POLY-2-ETHYL-2-OXAZOLINE AS A FIBER BINDER

Abstract: A composite comprising a fiber, a polymeric resin, and a poly-2-oxazoline polymer, characterized in that the fibers are dispersed in the composite material and the fibers are coated with the poly-2-oxazoline polymer.

Description: Poly-2-Ethyl-2-Oxazoline As A Fiber Binder The present invention relates to a binder composition useful for the preparation of a thermoplastic composite. More specifically, the present invention relates to a binder material which when applied to a fiber substrate improves the compatibility and dispersion of the fiber in the thermoplastic resin matrix thereby providing an improved thermoplastic composite material with optimum mechanical and electrical performance. In the field of polymer materials, it is well known that the bulk properties of the polymer can be altered considerably by the incorporation of additives. In general, additives should be stable under processing and service conditions, they should not bleed or bloom, they should be inexpensive, and they should favorably alter the properties of the plastic host to provide some improved performance characteristic. When a fiber or other filler is incorporated into a plastic resin, it turns out that the fiber/plastic interface usually is not stress-bearing, and as a consequence, a point of mechanical weakness develops in the composite. In addition, the fibers, which are often inorganic based, tend to clump together in the presence of an organic polymer matrix, such that fiber distribution is non-uniform. The above being the case, there has been a long-standing effort to improve the level of wetting of the fiber by the polymer. One approach, which has been used for many years, is to coat the fiber with an additive that may be considered to have two active parts. One part is compatible with the fiber, the other with the polymer and adhesion between the polymer and fiber is increased by covalent bonds of the coupling agent. A modern example of this approach can be found in the treatment of glass fibers with silane compounds. In this case, the silane compound has been found to undergo covalent coupling through the hydroxy functionality on the glass surface, followed by bonding into the polymer resin backbone. More specifically, vinyl trichlorosilane is hydrolyzed in the presence of glass fiber and this condenses with hydroxyl groups on the surface of the glass. Such an approach has been widely used for the formation of polyester-glass fiber laminates. In recent years, the plastic industry has explored the incorporation of fiber reinforcement into thermoplastic resins, as part of a continuing effort to maximize the performance characteristics of such molding grade materials. The advantage of preparing a thermoplastic composite, as opposed to the more traditional thermoset composite, lies in the fact that melt processing techniques could be utilized to prepare the final composite material. Accordingly, as this field of thermoplastic composite materials developed, there became an ever growing need to develop new binder type materials which would improve the binding as between the fibers and the thermoplastic resin polymer host, as well as improve the dispersion of the fibers therein. A water soluble polymeric material that has been reported for some time, and which is now commercially available, is the polymer known as poly(2-ethyl-2- oxazoline). Poly(2-ethyl-2-oxazoline) is known to be heat stable (380 °C TGA in air), is available in a variety of molecular weights, is thermoplastic, non-ionic, non-toxic, and water soluble. It is sold under the tradename "AQUAZOL", and is available from Polymer Chemistry Innovations, Inc., Tuscon, Arizona. It has been suggested for use in a variety of applications, such as adhesives, thickeners, greenware binders, and flocculates. A variety of U.S. Patents have therefore been issued which have explored the use of poly(2-ethyl-2-oxazoline) in one form or another. A list and their associated titles is as follows: 4,001,147 "Oxazoline and/or Oxazine Modified Polymers"; 4,163,718 "Complexing Agents for Phenolics"; 4,152,341 "Oleophilic Amidopolyethylene-Polyamines; 4, 104,228 "Linear, Partially Deacylated Poly(N- Acyl) Alkylenimines as Tannin Migration Inhibitors; 4,132,831 "Laminates Having a Linear, Acylated Polyalkylenepolyamine Intermediate Binding Layer and Method of Preparation"; 4,144,21 