MXPA99006757A - Filling lignocellulosic fibers for compositions of thermoplasti compounds - Google Patents

Abstract

Discontinuous lignocellulose fibers are described for use as a reinforcing filler for thermoplastic composition. The fiber filling includes a significant percentage by weight of long hair-like fibers. Specifically, at least about 20% by weight of the fiber filling comprises discontinuous lignocellulose fibers with a fiber length greater than about 15 millimeters and a smaller fiber diameter. to approximately 0.5 minilimeter. A moldable thermoplastic composition comprising the discontinuous lignocellulose fibers comprises from about 20 to about 50% of the fiber filling and from about 50 to about 80% by weight of thermoplastic. Filling discontinuous lignocellulose fibers produces thermoplastic composite compositions having improved physical properties over basic thermoplastic. Improved physical properties can be achieved without the use of coupling agents, although coupling agents can be employed to further improve the properties of the compound. The discontinuous lignocellulose fibers are preferably derived from virgin waste wood, either from soft wood species or hardwood, depending on the final use of the compound composition. The thermoplastic can be selected from a number of post-consumer or post-industrial waste sources. The process for the manufacture of the reinforcing filler of discontinuous lignocellulose fibers and the compositions of thermoplastic compound are also described.

Description

FILLING OF LIGNOCELLULOSIC FIBERS FOR COMPOSITIONS OF THERMOPLASTIC COMPOUNDS BACKGROUND This invention relates generally to a reinforcing filler for compositions of thermoplastic compounds and more particularly refers to a filling of batch lignocellulosic fibers. The intention of reinforced and filled thermoplastic composite technology is to create new materials and market applications by reducing the cost or improving the physical properties of thermoplastics. The cost and performance of thermoplastic compounds in general are a function of three variables: (1) the cost and performance of composite materials, (2) the performance of the resulting composite material, and (3) the performance of the interfacial junction between the filling materials and thermoplastic material. The art of incorporating discontinuous cellulosic fibers or discontinuous lignocellulosic fibers as a filler into thermoplastic resins to create moldable compositions is well known. These compositions are known to produce compositions of castable compounds with improved tensile and flexural properties. Unfortunately, the physical properties of the filling of discontinuous lignocellulosic fibers or discontinuous cellulosic fibers have not yet been treated as a significant factor with respect to the properties of the resulting thermoplastic compound. In fact, compositions of thermoplastic compounds filled with conventional fibers, are relatively indiscriminate in terms of the source of the fibers, deriving the filling of wood flour fibers, pieces of wood, rice husks, waste paper, pulp, cellulose powder and mixtures thereof. Furthermore, when using a source of wood fibers, the selection of softwood or hardwood to achieve the desired product performance properties is already indiscriminate or unnecessarily specific.

