Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-05-19
2001-05-01
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S442000, C524S443000, C524S492000, C524S493000, C524S789000, C524S791000
Reexamination Certificate
active
06225374
ABSTRACT:
SUMMARY OF THE INVENTION
The process of the invention herein produces silicate-polymer composites in a solvent-free process and without in situ formation of the polymer. This process provides less expensive and environmentally safer synthetic pathways to produce known silicate-polymer composites and also makes possible production of silicate-polymer composites for which suitable processing solvents do not exist.
The method herein comprises the steps of forming a solvent-free admixture of (a) 2:1 layered gallery-containing crystalline silicate having charge-balancing cation selected from the group consisting of sodium ion, potassium ion, lithium ion, calcium ion, magnesium ion and organic cation and (ii) polymer, in a weight ratio of silicate to polymer ranging from 1:1000 to 100:1, and (b) reacting the silicate and the polymer in said admixture to cause the intercalation of the polymer into the galleries of the silicate, e.g., by heating said admixture in air or vacuum at above the melting or glass transition temperature of the polymer.
A first embodiment involves intercalating polymer in layer(s) of heights of less than 1 nanometer into a matrix of the silicate to produce composites which show no melting or glass transition and which are therefore dimensionally stable. This is carried out without causing delamination of the layers defining the galleries of the silicate into which the polymer intercalates; this is accomplished by carrying out step (b) in the substantial absence of shear forces.
In one example of this embodiment, the silicate is sodium montmorillonite and the polymer is crystalline poly(ethylene oxide) having a molecular weight ranging from 1000 to 1,000,000, in one alternative ranging from 50,000 to 150,000, and the weight ratio of silicate to polymer ranges from 10:1 to 1.5:1.
In another example of this embodiment, the silicate is quaternary ammonium montmorillonite wherein the quaternary ammonium moiety contains at least one organophilic group and the polymer is amorphous polystyrene having a molecular weight ranging from 1,000 to 1,000,000, in one alternative ranging from 25,000 to 500,000, and the weight ratio of silicate to polymer ranges from 10:1 to 1.5:1.
A second embodiment involves carrying out step (b) under conditions which cause delamination of layers defining the galleries of the silicate into which the polymer intercalates, e.g., by subjecting the admixture of silicate and polymer to shear forces during step (b). This produces a composite containing layers of silicate which are delaminated from the crystal structure of the silicate starting material. In one alternative of this embodiment, the weight ratio of silicate to polymer is such that a composite is produced comprising a polymer matrix containing layers of silicate of height of less than 1 nanometer; a weight ratio of silicate to polymer of 1:200 to 1.5:1 provides a preferred product of this type.
The term “solvent-free” is used herein to mean that solvent is not used as a carrier for the polymer. It does not exclude the water which may normally be contained in the silicates.
DETAILED DESCRIPTION
We turn firstly to the polymer. It can be either thermoplastic or thermosetting. Thermoplastic polymers are preferred. Examples of thermoplastic polymers include vinyl polymers (e.g., polystyrene, polyethylene, polypropylene, ethylene-propylene diene monomer polymers, acrylonitrile-styrene-butadiene copolymers and rubber), polyalkylene oxides (e.g., poly(ethylene oxide)), polyamides (e.g., nylons, such as nylon-6 (polycaprolactam), nylon-66 (poly(hexamethylene adipamide)) nylon-11, nylon-12, nylon-46, nylon-7, or nylon-8), polyesters (e.g., polyethylene terephthalate and polybutylene terephthalate), vinylidene polymers (e.g., poly(vinylidene fluoride) and poly(vinylidene chloride)), fluoropolymers (e.g., polytetrafluorethylene and polychlorotrifluoroethylene), polysiloxanes (e.g., polydimethylsiloxanes), polyphenylene sulfides, polyacetals, polycarbonates, polysulfones and polyether sulfones. Examples of thermosetting resins are phenolic resins, epoxy resins, unsaturated polyester resins, alkyd resins, furan resins, urea resins, melamine resins, polyurethane resins and aniline resins.
We turn now to the 2:1 layered gallery-containing silicates. The term “2:1 layered silicates” is a known term and describes silicates containing lattice layers containing two tetrahedral sheets that share an edge with an octahedral sheet of either aluminum or magnesium hydroxide. The stacking of the layers provides interlayers or galleries between the layers. The galleries are normally occupied by cations that balance the charge deficiency that is generated by the isomorphous substitution within the layers. Besides the charge-balancing cations, water is also present in the galleries where it tends to associate with the cations. The silicates are referred to as gallery-containing to describe this characteristic of 2:1 layered silicates, to provide antecedent basis for recitation in step (b) of intercalation of polymers into the galleries of the silicate. The silicates may be either natural or synthetic. The natural silicates include, for example, smectite clay minerals (e.g., montmorillonite, saponite, beidellite, nontronite, hectorite and stevensite), vermiculite and halloysite. The synthetic silicates include, for example, laponite, fluorhectorite, hydroxyl hectorite, boron fluophlogopite, hydroxyl boron phlogopite, and solid solutions among those and between those and structurally-compatible natural silicates selected from the group consisting of talc, fluortalc, polylithionite, fluorpolylithionite, phlogapite, and fluorphlogopite. These normally are associated with, i.e., in the pristine state contain, charge balancing cations selected from the group consisting of sodium ions, potassium ions, lithium ions, calcium ions and magnesium ions. In the case of polymers which do not contain hydrophilic moiety, intercalation is not obtained when the charge balancing cations are those normally present in the pristine state of the silicate, i.e., sodium ions, potassium ions, lithium ions, calcium ions or magnesium ions. In this case, the charge-balancing cation must at least partly be organic cation with at least one organophilic group for intercalation to be obtained. The pristine silicates are readily modified to contain such organic cation by ion exchange, e.g., as taught in the Okada et al and Kawasumi et al patents. Suitable organic cations include, for example, substituted ammonium ions, e.g., octadecyl dimethyl ammonium ion or dodecylammonium ion or other mono or di C
8
-C
18
alkylammonium ion or where substitution is by —R—COOH wherein R denotes an alkylene group which may contain phenylene, vinylene, branching and/or other linkages, e.g., 12-amino-dodecanoic acid ion, or organophosphonium ions, e.g., C
8
-C
18
alkylphosponium ion, or organosulfonium ions, e.g., C
8
-C
18
alkylsulfonium ions.
As indicated above, the weight ratio of silicate to polymer in the admixture of step (a) ranges from 1:1000 to 100:1. In the embodiment where the polymer is intercalated in layer(s) of height less than 1 nanometer into a matrix of silicate, the ratio of silicate to polymer preferably ranges from 10:1 to 1.5:1 and very preferably ranges from 2:1 to 3:1. In the embodiment involving producing a polymer matrix containing layers of silicate of height less than a nanometer, the weight ratio of silicate to polymer preferably ranges from 1:200 to 1.5:1 and very preferably ranges 1:3 to 1:10.
The polymer and silicate are used in step (a) in the form of dry powders. In general, the polymer normally has particle size of 0.01 micron to 1 centimeter and the silicate has particle size ranging from 0.01 to 25 microns. These particle sizes refer to the largest dimension of the particles.
The admixture of step (a) is readily formed by any technique that succeeds in mixing dry powders, e.g., using a mortar and pestle or ball milling.
It is preferred that step (a) also include cold pressing of the mixture of dry powders to compress the polymer
Giannelis Emmanuel P.
Tse Oliver K.
Vaia Richard A.
Cornell Research Foundation Inc.
Yoon Tae H.
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