1 "Novel Complexes of Polyoxazolines/Polyozazines and Halogens, Interhalogens/'Pseudo-Halogens & Process for Preparing Same"; 4,153,466 "Compositions Comprising Phosphate Salts of Poly-2-Oxazoline and Fire Retardant Formulations"; 4,436,789 "Polyoxazoline Modified Paper Coating Composition"; 4,182,794 "Method for Applying a Fire Retardant Composition to Wood"; 4,481,167 "Sanitizing Complexes of Polyoxazolines or Polyoxazines and Polyhalide Anions"; 4,408,001 "Degneration Inhibiting Sanitizing Complexes"; 4,474,928 "Polyolefm Resin Blends with Enhanced Adhesion and Laminates"; 4,485,220 "Polyoxazoline Modified Unsaturated Polyesteramides"; 4,584,352 "Process for Polymerizing Polyoxazoline in an Ethylbenzene Dilutent"; 4,702,854 "Water Based Hydraulic Fluids Comprising Poly-oxazines or Polyoxazolines"; 4,582,877 "Transamidated Poly-2-Oxazoline Compositions Useful as Wetting Agents for Polymer and Absorbents for Polar Materials"; 4,741,970 "Thermoplastic Laminate Tie Layer Using a Polymeric Blend Adhesive"; 4,830,994 "Ceramic Greenware Binder"; 4,867,759 "Binder for Abrasive Greenware" and 5,032,434 "Compatibilized Blend Comprising Skin Polymer, Ethylene-Vinyl Alcohol Copolymer and Poly-2-oxazoline". Accordingly, it is therefore an object of the present invention to develop another novel and unique application for a poly-2-oxazoline compound as a binder resin coating on fiber type fillers used to prepare a thermoplastic composite material. More specifically, it is an object of this invention to apply poly-2-oxazoline type coatings on glass, carbon and nickel plated carbon fibers, and incorporate such coated fibers into thermoplastic resins such as a polyether-imides, polycarbonates, polysulphones, polyesters, nylons, acrylonitrile-butadiene-styrene resins, and mixtures thereof. Finally, it is also an object of the present invention to develop a process for preparing poly-2-oxazoline coated fiber materials, wherein such process allows one to effectively control the weight percent of poly-2-oxazoline on said fiber surface as a coating or impregnating material. A composite comprising a fiber, a polymeric resin, and a poly-2-oxazoline polymer, wherein said fibers are dispersed in said composite material, and said fibers are coated with said poly-2-oxazoline polymer. In process form, the present invention comprises a method for preparing a plastic composite material comprising supplying fiber material, followed by preparation of an aqueous solution containing a water soluble binder polymer such as poly-2-oxazoline polymer, and drawing said fiber material through said aqueous solution and coating said fibers with said binder polymer, followed by drying and cutting said fibers to a desired length, and incorporating said coated fibers into a plastic resin to produce a plastic composite material. While the present invention has been described above in summary form, preferably, the present invention comprises more specifically a thermoplastic composite type material, which combines a poly-2-oxazoline coated fiber with a thermoplastic polymer resin material. In accordance with such invention, it has been found that preferably, the poly-2-oxazoline polymer is poly-2-ethyl-2-oxazoline polymer, which is available from Polymer Chemistry Innovations, Inc., and sold under the tradename "AQUAZOL". A particularly preferred grade of "AQUAZOL", is "AQUAZOL 50", which has a molecular weight of about 50,000, a polydispersity index of 1.9, and a kinematic viscosity of 5-7 cSt. In accordance with the present invention, the poly-2-ethyl-2-oxazoline is coated onto the fiber material, and preferably, the poly-2-ethyl-2-oxazoline is present in the fiber at a level of about 1.5-40% (wt). Furthermore, after said coated fiber is incorporated into the thermoplastic resin, the coated fiber itself is preferably present at about 3-30% by weight of the final composite formulation. With regards to the resins that have been found particularly suitable for preparation of the composite herein, such resins preferably include the following thermoplastic materials: polyetherimides, polycarbonates, polysulphones, acrylic polymers, polyesters, nylons, acrylonitrile-butadiene styrene materials, and mixtures thereof. However, under the broad scope of the present invention, resins may also include any type of matrix polymeric resin material which when combined with a poly-2-oxazoline coated fiber material