There is some evidence that the physical properties of fiber fill and the resulting thermoplastic compound vary as the source of the fibers varies. For example, the rupture modulus (MOR), a measure of the fragility of the thermoplastic compounds of discontinuous lignocellulosic fibers, is known to be primarily a function of the source and nature of discontinuous lignocellulosic fibers. Specifically, using discontinuous lignocellulosic fibers derived from chemically unaltered wood (hereinafter referred to as "virgin") leads to thermoplastic compounds that possess significantly superior MOR properties than thermoplastic composites filled with non-virgin or non-virgin cellulose sources. wood. In addition, the lignocellulose and discontinuous cellulose fibers commonly used in thermoplastic composites are fine fibers, typically referred to as "wood flour" or "powder". However, longer discontinuous lignocellulose fibers have the ability to withstand greater stress, and thus have higher tensile properties than shorter fibers of a similar nature. Under load, the tensile stress transferred from the composite matrix to the fiber increases from zero at the end of the fiber to a maximum value at the center of the fiber. As the length of the fiber increases, the surface area of the fiber increases, thus increasing the distribution of the applied stress. As the distributed stress load increases over the larger surface area of a longer discontinuous lignocellulose fiber, the amount of stress at a given load at the center of the fiber decreases. As a result, a longer fiber can absorb more effort before failure than a shorter fiber. The performance of the discontinuous lignocellulosic fiber thermoplastic composites is also a function of the concentration of discontinuous lignocellulose fibers in the formulated composition. For exampleAs the content of wood pulp fibers in a thermoplastic composite of polypropylene fibers increases, the tensile and flexural properties of the composition are improved until a 50% concentration of wood pulp fibers by weight of the composition is reached. compound. Beyond the 50% loading ratio of wood pulp fibers, the tensile and flexural properties of the compound decline. Related to the concentration of discontinuous lignocellulosic fibers in thermoplastic compound compositions is the volume of the fiber in the composite. The volume of fiber is a function of the size of the discontinuous Iignocellulosic fiber and the density of the fiber. The density of the fiber is determined by the density of the three selected species as the source of the fiber. At given length and density, a fiber with a larger diameter will weigh more than a fiber with a small diameter of a similar nature provided to the change in the surface area of the fiber. However, as the weight of the individual fibers increases, the number of fibers at a certain concentration in a composition in the thermoplastic compound decreases. This decrease in discontinuous lignocellulose fibers within the thermoplastic matrix of discontinuous lignocellulose fibers reduces the number of interfaces of thermoplastic and discontinuous lignocellulose fibers, which has the same effect as reducing the concentration of discontinuous lignocellulose fibers in the composite, resulting in a compound with reduced flexural and traction performance. Coupling agents are usually required to improve the interfacial bond between the wood and thermoplastic fibers. The coupling agent effectively creates a bridge between the fibers and the thermoplastic, which improves the tensile and flexural properties of the thermoplastic under load. However, the use of coupling agents contributes to the cost of manufacturing the composition of the compound. For the above reasons, there is a need for an improved batch of discontinuous lignocellulose fibers for compositions of thermoplastic compounds. The discontinuous lignocellulose fiber should include a relatively high percentage of long fibers, to create a large surface area for interfacing between the fiber and the thermoplastic. The concentration of the new discontinuous lignocellulosic fibers in the composite composition should produce increased properties of tensile and flexural strength in the composition of the composite. The tensile and flexural properties of the composite product should improve as the percentage of long fibers increases. Ideally, the source of the composite material and the manufacture of the discontinuous lignocellulosic fibers and the composite composition are simple and cost effective.

COMPENDI The present invention relates to discontinuous lignocellulose fibers that meet these needs. A batch of discontinuous lignocellulose fibers for thermoplastic compositions having characteristics of the present invention includes a significant percentage by weight of long "hair-type" fibers. Preferably, at least about 20% by weight of the fiber filler comprises discontinuous lignocellulose fibers, with a fiber length of greater than about 15 millimeters and a fiber diameter of less than about 0.5 millimeter. A thermomechanical process is employed to produce the present discontinuous lignocellulose fibers, comprising the steps of conditioning pieces of wood below about 5.62 to 7.03 kg / cm2 (about 80 to about 100 psi) of vapor pressure for an approximate period of time. 1 to about 4 minutes, and mechanically separate the pieces into discrete staple fibers. A moldable thermoplastic composition comprising the discontinuous lignocellulose fibers of the present invention, comprises from about 20 to about 50% by weight of the fiber filler and from about 50% to about 80% by weight of the thermoplastic. Optionally, the thermoplastic composition can further comprise up to about 10% by weight of a coupling agent. The composition is prepared by a process comprising the steps of mixing the discontinuous lignocellulose fibers, thermoplastic and the coupling agent or other additives, extruding the mixed materials at an operating temperature in the lower extruder at about 232 ° C (450 ° C). F) and form the extruded compounds in finished products by profile extrusion, cold compression molding, hot compression molding or injection molding. Accordingly, an object of the present invention is to provide a novel discontinuous lignocellulose fiber for compositions of thermoplastic compounds having one or more of the novel features of this invention as set forth above or as shown or described below.

