Patent Application
20080073627
The current invention comprises a cellulose fiber-plastic composite composition comprising a natural fiber; a thermoplastic olefinic polymer or copolymer; a coupling agent; one or more flame retardants; and one or more synergists. Another embodiment of the current invention further comprises a char former in the wood-plastic composite composition.
Preferably, the current invention comprises one or more brominated or chlorinated flame retardant, one or more synergists, and one or more char formers in combination with a coupling agent to achieve unexpected flame retardancy, physical properties, and long term durability in polyolefin-based wood polymer composites.
The example below describes the invention in an embodiment using wood-filled polypropylene with a maleic anhydride functionalized polypropylene coupling agent and a decabromophenylethane/antimony oxide flame retardant combination. However, the invention also includes other natural fiber-thermoplastic composites using other coupling agents and flame retardants.
Preferred thermoplastics for use in the current invention include a member selected from the group consisting of high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), copolymers of ethylene and propylene, SAN, Polystyrene, ABS, EVA, polyamides, and combinations thereof.
Natural cellulose fibers for use in the current invention include a member selected from the group consisting of “virgin” or recycled wood fiber, hemp, flax, kenaf, rice hulls, bamboo, banana leaves, nut shells, recycled fibers, including fibers from newspaper and boxes, and combinations thereof.
Compatibilizers or coupling agents for use with the current invention include maleic anhydride functionalized high-density polyethylene (HDPE), maleic anhydride functionalize low-density polyethylene (LDPE), maleic anhydride functionalized ethylene-propylene (EP) copolymers, acrylic acid functionalized polypropylene (PP), high-density polyethylene(HDPE), low-density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene-propylene (EP) copolymers, styrene/maleic anhydride copolymers, and vinyl trialkoxy silanes.
The invention includes flame retardant compounds of the following formulas.
Halogen-free flame retardants include ammonium polyphosphate, phosphonate and phosphinate salts; phosphate esters of alkyl and aryl; bis phosphates being either monomeric or polymeric; melamine cyanurate; bis-melaminepentate; pentaerythritol phosphate; and char forming synergists such as phenolic resins, melamine, melamine phosphates, melamine pyrophosphates, tris 2 hydroxy ethyl isocyanurate, 1,4-Bis(5,5-dimethyl-1,3-dioxacyclophosphorimide)benzene, aerythritols such as dipentaerythritol, polyurea, polyhedral oligomeric silsequioxane, polysiloxane, can also be used with the invention using a compatibilization system to enhance physical properties and long term durability of the wood-polymer composites.
Desirable formulations of flame retardants contain between 1% and 40% alone or in blends of flame retardants in combination with between 1% and 20% of synergists or blends of synergists. The formulation can optionally include 1% to 30% of one or a blend of char formers. The preferred concentration is from 10% to 35% of one or a combination of flame retardants in combination with 3% to 15% of synergists or blends of synergists with or without 5% to 25% of one or a blend of char formers.
The most preferred concentrations are from 20% to 30% of one or a combination of flame retardants in combination with 5% to 12% of synergists or blends of synergists yielding between two and three parts of halogen (bromine or chlorine) to one part of antimony in the case of an antimony-based synergist. Where a char former is required, the preferred concentration is between 7% to 20% alone or in blends.
The coupling agent concentrations are desirably in a concentration range of 0.1% to 10% of the weight of the overall formulation. Preferably the coupling agents cited herein are in a concentration of 0.25% to 5% of the weight of the overall formulation.
Synergists for use in the current invention include antimony trioxide, sodium antimonate, zinc sulfide, zinc stannate, zinc hydroxy stannate, zinc oxide, and combinations thereof.
Char formers for use in the current invention include zinc borate, magnesium hydroxide, silicones, polysiloxanes, melamine, melamine phosphate, melamine pyrophosphates, urea, polyurea, phenolic resins, and combinations thereof.
The invention includes a method for providing a fire-retardant, cellulose fiber-plastic composition. The method involves mixing a cellulose fiber with a thermoplastic at a temperature and pressure sufficient to bond said fiber and said thermoplastic. The next step is incorporating an effective concentration of at least one flame retardant, at least one coupling agent, and at least one synergist. The mixture then undergoes molding and cooling the composition into a preform.
Table 1 lists the materials used in these examples. The 4020 wood flour is a 40 mesh soft wood fiber typically used in wood-filled PP composites. The HB9200 is a 4 MFR polypropylene homopolymer made by Innovene. Polybond 3200 from Chemtura Corporation is a functionalized polypropylene containing 1% by weight of maleic anhydride and having a MFR of 110 gm per 10 minutes at 190° C. and 2.16 kg. Firemaster 2100 (decabromophenylethane) and antimony trioxide are also products of Chemtura Corporation. Naugard B-25 is a blend of phenolic and phosphate antioxidants from Chemtura and was added to prevent degradation during processing and subsequent testing.
Duplicate samples of each of the formulations were mixed by preblending the powder ingredients in 60 to 70 gram batches and then mixing in a Brabender internal mixer for approximately 15 minutes at a mixer temperature of 190° C. Plaques (5″ long×4½″ wide×⅛″ thick) were then compression molded at 190° C. for three minutes under 40M lbs force in a Tetrahedron automated compression molding press. After conditioning for 16 hours in a dry environment, the samples were tested for flexural properties (ASTM D-790), specific gravity (ASTM D-792), water uptake after 24 hours of immersion in deionized water, and flammability (UL-94).
These data clearly demonstrate that the addition of both a coupling agent and a flame retardant resulted in improved flexural modulus and strength plus better flame retardancy.
We claim the benefit under Title 35, United States Code, §119 of U.S. Provisional Application No. 60/847,298, filed Sep. 25, 2006, entitled “Flame Resistance Natural Fiber-Filled Thermoplastics with Improved Properties.”
| Number | Date | Country | |
|---|---|---|---|
| 60847298 | Sep 2006 | US |