results in improved dispersion of the fiber in the polymeric resin matrix, and as noted, affords a substantially uniform dispersion of the fibers and improved mechanical and electrical properties. As a consequence of preparing coated fiber as noted above, it has been found that the fibers are more substantially uniformly dispersed in the thermoplastic resin composites disclosed herein. In other words, in the absence of the water soluble poly- 2-ethyl-2-oxazoline coating, the fibers were observed to clump together when incorporated into a theremoplastic resin matrix, thereby leading to a non-homogenous distribution of the fibers in the final composite material. Alternatively, when coated with the poly-2-ethyl-2-oxazoline as herein described, the fibers tended to wet-out much better when combined with the thermoplastic and thereby became substantially uniformly dispersed. In addition, the coated fibers herein demonstrate improved mechanical properties as opposed to uncoated fibers. The following is illustrative of the invention. ABS used is Diamond 7501 (high impact ABS). Two kinds of PC (polycarbonate) were used: Apec DP9-93330- 1000 (high heat PC) and Makrolon FCR-2458-1 112 (general purpose PC). Aquazol was mixed with water and surfactant to make a coating solution. NCG (nickel coated graphite) fiber was pulled through the solution and dried in a circulating heater continually. The treated NCG fiber was chopped V" long and tumbled with ABS and PC at different percentages. The commercial fiber was also used to reinforce ABS and PC for a reference. The tensile, flexural and impact tests were carried out. The electrical properties were also measured. Results: Percentage of quazol on treated NCG fiber: Table I shows that the percentage of aquazol on the treated fiber increased with the increasing content of poly-2-ethyl-2-oxazoline and surfactant in the solution. The more aquazol on the fiber, the easier to chop the treated fiber. Reinforced ABS: Table II shows that aquazol treated NCG fiber is very compatible with ABS. When only poly-2-ethyl-2-oxazoline was mixed with ABS, both break stress and flexural modulus increased. The poly-2-ethyl-2-oxazoline treated fiber increased the break stress and flexural modulus more than the commercial fiber did. The impact test also shows that ABS reinforced with poly-2- ethyl-2-oxazoline treated fiber had the higher impact strength. Reinforced PC: It is shown clearly in Table III and Table IV that the poly-2- ethyl-2-oxazoline treated fiber increased the properties of both Apec and Makrolon substantially. However, with the addition of commercial fiber, the properties of PC deteriorated. The impact test also shows the substantial deterioration of the impact strength for the commercial fiber reinforced PC. Electrical properties: With the commercial fiber and poly-2-ethyl-2- oxazoline treated fiber the surface resistivity and volume resistivity of ABS and PC are about the same. With 7.5% fiber, the surface resistivity is about 10 7 Ohms/square and plastics are static dissipative. With 15% fiber, the surface resistivity is below 10 3 Ohms/square and plastics are considered conductive. Table I. Percentage of Aquazol on the Treated NCG Fiber SUBSΪlTϋ ' ϊ ii ϊirl£Ef (RULE 26) TABLE II REINFORCED ABS TABLE III REINFORCED APEC TABLE IV REINFORCED MAKROLON TABLE V IMPACT TEST Impact Strength(ft-lb/in): Notched Izod, 0.25in. Thickness, 73F Accordingly, as can be seen from the above measurements, quite apart from the feature of more uniform dispersion discussed above, there is a difference in bonding strength as between polymer resin and fiber without the poly-2-ethyl-2- oxazoline coating, and resin and fiber with such coating, as measured by the above physical property tests. In the context of the preferred process for preparing the thermoplastic composite herein, and as noted in the illustrative example, it has been found advantageous to begin with an aqueous solution of the poly-2-ethyl-2-oxazoline, which bath preferably contains a small amount of surfactant. A particularly preferred surfactant is sold under the tradename "Cyanamid Aersol OT", which is present in the solution at a level of about 0.2 % (wt). Preferably, 15% by weight AQUAZOL 50 is placed into warm water (100 °F) followed by addition of surfactant. The solution is mixed and placed into a stainless steel trough, which is set-up for continuous fiber coating, as