Another objective of the present invention is to engineer discontinuous lignocellulose fibers to improve the physical properties of this component, of the thermoplastic compound, resulting in cost effective compounds with improved properties over the basic thermoplastic. A related object of the present invention is to improve the stiffness and strength properties of the thermoplastic compound by incorporating the new fiber filler, thereby creating compositions with suitable properties for a wide range of applications on the market that will include, but are not limited to a, structural packaging, decorative finishes for automotive interiors, architectural components, furniture components and the like. A further objective of the present invention is to produce improved thermoplastic compound compositions, comprising the new discontinuous lignocellulosic fiber fillers without the need for coupling or binding agent or other additives. A feature of the invention is the size distribution of the reinforcement filler of discontinuous lignocellulose fibers, which includes a high weight percentage of long, hair-like fibers. The fiber size distribution as a total weight percent that is retained in ASTM sieves is from about 20 to about 50% by weight retained in an 8 mesh screen, approximately 20 to 40% by weight retained in a 16 mesh screen, about 20 to about 30% by weight retained on a 50 mesh screen and about 10% thinner than a 50 mesh screen. The discontinuous lignocellulose fiber is preferably derived from waste wood, virgin, from either tree species of wood soft or hard wood, depending on the final use of the constituents of the compound. The thermoplastic can be selected from a number of post-industrial or post-consumer waste sources. Coupling agents are optional, but can be used to further improve the tensile and flexural properties of the composite compositions. The filling of the discontinuous lignocellulose fiber reinforcement of the present invention, when incorporated into the thermoplastic compounds at concentrations of at least about 20% by weight, improves the tensile and flexural properties of the thermoplastic and produces composite compositions with strength properties and improved stiffness. Furthermore, improved fiber fill and composite can be prepared using conventional manufacturing equipment and from waste wood and recycled thermoplastic, thereby minimizing manufacturing and material costs. These and other features, objects and advantages of the present invention will be apparent with reference to the following description and appended claims.

DESCRIPTION Discontinuous lignocellulosic fibers are described for use as a reinforcing filler in thermoplastic compound compositions. The lignocellulose fibers of the present invention are derived from a source of virgin wood using a thermomechanical process that produces a fiber filling having a predetermined size distribution including a high weight percentage of long "hair type" fibers. The batch of discontinuous lignocellulose fibers is mixed with the thermoplastic and extruded to produce a composition having improved physical properties. A coupling agent can be used to improve the interfacial bond between the fibers and thermoplastics. According to the present invention, the source of discontinuous lignocellulose fibers is a significant factor. Chemically unaltered or "virgin" wood is the preferred source since, as discussed above, the MOR of the molded thermoplastic compound is improved. The source of virgin wood can already be soft wood or hard wood, depending on the performance properties of the desired compound. Softwood is preferred for composite applications that require higher impact resistance such as gaskets and the like. Hardwood is preferred for applications that require greater strength or rigidity, such as backs for office seats and the like.

Southern pine and white poplar, are the preferred representatives of the groups of soft woods, hardwood, respectively, due to lower cost and availability. However, within their respective groups, other tree species such as, but not limited to aspen, birch, poplar, Oregon pine, oak, spruce, incense pine and others, are suitable for use as sources of fiber in the present invention. The preferred virgin wood source of southern pine or white poplar or black poplar is wood waste, such as waste or discarded pallets, furniture manufacturing waste and the like. The primary reason is that wood waste has usually been dried in an oven or air prior to a moisture content that is in the range of 7 to about 12% by weight. This is close to the typical moisture content for discontinuous lignocellulose fibers as a component of a thermoplastic compound of about 5% or less by weight. Composite compositions containing discontinuous cellulose and lignocellulose fibers with moisture contents exceeding 5% by weight, often result in molded products that visually have unpleasant blisters. The formation of blisters is a result of conversion of moisture within the fiber into steam during the extrusion step of the compound production process. In addition, mill pieces for green wood have a moisture content that is in the range of about 45 to about 50% by weight. In this way, drying wood waste to the appropriate moisture control content requires less energy than drying pieces of green wood mill, which lowers the cost of processing. The batch of discontinuous lignocellulose fibers of the present invention comprises a significant percentage by weight of long fibers, which preferably exceeds approximately 15 millimeters. I have observed that as the concentration of long fibers in a composition of thermoplastic compounds increases, the tensile and flexural properties of the compound are improved independently of the tree species. The preferred diameter of the long discontinuous lignocellulose fibers is between about 0.1 and about 0.5 millimeter. In this range of diameters, the distribution of the discontinuous lignocellulose fibers in the composite matrix of thermoplastic with discontinuous lignocellulosic fibers is optimized.

