Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1986-02-04
1987-11-10
Kight, John
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524733, 524734, 527300, 527312, 527313, 527314, C08J 302, C08G 8300
Patent
active
047058250
DESCRIPTION:
BRIEF SUMMARY
It is known to make substantially homogeneous polymeric products comprising units of polymerised ethylenically unsaturated monomer and polysaccharide units (often gelatinised polysaccharide units) by polymerising the monomer in the presence of the polysaccharide.
Depending upon the process conditions it is possible for the product to include homopolymer together with a graft polymer of the monomer and the polysaccharide but, as explained in U.S. Pat. Nos. 3,332,897 and 4,322,472, the presence of substantial amounts of the homopolymer has generally been regarded as undesirable. Accordingly the normal procedure has been to conduct the polymerisation in the presence of initiators such as ceric or other multivalent ion that will promote graft polymerisation rather than homopolymerisation. For instance in U.S. Pat. Nos. 3,332,897 polymerisation is conducted in the presence of ceric ion. In U.S. Pat. No. 4,322,472 polymerisation is conducted in the presence of cupric or ferric salts. In a comparative example it is shown that when polymerising in the presence of large amounts of sodium nitrate together with ammonium persulphate and sodium metabisulphite the addition of cupric or ferric salt reduces the solution viscosity, indicating reduced amounts of homopolymerisation. However even in the comparative example in which cupric and ferric or other polyvalent metal salt is not used the solution viscosity is still very low (a 45% solution having a viscosity of 4,000 cps measured on a Brookfield viscometer no. 2 spindle, 10 rpm 90.degree. C.).
The polysaccharide is generally ungelatinised before the polymerisation and so polymerisation can be conducted on an aqueous dispersion of ungelatinised polysaccharide particles in aqueous monomer. Generally the temperature of the reaction mixture is held below the gelatinisation temperature. Thus in U.S. Pat. No. 3,332,897 (that utilises ceric ion as a grafting initiator) it is warned that it is best not to exceed the gelatinisation temperature, to avoid possible degradation of polysaccharide.
Despite this warning against conducting polymerisation and gelatinisation substantially simultaneously some processes have been described in which it is required. In U.S. Pat. No. 3,640,925 combined gelatinisation of polysaccharide and graft polymerisation is achieved by rapidly heating an aqueous slurry of ungelatinised starch, monomer and initiator. For instance a slurry of about 5% ungelatinised starch, about 0.5% acrylamide, about 95% water, copper sulphate and peroxide initiator is substantially instantaneously heated in a starch cooker to cause gelatinisation and graft polymerisation. The product is described as a paste having 100% graft polymerisation.
In U.S. Pat. No. 4,322,472 a slurry is formed of, for instance, about 50% water, about 30% ungelatinised starch, about 7 to 10% acrylamide, cupric or other graft polymerisation initiator (except in the comparative example) and ammonium persulphate and sodium metabisulphite in amounts, respectively, of about 0.16% and 0.1% based on the weight of starch. Steam is injected into the slurry to heat it rapidly to about 95.degree. C. in order to simultaneously gelatinise the starch and form the graft copolymer, although products having solution viscosities of 780 to 4,000 cps (as measured above) are said to contain a substantial amount of homopolymer. These products are pourable liquids. The highly oxidising initiator system and the other conditions prevailing in the reaction will probably have caused significant chemical degradation of the starch and will have resulted in any homopolymer chains being of low molecular weight.
It is also known to conduct polymerisation of monomer on to starch that has previously been gelatinised. Thus graft polymerisation in the presence of ceric ion on previously gelatinised starch is described in U.S. Pat. No. 4,400,496. Since gelatinised starch that has not been chemically degraded by oxidation, acid hydrolysis or other adverse reaction forms a very viscous solution and since it is necessary to mix the mo
REFERENCES:
patent: 3640925 (1972-02-01), Touzinsky et al.
patent: 3966696 (1976-06-01), Kidoh et al.
patent: 4322472 (1982-03-01), Kaspar et al.
patent: 4552938 (1985-11-01), Mikita et al.
Langley John
Mistry Kishor K.
Symes Kenneth C.
Allied Colloids Limited
Kight John
Nutter Nathan M.
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