Source: http://www.google.com/patents/US6838507?dq=6233389
Timestamp: 2018-01-19 16:13:19
Document Index: 8549985

Matched Legal Cases: ['application No. 60', 'arts 60', 'arts 0', 'arts 60', 'arts 0', 'arts 60', 'arts 0', 'arts 60', 'arts 0', 'arts 60', 'arts 0']

Patent US6838507 - Aqueous nanocomposite dispersions: processes, compositions, and uses thereof - Google Patents
Processes for utilizing various emulsion polymerization procedures for preparing aqueous nanocomposite dispersions are disclosed. The disclosed processes include both in-situ polymerizations in the presence of at least partially exfoliated unmodified clays as well as admixtures of polymer dispersions...http://www.google.com/patents/US6838507?utm_source=gb-gplus-sharePatent US6838507 - Aqueous nanocomposite dispersions: processes, compositions, and uses thereof
Publication number US6838507 B2
Application number US 09/954,132
Also published as CN1230450C, CN1317328C, CN1331893C, CN1462280A, CN1462281A, CN1462282A, CN1622959A, CN1664001A, CN100354314C, CN100475854C, DE60124940D1, DE60124940T2, EP1325037A2, EP1325038A2, EP1328553A2, EP1328553B1, EP1328555A2, US6646086, US6759463, US6765049, US6818684, US7259203, US7291665, US20020055580, US20020055581, US20020055599, US20020086908, US20040054068, US20040220317, US20050059769, WO2002024757A2, WO2002024757A3, WO2002024758A2, WO2002024758A3, WO2002024760A2, WO2002024760A3, WO2002055563A2, WO2002055563A3
Publication number 09954132, 954132, US 6838507 B2, US 6838507B2, US-B2-6838507, US6838507 B2, US6838507B2
Inventors Chuen-Shyong Chou, Edward Ewart LaFleur, Dennis Paul Lorah, Robert Victor Slone, Katerina Dukes Neglia
Patent Citations (22), Non-Patent Citations (23), Referenced by (43), Classifications (53), Legal Events (5)
Aqueous nanocomposite dispersions: processes, compositions, and uses thereof
US 6838507 B2
Processes for utilizing various emulsion polymerization procedures for preparing aqueous nanocomposite dispersions are disclosed. The disclosed processes include both in-situ polymerizations in the presence of at least partially exfoliated unmodified clays as well as admixtures of polymer dispersions with at least partially exfoliated unmodified clay dispersions. The disclosed nanocomposite dispersions are useful for preparing a variety of materials, such as coatings, adhesives, caulks, sealants, plastics additives, and thermoplastic resins. Processes for preparing polymer clay nanocomposite powders and use of these powders as plastic resin and plastics additives are also disclosed.
1. A process for preparing an aqueous polymer clay nanocomposite dispersion comprising the steps of:
providing a first aqueous reaction mixture comprising at least one ethylenically unsaturated monomer;
providing a second aqueous reaction mixture comprising an at least partially exfoliated aqueous clay dispersion having at least one unmodified clay and at least one ethylenically unsaturated monomer;
combining the first aqueous reaction mixture with the second aqueous reaction mixture; and
polymerizing at least a portion of said ethylenically unsaturated monomers, wherein at least one of the ethylenically unsaturated monomers in either the first aqueous reaction mixture or the second aqueous reaction mixture is an acid containing monomer.
2. A process for preparing an aqueous polymer clay nanocomposite dispersion comprising the steps of:
polymerizing at least a portion of said ethylenically unsaturated monomers, wherein the glass transition temperature of the polymer within the polymer clay nanocomposite dispersion is in the range of from −80° C. to 50° C.
3. A process for preparing an aqueous polymer clay nanocomposite dispersion comprising the steps of:
polymerizing at least a portion of said ethylenically unsaturated monomers, wherein the second aqueous reaction mixture is combined with the first aqueous reaction mixture on a gradual basis during the polymerization step.
4. The process according to claim 1, 2, or 3, wherein:
one of the first or the second aqueous reaction mixtures is polymerized to form a first stage emulsion polymer core particle having a particle diameter in the range of from 20 to 500 nanometers, said polymer being present in the amount of 10 to 99% based on dry weight of the total dry polymer weight in said nanocomposite dispersion; and
the other aqueous reaction mixture is polymerized to form a second stage emulsion polymer shell around said core particle.
5. The process according to claim 1, 2, or 3, wherein the aqueous clay dispersion has a clay concentration in the range of from 0.1 to 20 weight percent based upon the weight of the monomer in the aqueous nanocomposite dispersion.
6. The process according to claim 1, 2, or 3, wherein the at least one ethylenically unsaturated monomer is selected from the group consisting of C1-C18 alkyl methacrylate, C1-C18 alkyl acrylate, 2-ethylhexyl (meth)acrylate, isobomyl (meth)acrylate, lauryl (meth)acrylate, allyl (meth)acrylate, stearyl (meth)acrylate, acrylic acid, itaconic acid, methacrylic acid, butadiene, vinyl acetate, vinyl versatate, styrene, ethylene, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, vinyl aromatic monomers, divinylbenzene, divinylpyridine, divinyltoluene, diallyl phthalate, ethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, divinylxylene, divinylethylbenzene, divinylsulfone, divinylketone, divinylsulfide, diallyl maleate, diallyl fumarate, diallyl succinate, diallyl carbonate, diallyl malonate, diallyl oxalate, diallyl adipate, diallyl sebacate, divinyl sebacate, diallyl tartrate, diallyl silicate, triallyl tricarballylate, triallyl aconitate, triallyl citrate, triallyl phosphate, N,N-methylene dimethacrylamide, N,N-methylene dimethacrylamide, N,N-ethylenediacrylamide, trivinylbenzene, and the polyvinyl ethers of glycol, glycerol, pentaerythritol, resorcinol, monothio and dithio derivatives of glycols, and combinations thereof.
7. The process according to claim 1 wherein the acid containing monomer is selected from the group consisting of methacrylic anhydride, maleic anhydride, itaconic anhydride, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, acryloxypropionic acid, (meth)acryloxypropionic acid, styrene sulfonic acid, ethylmethacrylate-2-sulphonic acid, 2-acrylamido-2-methylpropane sulphonic acid; phosphoethylmethacrylate; the corresponding salts of the acid containing monomer, and combinations thereof.
8. The process according to claim 7 wherein 50% by weight or less of the acid containing monomer is present within the second aqueous reaction mixture and the remainder of the acid containing monomer is present in the first aqueous reaction mixture.
9. The process according to claim 8 wherein 25% by weight or less of the acid containing monomer is present within the second aqueous reaction mixture and the remainder of the acid containing monomer is present in the first aqueous reaction mixture.
10. The process according to claim 1, 2, or 3, wherein the at least one clay is selected from the group consisting of smectite, phyllosilicate, montmorillonite, saponite, beidellite, montronite, hectorite, stevensite, vermiculite, kaolinite, hallosite, synthetic phyllosilicates, and combinations thereof.
11. The process according to claim 1, 2, or 3, wherein the clay dispersion comprises a redox-active multivalent metal ion.
12. The process according to claim 11, wherein an oxidant is added to the clay dispersion.
13. The process according to claim 11, wherein a reductant is added to the clay dispersion.
14. The process according to claim 11, wherein an oxidant and a reductant is added to the clay dispersion.
15. The process according to claim 1, 2, or 3, wherein:
the at least one ethylenically unsaturated monomer of the first aqueous reaction mixture is selected to provide a rubbery first stage core polymer particle having a glass transition temperature less than or equal to 25° C.; and
the at least one ethylenically unsaturated monomer of the second aqueous reaction mixture is selected to provide a hard second stage shell polymer having a glass transition temperature greater than or equal to 25° C.
16. A plastics additive product comprising the aqueous nanocomposite dispersion prepared according to the process of claim 1, 2, or 3.
17. A nanocomposite powder product prepared by drying the aqueous nanocomposite dispersion prepared according to the process of claims 1, 2, or 3.
18. A material comprising the nanocomposite powder product of claim 17, wherein said material is selected from the group consisting of thermoplastic resin and plastics additive.
19. A process for preparing an aqueous nanocomposite dispersion, comprising:
admixing an aqueous emulsion polymer polymerized from at least one ethylenically unsaturated monomer wherein at least one ethylenically unsaturated monomer is an acid containing monomer and 0.1 to 20 weight percent based on dry weight of said emulsion polymer of at least one unmodified clay.
20. The process according to claim 19 wherein said clay is predispersed in water, wherein the clay is at least partially exfoliated in the water.
21. The process according to claim 19, wherein the glass transition temperature of said polymer is in the range of from −80° C. to 50° C.
22. The process according to claim 19, wherein the other of the at least one ethylenically unsaturated monomer is selected from the group consisting of: C1-C18 alkyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobomyl (meth)acrylate, lauryl (meth)acrylate, allyl (meth)acrylate, stearyl (meth)acrylate, acrylic acid, itaconic acid, methacrylic acid, butadiene, vinyl acetate, vinyl versatate, styrene, ethylene, vinyl aromatic monomers, divinylbenzene, divinylpyridine, divinyltoluene, diallyl phthalate, ethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, divinylxylene, divinylethylbenzene, divinylsulfone, divinylketone, divinylsulfide, diallyl maleate, diallyl fumarate, diallyl succinate, diallyl carbonate, diallyl malonate, diallyl oxalate, diallyl adipate, diallyl sebacate, divinyl sebacate, diallyl tartrate, diallyl silicate, triallyl tricarballylate, triallyl aconitate, triallyl citrate, triallyl phosphate, N,N-methylene dimethacrylamide, N,N-methylene dimethacrylamide, N,N-ethylenediacrylamide, trivinylbenzene, and the polyvinyl ethers of glycol, glycerol, pentaerythritol, resorcinol, monothio and dithio derivatives of glycols, and combinations thereof.
23. The process according to claim 19, wherein the at least one clay is selected from the group consisting of smectite clay, phyllosilicate, montmorillonite, saponite, beidellite, montronite, hectorite, stevensite, vermiculite, kaolinite, hallosite, synthetic phyllosilicates, and combinations thereof.
24. A product comprising the aqueous nanocomposite dispersion prepared according to the process of claim 19, wherein said product is selected from the group consisting of coating, adhesive, caulking, and sealant.
25. A process for preparing an aqueous nanocomposite dispersion, comprising the steps of:
providing an at least partially exfoliated unmodified aqueous clay dispersion, wherein said clay dispersion comprises from 0.1 to 20% based on dry weight of said nanocomposite dispersion; and
adding at least one ethylenically unsaturated monomer to said clay dispersion, wherein said monomers comprise from 80 to 99.9% based on dry weight of said nanocomposite dispersion and at least one of the monomers is an acid containing monomer; and
polymerizing said monomer to form a polymer clay nanocomposite dispersion.
26. A process for preparing an aqueous nanocomposite dispersion, comprising the steps of:
adding at least one ethylenically unsaturated monomer to said clay dispersion, wherein said monomers comprise from 80 to 99.9% based on dry weight of said nanocomposite dispersion; and
polymerizing said monomer to form a polymer clay nanocomposite dispersion, wherein the glass transition temperature of the polymer within the polymer clay nanocomposite dispersion is in the range of from −80° C. to 50° C.
27. A process for preparing an aqueous nanocomposite dispersion, comprising the steps of:
polymerizing said monomer to form a polymer clay nanocomposite dispersion, wherein the monomer is added to the clay dispersion on a gradual basis during the polymerization step.
28. The process according to claim 24 or 26, wherein the glass transition temperature of said polymer is in the range of from −80° C. to 50° C.