Using fibers with diameters exceeding approximately 0.5 millimeter is not convenient, since at a given concentration of weight and length the composition and volume of discontinuous lignocellulose fibers will be reduced. For example, the volume of discontinuous lignocellulose fibers measuring one millimeter in diameter will be about half that of fibers that measure 0.5 millimeter in diameter. This would reduce the number of fiber and thermoplastic interfaces by approximately 50% and result in a compound that decreases flexural and tensile performance. Still further, to increase the fiber weight concentration of 1 millimeter in diameter to achieve comparable distribution properties in the composite with that of smaller diameter fibers, would result in a heavier composite composition. However, in many applications, such as an automotive interior decorative finish, adding weight to the product is undesirable. A thermomechanical pulp process is used to derive the discontinuous lignocellulose fibers, to achieve the preferred size and distribution in the fiber filling. Thermomechanical fiber separation is preferred over mechanical fiber separation methods, such as hammer milling or stone milling, because these separation of mechanical fibers are incapable of producing the size distribution of discontinuous lignocellulose fibers of the invention. A thermomechanical pulp process suitable for preparing discontinuous lignocellulose fibers, particularly discontinuous hair-type lignocellulose fibers, is illustrated by the present inventor in US Pat. No. 5,330,824 to be granted on July 19, 1994, the contents of which are hereby incorporated by reference. The process is manipulated, as described below, to achieve a size distribution of discontinuous lignocellulose fibers with a length exceeding approximately 15 millimeters and a diameter of less than approximately 0.5 millimeters. In the process, pieces of wood are conditioned under pressure and mechanically separated into bundles of discrete staple fibers, here referred to as "fibers". The conditioning stage consists of feeding either pieces of soft wood or hardwood of similar species derived from wood mills or wood waste in a pressure vessel with steam between approximately 5.62 and 7.03 kg / cm2 (80 to approximately 100 psi). ) for a period of approximately 1 to approximately 4 minutes. The residence time in the pressure vessel for less than about 1 minute results in poor fiber separation, resulting in fibers with diameters exceeding the preferred .5 millimeter value. The residence time beyond four minutes does not produce benefits by additional fiber separation while slowing down the production process. The pieces of wood leave the pressure vessel by means of a screw or screw conveyor, which is maintained at a pressure of approximately 4.57 to 5.98 kg / cm2 (65 to 85 psi, approximately). The spindle conveyor transports the pieces of wood under pressure to a defibrator model Sunds of 91.44 cm (36"), where the pieces of wood are separated mechanically under pressure in individual fibers when passing the pieces of wood under pressure between a disk static and a rotating disc The distance between the rotating disc and the static disc is set to approximately .0072 and .254 millimeters (approximately .003 to approximately .01") with a preferred rotating disc speed of approximately 1.200 RPM. Discontinuous lignocellulose fibers produced by this process are in the length range from a few microns to approximately 30 millimeters, and in diameter from a few microns to approximately 2 millimeters. The resulting size distribution of discontinuous lignocellulose fibers is preferred to be from about 20 to about 50% by weight retained in an 8 mesh screen, from about 20 to about 40% by weight retained in a 16 mesh screen, from about 20 to about 40% by weight retained in a 50 mesh screen and the remaining fibers sufficiently fine to pass through a 50 mesh screen. subsequently they are dried at a moisture content of about 5% by weight. Any suitable dryer such as an instant evaporative dryer, with Procter and Schwartz gas burner, is employed.

