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...
Reexamination Certificate
2000-06-02
2001-08-28
Pezzuto, Helen L. (Department: 1713)
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...
C524S420000, C524S423000
Reexamination Certificate
active
06281276
ABSTRACT:
The present invention relates to polymer compositions, and in particular to compositions of thermoplastic polymer with a by-product of a pulp and paper mill that is known in the trade as smelt. Smelt may also be referred to in the trade as “top ash”, “precipitator ash” or “recovery boiler residues”, all of which are referred to herein as smelt.
One of the by-products of a pulp and paper mill is a mixture of inorganic chemicals that are primarily salts of sodium. The by-product is known as smelt, as discussed above, and is regarded as an environmentally hazardous mixture of inorganic chemicals. Typical examples of such chemicals are sodium carbonate, sodium sulphide, sodium sulphate and sodium chloride. Salts of potassium and/or magnesium may also be present
The by-product i.e. smelt, is typically disposed of in a landfill and environmentally more acceptable methods of disposal of smelt would be worthwhile.
In an landfill, or in other locations, smelt will come in contact with moisture. Such moisture results in chemical reactions, such as the alkaline hydrolysis of the sodium and potassium carbonate and sodium sulphide. The latter is frequently accompanied by the generation of gaseous hydrogen sulphide.
Chemical substances that are alkaline in nature, when mixed into at least some polymers, tend to adversely affect the physical properties of the polymer.
In particular, depending on the type of polymer, alkaline substances have a tendency to cause degradation of the polymer.
Polymer compositions of plastics with smelt as a filler, a foaming agent, or a stabilizer, or other component, have now been found, and such compositions have useful properties.
Accordingly, the present invention provides a composition of polymer and smelt, especially a composition of thermoplastic polymer and smelt.
In preferred embodiments of the composition of the present invention, the smelt acts as a filler, a foaming agent and/or as a stabilizer for the polymer.
In another embodiment, the polymer is a thermoplastic polymer.
In further embodiments of the invention, the polymer is selected from polyolefin, polyamide, polyurethane, polyester, polycarbonate, acrylic polymers and elastomers.
In a still further embodiment, the composition additionally contains a mono- or polyfunctional organic acid.
The present invention relates to the use of smelt in polymer compositions. As used herein, “smelt” refers to an incinerated pulping and bleaching liquor from the pulp and paper industry, that has been concentrated by thermal evaporation followed by recovery boiler combustion. In particular, the liquor is from so-called Chemi-Thermo-Mechanical Pulp (CTMP) and peroxide bleaching. The smelt collected as solid plaques at the bottom of the recovery boiler tends to be grey/pink in colour when dry and grey/blue in colour in the presence of water. For use in plastics, the solid plaques must be ground to a suitable mesh size. The precipitator ash, or top ash, collected at the top of the boiler is a very fine, white color powder, generally having a particle size less than 100 mesh.
In examples of smelt, the composition may be as follows: sodium carbonate 30-99% by weight, potassium carbonate 0.01-10% by weight, sodium sulphate 0.5-30%, sodium sulphide 0.01-20% by weight, sodium chloride 0-5% by weight and water-insoluble chemicals, including silicates, oxides or organic material 0-40% by weight, with the balance typically being other chemicals, including magnesium compounds. However, it will be understood that the composition of smelt from a particular pulp and paper mill will vary and further variations may be expected from one mill to another, especially where the mills are operated by different companies or utilize different procedures.
The polymer of the polymer composition is a thermoplastic polymer. Examples of such polymers include polymers or copolymers of olefin monomers including ethylene, propylene, vinyl chloride, styrene, butylene, isobutylene, and vinyl acetate. Other polyolefins may be used. In addition, the thermoplastic polymer may be a copolymer of acrylic monomers such as acrylic acid, and ionomers thereof, including sodium acrylate and acrylic esters e.g. methyl and ethyl acrylate, methyl or ethyl methacrylate, and ethylene/acrylic acid (EAA) copolymers. Copolymers of acrylic monomers with olefines and vinyl monomers are also included, e.g. ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, acrylonitrile-butadiene-styrene polymers. Elastomeric copolymers or terpolymers of olefines may be used, such as ethylene-propylene elastomer, ethylene-propylene-diene (e.g. butadiene) elastomer e.g. EPDM polymers. In addition the thermoplastic polymer may be a polycondensation product such as polyamides, polyurethanes, polyesters and polycarbonates. Examples of polyurethanes are condensation products of polyisocyanates and a hydroxyl-containing material, including polymers of hexamethylene disocyanate and 1,4-butanediol. Examples of polyamides are polymers of lactams and amino carboxylic acids and polymers of dicarboxylic acids and diamines, including nylon 6, nylon 11, nylon 12, nylon 6,6, nylon 6,10, nylon 12,12 and the like. Examples of polyesters are polymers of dicarboxylic acids and dihydroxy compounds including polyethylene terephthalate and polybutylene terephthalate. The polymer composition may contain one polymer or a mixture of two or more polymers as the final application requires. The polymers are of a molecular weight that is typical of polymers that are used in melt processing apparatus.
The amount of smelt that may be incorporated into the polymer may be varied over a wide range. For instance, the amount of smelt may be up 90% by weight of the polymer. The upper limit on the amount of smelt in the polymer is primarily governed by the ability to incorporate the smelt into the polymer in melt processing apparatus. For example, the amount of smelt may be in the range of 1-90% by weight, and in preferred embodiments is in the range of 10-75% by weight and especially in the range of 25-60% by weight. polymer in Other additives may be incorporated into the polymer in addition to the smelt. For instance, the polymer may contain up to about 50%, preferably up to 36% and especially up to about 25% by weight of other additives such as organic acids as well as plastifiers, stabilisers, pigments, and fillers or colorants. The organic acids may be mono or polyfunctional organic acids having one, two or three carboxylic acid functional groups. Examples of such organic acids include oxalic acid, tartaric acid, citric acid, malic acid, maleic acid, malonic acid and succinic acid. When the smelt is used for foaming, acid has to be added to the composition. This amount of acid depends on the type of the acid and can be up to 50% by weight.
As noted above, smelt is a by-product of the pulp and paper industry, and is regarded as being primarily a mixture of inorganic chemicals. Typical chemicals found in smelt include sodium carbonate, potassium carbonate, sodium sulphate, sodium sulphide, sodium chloride as well as other water-insoluble chemicals eg. silicates and oxides. Smelt may also includes organic carbon compounds.
Due to its particular chemical composition, the smelt powder is believed to be useful as a filler without having any inconvenience generated by the alkaline character of it. Moreover, the presence of the sulfide anion provides a stabilizing effect to many polymers, in the same manner as different hydrides do. In addition, the carbonate content of the smelt mixed together in plastics with a solid organic acid acts as a foaming agent by generating carbon dioxide during thermal processing.
In an embodiment of the invention, the composition of smelt is as follows: sodium carbonate 63-91% by weight, potassium carbonate 1-5% by weight, sodium sulphate 4-10% by weight, sodium sulphide 0.01-12% by weight, sodium chloride 0.09-2% by weight and water insoluble chemicals 3.9-8% by weight. In another embodiment, smelt has a composition of sodium carbonate 41-99% by weight, potassium carbonate 0.
Mortimer Jacques
Tivadar Ladislau A.
Ohlandt Greeley Ruggiero & Perle L.L.P.
Pezzuto Helen L.
The Dow Chemical Company
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