29. The process according to claim 24, 25, or 26, wherein the at least one ethylenically unsaturated monomer is selected from the group consisting of: C1-C18 alkyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobomyl (meth)acrylate, lauryl (meth)acrylate, allyl (meth)acrylate, stearyl (meth)acrylate, acrylic acid, itaconic acid, methacrylic acid, butadiene, vinyl acetate, vinyl versatate, ethylene, styrene, vinyl aromatic monomers, divinylbenzene, divinylpyridine, divinyltoluene, diallyl phthalate, ethylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, divinylxylene, divinylethylbenzene, divinylsulfone, divinylketone, divinylsulfide, diallyl maleate, diallyl fumarate, diallyl succinate, diallyl carbonate, diallyl malonate, diallyl oxalate, diallyl adipate, diallyl sebacate, divinyl sebacate, diallyl tartrate, diallyl silicate, triallyl tricarballylate, triallyl aconitate, triallyl citrate, triallyl phosphate, N,N-methylene dimethacrylamide, N,N -methylene dimethacrylamide, N,N-ethylenediacrylamide, trivinylbenzene, and the polyvinyl ethers of glycol, glycerol, pentaerythritol, resorcinol, monothio and dithio derivatives of glycols, and combinations thereof.
30. The process according to claim 24, 25, or 26, wherein the at least one clay is selected from the group consisting of smectite clay, phyllosilicate, montmorillonite, saponite, beidellite, montronite, hectorite, stevensite, vermiculite, kaolinite, hallosite, synthetic phyllosilicates and combinations thereof.
31. A product comprising the aqueous nanocomposite dispersion prepared according to the process of claim 24, 25, or 26, wherein said product is selected from the group consisting of coating, adhesive, caulking, and sealant.
32. The process according to claim 24, 25, or 26, wherein the clay dispersion comprises a redox-active multivalent metal ion.
33. The process according to claim 32, wherein an oxidant is added to the clay dispersion.
34. The process according to claim 32, wherein a reductant is added to the clay dispersion.
35. The process according to claim 32, wherein an oxidant and a reductant is added to the clay dispersion.
This application claims priority to provisional application No. 60/234,263 filed Sep. 21, 2000.
One way of improving thermoplastic resins is by adding polymer particles to modify the mechanical and melt processing properties of thermoplastic resins. For example, polyvinyl chloride resin (hereafter “PVC”) has a combination of properties that make it particularly suitable for use as a structural material. However, PVC may suffer from being brittle. To remedy this, PVC may be blended with polymer particles having a rubber phase to improve its impact strength (e.g., as an impact-modifier). Typical uses for impact-modified PVC include siding for buildings, shutters, technical profiles for window and door frames, rain carrying systems (e.g., gutters and downspouts), and fencings. Although impact modifiers may improve the impact-strength of plastic articles, there is a concomitant decrease in tensile and flexural strength (i.e., modulus) of the modified plastic. Thus, there is a need for a plastics additive in plastic articles such as thermoplastic resins that provide impact strength while minimizing the reduction in modulus.
In composite materials, certain thermoplastics, such as extrudable thermoplastic resins with a co-extruded capstock layer, may be used to provide a tough and strong outer layer for articles having a weaker plastic substrate. Examples of extrudable thermoplastic resins include, but are not limited to, PVC, chlorinated polyvinylchloride (“CPVC”), high impact polystyrene (“HIPS”), polypropylene (“PP”) and acrylonitrile-butadiene-styrene (“ABS”). To protect these thermoplastic resins from weathering and/or physical impacts, a capstock layer such as, for example, an acrylic material, may be coextruded atop the substrate, such as PVC. The resultant composite material has improved scratch resistance, impact strength, tensile strength, adhesion, appearance, and weatherability. The capstock layers are typically much thinner than the substrate plastic and may range from 10 to 25% of the total thickness of the composite (i.e., the composite being defined as the combination of the capstock layer(s) and the substrate plastic).
Capstock materials generally possess a certain combination of processing properties and other physical, chemical, and aesthetic properties, including exceptional weathering characteristics such as excellent color retention and high mechanical (e.g., impact and tensile) strength. Further, capstock materials typically do not adversely affect those properties which make PVC such a widely used building material. In particular, capstock compositions are typically strong and tough to provide these physical property improvements. Although latex polymers, such as multi-stage “core-shell” acrylic polymers may be used as the modifiers in the capstock layer, there is a continuing need for property improvements.
Clay minerals are typically comprised of hydrated aluminum silicates that are fine-grained and have a platy habit. The crystalline structure of a typical clay mineral is a multi-layered structure comprised of combinations of layers of SiO4 tetrahedra that are joined to layers of AlO(OH)2 octahedra. The term “gallery”, as used herein, describes the interlayer spaces of the layered clay minerals. The terms “d-spacing” or “basal spacing”, as used herein, define the sum of the single layer thickness and the thickness of the interlayer or gallery, which is the repeat unit of the multi-layer mineral. Depending upon the clay mineral, the gallery may contain water and/or other constituents such as potassium, sodium, or calcium cations. Clay minerals vary based upon the combination of their constituent layers and cations. Isomorphic substitution of the cations of clay mineral, such as Al3+ or Fe3+ substituting for the Si4+ ions in the tetrahedral network, or Al3+, Mg2+ or Fe2+ substituting for other cations in the octahedral network, typically occurs and may impart a net negative charge on the clay structure. Naturally occurring elements within the gallery of the clay, such as water molecules or sodium or potassium cations, are attracted to the surface of the clay layers due to this net negative charge.
Nanocomposites are compositions in which at least one of its constituents has one or more dimensions, such as length, width or thickness, in the nanometer size range. The term “nanocomposite”, as used herein, denotes the state of matter wherein polymer molecules exist among at least partially exfoliated clay layers. Recently, nanocomposites, that contain layered clay materials such as montmorillonite having silicate layers of a thickness of 1 nanometer dispersed within a polymeric matrix, have been developed as a means to improve the physical properties of polymers. In order to effectively improve the physical or mechanical properties, the clay is typically uniformly dispersed throughout the polymer in order to promote more interfaces between the clay and polymer and enhance the affinity of the clay to the polymer at these interfaces. Further, if the clay is uniformly dispersed throughout the polymer, less clay material may be added to the nanocomposite composition while maintaining the physical properties of the nanocomposite.
In order to promote more affinity between the clay and the polymer at the interface and provide a uniform dispersion of the clay within the polymer, the interlayer surface chemistry of the clay may be modified to render the silicate layers less hydrophilic. Previous methods of altering the interlayer surface chemistry of the clay include the use of modifying agents, such as surfactants or silanes, to prepare a clay dispersion prior to its incorporation into a polymer. For example, surfactants may typically comprise a molecule having a hydrophilic functions (which has an affinity to polar media such as water or clay) and an hydrophobic function (which has an affinity to organic molecules such as oil or polymer). The use of surfactants generally permits the dispersion of a clay within a polymer. As used herein, the term “hydrophobically modified clays” denotes clays that may have its surface chemistry modified through the use of an agent such as a surfactant, silane, or other modifier. As used herein, the term “unmodified clays” denotes clays that have not been hydrophobically modified by a modifying agent, or are used in their natural state.
Typical modifying agents used to render a clay less hydrophilic may include, but are not limited to, amino acids, alkylammonium ions, silanes, aminomethylstyrene, or living free radical polymerization initiator (“LFRP”). Further non-limiting examples of other suitable agents for the synthesis of nanocomposites are provided in the reference, M. Ogawa et al., “Preparation of inorganic-organic nanocomposites through intercalation of organoammonium ions into layered silicates”, Bull. Chem. Soc. Jpn., 70, 2593-2619 (1997).
Amino acid surfactants are molecules that may consist of a basic amino group (—NH2) and an acidic carboxyl group (—COOH). When introduced into an acidic medium, a proton may be transferred from the —COOH group to the intramolecular —NH2 group. It is believed that a cation exchange occurs between the —NH3+ functional group that is formed and the naturally occurring cations (i.e., Na+, K+, etc.) present between the clay layers. This results in an intercalated state wherein the —NH3+ functional groups are “sandwiched” between the individual layers replacing the naturally occurring cation. The term “intercalate”, as used herein, refers to incorporating foreign molecules, atoms, or ions in between the layers of the clay material. As a result of this intercalated state, the clay become hydrophobic. Amino acid surfactants are commonly used in the preparation of polyamide 6-clay hybrids because their acid functional group may polymerize with ε-caprolactam that is intercalated between the layers. As a result, the intragallery polymerization delaminates the clay in the polymer matrix thereby forming a nanocomposite.
Alkylammonium ion surfactants, such as onium salts, are commonly used to prepare clay dispersions for nanocomposite materials. The basic formula for a typical alkylammmonium ion is CH3—(CH2)n—NH3+ where n is from 1 to 18. It is believed that the alkylammonium ions also readily exchange with the naturally occurring cations present between the clay platelets resulting in an intercalated state. Further, it is believed that the alkylammonium ions may increase the d-spacing between the clay layers and also may lower the surface energy of the clay thereby allowing organic species with different polarities to become intercalated between the clay layers.
Silanes may also be used in the synthesis of unsaturated polyester-clay nanocomposites. Silanes are a family of organosilicon monomers, which may be characterized by the formula R—SiX3, where R is an organofunctional group attached to silicon in a hydrolytically stable manner and X designates hydrolyzable groups that may be converted to silanol groups upon hydrolysis. It is believed that silanes interact with inorganic surfaces such as clay that have hydroxyl groups attached primarily to silicon or aluminum thereby forming a bond with the inorganic surface.
Hydrophobically modified clays have been oftentimes used in the preparation of nanocomposite materials. The article, “Synthesis and Characterization of Thermoset-Clay Nanocomposites” by Xavier Kornmann (referred to herein as the “Kornmann”) provides some examples for synthesizing nanocomposites using hydrophobically modified clays using in-situ polymerization, melt intercalation, or solution-based polymerization methods. In the in-situ polymerization method, the hydrophobically modified clay, referred to in the article as “organoclay”, is swollen in a monomer and then the polymerization reaction is initiated, through the addition of a curing agent or by an increase in temperature, to form the nanocomposite. It is believed that the polymerization reaction leads to the delamination of the clay. In the melt intercalation method, a molten thermoplastic is blended with a hydrophobically modified clay and then annealed at a temperature above the glass transition temperature of the polymer to form the nanocomposite. Lastly, in the solution polymerization method, the hydrophobically modified clay is first swollen in a solvent such as toluene or N, N-dimethylformamide. The polymer is then dissolved into the solvent where it intercalates between the clay layers. The solvent is then removed from the resulting nanocomposite via evaporation.
The article “Preparation and Characterization of PMMA-Clay Hybrid Composite by Emulsion Polymerization”, Journal of Applied Polymer Science, Vol. 61 No. 7, Aug. 15, 1996, written by Dong Choo Lee and Lee Wook Jang (referred to herein as “Lee”) discusses a batch emulsion polymerization method in which a methyl methyacrylate (“MMA”) monomer is dispersed in a water phase and polymerized with a water soluble radical initiator in the presence of a sodium montmorillonite clay. The resultant polymer clay nanocomposite has a higher Tg along with an elevation in strength. We have suprisingly and unexpectedly found it is desirable to form polymer clay nanocomposites with a lower Tg that still exhibit an elevation in strength but not the expected rise in Tg as measured by as measured by differential scanning calorimetry (“DSC”). Lee does not disclose the polymerization of acid containing monomers which surprisingly and unexpectedly further enhances the affinity between the polymer and the clay within the nanocomposite resulting in improved physical properties. Lee also does not disclose the preparation of an emulsion polymer via a semi-batch or gradual addition method which allows, inter alia, better control of particle size, exotherm temperature, and percentage solids in comparison with batch emulsion polymerization methods. Further, Lee does not disclose core shell nanocomposite polymer compositions.