The discontinuous lignocellulose fibers preferably enter the dryer at a dryer temperature of about 362 ° (380 ° F) and exit the dryer at a temperature of about 152 ° C (170 ° F). The residence time of the discontinuous lignocellulose fibers within the dryer is usually less than about 1 minute. The thermoplastic component selected for use in the composition of the compound of the present invention is chosen for its physical properties with respect to the desired performance characteristics of the composition of the compound. The broad set of commercially available thermoplastics, such as polyethylenes, polypropylenes, ABS and the like, possess different physical properties. For example, according to ASTM D638, unfilled or unfilled general purpose polystyrene has a tensile performance value in the range from 351.50 to 562.40 kg / cm2 (approximately 5000 to 8000 pounds per square inch) compared to polyethylene high density unfilled, with a tensile performance value in the range from 98.4 to 281.20 kg / cm2 (1400 to 4000 pounds per square inch). Izod polyethylene notch values in accordance with ASTM D256 are in the range from .005 to .008 kg-m / cm2 (.25 to .35 ft.-lbs. Per square inch), compared to high density polyethylene with values Izod notched in the range from .009 a. 129 kg-m / cm2 (.4 to 6.0 foot-pounds per square inch). Comparatively, polystyrene will be selected against high density polyethylene for applications requiring high strength. In contrast, high density polyethylene will be chosen over polyethylene for applications that require high impact properties. The thermoplastic component can be derived from recycled or non-recycled thermoplastic sources. It is also convenient that the thermoplastic has a treatment or melting temperature of less than about 232 ° C (450 ° F). The processing of the blend of microcellulose and thermoplastic fibers at a melting temperature greater than 232 ° C (450 ° F) can lead to burnout of the discontinuous lignocellulose fibers which causes the composite compositions to lose their advantageous physical properties. The thermoplastic is prepared according to any conventional method, such as milling, crumbling and nodulating and the like. Ideally, the thermoplastic pieces are less than about 635 cm (1/4") in all dimensions.The steps to process the component materials to produce the composite include low shear mechanical mixing of discontinuous lignocellulose fibers and thermoplastic and subsequent extrusion followed by profile forming, cold or hot compression molding or injection molding and cooling.

In the mixing step, the discontinuous lignocellulose fibers are combined with the thermoplastic component in a low shear mixing device. Low shear devices are preferred in order to minimize the reduction in length and fracturing of discontinuous lignocellulose fibers. The preferred concentration of discontinuous lignocellulosic fiber filling in the thermoplastic composition of the present invention is in the range of from about 20 to about 50% by weight of the compound, depending on the desired physical properties of the compound. Products molded with compounds that incorporate the filling of lignocellulose fibers at concentrations outside this range, produce negligible improvements in structural and tensile properties and lose their hybrid properties. Molded products incorporating less than about 20% by weight of the discontinuous lignocellulosic fiber filler of the present invention are more similar than the thermoplastic, while at concentrations greater than about 50% by weight, the products become wood type, none of which which is a desired feature of a thermoplastic with filling, reinforced. Composite products molded from composite compositions prepared in accordance with the present invention demonstrate improved tensile and flexural properties as the concentration of discontinuous lignocellulose fiber filling increases within the above range. However, it has been observed that as the tensile and flexural properties improve, the improved notched Izod properties decline. Consequently, the concentration of the discontinuous lignocellulose fiber filling in the composite is directed by the requirements of the molded product application either for flexibility or rigidity. Additional components, such as coupling agents, foaming agents, coloring agents, UV stabilizers, and the like, may optionally be added to the compound during or before mixing. As noted above, coupling agents are employed, for example to improve the interfacial bond between the discontinuous lignocellulose fibers and the thermoplastic. When used for interfacial binding improvements in the compound composition of the present invention, preferred coupling agents include polypropylene or polyethylene grafted with maleic or maleic anhydride, ethylene methacrylic acid or acrylic acid. Polyethylene grafted with maleic anhydride is the preferred coupling agent when polyethylene is the base resin of the thermoplastic compound. Polypropylene grafted with maleic anhydride is the preferred coupling agent for compound compositions wherein the base resin is polypropylene. Based on the compatibility constraints observed between maleated polyeolefins and the base resin, ethylene methacrylic or acrylic acid is the preferred coupling agent when the base thermoplastic resin is a mixture of polyethylene and polypropylene (common in the use of thermoplastic waste post -consumer) or other resins or mixtures of thermoplastic resins with melting or softening temperatures below about 232 ° C (450 ° F) this will include, but is not limited to, polyvinyl chloride, polyethylene, polyanimides, polyesters, ABS and the like. The amount of coupling agent in the composite composition is preferably up to about 10% by weight of the compound. Concentrations of the preferred coupling agents exceeding about 10% by weight give little, if any, gain in compound performance. The formulated material is fed to an extruder. A single screw extruder or twin spindles or an aesth mixer can be used to crush the plastic and mix its composite components. A single-screw extruder or kin mixer is preferred due to lower shear and less fiber fracture.

