Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-12-31
2004-09-28
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S340000, C525S369000
Reexamination Certificate
active
06797785
ABSTRACT:
This invention relates to the technical sector of synthetic agents characterized by flocculating and/or coagulating action.
The invention relates specifically to the technical sector of synthesis and applications of polyvinylamines (PVA).
In particular, the invention relates to applications of such PVAs in manufacture of paper and especially for production of paper or cardboard sheets exhibiting an array of interesting properties.
The invention also relates to application of PVAs in the water treatment industry and to the area of petroleum and parapetroleum activities.
The invention also relates to all known applications of flocculants and coagulants.
GENERAL PRIOR ART
During manufacture of paper, cardboard, or the like, or in preparation of fluids for petroleum or parapetroleum use, or in treatment of waste water, specifically “municipal” waste water containing urban waste, use of flocculant and/or coagulant agents is well known, especially retention agents of the polymer type whose function it is to retain a maximum of fines and charges in a sheet of paper, or again flocculation/coagulation agents whose function it will be to flocculate waste suspended in waste water, etc.
In the area of paper the beneficial effects resulting from a retention agent are essentially:
increase in production and lowering of manufacturing costs: energy savings, smoother running of the machine, higher yield of fibers, fines, charges, and anionic upgrading products, lower acidity in the circuit combined with decreased use of aluminum sulfate and accordingly fewer corrosion problems;
improvement in quality: better formation and better look-through; improvement in moisture content of the sheet, opacity, breaker stack, absorptivity, and decrease in the porosity of paper.
Polymers were introduced as flocculants about forty years ago, with the molecular weights which were relatively low at the time. U.S. Pat. No. 3,235,490 (Goren) describes various gel polymers.
Certain Goren polymers have been used as coagulants, especially for the purpose of coagulating very fine solids in suspension.
The addition of bentonite to the paste was proposed long ago; it may be added to other mineral products such aluminum sulfates, even synthetic polymers, in particular polyethylene imine (see, for example, documents DE-A-2 262 90s and U.S. Pat. No. 2,368,635).
Document U.S. Pat. No. 3,052,595 proposed combination of bentonite with a polyacrylamide with an essentially linear characteristic. This process was found to compete with systems easier to apply while being characterized by performance just as high. In addition, even with the current linear polyacrylamides, the retaining power is still insufficient.
Document EP-A-0 017 353 proposes combination of a non-ionic to slightly anionic copolyacrylamide with bentonite for retention of low-charge pastes (maximum of 5% of charges). This process makes hardly any progress, since these polymers are relatively low-performing with respect to retention, in particular charged pastes, undoubtedly as a result of insufficient synergy between these polymers and bentonite, which has little tendency to recoagulate.
Document EP-A-0 235 893 proposes resort to cationic polyacrylamides of molecular weight higher than one million, thirty million or more, essentially linear polyacrylamides. In this way a retention effect is obtained which is certainly satisfactory but still deemed insufficient in application to paper, since bentonite entails difficulties during subsequent treatment of effluents at the machine outlet, and users select this system only if there are significant advantages.
In notes presented in connection with a course in Seattle, 11-13 October 1989, and published with the title “Supercoagulation in the control of wet end chemistry by synthetic polymer and activated bentonite,” R. Kajasvirta described the mechanism of supercoagulation of activated bentonite in the presence of a cationic copolyacrylamide, without specifying the exact nature of the mechanism. This process entails the same disadvantages as the one referred to in the preceding paragraph.
Lastly, EP 0 574 335 has disclosed an important improvement, use of branched polymers (polyacrylamides in particular) in powder form.
Also known in the prior art are systems of retention agents for manufacture of a sheet of paper, cardboard, or the like which consist of a combination of two retention agents, generally a primary retention agent and a secondary retention agent. What is involved in this instance is a system qualified as “dual.”
Patent U.S. Pat. No. 4,753,710 thus advocates use of a linear acrylic polymer of high molecular weight as primary retention agent which is added to the fibrous mass, then shearing, particularly in the mixing pump or “fan pump,” and then addition of bentonite (which is a swelling clay) as secondary retention agent.
In the area of waste water treatment there are, for example, patents EP 0 202 780 or EP 0 201 237, the teachings of which overlap. In this industry effort is applied to achieve clearness of water, an imperative for customer satisfaction, but also the greatest degree of dryness possible of the residue obtained and separated, since gain even of a minimal degree of dry content represents enormous savings in transportation of residues because of the smaller amount of water which has to be hauled.
Also of the state of the art among other polymers is polyethyleneimine or PEI, which is one of the oldest synthetic cationic flocculants. PEI is often used to treat industrial or municipal waste, but above all as draining and retention agent in the paper industry (the reference being to “polymin SK”™).
Use of PVA or polyvinylamine, especially in the sphere of paper, has also been proposed in the prior art. PVA is known to form a structure of flakes both very solid and of small dimension, one including little bound moisture.
Patent BASF DE 44 09 903 describes a process of PVA synthesis which is applied at around 40° C. and which yields a gel which is then dispersed in methanol. The polymerization system employs a pure azoic catalyst; no redox system is in operation in accordance with the technique described. In addition, the process is very slow and highly complex.
The patent Mitsubishi JP 07 118 333 discloses polymerization by precipitation based on solution in a solvent of the methanol type. The process is slow and complex because of the constraints associated with use and recirculation of a solvent.
Patent Mitsubishi GB 2 308 123 discloses a complex process of precipitation by PEG (polyethylene glycol) and hydrolysis of the solution obtained on the basis of the resulting product.
These two patents utilize pure azoics.
Also known is the patent Mitsui JP 0 628 7232, which also discloses use of an azoic catalyst.
Patent BETZ Canada 2110366 uniquely describes polymerization in solution with a pure azoic system and an application as coagulant.
Other documents (among others, GRACE) describe a bentonite paper application combined with a PVA and a polyacrylamide.
Patent BETZ U.S. Pat. No. 5,292,441 describes a process of PVA quaternization.
The patent BASF U.S. Pat. No. 5,290,880 describes a PVA synthesis which utilizes initiation of polymerization at 25-80° C. by a complex redox system combined with an azoic catalyst, with heavy mechanical constraints such as mixture constraints with prepolymerization. All the examples include initiation which is conducted only with a pure azoic, at a temperature of the order of 60° C. According to this document polymerization is carried out at a temperature which may reach 150° C.
This patent is to be compared to patent U.S. Pat. No. 4,808,683, which claims polymerization at temperatures ranging from 30 to 100° C., with examples around 60°, or again patent U.S. Pat. No. 4,421,602, which specifies polymerization by means of a complex redox initiator system combined with an azoic, with polymerization temperatures of 30 to 140° C., with examples at 40, 50, and 60° C.
There is also patent EP 0 220 603, which describes conduct of PVA synthesis in supercritical CO2.
As is to
Hund Rene
Jehn-Rendu Christian
Arent & Fox PLLC
Lipman Bernard
SNF S.A.
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