The reference, Huang et al. “Synthesis and Characterization of PMMA Nanocomposites by Suspension and Emulsion Polymerization”, Amer. Chem. S. (2000) (“Huang”) describes the use of hydrophobically modified clays to form a PMMA nanocomposite via emulsion polymerization. During the emulsion polymerization, the surfactant was used as the emulsifier and the unmodified clay was added after polymerization. The Tg of the resultant nanocomposites are too high to be useful for many of the applications disclosed herein. Further, the nanocomposites are formed by a “melt press” process rather than in an aqueous system.
Another disadvantage of using hydrophobically modified clays is that the surfactants, particularly cationic surfactants, used to modify the clay may destabilize polymer latex emulsions. Many of the surfactants, such as onium salts, that are used to disperse clays are also emulsifying agents. In some cases, extreme difficulties may be encountered in the preparation of a stable polymer latex in the presence of such onium salt modified clays. To keep such emulsions stable in the presence of such onium salts, a large quantity of emulsifier is typically required. Larger quantities of emulsifier can degrade properties of the polymer in its final use (e.g., poorer water resistance). Furthermore, large quantities of emulsifier may deleteriously affect the formation of polymer latex particles. Non-uniform polymer latex particle formation may lead to variations in emulsion droplet size resulting in non-uniform polymer particle sizes. Large quantities of emulsifier may also lead to the formation of “secondary particles” which may further broaden the particle size distribution. As well, there are often problems associated with broad particle size distributions such as shear instability of the emulsion, variability in polymer molecular weight (leading to variations in polymer process and properties), and degradation of properties when dried to a powder (e.g., dust resulting from the presence of small polymer particles).
In another embodiment of the present invention, there is provided a process for preparing an aqueous nanocomposite dispersion which includes the steps of providing an emulsion which contains a plurality of polymer seeds having a mean particle diameter of 20 to 500 nanometers wherein the polymer seeds are present in the emulsion in an amount ranging from 0.1 to 10% based on dry weight of total dry polymer weight in the nanocomposite dispersion, providing a monomer mixture comprising at least one ethylenically unsaturated monomer, combining the monomer mixture and the aqueous emulsion and then adding an aqueous dispersion to the emulsion. This aqueous dispersion includes 0.1 to 20 weight percent based on dry weight of total dry polymer weight in the nanocomposite of a layered, unmodified clay. At least a portion of the monomer is polymerized thereby forming the polymer clay nanocomposite dispersion. It is understood, however, that these steps may be performed in a variety of different orders.
In certain embodiments of the present invention, the nanocomposite is prepared via an emulsion-based polymerization technique. For example, in connection with the preparation of an aqueous nanocomposite dispersion, two or more separate aqueous reaction mixtures may be prepared initially which is followed by a multi-stage emulsion polymerization of the monomer within one or all of the reaction mixtures. While the present application discusses multi-stage polymerization primarily in terms of two stages, it is understood that more than two stages of polymerization of the monomer is further envisioned. The term “stage”, “multi-stage”, and “core shell” as used herein, is intended to encompass its broadest possible meaning, such as, for example, the meaning conveyed in U.S. Pat. Nos. 3,793,402, 3,971,835, 5,534,594, and 5,599,854, which disclose various means for achieving “staged” and “multi-staged” polymers. The first aqueous reaction mixture typically comprises a monomer mixture whereas the second aqueous reaction mixture comprises an aqueous clay dispersion and, optionally, a monomer mixture. In certain embodiments, however, the first aqueous reaction mixture may also comprise an aqueous clay dispersion. The term “aqueous nanocomposite dispersion” relates to a clay and polymer clay nanocomposite that further comprises an aqueous, or water phase. In certain embodiments, the monomer mixture in the first and/or the second aqueous reaction mixtures may be emulsified. In one embodiment of the present invention, the percent weight of clay to the total amount of monomer within the aqueous nanocomposite dispersion can be in the range of from 0.05% to 20%, preferably from 0.1% to 15%, and more preferably from 0.1% to 10% and even more preferably from 0.5% to 5%.
The aqueous nanocomposite dispersion contains polymerized units derived from at least one type of ethylenically unsaturated monomer. The term “units derived from”, as used herein, refers to polymer molecules that are synthesized according to known polymerization techniques wherein a polymer contains “units derived from” its constituent monomers. Preferably, the ethylenically unsaturated monomer is selected such that the polymerized units within the aqueous nanocomposite dispersion are water insoluble, i.e., have low or no water solubility. By “water-insoluble” it is meant having a water solubility of no greater than 150 millimoles/liter at 25° C. to 50° C.
The preparation of the monomer mixture typically involves the vigorous mixing of at least one ethylenically unsaturated monomer with water and an emulsifier. In other embodiments of the present invention the monomer may be added “neat”, i.e., added without water. The amounts of monomer, water, and emulsifier in the monomer mixture may vary depending upon, for example, the particular monomer and/or emulsifier selected, the intended end-use, and the like. In certain embodiments, the amount of monomer in the monomer mixture is preferably in the range of from 25 to 100, preferably from 40 to 90, and even more preferably from 60 to 80 weight percent. The amount of water in the monomer mixture, if aqueous based, is preferably in the range of from 0.1 to 75, more preferably from 10 to 60, and even more preferably from 20 to 40 weight percent based on the total weight of the emulsified monomer mixture (e.g., monomers, emulsifier, and water). The amount of emulsifier in the monomer mixture, if added, is preferably in the range of from 0.01 to 10, preferably from 0.05 to 2, and even more preferably from 0.1 to 1 weight percent. If the emulsifier amount is too low then the monomer emulsion droplet size may be too large or cause an unstable emulsion. If the emulsifier amount is too high then excess emulsifier may interfere with the polymerization process.
The monomers which may be polymerized include any of the ethylenically unsaturated monomers commonly known in the art, such as those listed in The Polymer Handbook, 3rd Edition, Brandrup and Immergut, Eds., Wiley Interscience, Chapter 2, (1989). Suitable ethylenically unsaturated monomers include, for example, the C1-C18 alkyl (meth)acrylate monomers (e.g. methyl-, ethyl-, propyl-, n-butyl-, sec-butyl-, tert-butyl, pentyl-, hexyl-, isobomyl-heptyl-, n-octyl-, 2-ethylhexyl-, decyl-, undecyl-, dodecyl-, lauryl, cetyl, and stearyl-(meth)acrylate and the like); vinyl aromatic monomers (e.g. styrene, alpha-methyl styrene, para-methyl styrene, chlorostyrene, vinyl toluene, dibromostyrene, tribromostyrene, vinyl naphthalene, isopropenyl naphthalene, divinylbenzene and the like); vinyl esters (e.g., vinyl acetate; vinyl versatate; and the like); vinyl-unsaturated carboxylic acids monomers (e.g., methacrylic acid, acrylic acid, maleic acid, itaconic acid); nitrogen-containing vinyl unsaturated monomers (e.g., acrylonitrile, methacrylonitrile, and C1-C18 alkyl (meth)acrylamides, and the like); dienes (e.g., butadiene and isoprene); ethylene, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, and the like. The term “(meth)acrylate”, as used herein, refers to both esters of methacrylate and acrylate.
Where it is desirable to covalently cross-link the polymers and/or to graft link multiple stage polymers (e.g., for preparing core-shell two-stage polymer particles), crosslinkers and/or graftlinkers may also be included in the monomer mixtures. The term “crosslinker”, as used herein, refers to multi-functional monomers capable of forming two or more covalent bonds between polymer molecules of the same type. The term “graftlinker”, as used herein, refers to multi-functional monomers capable of forming two or more covalent bonds between polymer molecules of one type with polymer molecules of another type. Suitable crosslinkers or graftlinkers include, for example, divinyl benzene, butylene glycol dimethacrylate, alkanepolyol-polyacrylates or alkanepolyol-polymethacrylates such as ethylene glycol di(meth)acrylate, butylene glycol diacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimeth-acrylate, trimethylol-propane diacrylate, trimethylolpropane dimeth-acrylate, trimethylol-propane triacrylate (“TMPTA”) or trimethylolpropane trimethacrylate, and unsaturated carboxylic acid allyl esters such as allyl acrylate, diallyl maleate, and typically allyl methacrylate, and the like.
In certain preferred embodiments, at least one of the monomers within the monomer-containing mixture is a polar monomer. The term “polar monomer”, as used herein, describes a monomer with a partially or completely negative charge. Examples of these monomers include, but are not limited to, monomers containing carboxylic acid, phosphate, or sulfate functional groups. Still further examples of polar monomers are monomers that include hydroxyl, ester, ether, amide, aldehyde and ketone functional groups. Preferably, the polar monomer is a carboxylic acid containing monomer. The term “acid containing monomer”, as used herein, refers to any ethylenically unsaturated monomer that contains one or more acid functional groups or functional groups that are capable of forming an acid, such as an anhydride, for example, methacrylic anhydride, maleic anhydride, or itaconic anhydride. Examples of acid containing monomers include, for example, carboxylic acid bearing ethylenically unsaturated monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid and fumaric acid; acryloxypropionic acid and (meth)acryloxypropionic acid; sulphonic acid-bearing monomers, such as styrene sulfonic acid, sodium vinyl sulfonate, sulfoethyl acrylate, sulfoethyl methacrylate, ethylmethacrylate-2-sulphonic acid, or 2-acrylamido-2-methylpropane sulphonic acid; phosphoethylmethacrylate; the corresponding salts of the acid containing monomer; or combinations thereof. In other embodiments of the present invention, the polar monomer comprises polar oligomers or unsaturated oligomers, such as trimers, that have a partially or completely negative charge and which have one or more points of unsaturation, such as terminal unsaturation. In certain other embodiments of the present invention, the polar monomer comprises low molecular weight polymeric stabilizers that may be soluble in base (i.e., contain many CO2H groups and are alkali soluble). Some non-limiting examples of these polar, polymeric stabilizers include MOREZ® 101 or TAMOL® 731, both of which are manufactured by Rohm and Haas, Inc. of Philadelphia, Pa. In these embodiments, the amount of polar stabilizer within the system may range from 15 to 50 weight percent.
In certain embodiments, the aqueous clay dispersion, or second reaction mixture, may comprise a monomer mixture of at least one ethylenically unsaturated monomer which is an anionic monomer. Preferably, the anionic monomer is an acid containing monomer. In these embodiments, a portion of the anionic monomer is “staged”, i.e., a portion of the anionic monomer, 50% or less, preferably 25% or less, even more preferably 10% or less, is added to the first aqueous reaction mixture containing no clay and the remainder of the anionic monomer is added to the second aqueous reaction mixture. In embodiments involving acid-containing monomers, it is believed that this allows the acid functional groups to equilibrate within the clay galleries and remain there during the polymerization process. The acid containing monomer may aid in lowering the viscosity of the aqueous reaction mixture containing clay and enhance the affinity of the polymer to the clay surface. This staged method of anionic monomer addition may advantageously result in an improvement in physical properties in comparison to a straight addition of the anionic monomer to the first aqueous reaction mixture.
Suitable emulsifiers may include, but are not limited to, those conventionally used in emulsion polymerization, such as salts of alkyl-, aryl-, aralkyl-, alkaryl-sulfates or sulfonates; alkyl-, aryl-, aralkyl-, alkaryl-poly(alkoxyalkyl) ethers; alkyl-, aryl-, aralkyl-, alkaryl-poly(alkoxyalkyl) sulfates; alkali salts of long-chain fatty acids such as potassium oleate, typically alkyl diphenyloxide disulfonate; and the like. The preferred emulsifiers may include, for example, dodecyl benzene sulfonate and dioctyl sulfosuccinate.
