. Methanol constitutes the preferred diluent. A mixture of the precited alcohols may be used. 
     In the case of poly(methyl methacrylate) for example, the following alcohols may be used as diluent medium being a solvent of the polymer and a bad solvent of hydrogen peroxide: all the aliphatic or cyclic C 4 , C 5  or C 6  . . . alcohols such as n-butanol, tert-butyl alcohol, tertiary amyl alcohol, hexanol, cyclohexanol, 2-butanol and the like. A mixture of two or more of these alcohols may be used. 
     The polymerization reactions are carried out preferably at ordinary temperature for the liquid monomers, for example between 10° and 20° C., and at boiling point for gaseous monomers. The technician skilled in the art will understand that, in the case of gaseous monomers, the polymerization can be carried out if necessary at ordinary temperature under pressure. 
     It is possible to use hydrogen peroxide with any concentration of perhydrol; preferably 110 or 130 volume hydrogen peroxide is used. 
     The hydrogen peroxide can be introduced in any proportion into the reaction mixture; generally, between 5 and 15% of hydrogen peroxide is used. 
     The concentration of the monomer may be at least of about 10% in weight of the reaction mixture. 
     The concentration of the diluent is always the complement to 100 of the hydrogen peroxide and of the monomer. 
     The UV radiation may be obtained, notably, from a low-pressure mercury vapor lamp, for example of the PCQ 9Gl type, manufactured by &#34;Ultra-Violet Products Inc&#34; (San Gabriel, California)80% of the energy provided of which corresponds to a wavelength of 2537 A and whose power is 2.5 Watts. This lamp may be for example dipped into the reaction medium. The tube of the lamp may be enclosed in a quartz tube, in order to obtain better exposure of the reaction mixture to the UV radiation. 
     It is another object of the present invention to provide oligomers and polymers obtained by the polymerization of monomers containing at least one ethylenic linkage in the presence of hydrogen peroxide under the effect of UV radiation in a diluent medium comprising essentially an alcohol. 
     These oligomers and polymers are hydroxytelechelic and have a number average weight comprised respectively between about 100 and about 2,000 and between about 2000 and about 1,000,000 in the case of polymethylmethacrylate. 
     The oligomers and polymers may be separated by any method known in itself and, for example, by a solvent/non solvent mixture such as, for example, a 15:85 benzene-methanol mixture by volume or a 15:25 by volume mixture of chloroform-ether. 
     EXAMPLES 
     Table IX below gives by way of example the molecular weight of some polymers and oligomers obtained by the process according to the invention and compares these weights with those obtained by the previously-used process of heat polymerization. It is evident that the weights of the oligomers obtained by the effect of UV radiation are notably less; thus, it is possible in certain cases to obtain dimers or trimers. 
     The number of hydroxyl groups may be determined by several methods; for example, NMR or determination by the action of acetyl chloride, may be mentioned. 
     Thus, the determination can be carried out from the NMR spectrum by the action of trifluoroacetic acid or by the reaction of the alcohol with trimethylchlorosilane. 
     It is also possible to carry out a determination with soda after reaction of the alcohol with acetyl chloride. 
     The results obtained are brought together in Table X below. It will be noted that the results obtained by the first method are systematically superior to those obtained with the two other methods. 
    
    
     The following examples of polymerisation are intended to illustrate the invention, and not to be limiting in any way. 
     EXAMPLE 1 
     40 g of methyl methacrylate were polymerized in the presence of 10 g of 110 volume hydrogen peroxide in 50 g of methanol. 
     The reaction was carried out at 18° C. in the presence of ultra-violet radiation emitted by a PCQ 9Gl lamp provided with a quartz tube and with stirring. 
     
                       TABLE IX______________________________________      Polymerization      under the effect of                  Polymerization      ultra-violet                  by heat (at      radiation   120° C. for 4 hours)      vapor pressure                  vapor pressure      osmometry   osmometryMonomer       Mn--   Solvent    Mn-- Solvent______________________________________isoprene     360     toluene   1500  toluenedimethyl-2,3 buta-        360     toluene   1500  toluenedienebutadiene    200     Et CO Me  700   tolueneisobutene    120     Et CO Mebutene-2     160     Et CO Me  285   THFmethyl acrylate        1100    Et CO Me  12,000                                toluenemethyl methacrylate        20,000  toluene   100,000                                toluenemethacrylonitrile        260     Et CO Meα-methyl styrene        240     toluene______________________________________ 
    
