Method for making odorless aqueous solutions of water soluble po

Details Method for making odorless aqueous solutions of water soluble po Method for making odorless aqueous solutions of water soluble po

1988-02-08

1989-06-13

Schofer, Joseph L.

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...

524831, 526 86, 526 93, 526 94, C08L 3100

Patent

active

048394173

DESCRIPTION:

BRIEF SUMMARY
The invention relates to water-soluble polymers and copolymers of acrylic and/or methacrylic acid of low to medium molecular weight, a process for their production, and their use in aqueous systems.


THE PRIOR ART

The polymerization of acrylic or methacrylic acid, optionally together with comonomers copolymerizable therewith, in aqueous solution to the corresponding aqueous solutions is a standard procedure. (See Houben-Weyl, Methoden der orgnischen Chemie, vol. 14/1, 1019-21.) The polymerization can be initiated at from 80.degree. to 90.degree. C. with potassium or ammonium persulfate or at room temperature or slightly higher temperature with redox systems such as potassium persulfate and sodium hydrosulfite.
Moreover, it is known to add water-soluble mercaptans such as thioglycolic acid as chain-transfer agents in the production of such polymers of low molecular weight.
It is difficult to produce polymers of specific molecular weight reproducibly by this process. The properties of polymers are markedly dependent on their molecular weight, and even minor fluctuations during production will therefore result in products with varying properties. To assure better reproducibility of the properties, European Pat. No. 127,388 proposes to fractionate polymers of acrylic acid obtained in aqueous solution on the basis of the molecular weight, which, however, necessitates an additional process step after polymerization.


THE OBJECT AND THE INVENTION

The invention has as its object the production of polymers of predetermined molecular weight of acrylic and/or methacrylic acid or of copolymers of these acids with other monomers copolymerizable therewith. Moreover, it is sought to avoid the unpleasant odor which polymers of low to medium molecular weight produced with mercaptans usually have.
It has been found that the polymerization of acrylic or methacrylic acid or the copolymerization of not less than 50 mole percent of acrylic and/or methacrylic acid with not more than 50 mole percent of one or more other monomers copolymerizable therewith, based in both cases on the mole total of the polymerizable monomers, in aqueous solution will yield in a readily reproducible manner a water-soluble polymer of predetermined molecular weight when the polymerization is initiated with a redox system of hydrogen peroxide, a water-soluble iron salt and a water-soluble mercaptan.
The reduced viscosity of the polymer being formed, which is a measure of the magnitude of the average molecular weight or of the degree of polymerization, has been found to be only slightly dependent, if at all, on the amount of hydrogen peroxide used, which renders the process largely insensitive to variations in the hydrogen peroxide concentration.
On the other hand, there is a definite and reproducible dependence of the reduced viscosity on the amount of the water-soluble mercaptan. This dependence extends all the way down to molecular weights of a few thousand, as is apparent from the table which follows. Molecular weight (weight or number average) of poly-acrylic acid produced in a 50% aqueous solution in the presence of from 1.5 to 7.5 wt. % hydrogen peroxide, 0.005 wt. % ferrous sulfate and from 1 to 5 wt. % mercaptoethanol (all based on acrylic acid) at an initial temperature of 20.degree. C. All molecular weights are based on a gel permeation chromatography calibration curve constructed on the basis of the sodium salt of polyacrylic acid.


______________________________________ Molecular Weight Mercapto- Hydrogen Weight Number Non- ethanol peroxide average average uniformity ______________________________________ 0.5 1.5 57,000 18,000 2.3 1 3.3 28,100 11,200 1.5 2 3.3 14,600 5,360 1.73 5 3.3 4,940 1,460 2.39 7 4.5 3,360 1,860 0.81 10 4.5 2,300 1,350 0.70 20 7.5 1,250 770 0.61 ______________________________________
The relatively slight nonuniformity is an advantage that benefits the specific effectiveness.
While it is known that low-molecular-weight polymers can be produced by the use of mercaptans, the re

REFERENCES:
patent: 2380475 (1945-07-01), Stewart
patent: 2471938 (1949-05-01), Crouch et al.
patent: 3080347 (1963-03-01), Sandberg et al.
patent: 4095035 (1978-06-01), Lamberti et al.
patent: 4282340 (1981-08-01), Anchor et al.

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