Suitable clays for the aqueous clay dispersion include any natural or synthetic layered mineral capable of being intercalated or exfoliated. Examples of such clays may include, for example, layered silicate minerals. The layered silicate minerals that may be employed include natural and synthetic minerals capable of forming intercalation compounds. Examples of some naturally occurring minerals include, but are not limited to those known as, smectite, phyllosilicate, montmorillonite, saponite, beidellite, montronite, hectorite, stevensite, vermiculite, kaolinite and hallosite. Preferably among these minerals is montmorillonite. Some non-limiting examples of synthetic minerals, or synthetic phyllosilicates, may include LAPONITE®, which is manufactured by Laporte Industries, Ltd. of Charlotte, N.C., magadiite, and fluorohectorite.
Clays typically have at least one naturally occurring cation, or first cation, such as potassium, calcium, or sodium, present within their galleries that are attracted to the net negative charge of the clay surface. For example, clays like montmorillonite may be mined with a naturally occurring or first cation such as sodium or calcium. The terms “sodium form” or “calcium form” refer to clays that have an exchangeable cation which is sodium or calcium, respectively.
Aqueous clay dispersions may be prepared by subjecting an aqueous clay mixture comprising at least one unmodified clay to shearing forces such as by mechanical mixing to partially and/or fully exfoliate the clay. Various high shearing methods to disrupt the physical integrity of clay particles in water to at least partially exfoliate the clay without requiring a modifying agent such as a surfactant are also envisioned. These methods include, but are not limited to, ultrasonication, megasonication, grinding/milling, high speed blending, homogenization, and the like. The aqueous clay dispersion may also be subjected to shearing forces at temperatures which range from 10 to 150° C., preferably from 20 to 100° C., and more preferably from 20 to 90° C. to further aid in exfoliating the clay layers. Although such high shearing methods may be used in the process of the present invention, these methods are not required to achieve an at least partially exfoliated state. In the various embodiments of this invention, the clay may include both exfoliated clay layers and non-exfoliated clay particles. In certain embodiments of the present invention, homogenization of the clay dispersion is not required.
Besides increasing the degree of exfoliation of the clay, increasing the clay concentration within the aqueous nanocomposite dispersion may also result in increased viscosities. To this end, viscosity may be controlled by dilution of the reaction media and/or clay dispersion by a suitable liquid, such as water. Typically, it may be desirable to control the viscosity of reaction media and/or clay dispersion by dilution prior to the polymerization step(s). For example, to obtain a high level of clay enrichment in the nanocomposites of the present invention (e.g., clay amounts greater than 5% based on total weight polymer within the aqueous nanocomposite dispersion), the reaction media may be diluted with a sufficient amount of water prior to subsequent polymerization steps to reduce the viscosity. The amount of dilution that is necessary to achieve a particular viscosity level may be readily determined by those skilled in the art. Typically, to obtain an appropriate viscosity range prior to adding subsequent reactants, the solids concentration of the reaction media may be controlled to less than 50%, typically from 10% to 40%, and even more typically from 20% to 30%. In certain embodiments, the viscosity of the aqueous dispersion prior to adding the reactants may range up to 5,000 centipoises (“cps”) using a Brookfield Viscometer and measured using a number 3 spindle at 60 revolutions per minute (“rpm”).
The emulsion polymerization step is typically carried out in a suitable reactor wherein the reactants (monomers, initiators, emulsifiers, unmodified aqueous clay dispersion, and optional chain transfer agents) are suitably combined, mixed, and reacted in an aqueous medium, and wherein heat may be transferred in to, and away from, the reactor. The reactants are typically added slowly (gradually, as in a semi-batch process) over time, continuously, or quickly as a “shot” (batchwise) into the reactor. Typically, the reactants are gradually added (“grad-add”) to the reactor.
The term “colloid” as used herein refers to composite particles having a number average particle size range from 0.05 to 1 μm. The term “mini-emulsion polymerization”, as used herein, generally relates to methods involving stable submicron oil-in-water dispersions in which the monomer droplets within the dispersion may range in size from 0.05 to 1 μm. Further discussion of mini-emulsion polymerization techniques is provided in “Miniemulsion Polymerization” by E. D. Sudol et al., Emulsion Polymerization and Emulsion Polymers, John Wiley and Sons, NY (1997), pp. 700-722. The references, Erdem et al., “Encapsulation of Inorganic Particles via Miniemulsion Polymerization”, Proc. Am. Chem. Soc. (Div Polym Mater Sci Eng) 1999, 80, 583 and Erdem et al., “Encapsulation of Inorganic Particles via Miniemulsion Polymerization. III. Characterization of Encapsulation”, Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 38, 4441-4450 (2000), provides some exemplary methods for mini—emulsion polymerization. The dispersion is typically obtained by shearing a system comprising oil, water, surfactant, and, optionally, a co-surfactant. Due to the small droplet size of the aqueous dispersion, it is believed that the monomer droplets within the miniemulsion may become the dominant site for particle nucleation.
The free-radical initiators which are typically used in the various steps of the process are those conventionally utilized in free-radical redox polymerizations conducted in the temperature range from 10° C. to 100° C., preferably from 20° C. to 95° C., and more preferably from 55° C. and 90° C. Temperatures higher than 100° C. are possible using equipment that is designed for elevated pressures. In some embodiments involving redox initiation, initiation temperatures are preferably kept below 85° C., more preferably below 55° C. for redox initiation. In other embodiments involving thermal initiation with persulfate salts, temperatures in the range 80° C. to 90° C. are used.
In one embodiment of the present invention, the monomers may be added batch-wise (“shot”) or fed continuously over time into the reactor. Continuous feeding by gradual addition of the aqueous reaction mixtures into the reactor over times from 0.5 to 18 hours, preferably from 1 to 12 hours, and even more preferably from 2 to 6 hours, is useful for controlling reaction temperature.
In certain embodiments of the present invention, the first aqueous reaction mixture comprises an emulsion containing a plurality of polymer seeds which are present in the emulsion in an amount ranging from 0.1 to 20, preferably 0.1 to 15, and more preferably 0.1 to 10% based on dry weight of total dry polymer weight in the resulting nanocomposite dispersion. An aqueous dispersion, comprising at least 0.1 to 20% of a layered clay based on dry weight of total dry polymer weight in said nanocomposite; is added, preferably on a gradual basis, to the emulsion. A monomer mixture comprising at least one ethylenically unsaturated monomer is combined with the emulsion comprising the seeds either prior to or along with the aqueous dispersion. At least a portion of the monomer is then polymerized thereby forming the polymer clay nanocomposite dispersion. In certain embodiments, the polymer seeds of the aqueous emulsion are formed in the same reaction vessel in which the monomer is polymerized. In these embodiments, the aqueous clay dispersion may comprise up to 200 weight percent based on dry weight of a layered clay. The lower percentage solids within the reactor vessel allows one to add higher clay levels while maintaining a usable viscosity.
Another process of the present invention involves preparing an aqueous nanocomposite dispersion by admixing an aqueous emulsion polymer and 0.1 to 10% based on dry weight of said emulsion polymer, of a layered clay. In this process, the aqueous emulsion polymer is typically prepared according to any of the various known methods of preparing emulsion polymers according to the art of emulsion polymerization. In one embodiment of this process it is typical that the nanocomposite dispersions are prepared using gradual addition “grad-add” processes. In this embodiment it is also typical that the nanocomposite polymers are prepared by multi-stage polymerizations, such as core-shell polymer particles having a rubber core and a hard shell. In this embodiment, the amount of clay is in the range of from 0.05% to 20%, preferably from 0.1% to 15%, and even more preferably from 0.1% to 10% based on dry weight of total dry polymer weight in the polymer seeds.
For preparing materials that have a rubbery component, it is desirable that the glass transition temperature of at least one constituent polymeric phase be less than the use temperature (e.g., ca. 25° C. for applications used at ambient conditions). The selection and amount of monomers required for controlling the glass transition may be readily determined through use of the Fox equation that is well known in the polymer art.
Larger core shell nanocomposites, e.g. 1,000 nanometers or greater, may be formed by polymerization techniques other than emulsion polymerization. These larger core shell nanocomposites may be formed via suspension polymerization as disclosed herein or via “swelling techniques” such as the techniques disclosed, for example, in “Aqueous Dispersions of Polymer-Oligomer Particles”, Polymer Colloids II, Robert Fitch editor, Plenum Press, New York, N.Y., 1980, pp. 83-93. For example, a latex may be prepared by conventional emulsion polymerization techniques. After polymerization, the latex is then swollen with monomer and a chain transfer agent and the monomer is then polymerized to form an oligomer in an aqueous dispersion. The aqueous dispersion of the oligomer and an emulsifier is then swollen with monomer and polymerized to provide larger sized particles. Clay may be added at some point during the process to provide a large core shell nanocomposite. These larger core shell nanocomposites may be useful as-is or, for example, as cores in plastics additives.
The admixing step of the modified layered clay in this embodiment is preferably completed without the need for a clay modifying agent such as a surfactant. In another embodiment, the clay is predispersed in water and admixed with the aqueous emulsion polymer. Any mechanical mixing device may be suitable as long as the clay particles are at least partially exfoliated. More preferably, the clay particles are mixed to uniformly disperse the clay within the nanocomposite dispersion. For example, a COWLES™ mechanical mixer may be used to prepare aqueous clay dispersions containing up to 20% clay, however it is more preferable to use a mechanical homogenizer to prepare aqueous clay dispersions containing from 0.1 to 10% clay.
In one embodiment of the present invention, the aqueous nanocomposite dispersions are capable of forming films upon drying (e.g., coatings and adhesives). In this embodiment, it is preferred that the polymers of the nanocomposites have a glass transition temperature in the range of from −80° C. to 50° C. Glass transition temperatures may be calculated by using the Fox equation (see T. G. Fox, Bull. Am. Physics Soc., Vol. 1, Issue No. 3, page 123(1956)).
In some embodiments of this invention, the aqueous nanocomposite dispersions desirably form films upon drying, with or without the addition of plasticizers or coalescents (e.g., coatings and adhesives). In these embodiments, it is preferred that the polymers of the nanocomposites have glass transition temperatures in the range of from −80° C. to 10° C.
In one embodiment of the present invention, a coating composition containing an aqueous nanocomposite dispersion is prepared. The coating composition of this invention may include, for example, coating or paint compositions which may be described in the art as architectural coatings, maintenance coatings, factory-applied coatings, automotive coatings, elastomeric wall or roof coatings, exterior insulating finishing system coatings, paper or paperboard coatings, overprint varnishes, fabric coatings and backcoatings, leather coatings, cementitious roof tile coatings, and traffic paints. Alternatively, the coating or paint compositions may be described as clear coatings, flat coatings, satin coatings, semi-gloss coatings, gloss coatings, primers, textured coatings, and the like. In these embodiments, it is preferred that the polymers of the nanocomposites have glass transition temperatures in the range from 0° C. to 70° C.
The coating compositions of the present invention may further include pigments and/or fillers such as, for example, titanium dioxide, iron oxide, zinc oxide, magnesium silicate, calcium carbonate, organic and inorganic colored pigments, and clays other than layered clay. Such pigmented coating compositions typically contain from 3 to 70% pigment on a volume basis, or more preferably from 15 to 60% titanium dioxide on a volume basis. The coating composition may be prepared by techniques that are well known in the coatings art. First, optionally, at least one pigment is dispersed within an aqueous medium under high shear such as is afforded by a COWLES™ mixer or, alternatively at least one predispersed pigment may be used. Then, the aqueous nanocomposite dispersion may be added under low shear stirring along with other coatings adjuvants, as desired. Alternatively, the aqueous nanocomposite dispersion may be included in the optional pigment dispersion step. The coating composition may also contain conventional coatings adjuvants such as, for example, tackifiers, emulsifiers, coalescing agents, plasticizers, buffers, neutralizers, thickeners or rheology modifiers, humectants, crosslinking agents including heat-, moisture-, light-, and other chemical- or energy-curable agents, wetting agents, biocides, plasticizers, antifoaming agents, colorants, waxes, water repellants, slip or mar aids, anti-oxidants, and the like. The coating composition, in addition to the aqueous nanocomposite dispersion described herein, may also contain at least one additional polymer, preferably an additional emulsion polymer(s) selected from film-forming and non-film-forming emulsion polymers, including, but not limited to polymeric pigments, such as solid particles, particles having a single void, or multivoided particles. These additional polymers, if added to the coating composition of the present invention, may be present at a level of 0 to 200%, based on dry weight of the total dry polymer weight in the nanocomposite dispersion.