An extruder with 15.24 cm (6") Sterling drilling with a spindle compression ratio of 34: 1 is convenient It is important that during extrusion, discontinuous lignocellulose fibers are not subjected to heat that is sufficient to burn the discontinuous lignocellulose fibers Therefore, the material is preferably extruded at a temperature from about 177 ° C to 232 ° C (about 350 ° F to about 450 ° F) and more preferably between 177 ° C and 204 ° C ( approximately 350 ° F and approximately 400 ° F.) Extrusion temperatures exceeding 232 ° C (450 ° F) will burn discontinuous lignocellulose fibers, resulting in deteriorated compound properties, and as the temperature of the extruded compound increases, Increases the compression mold cycle time to cold, resulting in lower productivity and higher costs Extrusion temperatures less than 177 ° C (350 ° F) fail to adequately reduce the viscosity of the thermoplastic, resulting in poor distribution of the composite and mixing discontinuous lignocellulose fibers. This contributes to a loss of composite flexural and tensile properties.

The extruded composite can be formed into finished pieces by a variety of means including, but not limited to, cold compression molding, hot compression molding, profile extrusion, injection molding and the like. The thermal resistance of the discontinuous lignocellulose fibers of the present invention reduces the temperature of the extruded compound resulting in faster mold cycle times, thereby improving productivity and reducing cost. For example, cold-compression molding of a molten extruded composite comprises 30% discontinuous lignocellulose fibers of the composite, resulting in mold cycle times that are about 10 to about 20% faster than those of the thermoplastic without the Filling of fibers. Once they are removed from the profile extruders or compression dam dams, the finished composite parts can already be cooled with air or water at room temperature, before handling or storage, shipping or use. The present invention is demonstrated by the following non-limiting examples.

Table I Thermomechanical pulp of virgin South pine, with 5% moisture content, fiber size expressed by grinding distribution as a percentage by weight of which 13 to 18% is greater than 8 mesh sieve, 60 to 77% finer than sieve 8 mesh, but larger than 50 mesh screen and 5 to 27% finer than 50 mesh screen. Thermomechanical pulp of virgin South pine, with 5% moisture content, fiber size expressed by grinding distribution as a percentage by weight of which 50% is larger than 8 mesh, 20% finer than 8 mesh, but larger than 16 mesh, 20% thinner than 16 mesh but larger than 50 mesh and 10% finer than 50 mesh Thermomechanical pulp of virgin white poplar, with 5% moisture content, fiber size expressed by grinding distribution as a percentage by weight of which 18% is greater than sieve 8 mesh, 60% to 77% finer than mesh screen 8, but larger than 50 mesh screen, and 5 to 27% finer than mesh screen 50. Thermomechanical pulp of virgin white poplar, with 5% moisture content, fiber size expressed by grinding distribution as a percentage by weight of which 50% is greater than 8 mesh screen, 20% finer than 8 mesh screen, but larger than 16 mesh sieve, 20% thinner than 16 mesh sieve, but larger than 50 mesh sieve and 10% thinner than 50 mesh sieve. Wasted wood dried in white poplar kiln, with 5% moisture content, fiber size expressed by grinding distribution as a percentage by weight of which 50% is greater than 8 mesh screen, 20% thinner than 8 mesh screen, but greater than 16 mesh screen, 20% thinner than 16 mesh screen, but greater than 50 mesh sieve and 10% finer than 50 mesh sieve. Recycled polyethylene with density of 9.41 g / cc (.34 pounds per cubic foot), 6. 927 gm / 10 minutes of melt flow rate according to ASTM D 1238. Recycled polyethylene with density of 9.41 g / cc (.34 pounds per cubic foot) .70 gm / 10 minutes of melt flow rate, according to ASTM D 1238. Epolene G 3003 by Eastman Chemical Company. 9 Polybond 3009 Uniroyal Chemical Corporation. 10 Crystalene by Apex Specialty Polymer, Ltd.

