Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-06-16
2002-09-17
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S186000, C524S504000, C524S505000, C525S064000, C525S070000
Reexamination Certificate
active
06451897
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to nanocomposite materials comprising a graft copolymer of a propylene polymer material, and a smectite-type clay that has been treated with a swelling agent.
BACKGROUND OF THE INVENTION
Layered clay minerals such as montmorillonite are composed of silicate layers with a thickness on a nanometer scale (1 nanometer=10 Å). Dispersion of such layered materials in polymers are frequently referred to as nanocomposites.
It is known that these silicates, such as smectite clays, e.g., sodium and calcium montmorillonite, can be treated with organic swelling agents such as organic ammonium ions, to intercalate the swelling agent molecules between adjacent, planar silicate layers, thereby substantially increasing the interlayer spacing and making the clay more hydrophobic and better suited for interaction with polymer precursors. The intercalated silicates can then be exfoliated, i.e., the silicate layers are separated, typically by high shear mixing. The individual silicate layers, when admixed with a matrix polymer before, after, or during the polymerization of the matrix polymer, have been found to substantially improve one or more properties of the polymer such as mechanical strength and/or high temperature characteristics.
For example, U.S. Pat. No. 4,810,734 discloses a process for producing a composite material by contacting a layered clay mineral with a swelling agent in the presence of a dispersion medium such as water, an alkanol, or dimethyl sulfoxide, mixing with a molten polymerizable monomer or a mixture of monomer and dispersion medium, and polymerizing the monomer in the mixture. Catalysts and accelerators for polymerization can also be present. The polymer that is formed can be, for example, a polyamide, a vinyl polymer, or a thermoset resin.
U.S. Pat. No. 5,514,734 discloses a composite material comprising a polymer matrix having layered or fibrillar particles, e.g., phyllosilicates, uniformly dispersed therein, the particles being bonded to organosilanes, organo titanates, or organo zirconates and having one or more moieties bonded to at least one polymer in the polymer matrix. The polymer matrix can be, for example, a polyester, polyolefin, or polyamide.
U.S. Pat. No. 5,760,121 discloses a composite material comprising a host material such as a polyamide, polyvinylamine, polyethylene terephthalate, polyolefin, or polyacrylate, and exfoliated platelets of a phyllosilicate material. The platelets are derived from an intercalate formed without an onium ion or silane coupling agent by contacting with an intercalant polymer-containing composition containing water and/or an organic solvent. Suitable intercalant polymers include polyolefins and acrylic polymers.
U.S. Pat. No. 5,910,523 discloses a composition comprising (a) a semi-crystalline polyolefin, (b) a clay filler having dispersible platelets in stacks, (c) an amino-functional silane reacted with the filler, and (d) a carboxylated or maleated semi-crystalline polyolefin that has been reacted with the aminofunctional silane after the silane was reacted with the filler.
Incorporating clay minerals into a polymer matrix, however, does not always result in markedly improved mechanical properties. This may be due in part to the inability to exfoliate all or at least a substantial portion of the layers of the silicate material. It may also be due in part to the lack of affinity between the layered silicate materials and the organic polymers. Attempts to overcome these problems have not been totally successful. There is therefore a need for novel composite materials that have desirable mechanical and physical properties.
SUMMARY OF THE INVENTION
The composite material of this invention comprises (1) a graft copolymer comprising a backbone of a particulate propylene polymer material having a weight average diameter of about 0.4-7 mm, a surface area of at least 0.1 m
2
/g, and a pore volume fraction of at least about 0.07 and wherein more than 40% of the pores in the particle have a diameter greater than 1 micron, to which is graft polymerized at least one grafting monomer capable of being polymerized by free radicals and (2) a smectite clay having exchangeable cations that has been treated with at least one organic swelling agent, uniformly dispersed in the particulate propylene polymer material, wherein the total inorganic content of the composite material is about 0.5% to about 10%, based on the total weight of the composite.
The composite material of this invention is made by a process comprising, in a substantially non-oxidizing environment, graft polymerizing at least one liquid monomer capable of being polymerized by free radicals to a particulate propylene polymer material having a weight average diameter of about 0.4-7 mm, a surface area of at least 0.1 m
2
/g, and a pore volume fraction of at least about 0.07 and wherein more than 40% of the pores in the particle have a diameter greater than 1 micron, in the presence of (1) a smectite clay having exchangeable cations that has been treated with at least one organic swelling agent, and (2) about 0.1 parts to about 6 parts per hundred parts of the propylene polymer material of an organic free radical polymerization initiator, at a reaction temperature of about 60° C. to about 125° C., whereby the chains of polymerized monomer that are formed intercalate the clay and produce a uniform dispersion of clay particles within the particulate propylene polymer material, the composite material having an inorganic content of about 0.5% to about 10%, based on the total weight of the composite.
The polymer nanocomposites produced according to the method of this invention have excellent mechanical properties such as heat distortion temperature, tensile strength, and flexural modulus.
DETAILED DESCRIPTION OF THE INVENTION
The propylene polymer material that is used as the backbone of the graft copolymer in the composite material of this invention can be:
(1) a homopolymer of propylene having an isotactic index greater than 80, preferably about 85 to about 99;
(2) a copolymer of propylene and an olefin selected from the group consisting of ethylene and 4-10 C alpha-olefins, provided that when the olefin is ethylene, the maximum polymerized ethylene content is about 10%, preferably about 4%, and when the olefin is a 4-10 C alpha-olefin, the maximum polymerized content thereof is about 20% by weight, preferably about 16%, the copolymer having an isotactic index greater than 85;
(3) a terpolymer of propylene and two olefins selected from the group consisting of ethylene and 4-8 C alpha-olefins, provided that the maximum polymerized 4-8 C alpha-olefin content is 20% by weight, preferably about 16%, and, when ethylene is one of the olefins, the maximum polymerized ethylene content is 5% by weight, preferably about 4%, the terpolymer having an isotactic index greater than 85;
(4) an olefin polymer composition comprising:
(a) about 10% to about 60% by weight, preferably about 15% to about 55%, of a propylene homopolymer having an isotactic index greater than 80, preferably about 85 to about 98, or a copolymer of monomers selected from the group consisting of (i) propylene and ethylene, (ii) propylene, ethylene and a 4-8 C alpha-olefin, and (iii) propylene and a 4-8 C alpha-olefin, the copolymer having a polymerized propylene content of more than 85% by weight, preferably about 90% to about 99%, and an isotactic index greater than 85;
(b) about 5% to about 25% by weight, preferably about 5% to about 20%, of a copolymer of ethylene and propylene or a 4-8 C alpha-olefin that is insoluble in xylene at ambient temperature; and
(c) about 30% to about 70% by weight, preferably about 40% to about 65%, of an elastomeric copolymer of monomers selected from the group consisting of (i) ethylene and propylene, (ii) ethylene, propylene, and a 4-8 C alpha-olefin, and (iii) ethylene and a 4-8 C alpha-olefin, the copolymer optionally containing about 0.5% to about 10% by weight of a polymerized diene and containing less than 70% by weight, preferab
Basell Technology Company BV
Lee Kataryna W.
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