The coating composition may be applied to a substrate such as, for example, paper or paperboard; consolidated wood products; glass; plastic; wood; metal; primed or previously painted surfaces; weathered surfaces; asphaltic substrates; ceramics; leather; and hydraulic substrates such as cement in ‘green’ or cured form, concrete, gypsum, and stucco. The coating composition applied to the substrate is typically dried, or allowed to dry, at a temperature from 10° C. to 95° C.
In another embodiment of this invention, an adhesive composition containing an aqueous nanocomposite dispersion is contemplated. The adhesive compositions may include, for example, those known in the art as pressure sensitive adhesives, laminating adhesives, packaging adhesives, hot melt adhesives, reactive adhesives, flocking adhesives, and flexible or rigid industrial adhesives. In these embodiments it is preferred that the polymers of the nanocomposites have glass transition temperatures in the range of from −80° C. to 80° C. The adhesives are typically prepared by admixing optional pigment and the optional adjuvants listed herein above as coatings adjuvants. The adhesive compositions are typically applied to substrates including plastic substrates such as film, sheet, and reinforced plastic composites; metal foil; fabric; metal; glass; cementitious substrates; and wood or wood composites. Application to the substrates is typically effected on machine by transfer roll coater, e.g., or by manual application devices.
In another embodiment of this invention, a caulk or sealant composition containing an aqueous nanocomposite dispersion is contemplated. In these embodiments it is preferred that the polymers of the nanocomposites have glass transition temperatures in the range of from −80° C. to 0° C. The caulk or sealant compositions are typically prepared by admixing pigment and such optional adjuvants listed hereinabove as coatings adjuvants as are appropriate. The caulk and sealant compositions are typically prepared at high solids content level such as 70 wt. % and above in order to minimize shrinkage on drying and consequently, may have a gel-like or paste-like consistency. Caulk and sealant compositions are typically applied to fill and/or seal junctions of substrates including metal; glass; cementitious substrates; wood or wood composites; and combinations thereof and are typically allowed to dry under ambient conditions.
In another embodiment of this invention, an ink composition containing an aqueous nanocomposite dispersion is contemplated. The ink compositions may include, for example, those known in the art as flexographic inks, gravure inks, ink jet inks, and pigment printing pastes. In these embodiments it is preferred that the polymers of the nanocomposites have glass transition temperatures in the range of from −50° C. to 50° C. The inks are typically prepared by admixing optional pigment, predispersed pigment, or dyes and the optional adjuvants listed herein above as coatings adjuvants. The ink compositions are typically applied to substrates including plastic substrates such as film, sheet, and reinforced plastic composites; paper or paperboard; metal foil; fabric; metal; glass; cloth; and wood or wood composites. Application to the substrates is typically effected on machine by flexographic blankets, gravure rolls, and silk screens.
In another embodiment of this invention, a nonwoven fabric binder containing an aqueous nanocomposite dispersion is contemplated. The nonwoven binder compositions may include, for example, those known in the art as binders for consumer and industrial nonwovens such as wipes and interlining, binders for insulating nonwovens such as fiberfill and fiberglass, and binders/strengthening agents for nonwovens and paper such as oil filter paper. In these embodiments it is preferred that the polymers of the nanocomposites have glass transition temperatures in the range of from −60° C. to 50° C. The nonwoven fabric binders are typically prepared by admixing optional pigment, and the optional adjuvants listed herein above as coatings adjuvants, as appropriate. The nonwoven fabric binder compositions are typically applied to substrates including nonwovens formed from cellulosic fibers such as paper and rayon; synthetic fibers such as polyester, aramid, and nylon; glass fibers and mixtures thereof. Application to the substrates is typically effected on machine by saturation bath, roll coater, spray, or the like.
In another embodiment of this invention, a polish containing an aqueous nanocomposite dispersion is contemplated. The polish compositions may include, for example, those known in the art as floor polishes, furniture polishes, and automobile polishes. In these embodiments it is preferred that the polymers of the nanocomposites have glass transition temperatures in the range of from 0° C. to 50° C. The polishes are typically prepared by admixing optional pigment, and the optional adjuvants listed herein above as coatings adjuvants, as appropriate, particularly waxes. The polish compositions are typically applied to substrates including wood, vinyl or polyurethane flooring, ceramic tiles, painted metal, and the like. Application to the substrates is typically effected by spray, roller, mop, or the like.
In another embodiment of this invention, a plastics additive containing an aqueous nanocomposite dispersion is contemplated. The plastics additive compositions may include, for example, those known in the art as processing aids and impact modifiers. In these embodiments it is preferred that the polymers of the nanocomposites have glass transition temperatures in the range of from −50° C. to 50° C. The plastics additives are typically prepared by admixing optional pigment, and the optional adjuvants listed herein above as coatings adjuvants, as appropriate, and, typically, drying the composition to a powdered form. The plastics additives compositions are typically mixed with the plastic such as, for example, polyvinyl chloride, polymethyl methacrylate and polypropylene, by milling or extrusion.
In a further aspect of the present invention, a digital imaging composition incorporating an aqueous nanocomposite dispersion and/or nanocomposite particles is contemplated. The term “digital imaging” as used herein generally relates to compositions that allow the reproduction of an image onto a substrate. Suitable applications for digital imaging compositions include toners for electrophotography such as xerography or compositions for ink jet printers or similar applications. The Tg and particle size for digital imaging compositions varies depending upon its method or system of use. Generally, digital imaging compositions for ink jet applications may have a lower particle size and Tg compared to the particle size and Tg for digital imaging compositions for electrophotography applications. For example, typical Tg values for ink jet applications may range from 45° C. to 60° C. whereas Tg values for electrophotography applications may range from 55° C. to 85° C. Further, non-limiting variables such as viscosity, surface tension, and pH of the digital imaging composition may also be adjusted based upon the end use of the composition.
In another aspect of the present invention the emulsion polymer of the nanocomposite may be prepared by a process which produces particles which when dry contain at least one void such as, for example, particles having a single void, multivoided particles, and particles having interpenetrating networks of void and polymer (polymer “sponge”).
TABLE I provides a summary of exemplary and reference compositions. The compositions in Table I vary with regard to whether the composition is single or multi-stage polymerized, the weight percentage of the unmodified clay added, and whether the clay is present by physically blending, referred to herein as “admixed”, with an aqueous emulsion copolymer or present during polymerization, referred to herein as “in situ”. Both the physical blending of the clay with the copolymer and the in situ polymerization of the acrylic monomers in the presence of the clay platelets is done in an aqueous emulsion media.
TABLES II through VI provide a comparison of the dielectric relaxation of thin polymer films, comprising exemplary polymer clay nanocomposites and reference compositions. These exemplary and reference compositions are cast upon identical aluminum substrate or test coupon to illustrate the differences in mechanical properties between the polymer clay nanocomposite and polymer reference compositions. Dielectric relaxation spectroscopy measurements were obtained using a Solartron Frequency Response Analyzer Model 1260, manufactured by Solartron Instruments, Inc., Allentown, Pa. The dielectric relaxation factor, also referred to herein as the dielectric storage factor, is related to the dynamic mechanical storage modulus of the composition.
TABLE II compares the dielectric relaxation measurements of a single stage copolymer comprising a 50:50 blend of methyl methacrylate (“MMA”) and butyl acrylate (“BA”) with two polymer clay nanocomposite compositions comprising 5% by weight of unmodified, sodium montmorillonite clay in the reaction mixture. The two polymer clay nanocomposite compositions differed in whether the clay was present in situ during polymerization or was admixed. While there is generally an improvement in the mechanical properties of both polymer clay nanocomposite compositions in comparison to the reference composition without the clay, the increase in dielectric storage factor is more pronounced in the polymer clay nanocomposite compositions with the admixed clay. However, polymer clay nanocomposite compositions wherein the clay is admixed result in films that are not as clear relative to polymer clay nanocomposite compositions formed during polymerization.
TABLE V provides the dielectric relaxation spectra for the reference copolymer, p(BA MAA=50:50) and three polymer clay nanocomposite compositions comprising the same copolymer physically blended with varying amounts of unmodified, sodium montmorillonite. TABLE V also shows that the dielectric storage factor increases with increasing amounts of clay in the composition.
A stock solution of an at least partially exfoliated, unmodified 2.22% sodium montmorillonite (clay) was prepared by a homogenization process. Other unmodified clays from various commercial sources, such as “PGV” which is the trade name for a sodium montmorillonite clay sold by Nanocor, Arlington Heights, Ill. or “sodium cloisite” is the trade name for a sodium clay available from Southern Clay Products, Gonzales, Tex., may also be used. Partial exfoliation was achieved by observing an increase in viscosity of the stock solution during homogenization as well as observing the presence of non-exfoliated, intercalated clay particles in the resulting polymer-clay nanocomposites via XRD. A quantity of 10 g of clay was added to 440 g of deionized water to form an aqueous clay dispersion. The dispersion was homogenized for 2 minutes at 20,000 rpm using a Cyclone IQ2 microprocessor controlled mechanical homogenizer using the smallest shaft. Because the clay dispersion remained clumpy, the homogenization process was repeated with a larger shaft for the same amount of time and at the same speed. This 2.22% clay dispersion was later used in the emulsion polymerization process.
The initial step in the emulsion polymerization process in the presence of the clay dispersion was to provide a reaction mixture. A monomer mixture, plus emulsifier, sodium lauryl sulfate (SLS) solution, and clay dispersion were homogenized for a maximum of two minutes at 20,000 rpm. The mixture comprised 30.6 weight percent of monomer, 68.83 weight percent of the 2.22 weight percent of the aqueous clay dispersion, and 0.58 weight percent of a 28 weight percent of SLS solution. This homogenized reaction mixture plus 33 g of deionized water rinse was then added to a 500-ml round bottom glass vessel fitted with stirrer, heating mantle, reflux condenser and nitrogen sweep. An initiator, consisting of 0.59 weight percent of sodium persulfate and 99.41 weight percent of deionized water, was added to the reaction mixture under room temperature conditions and stirring at 140 rpm. An additional 30 g of deionized water, was added to the reaction vessel. The entire mixture was heated to 60° C. and the reaction was allowed to exotherm. At the exotherm peak temperature, the reaction was held at 80° C. for one hour. The reaction mixture was cooled, filtered, and tested for total solids and particle size.
Reference Example 1 (Single Stage 50 MMA/50 BA Copolymer, No Clay)
The emulsion polymerization process described above was used to polymerize a monomer mixture comprising methyl methacrylate (“MMA”) and butyl acrylate (“BA”) in a 50:50 ratio. No clay dispersion was present. A portion of the emulsion was coated onto a 0.002 cm thick aluminum sheet to yield a 0.013 cm thick film. The entire arrangement of film and substrate, or laminate, was dried overnight in a vacuum oven at 75° C. After drying, a disk of 2.4439 cm2 surface area was cut from the laminate and examined using dielectric relaxation spectroscopy. The results of this examination is provided in TABLE II.