the fiber is passed through the solution at a controlled rate. Accordingly, those skilled in the art will appreciate that a variety of variables can be adjusted to optimize coating or impregnation of binder onto the fibers. For example, one can select different molecular weights for the poly-2-ethyl-2-oxazoline, one can adjust the concentration of such polymer in the water bath, water temperature can be modified, and surfactant type and level can also be adjusted. By controlling such variables, one can readily promote different levels of binder coating on the fibers. However, in the context of the present invention it has been found preferable to incorporate binder on or in the fibers at a level of about 1.5-40% (wt), more preferably 15-18% (wt.). Upon passing the fiber through the binder bath, one can also appreciate that the residence time in the bath can be adjusted, which again would influence the amount of binder absorbed onto the fibers themselves. Once passing through the bath, the fibers are then dried to remove water, and drying can be conveniently carried out by hot air or infrared type heating. Alternatively, once the fibers are dried, they can be promptly introduced into a cross-head extruder and over-extruded with a thermoplastic resin. In this manner, one forms what could be described as a fiber concentrate; i.e., a pellet containing thermoplastic resin and fiber. By way of such alternative, one produces a fiber concentrate that is more conveniently handled, and such fiber concentrate then can be mixed with additional thermoplastic resin to the final let-down value of about 15-18 % (wt.) noted above. A variety of fibers can be coated in accordance with the present invention. For example, fibers such as glass, carbon, nickel plated carbon, aromatic polyamide fiber (e.g., KEVLAR), and stainless steel, can be coated or become impregnated with the water soluble poly-2-ethyl-2-oxazoline binder disclosed herein.

Claims: What is claimed is: 1. A composite comprising a fiber, a polymeric resin, and a poly-2- oxazoline polymer, characterized in said fibers are dispersed in said composite material, and said fibers are coated with said poly-2-oxazoline polymer. 2. The composite material of claim 1 wherein said poly-2-oxazoline polymer is poly-2-ethyl oxazoline with a molecular weight of about 50,000. 3. The composite material of claim 1 wherein said fiber is selected from the group consisting of glass, carbon, nickel plated carbon, aromatic polyamide fiber, stainless steel, or mixtures thereof. 4. The composite material of claim 1 wherein said fiber is present at about 1.5-40 % (wt.). 5. The composite material of claim 1 wherein said thermoplastic resin is selected from the group consisting of a polyetherimide, a polycarbonate, a polyester, a nylon, acrylonitrile-butadiene styrene materials, and mixtures thereof. 6. A process for preparing a thermoplastic composite material comprising a. supplying a fiber material; b. supplying an aqueous solution containing a poly-2-oxazoline polymer; c. drawing said fiber material through said aqueous solution and coating said fiber with said poly-2-oxazoline polymer; d. drying said fibers and cutting said fibers to a desired length; and e. blending said coated fibers with a thermoplastic resin to produce said thermoplastic composite material. 7. The process of claim 6 wherein said fiber material is selected from the group consisting of glass, carbon, nickel plated carbon, aromatic polyamide fiber material, stainless steel, or mixtures thereof. 8. The process of claim 6 wherein said fibers are dried by exposure to heated air and infrared light. 9. A process for preparing a thermoplastic composite material comprising a. supplying a fiber material; b. supplying an aqueous solution containing a binder comprising poly-2- oxazoline; c. drawing said fiber material through said aqueous binder solution and coating said fiber with said binder material; d. drying said fibers; e. over-extruding said fibers with a thermoplastic resin wherein said fibers are present in said thermoplastic resin to form said composite material.

Inventors: ACQUARULO LAWRENCE A JR, XU JIANWEI, ACQUARULO, LAWRENCE, A., JR., XU, JIANWEI
Applicants: ACQUARULO LAWRENCE A JR, NEIL CHARLES O, XU JIANWEI, ACQUARULO, LAWRENCE, A., JR., O'NEIL, CHARLES, XU, JIANWEI
Application year: 2000
Main classification: B32B27
IPC codes: B29C47, C03C25, C08J5, D06M15