     
                                           TABLE X__________________________________________________________________________     DETERMINATION OF THE HYDROXYL GROUPS     by nuclear magnetic resonance     Direct      Indirect NMR by CLSi                             by acetylation     NMR by TFA ac.                 (CH.sub.3).sub.3                             by CH.sub.3 CO Cl          Amount OH/  Amount OH/  Amount OH/MONOMER   Solvent          mole   Solvent                      mole   Solvent                                  mole__________________________________________________________________________isoprene  DC Cl.sub.3          2      HCCl.sub.3                      0.3    EtCOMe                                  1.9dimethyl-2,3     DC Cl.sub.3          4      HCCl.sub.3                      1.4    toluene                                  1.4butadienebutadiene DC Cl.sub.3          2      HCCl.sub.3                      0.3    EtCOMe                                  1.8isobutene 1     DC Cl.sub.3          4.5    HCCl.sub.3                      1.6    EtCOMe                                  1.6isobutene 2     DC Cl.sub.3          3      HCCl.sub.3                      0.7    EtCOMe                                  1.2isobutene 3     DC Cl.sub.3          2.4    HCCl.sub.3                      0.2    EtCOMe                                  0.8butene-2  DC Cl.sub.3          3      HCCl.sub.3                      0.7    EtCOMe                                  1.1methyl acrylate     DC Cl.sub.3          --     HCCl.sub.3                      0.7    EtCOMe                                  0.1methyl methacrylate     DC Cl.sub.3          5      benzene                      1.1    toluene                                  1.1methacrylonitrile     DC Cl.sub.3          1.6    HCCl.sub.3                      1.2    EtCOMe                                  1α-methyl-styrene     DC Cl.sub.3          0.7         --Butene-2 isobutene     DC Cl.sub.3          2      HCCl.sub.3                      1.8    EtCOMe                                  1.4copolymer__________________________________________________________________________ 
    
     The reaction lasted 3 hours. 
     In this way, 20 g of a polymer was obtained, having an average weight Mn=15,970 and 8 g of an oligomer of average weight Mn=524. 
     These macromolecules were hydroxytelechelic and possessed an average number of OH groups per molecule equal to 1.3 (measured by silylation). 
     It has now been studied the polymerization of methylmethacrylate from the mixture [hydrogen peroxide (110 vol)--methyl methacrylate-methanol] U.V. (2537 A) at room temperature. 
     The evolution of the conversion rates, average molecular weights, polydispersity indexes of polymers and oligomers, average number of OH/mole of oligomers, was studied as a function of the reaction duration, and the results are brought together in table I. 
     
                                           TABLE I__________________________________________________________________________                                 average num-                                 ber of OH/reaction                              mole of oli-duration,conversion rates               Mn (GPC)--                      I polydispersity                                 gomer (si-hourspolymers     oligomers           polymers                oligomers                      polymers                           oligomers                                 lylation)__________________________________________________________________________1    12   3     16610                683   2.76 2.27  1.22    29   7     16826                817   2.77 3.46  0.93    45   11    15970                524   2.86 3.25  1.55    83   17    17232                529   2.93 2.36  1.07    85   15    15471                428   3.15 2.25  0.9__________________________________________________________________________ 
    
     It has now been studied the polymerization of methyl methacrylate from the mixture [hydrogen peroxide (110 vol)--methyl methacrylate-methanol]-U.V. (2537 A) during four hours at room temperature. 
     It was studied the evolution of the conversion rates, average molecular weights, polydispersity indexes of polymers and oligomers, and of molecular weight at the top of the GPC peak of each simple fraction, as a function of the hydrogen peroxide quantities. Reaction mixture (mixture H 2  O-H 2  O 2  (110 vol): 6.7 g--methyl methacrylate: 20 g-methanol: 40 g The results are brought together in table II. 
     