Example 1 (Single Stage, In-Situ Copolymerization of 50 MMA/50 BA with 5% Clay)
A reaction mixture comprising a monomer mixture of MMA and BA in a 50:50 weight ratio of 50:50 and an aqueous clay dispersion was polymerized using the emulsion polymerization process described above to yield a nanocomposite dispersion containing 5% based on dry weight of clay. The final size of the polymer particles was 92 nm. The total solids content of the nanocomposite dispersion was 23.16 weight percent. A portion of the nanocomposite dispersion was coated onto a 0.002 cm thick aluminum sheet to yield a 0.015 cm thick film. The entire arrangement of film and substrate was dried overnight in a vacuum oven at 75° C. After drying, a disk of 2.4439 cm2 surface area was cut from the laminate and evaluated by dielectric relaxation spectroscopy and the results are provided in TABLE II. As TABLE II illustrates, the dielectric storage factor for the composition in Example 1 is at least twice that of the Reference Example 1.
Example 2 (50 MMA/50 BA Copolymer Dispersion Admixed with Clay to 5%)
The emulsion prepared copolymer of Reference Example 1 was combined with an adequate quantity of an aqueous clay dispersion to yield a 5% nanocomposite dispersion based on dry weight of clay. The mixture was thoroughly homogenized by the process described in the general emulsion procedure. A portion of the homogeneous mixture was coated onto a 0.002 cm thick aluminum sheet to yield a 0.004 cm thick film. The entire arrangement of film and substrate was dried overnight in a vacuum oven at 75° C. After drying a disk of surface area 2.4439 cm was cut from the laminate and evaluated, by dielectric relaxation spectroscopy, for improvement in the dielectric storage factor. The data provided in TABLE II reveals that the dielectric storage factor is slightly greater than that of Reference Example 1.
Reference Example 2 (Single Stage Copolymerization of 88 MMA/12 BA with No Clay)
An emulsion prepared copolymer of composition, p(MMA/BA=88:12) was coated onto a 0.002 cm thick aluminum sheet to yield a 0.005 cm thick film. The entire arrangement of film and substrate (“laminate”) was dried overnight in a vacuum oven at 75° C. A disk of surface area 2.4439 cm was cut from the laminate and evaluated, by dielectric relaxation spectroscopy, for improvement in the dielectric storage factor. TABLE III provides the dielectric storage factor for the reference composition.
Example 3 (88 MMA/12 BA Copolymer Dispersion Admixed with Clay Dispersion to 5%)
A portion of an emulsion prepared copolymer of composition p(MMA/BA=88:12) was combined with an adequate quantity of an aqueous clay dispersion to yield a nanocomposite dispersion containing 5% of unmodified clays, based upon the dry weight of clay within the mixture. The mixture was thoroughly homogenized by the process described in the general emulsion procedure. A portion of the homogeneous mixture was coated onto a 0.002 cm thick aluminum sheet to yield a 0.004 cm thick film. The entire arrangement of film and substrate was dried overnight in a vacuum oven at 75° C. After drying, a disk of surface area 2.4439 cm2 was cut from the laminate and evaluated, by dielectric relaxation spectroscopy, for improvement in the dielectric storage factor. The data listed in TABLE III reveal that the dielectric storage factor is slightly better than of the Reference Example 2 polymer.
Examples 4 to 6 (98 MMA/2 BA Copolymer Dispersion Admixed with Clay to 0%, 2%, and 5%)
An emulsion prepared copolymer of composition p(MMA BA=98:2) was combined with a sufficient quantity of an aqueous clay dispersion to yield a 0%, 2% and 5% of total clay (Examples 4, 5, and 6, respectively), based on the overall weight of polymer clay mixtures. These mixtures were thoroughly homogenized by the process described in the general emulsion procedure. Portions of the neat polymer emulsion and the homogeneous mixtures were each coated onto a 0.002 cm thick aluminum sheet to yield: 0.015 cm, 0.021 cm and 0.034 cm thick films, respectively, for Examples 4, 5, and 6. The entire arrangements of films and substrates were dried overnight in a vacuum oven at 75° C. After drying, disks of surface area 2.4439 cm2 were cut from the laminates and evaluated, by dielectric relaxation spectroscopy, for improvement in the dielectric storage factor. The data listed in TABLE IV show that the dielectric storage factor generally increases as the amount of clay increases.
Examples 7 to 10 (50 MMA/50 BA Copolymer Dispersion Admixed with Clay to 0%, 5%, 10% and 20%)
Portions of an emulsion prepared copolymer of composition p(MMA/BA=50:50) are combined with adequate quantity of clay dispersion to yield: 0%, 5%, 10% and 20% of total clay (Examples, 7, 8, 9, and 10, respectively), based on the overall weight of polymer clay mixtures. These mixtures were thoroughly homogenized by the process described in the general emulsion procedure. Portions of the neat polymer emulsion and the homogeneous mixtures were each coated onto a 0.002 cm thick aluminum sheet to yield: 0.013 cm, 0.004 cm and 0.007 cm and 0.006 cm thick films. respectively. The entire arrangements of films and substrates were dried overnight in a vacuum oven at 75° C. After drying, disks of surface area 2.4439 cm2 were cut from the laminates and evaluated, by dielectric relaxation spectroscopy, for improvement in the dielectric storage factor. The data listed in TABLE V reveal that the dielectric storage factor is generally increased with an increased amount of clay.
The two stage (core-shell) polymers that follow were prepared at a 5-L scale by a 40:60 core:shell gradual feed emulsion polymerization process starting with 40 nm diameter polymer seeds derived from 51 parts ethyl acrylate (“EA”), 49 parts MMA, and 1 part of MAA. The polymers with clay were prepared by first pre-emulsifying the monomer emulsion through simple manual agitation and then homogenizing the mixture with 10 g of clay for 2 minutes at 20,000 rpm in a Cyclone IQ2 mechanical homogenizer.
Each of the two stage copolymer reactions was carried out by adding 99.96% of deionized water and 0.04% of acetic acid to a 5-L round bottom flask fitted with stirrer, heating mantle, reflux condenser, nitrogen sparge tube and feed tubes for both the monomer emulsion and the catalyst feeds. With the stirring set at 150 rpm, the mixture was sparged with nitrogen for one hour and heated to 50° C. The nitrogen sparge was changed to a sweep and an activator solution, consisting of 1.92% of sodium formaldehyde sulfoxylate (SSF) and 64.26% of deionized water, was added to the reaction vessel followed by 33.82% of deionized water rinse. A 61.6% polymer seed shot was then added with a 38.4% deionized water rinse. The temperature of the reaction mixture reached 50° C. before starting the gradual feed of the monomer emulsion and the catalyst.
The first stage monomer emulsion consisted of 81.1% of butyl acrylate (BA), 0.82% of allyl methacrylate (ALMA), 1.71% of a 23% solution of DS-4 or 1.71% of a 75% solution of dioctyl sulfosuccinate, and 16.37% of deionized water. The first stage catalyst feed consisted of 1.71% tert-butyl hydroperoxide (t-BHP) and 98.29% of deionized water. At the set temperature of 50° C., the heating was stopped and the reaction mixture was monitored to observe an exotherm. The monomer emulsion and catalyst feeds were started simultaneously. Both the monomer emulsion and catalyst solutions were set to feed for duration of 90 minutes. The monomer emulsion feed was fed at a rate of 9.63 g/min. and the t-BHP initiator feed was delivered at a rate of 0.4 g/min. At the end of 80 minutes of feeding the emulsified monomer mixture the remaining 126.9 g of emulsion was added to the reaction vessel. The monomer feed was followed by addition of 30 g deionized water, line rinse feed, into the reactor. At the end of the initiator feed, 15 g of deionized water, line rinse feed, was fed into the reactor. After all the line rinses were added, the first stage latex was sampled for particle size and polymer conversion.
For the second stage of the polymerization, the first stage reaction mixture was stirred at 170 rpm. The stage 2 activator solution, consisting of 2.62% SSF, 86.91% of deionized water and a 10.47% deionized water rinse was added to the reaction. At this time a 120 minute monomer emulsion and initiator, t-BHP feeds were started. The monomer emulsion for the in situ polymerization with clay consisted of 69.74% of MMA, 3.67% of BA, 24.47% of deionized water, 1.28% of a 23% solution of DS-4 or 1.71% of a 75% solution of dioctyl sulfosuccinate, 0.15% of n-dodecyl mercaptan (n-DDM), and 0.7% of clay. The monomer emulsion for the examples without clay consisted of 70.23% of MMA, 3.70% of BA, 24.64% of deionized water, 1.29% of a 23% solution of DS-4, 0.15% of n-DDM and 0% of clay. The catalyst solution was made up of 11.1% of t-BHP and 88.9% of deionized water. The monomer emulsion was fed at a rate of 11.9 g/min. and the initiator was fed at a rate of 0.562 g/min. During the course of the reaction, heat was applied to the reaction vessel if the reaction temperature fell below 65° C. At the end of the feeds, rinse feeds of 30 g of deionized water, for the monomer emulsion and 15 g of deionized water were added. The reaction mixture was held at its peak temperature for 30 minutes before being cooled and filtered.
Reference Example 3 (Multi-Stage Copolymerization of 40 (99 BA/1 ALMA) II 60 (95 MMA/5 BA), with DOSS Emulsifier, but with No Clay)
Using the emulsion polymerization process described above for the two stage copolymer, a two stage copolymer composed of methyl methacrylate: butyl acrylate ratio of 60:40 was synthesized to yield a polymer latex with 204 nm average particles (no clay). The emulsifier used in the polymerization process was 1.28% of a 75% solution of dioctyl sulfosuccinate sodium salt. The total solids content of the emulsion was 48.55 weight percent. A portion of the emulsion was coated onto a 0.002 cm thick aluminum sheet to yield a 0.069 cm thick film. The entire arrangement of film and substrate was dried overnight in a vacuum oven at 75° C. After drying a disk of surface area 2.7318 cm2 was cut from the laminate and evaluated, by dielectric relaxation spectroscopy, for assessment of the magnitude of the dielectric storage factor. The data listed in TABLE VI, reveal the value of the dielectric storage factor. A list of the mechanical properties are given in TABLE VII.
Example 11 (Multi-Stage Copolymerization of 40 (99 BA/1 ALMA)//60 (95 MMA/5 BA) with DOSS Emulsifier, and with 0.7% Clay in Second Stage)
The emulsion polymerization process described in Reference Example 3 for the two stage copolymer was employed in the preparation of a two stage copolymer that composed of MMA: BA ratio of 60:40. The copolymer was synthesized in the presence of 0.7 weight percent of clay to yield a polymer latex with 204 nm average particles. The emulsifier used in the polymerization process was a 1.28% of a 75% solution of dioctyl sulfosuccinate sodium salt (DOSS). The total solids content of the emulsion was 48.55 weight percent. A portion of the emulsion was coated onto a 0.002 cm thick aluminum sheet to yield a 0.047 cm thick film. The entire arrangement of film and substrate was dried overnight in a vacuum oven at 75° C. After drying a disk of surface area 1.4935 cm2 was cut from the laminate and evaluated, by dielectric relaxation spectroscopy, for assessment of the magnitude of the dielectric storage factor. The data listed in TABLE VI reveal that the dielectric storage factor is at least twice the size of that for the polymer defined in the reference example 3. The mechanical properties listed in TABLE VII supports the improvement in dielectric storage factor.
Reference Example 4 (Multi-Stage Copolymerization of 40 (99 BA/1 ALMA)//60 (95 MMA/5 BA), with DDBS Emulsifier, but with No Clay)
The emulsion polymerization process described above for the two stage copolymer was employed in the preparation of a two stage copolymer that composed of MMA: BA ratio of 60:40. The copolymer was synthesized in the presence of no clay to yield a polymer latex with 204 nm average particles. The emulsifier used in the polymerization process was a 1.28% of a 75% solution of dodecyl benzene sulfonate (DDBS). The total solids content of the emulsion was 48.55 weight percent. The mechanical properties are listed in TABLE VII.
Example 12 (Multi-stage Copolymerization of 40 (99 BA/1 ALMA)//60 (95 MMA/5 BA) with DDBS Emulsifier, and with 0.7% Clay in Second Stage)
A multi-stage nanocomposite dispersion was prepared according to Example 11 with the exception that DDBS was used as the emulsion instead of DOSS. The mechanical properties listed in TABLE VII, shows that using DDBS provides enhanced Dynatup Impact strength over using DOSS in multi-stage nanocomposite dispersions.
Example 13 (40 (99 BA/1 ALMA)//60 (95 MMA/5 BA) Core-Shell Copolymer Dispersion Admixed with Clay to 0.6%)
In this example, the emulsion polymerization process described above for the two stage copolymer was used in the preparation of a two stage copolymer that composed of MMA: BA in a 60:40 ratio. The copolymer was synthesized in the presence of no clay to yield a polymer latex with 204 nm average particles. The emulsifier used in the polymerization process is a 1.28% of a 75% solution of dodecyl benzene sulfonate. The total solids content of the emulsion was 48.56 weight percent. A portion of the emulsion was combined with a homogeneous aqueous clay dispersion to yield a 0.6% of polymer clay mixture. The mixture was thoroughly homogenized by the process described in the general emulsion procedure. A portion of the emulsion was coated onto a 0.002 cm thick aluminum sheet to yield a 0.104 cm thick film. The entire arrangement of film and substrate was dried overnight in a vacuum oven at 75° C. After drying a disk of surface area 2.4885 cm2 was cut from the laminate and evaluated, by dielectric relaxation spectroscopy, for assessment of the magnitude of the dielectric storage factor. The data listed in TABLE VI reveal that the dielectric storage factor is at least twice that for the polymer defined in the reference example 3. The mechanical properties listed in TABLE VII, falling dart impact energy, is consistent with the relatively low dielectric storage factor.
% wt Clay
Ex. Stage I Polymer Stage II Polymer Clay Addition
Ref. 1 p(MMA/BA) = 50:50) — 0.0 —
Ref. 2 p(MMA/BA = 88:12) — 0.0 —
1 p(MMA/BA) = 50:50) — 5.0 in-situ
2 p(MMA/BA) = 50:50) — 5.0 admixed
3 p(MMA/BA = 88:12) — 5.0 admixed
4 p(MMA/BA = 98:2) — 0.0 —
5 p(MMA/BA = 98:2) — 2.0 admixed
6 p(MMA/BA = 98:2) — 5.0 admixed
7 p(MMA/BA = 50:50) — 0.0 admixed
8 p(MMA/BA = 50:50) — 5.0 admixed
9 p(MMA/BA = 50:50) — 10.0 admixed
10  p(MMA/BA = 50:50) — 20.0 admixed
Ref.3 40 parts 60 parts 0.0 —
p(BA-ALMA = 99:1) p(MMA/BA = 95:5)
11  40 parts 60 parts 0.7 in-situ Stage
p(BA-ALMA = 99:1) p(MMA/BA = 95:5) II
Ref 4 40 parts 60 parts 0.0 —
12  40 parts 60 parts 0.7 in-situ Stage
13  40 parts 60 parts 0.6 admixed
Dielectric Relaxation of Single Stage Copolymer
and Composites in the p(MMA/BA = 50:50) +
Reference Example 1 Example 2
FREQUENCY Example 1 (5% in-situ (5% admixed
(Hz) (No Clay) clay) clay)
1.00E+06 2.58E−13 6.29E−13 8.93E−13
3.16E+05 5.38E−13 7.54E−13 1.25E−12
1.00E+05 6.86E−13 8.29E−13 1.44E−12
3.16E+04 7.10E−13 8.87E−13 1.50E−12
1.00E+04 7.18E−13 9.62E−13 1.56E−12
3.16E+03 7.56E−13 1.06E−12 1.66E−12
1.00E+03 6.80E−13 1.18E−12 1.75E−12
Dielectric Relaxation of Single Stage Copolymer and Composites in
the p(MMA/BA = 88:12) + Clay System
Frequency Reference Example 2 Example 3
(Hz) (No Clay) (5% admixed clay)
1.00E+06 5.90E−13 5.79E−13
3.16E+05 7.07E−13 9.35E−13
1.00E+05 7.61E−13 1.14E−12
3.16E+04 7.72E−13 1.24E−12
1.00E+04 7.73E−13 1.36E−12
3.16E+03 7.82E−13 1.55E−12
1.00E+03 7.65E−13 1.78E−12
Frequency Reference Example 4 Example 5 Example 6
(Hz) 0% Clay 2% Clay 5% Clay
1.00E+06 4.80E−13 5.32E−13 1.52E−12
3.16E+05 8.21E−13 1.02E−12 2.55E−12
1.00E+05 1.00E−12 1.28E−12 3.16E−12
3.16E+04 1.02E−12 1.33E−12 3.47E−12
1.00E+04 1.04E−12 1.35E−12 3.86E−12
3.16E+03 1.06E−12 1.38E−12 4.42E−12
1.00E+03 1.08E−12 1.42E−12 5.22E−12
Frequency Example 7 Example 8 Example 9 Example 10
(Hz) 0% Clay 5% Clay 10% Clay 20% Clay
1.00E+06 2.58E−13 6.29E−13 8.28E−13 1.47E−12
3.16E+05 5.38E−13 7.54E−13 1.08E−12 1.76E−12
1.00E+05 6.86E−13 8.29E−13 1.25E−12 1.92E−12
3.16E+04 7.10E−13 8.87E−13 1.39E−12 2.03E−12
1.00E+04 7.18E−13 9.62E−13 1.60E−12 2.16E−12
3.16E+03 7.56E−13 1.06E−12 1.88E−12 2.28E−12
1.00E+03 6.80E−13 1.18E−12 2.36E−12 2.35E−12
Dielectric Relaxation of Multi-Stage Copolymer and Composites
in the 40 (99 BA/1 ALMA)//60 (95 MMA/5BA) + Clay System
Reference Example 11 Example 13
Frequency Example 3 (0.7% in-situ (0.6% admixed
1.00E+06 3.26E−13 9.40E−13 3.84E−13
3.16E+05 4.84E−13 1.14E−12 6.46E−13
1.00E+05 4.73E−13 1.12E−12 6.27E−13
3.16E+04 4.62E−13 1.11E−12 6.26E−13
1.00E+04 4.69E−13 1.10E−12 6.44E−13
EXAMPLE REF. EX-3 EXAMPLE 11 EXAMPLE 4 EXAMPLE 12 EXAMPLE 13
(note 1) Value Std Dev Value Std Dev Value Std Dev Value Std Dev Value Std Dev
Dynatup Impact (D3763),
⅛″ plagues, n = 5
Total Energy (ft-lb) 8.7 1.5 9.3 2.5 8.1 1.4 11.7 1.2 5.4 0.7
% Ductile 0 0 20 0 0
Notched Izod (D256),
⅛″ Izod (ft-lb/in) 1.41 0.11 1.48 0.06 1.45 0.19 1.48 0.02 1.18 0.03
% Hinged 0 0 0 0 0
¼″ Izod (ft-lb/in) 0.75 0.07 0.89 0.06 0.89 0.11 0.89 0.09 0.51 0.03
Tensile Impact (D1822),
Strength (ft-lb) 99.3 9.5 131.7 33.8 89.7 19.7 99.6 21.3 84.6 14.9
Tensile Properties (D638)
Type 5, n = 5
Yield (%) 5.4 0.1 5.3 0.1 5.9 0.7 5.7 0.1 5.8 0.2
(psi) 4198 33 3924 30 4358 172 4578 44 4658 31
Max (%) 79.1 7.4 85.2 13.3 101.3 6.2 69.3 6.9 95.0 8.1
(psi) 4655 224 4530 319 5174 144 5190 211 5202 2
Break (%) 79.5 6.7 85.4 12.8 101.3 6.2 69.5 6.6 95.1 8.0
(psi) 4648 236 4526 327 5174 144 5184 223 5198 265
Tan Modulus (psi) 185,425 1,276 173,800 1,751 187,140 11,408 204,600 3,130 195,920 5,116
Flexural Properties (D790),
Modulus (psi) 160,013 3,048 145,742 2,404 166,618 468 162,684 1,058 178,726 1,101
DTUFL (D648),
@ 264 psi, As Received, n = 2
DTUFL (° C.) 59.8 1.8 58.1 0.8 62.3 1.6 61.6 1.3 64.8 1.5
Rockwell Hardness (D785),
‘R’ Scale, n = 3
Rockwell (‘R’) 49.6 1.0 34.9 4.3 63.9 1.7 53.7 1.5 68.2 1.7
A latex was synthesized via the following method: To an empty reactor kettle was added 436.00 g DI water, 5.08 g anionic surfactant (30% aqueous solution), and 3.10 g sodium carbonate. A monomer emulsion was formed containing 626.60 g water, 36.90 g anionic surfactant (30% aqueous solution), 654.67 g Butyl Acrylate, 350.00 g Methyl Methacrylate, and 15.10 g methacrylic acid. The kettle contents were heated to 85° C. A 55.80 g quantity of the monomer emulsion was added to the kettle to form a polymer seed. Then, 4.03 g ammonium persulfate (dissolved in 28 g water) was added to initiate polymerization. The monomer emulsion was fed into the kettle such that a reactor temperature of 85° C. was maintained. After monomer feeds were completed, the batch was cooled to 65° C., and upon reaching 65° C. 5.58 g ferrous sulfate (0.15% aqueous) was added to the reactor. Then, a 1.12 g quantity of 70% tert-butyl hydroperoxide in 20 g of water was added along with a 0.56 g quantity of isoascorbic acid in 20.00 g water. The temperature was reduced to below 45 C. The pH of the batch was raised to 7.5 using ammonium hydroxide (28% aqueous) and a bactericide (4.77 g Kathon LX (1.4% aqueous) with 6.20 g water) was added. The sample was filtered through a 100 mesh screen to remove any large pieces of coagulated material.
A nanocomposite dispersion was prepared according to the polymerization method described in Reference Example 14 with 5% unmodified phyllosilicate clay (% based on weight on monomer charged) present in the reactor. After the 55.80 g monomer emulsion charge had been added to the kettle to form the polymer seed, the clay was introduced to the remaining monomer emulsion with vigorous agitation, and fed into the reactor.
A blend of a latex prepared as in Reference Example 14 was homogenized with 5% phyllosilicate clay for 1 hour using a PRO250 homogenizer (manufactured by Pro Scientific Monroe, Conn.).
Application Test Results for Examples 14 to 16
Films of each of the “unformulated” coatings in Examples 14 to 16 were prepared. Tensile strength and elongation data for the unformulated coatings were collected using an Instron Model 1122 instrument (manufactured by Instron Corporation, Canton, Mass.). Samples were pulled at a rate of 5.08 cm/min. Sample data was calibrated for film thickness, width, and weight of each sample film. The initial distance between the clamps holding the sample being tested is 2.54 cm. Experiments were run in a controlled environment room with a temperature of 22° C. and a humidity level of 50%. Tensile measurements are provided in Table VIII.
Tensilemax/Elongation Tensile Strength/Elongationmax
Example lbs per inch/% lbs per inch/%
14 211/920 21/3200
15 (In situ) 517/660 501/740
16 (Blend) 548/940 539/985
Formulated coatings were prepared using the dispersions of Examples 14 to 16 and tested for rheology modifier (“RM”) demand, gloss, and average scrub resistance. RM demand was measured as the weight of rheology modifier needed per hundred pounds of formulated paint so that the formulated paint achieves a viscosity of approximately 90 KU units or 1.3 on the ICI viscosity scale. Gloss was measured from draw down charts at 20 degree and 60 degree angles according to ASTM D-523-89. Scrub resistance was measured according to ASTM D-2486-74A. These measurements are recorded in Table IX.