                                           TABLE II__________________________________________________________________________                 I (GPC)Hydrogen conversion      polydispersity                         Ms weight at the topperoxide rates (GPC)           Mn (GPC)--                 index   of the GPC peak110 vol oli-     poly-         oli-             poly-                 oli-                     poly-                         oli- poly-g     gomers     mers         gomers             mers                 gomers                     mers                         gomers                              mers__________________________________________________________________________0     --  --  --  --  --  --  --   --1     2.5 19   1158             45564                 2.22                     3.05                         400 and                              60000 and                         2100 3400002     3.5 23.5         928 39140                 2.02                     3.25                         400 and                              49999 and                         1750 3300003     6.5 43  760 36284                 1.79                     4.6 400 and                              40000 and                         1200 340000__________________________________________________________________________ 
    
     It was studied the evolution of the conversion rates of polymers and oligomers, the average number of OH/mole of oligomer, as a function of the percentage in monomer. The reaction mixture comprised: hydrogen peroxide (110 vol): 10% in weight; methyl methacrylate; methanol, UV. 2537 A). 
     The results are brought together in table III. 
     
                       TABLE III______________________________________                           average number                conversion of OH/molemethyl metha-        rates (GPC)                           of oligomercrylate % in     methanol   poly-  oli-  sily- acety-weight    % in weight                mers   gomers                             lation                                   lation______________________________________10        80         26     42    0.7   0.820        70         48     22    1.4   0.830        60         56     19    1.3   0.540        50         50     20    1.3   1.150        40         69     15    0.9   0.260        30         77     13    1.2   0.970        20         82     15    1.9   0.680        10         82     14    2.2   1.290         0         50     10    --    --______________________________________ 
    
     It was studied the evolution of the average molecular weights (Mn), polydispersity indexes (I) of oligomers and polymers and of weights (Ms) of simple fractions of oligomers and polymers at the top of the peak of GPC, as a function of the percentage in monomer. The reaction mixtures comprised: hydrogen peroxide (110 vol): 10% in weight; methyl methacrylate; methanol, U.V. (2537 A). The results are brought together in table IV. 
     
                                           TABLE IV__________________________________________________________________________methyl me-             Ithacrylate      Mn (GPC)--                  polydispersity                          Ms% in    methanol          poly-              oli-                  poly-                      oli-                          poly-                              oli-weight  in weight          mers              gomers                  mers                      gomers                          mers                              gomers__________________________________________________________________________10      80     3270              334 4.42                      1.3 3350                              25020      70     7728              407 3.89                      1.4 10500                              38030      60     11622              490 3.13                      1.6 16500                              42040      50     18994              524 2.5 2.2 24000                              95050      40     30140              919 1.2 2.2 28000                              122060      30     20488              936 2.1 2.7 30000                              152070      20     31732               1446                  2.2 3.3 49000                              175080      10     37873               1695                  2.4 3.7 65000                              217090      0      48034               2441                  2.8 4.2 73000                              3124__________________________________________________________________________ 
    
     EXAMPLES 2 to 19 
     The following monomers were polymerized by the process of the invention. 
     
                       TABLE V______________________________________LIST A            LIST B______________________________________acrylic acid      isoprenemethacrylic acid  dimethyl-2,3-butadieneacrylamide        butadieneacrylonitrile     isobuteneethyl acrylate    butene-2vinyl acetate     methyl acrylatestyrene           methyl methacrylatevinyl chloride    methacrylonitrile             α-methyl styrene______________________________________ 
    
     The monomers of list A might be polymerized as indicated in table VI hereinafter, that is to say without H 2  O 2  ; in this case it is evident that hydroxytelechelic polymers would not be obtained. 
     On the contrary, the monomers of list B imply the use of H 2  O 2  for polymerizing through U.V. photolysis process according to the present invention. 
     