2020npr(a)/8W(b)
Example (lbs) Gloss 20/60 Average scrub
Ref.14 25/3.8 20/64 320
Ex. 15 (in-situ) 10/0 20/67 645
Ex. 16 (blend) 20.4/0  9/52 926
(a)ACRYSOL (TM) RM-2020NPR, Robin and Haas Company, Philadelphia, Pennsylvania
(b)ACRYSOL (TM) RM-8W, Robin and Haas Company, Philadelphia, Pennsylvania
Examples 17 to 21 indicate that various ways of preparing polymer-clay nanocomposite dispersions are possible using the processes of the present invention. In these examples, nanocomposite dispersions were prepared according to the polymerization of Reference Example 14 with PGV unmodified montmorillonite clay (provided by Nanocor, Inc., Arlington Heights, Ill.) using the following process variations:
Ex # Method of Clay Addition
Ref. 14 —
17 Homogenized in emulsified monomer mixture water
18 Mechanical stirring, no homogenization, of 5% PGV clay in reactor
water before polymer seed formation.
18B 2.65 g of sodium hydrosulfite and 20 g DI water added to reactor after
(redox heating to 85° C. and before addition of 5% PGV clay in reactor water
process) before polymer seed formation (mechanical stirring only).
18C Addition of 5% PGV clay to reactor water before polymer seed
(staged formation (mechanical stirring only). ½ of MAA (7.55 g) added to
acid) kettle after the PGV clay but before the 55.80 g of monomer emulsion
seed is charged. The remainder of the MAA is added to the monomer
emulsion as usual.
18D 2.65 g of sodium hydrosulfite and 20 g DI water added to reactor after
process and before polymer seed formation (mechanical stirring only). ½ of MAA
staged acid) (7.55 g) added to kettle after the PGV clay but before the 55.80 g of
monomer emulsion seed is charged. The remainder of the MAA is
added to the monomer emulsion as usual.
18E Addition of 5% PGV clay to reactor water before polymer seed
(staged acid formation (mechanical stirring only). ½ of MAA (7.55 g) added to
then redox kettle after the PGV clay but before the 55.80 g of monomer emulsion
process) seed is charged. 2.65 g of sodium hycirosulfite and 20 g DI water
added to reactor after the staged acid and before the ammonium
persulfate. The remainder of the MAA is added to the monomer
19 Mechanical stirring, no homogenization, of 5% PGV clay in reactor
water after polymer seed formation.
20 2% PGV clay homogenized in reactor water (before seed formation)
21 5% PGV clay homogenized in reactor water (before seed formation)
Tensile strength and elongation data of films prepared from unformulated coatings of nanocomposite dispersions made according to the above described process variations were collected on a Tinius Olsen Benchtop Universal Testing Machine (manufactured by Tinius Olsen Testing Machine Company, Willow Grove, Pa.). Films were pulled at a rate of 5.08 cm/min. Sample data was calibrated for film thickness, width, and weight of each sample film. The initial distance between the clamps holding the sample being tested is 2.54 cm. Experiments were run in a controlled environment room with a temperature of 22° C. and a humidity level of 50%. Tensile measurements are provided in the following table:
Ex Clay Level & Tensilemax/
# Type Elongation
Ref. No clay 58.8 psi/1067%
17 5% PGV 84.9 psi/1085%
18 5% PGV 84.0 psi/1110%
18B 5% PGV 205.0 psi/947%
18C 5% PGV 186.4 psi/948%
18D 5% PGV 245.0 psi/1136%
18E 5% PGV 167.0 psi/1283%
19 5% PGV 78.8 psi/1163%
20 2% PGV 84.0 psi/1253%
21 5% PGV 109.3 psi/1225%
1Average of the values 29.2 psi/3180% and 75 psi/1578%
Tensilemax values are +/−3 psi.
As Table XI illustrates, the polymer clay nanocomposite compositions, in which a reduction-oxidation reaction was fostered using the reduction of Fe within the clay to form radicals such as in Example 18B and in which the reduction-oxidation reaction was fostered along with a staged acid approach such as in Example 18D, displayed dramatic improvements in tensile properties in comparison with polymers and polymer clay nanocomposite compositions polymerized from the same monomers.
A 98.1 BA/1.9 MAA latex was synthesized via the following method: To an empty reactor kettle was added 650.00 g DI water, 26.30 g polymer preform (45% solids latex), and 0.90 g sodium carbonate. A monomer emulsion was formed using 1200.00 g water, 17.90 g anionic surfactant (23% aqueous solution), 1748.00 g Butyl Acrylate, and 32.60 g methacrylic acid. The kettle contents were heated to 85° C. Then, 7.60 g ammonium persulfate and 1.90 g sodium carbonate (dissolved in a total of 182.00 g water) was added gradually to initiate polymerization. The monomer emulsion was fed into the kettle such that a reactor temperature of 85° C. was maintained. After feeds were completed, the batch was cooled to 65° C., and upon reaching 65° C., a 0.80 g quantity of ferrous sulfate (0.15% aqueous) was added to the reactor along with 1.20 g of versene (0.1% aqueous). Then, a 4.00 g quantity of 70% tert-butyl hydroperoxide in 45 g of water was added along with a 2.00 g quantity of sodium sulfoxylate formaldehyde in 45.00 g water. The temperature was then lowered to below 45° C. The pH of the batch was raised to 7.5 using ammonium hydroxide (28% aqueous) and a bactericide (4.90 g Kathon LX (1.4% aqueous) with 5.00 g water) was added. The sample was then filtered through a 100 mesh screen to isolate any large pieces of coagulated material.
A nanocomposite dispersion was synthesized according to the process of Example 22, with the addition of 2% unmodified phyllosilicate clay (% by weight on monomer charged) present in the reactor. The clay was introduced to the monomer emulsion with vigorous agitation, and fed into the reactor.
A blend of a latex prepared as in Example 22 was homogenized with 2% unmodified phyllosilicate clay for 1 hour using a PRO250 homogenizer (Pro Scientific Monroe, Conn.) to prepare an admixed nanocomposite dispersion.
Application Test Results for Examples 22 to 24
The aqueous nanocomposite dispersions of examples 22 to 24 were tested as pressure sensitive adhesives according to the following methods: Peel: PSTC-1 Peel Adhesion of Single Coated Pressure Sensitive Tapes at 180° Angle (PSTC=Pressure Sensitive Tape Council, 401 N. Michigan Avenue, #00, Chicago, Ill. 60611). Loop Tack: ASTM D6195 Standard Test Methods for Loop Tack. Shear: ASTM D6463 Standard Test Methods for Time to Failure of Pressure Sensitive Articles under Sustained Shear Loading using either 1″×1″×1 kg (2.54 cm×2.54 cm×1 kg) or 0.5″×1″×1 kg (1.27 cm×2.54 cm×1 kg) test geometry. The PSA properties are provided in Table XII.
180° Peel SS 0.5″ × 1″, 1 kg Loop Tack
Example (oz./in) (N/12.7 mm) hrs (oz.) (N)
22 24.0 6.7 6.7 36.7 10.2
23 (In situ) 22.8 6.3 14.2 35.2 9.8
24 (Blend) 18.8 5.2 10.5 24.9 6.9
Examples 25 to 28 Dirt Pickup Resistance of Coatings
Coatings prepared according to the present invention as well as commercially-available comparative coatings were applied to concrete roof tiles and tested for dirt pickup resistance. Aqueous nanocomposite dispersions for the roofing tile formulations were prepared according to the processes described in Example 15 (aqueous nanocomposite dispersion prepared with in-situ clay) and Reference Example 14 (no clay dispersion), denoted respectively Example 25 and Reference Example 26. These dispersions were prepared with the following monomer amounts: 452.25 g BA, 537.68 g MMA, and 15.10 g MAA to provide polymers having a comonomer ratio of 45.0 BA/53.5 MMA/1.5 MAA. Concrete formulations and preparation of formulated samples from each of the nanocomposite and reference dispersions follow those described, for example, in U.S. Pat. No. 5,718,943.
ASTM Standard Test No. D3719-78 was modified as follows for testing the roofing tile coatings: Formulated coatings were drawn down with a 4 mil bar on an aluminum panel. The films were dried overnight. Mapico 422 iron oxide slurry was brushed onto the films. The slurry coated panels were air dried, then placed into a 140° F. oven for one hour. The panels were then allowed to return to room temperature. The panels were washed under tepid water while lightly rubbing and evenly with a cheesecloth pad. After air drying the films were evaluated for dirt pickup resistance (DPUR), and rated on a 0-10 scale; 0 being no removal of iron oxide or no dirt pickup resistance and 10 being complete removal of iron oxide or outstanding dirt pickup resistance. The DPUR results (Table XIII) show that the coating prepared with nanocomposite clay dispersion (Example 25) had a significantly better DPUR than a similar reference coating which was not prepared with clay (Reference Example 26) as well as comparable commercial coatings (Comparative Examples 27 and 28).
Formulated Coatings DPUR Rating
Example 25 8.5
Reference Example 26 7.0
Comparative Example 27 6.0
PRIMAL ™a MRB-102 K, no clay
Comparative Example 28 5.0
PRIMAL ™a MLT#4, no clay
Example 29 Redox Process Feed
A latex is synthesized via the following method. An empty reactor kettle is charged with 436.00 g DI water, 24.40 g of PGV sodium montmorillonite clay, 5.08 g anionic surfactant (30% aqueous solution), and 3.10 g sodium carbonate. In a separate vessel, a monomer emulsion is formed containing 626.60 g water, 36.90 g anionic surfactant (30% aqueous solution), 654.67 g Butyl Acrylate, 350.00 g Methyl Methacrylate, and 15.10 g methacrylic acid. The kettle contents are heated to 85° C. A 55.80 g quantity of the monomer emulsion is added to the kettle to form a polymer seed. Through three spatially separated inlets, the monomer emulsion is fed into the kettle along with an aqueous solution of 2.0 g of 70% tert-butyl hydroperoxide in 40 g of water and 2 g of isoascorbic acid in 40 g of water such that a reactor temperature of 65° C. was maintained. After the monomer feeds are completed, 5.58 g ferrous sulfate (0.15% aqueous) is added to the reactor. Then, a 1.12 g quantity of 70% tert-butyl hydroperoxide in 20 g of water is added along with a 0.56 g quantity of isoascorbic acid in 20.00 g water. The temperature is reduced to below 45° C. The pH of the batch is raised to 7.5 using ammonium hydroxide (28% aqueous) and a bactericide (4.77 g Kathon LX (1.4% aqueous) with 6.20 g water) is added. The sample is filtered through a 100 mesh screen to remove any large pieces of coagulated material. The resultant polymer clay nanocomposite may exhibit a higher degree of film clarity than nanocomposites or polymers that do not include the redox process.
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U.S. Classification 524/445, 526/128, 524/446, 524/186, 526/348, 526/126
International Classification C09D5/00, C09D157/10, C09D201/00, C08K9/00, C01B33/40, C09J151/00, C09D151/00, C09D151/10, C08L51/00, C04B22/06, C08F265/04, C08F2/10, C09D5/02, C01B33/44, C08F291/00, C09D135/00, C04B103/40, C09D11/02, C08F2/16, C09J11/04, C09D133/00, C09D125/00, C09J201/00, C09D7/12, C08L101/00, C04B24/26, C08F2/44, C08F2/00, C08K9/04, C08F265/06, C08F292/00, C08K9/08
Cooperative Classification C08K9/04, C08F2/00, C08K9/08, B82Y30/00, C08K2201/011, C08F2/44, C08F265/06, C08F292/00
European Classification B82Y30/00, C08K9/08, C08F2/44, C08F2/00, C08F265/06, C08F292/00, C08K9/04
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