                                           TABLE VI__________________________________________________________________________reaction mixture % in weight                      reaction                           global H.sub.2 O.sub.2              metha-  duration                           conversionMonomer (110 vol)      H.sub.2 O         monomer              nol T °C.                      (minutes)                           rates remarks__________________________________________________________________________vinyl 10   -- 50   40  24  16   75    colorlessacetate 30   -- 40   30  24  22   85    viscous --   10 30   60  24  10   90    liquid - -- -- 30 70 24 24 60 --   -- 100  --  24  24   70styrene 10   -- 20   70  16  27   38 10   -- 20   70  2   22   30    yellow --   10 20   70  16  22   20    oilvinyl 20   -- 30   50  -14 1.00 2chloride --   20 30   50  -14 0.20 2     white --   -- 50   50  -14 0.20 2     powder --   -- 100  --  -14 0.10 2acrylic 10   -- 20   70  17  22   90    whiteacid  --   10 20   70  17  7    75    powdermethacry- 10   -- 20   70  16  22   88    whitelicacid  --   10 20   70  16  22   90    powder --   -- 30   70  16  22   90 --   -- 100  --  16  3    100acrylamide 10   -- 20   70  11  22   100   viscous --   10 20   70  11  22   100   colorless                                 liquidacryloni- 10   -- 50   40  14  2    7     whitetrile --   10 50   40  14  2    7     powder --   -- 50   50  14  2    9 --   -- 100  --  14  2    7ethyl 10   -- 40   50  13  5    100   coloressacrylate --   10 40   50  13  0.10 100   viscous --   -- 60   40  13  0.10 100   liquid --   -- 100  --  15  0.05 100isoprene 10   -- 20   70  14  22   30    yellow 10   -- 50   40  14  22   15    oil --   10 20   70  14  22   8 --   -- 50   50  14  22   6 --   -- 100  --  14  22   1dimethy 10   -- 20   70  25  22   452,3-  --   10 20   70  25  22   3     yellowbutadiene --   -- 40   60  25  22   5     oil --   -- 100  --  25  22   3butadiene 10   -- 20   70  14  17   12    colorless 20   -- 30   50  -7  17   17    oil --   20 30   50  -7  17   0.3 --   -- 30   70  -7  17   0.5 --   -- 100  --  -7  17   0.2isobutene 20   -- 30   50  -3  22   20 20   -- 30   50  -12 22   20 --   20 30   50  -3  22   0.2   colorless --   20 30   50  -12 22   0.2   oil --   -- 30   70  -12 22   0.2 --   -- 100  --  -12 22   0butene-2 20   20 30   50  4   22   10    colorless --   -- 20   80  4   22   0.7   oilmethyl 10   -- 20   70  13  7    95    colorlessacrylate --   10 20   70  13  22   0     viscous --   -- 20   80  13  22   0     liquid --   -- 100  --  13  22   0methyl 10   -- 40   50  18  22   55    whitemethacry- --   10 40   50  18  22   3     powderlate  --   -- 40   60  18  22   4 --   -- 100  --  18  22   0methacry- 10   -- 20   70  13  22   90    yellowlontrile --   10 40   50  13  22   9     oil --   -- 50   50  13  22   4 --   -- 100  --  13  22   4α-methyl 10   -- 20   70  16  22   15    yellowstyrene --   10 20   70  16  22   0     oil --   -- 30   70  16  22   0 --   -- 100  --  16  22   0__________________________________________________________________________ 
    
     It was studied the influence of the kind of the alcoholic diluent on the repartition of molecular weights, conversion rates, average molecular weights and polydispersity indexes, by comparison with methyl methacrylate when polymerized from a simple mixture (H 2  O 2  -monomer-methanol-U.V.) 
     EXAMPLE 20 
     Polymerization of methyl methacrylate from the reaction mixture (H 2  O 2  -methyl methacrylate cyclohexanol; U.V. (2537 A); Reaction durational hour. 
     
                                           TABLE VII__________________________________________________________________________Composition of the reactionmixture % in weightmethyl     ConversionH.sub.2 O.sub.2methyacry-      cycloho-           rates   Mn GPC--  Polydispersity index(110 vol)late  xanol           olig.              polym.                  global                      olig.                         polym.                             global                                 olig.                                    polym.__________________________________________________________________________10   20    70   9  32  7936                      1971                         26208                             5.73                                 1.47                                    2.0310   50    40   2  28  27116                      2442                         45320                             3.80                                 1.51                                    2.0610   70    20   1  19  38373                      5340                         76387                             3.71                                 1.36                                    2.31__________________________________________________________________________ 
    
     EXAMPLE 21 
     Polymerization of methyl methacrylate from the reaction mixture H 2  O 2  -methyl methacrylate-tertio amyl alcohol; UV (2537 A). 
     
                                           TABLE VIII__________________________________________________________________________Composition of the reactionmixture % in weightmethyl      ConversionH.sub.2 O.sub.2methacry-   rates   Mn GPC--  Polydispersity index(110 vol)late  t. am. OH            olig.               polym.                   global                       olig.                          polym.                              global                                  olig.                                     polym.__________________________________________________________________________5    60    35    1.6               22.3                   23898                       2220                          46628                              3.90                                  1.43                                     2.15__________________________________________________________________________