Filling samples based on discontinuous lignocellulose fibers were prepared by preparing pieces of wood from the sources listed in a pressure vessel for a period of between 1 and 4 minutes at a pressure of 5.62 at 7. 03 kg / cm2 (80 to 100 psi). The conditioned pieces were transported by spindle at 4.57-5.98 kg / cm2 (65 to 85 psi) to a 91.44 cm (36") Sunds shredder and defibrated to the size of fibers and grind distribution of selected fibers. The discontinuous samples were dried to a content of less than about 5% by weight All the composite samples were prepared by recycling the filling of discontinuous lignocellulose fibers with thermoplastic, with or without coupling agents, at the concentrations listed in Table I, and a low shear mechanical mixing device The other samples were extruded through an extruder with 15.24 cm (6") Sterling drilling, with a spindle compression ratio of 34: 1 at 204 ° C (400 ° C) F) except for sample 6 which was extruded through a twin screw extruder of 30 mm, ZSK at 190 ° C (374 ° F). The compositions of the extruded compound were cold compression molded into test plates. Mold temperatures for test plate were in the range between 21 and 38 ° C (70 and 100 ° F). Mold cycle times were 3 minutes. All test plates were aged at least 72 hours before the test.

Table II Table II shows the chemical properties of the thermoplastic samples.

Table ni Table III shows the improvement in flexural properties achieved with incorporation of discontinuous lignocellulose reinforcing fibers from southern pine, at a concentration of 30% by weight in waste polyethylene without the use of coupling agents or union (sample 1) on a polyethylene thermoplastic (sample 2). The sample composition 1 would be sufficient for applications that require an improvement in rigidity on a thermoplastic.

Table IV Table IV shows the improvement in tensile and flexural properties of discontinuous lignocellulosic thermoplastic-fiber compositions, with the addition of polypropylene grafted with maleic anhydride (samples 3 and 4), polyethylene inserted with maleic anhydride (sample 6) and agents of ethylene methacrylic coupling. With polyethylene as the base resin, the compound with polyethylene grafted with maleic anhydride (sample 6) showed superior performance against similar compounds with polypropylene inserted with maleic anhydride (samples 3 and 4). The ethylene-methacrylic compound as coupling agents (sample 7) does not demonstrate the same proportion of improved flexural and tensile properties that are obtained with similar compounds consisting of unmarogenated polypropylene and maleated polyethylene as coupling agents. The increase in the content of the polypropylene grafted with maleic anhydride from 3 to 6% by weight of the compound compositions, as in samples 3 and 4, gave little gain in the performance of the compound.

Table V Table V shows the performance of composite samples having the same concentration of discontinuous lignocellulose fiber fill but with varying concentrations of long fibers. The results indicate that regardless of the three species in terms of the percentage of discontinuous lignocellulosic fibers with lengths exceeding 15 millimeters, it increases from 18 to 50% by weight within the polyethylene compound, the tensile properties of the composite were improved. This improvement in tensile properties of the component ratio with the higher percentage of long discontinuous lignocellulose fibers, show that the long figures of the discontinuous lignocellulose fiber filling of the present invention provide superior properties of traction against shorter particles and fibers. Table V also shows that virgin wood fibers derived from softwood and hardwood species result in compositions of thermoplastic composites - discontinuous molded lignocellulose fibers with different properties. Compounds, including fibers derived from hardwood have superior tensile and flexural properties, while compounds that include fibers derived from softwood and have superior Izod properties. Sample No. 7 derived from Southern pine produces a compound with lower tensile (strength) and flexural properties (rigidity), but greater Izod (impact) properties than sample No. 9 which is an identical composition derived from white poplar. Sample 12 demonstrates the comparable performance of discontinuous lignocellulosic thermoplastic-fiber composites, wherein the fibers are derived from kiln-dried hardwood waste in Example I. Samples 18 were cold-compressed into spool flanges of cable measuring 91.44 cm (36") in diameter by 3.81 cm (1.5") in width. In destructive drop tests, the cable reel flanges produced in accordance with the present invention withstood a vertical drop of 122 cm (48") which transported 317.80 kg (700 pounds) of cable without fracture, fatigue or failure. , in a practical application, the present invention derived from virgin wood has demonstrated its ability to overcome the typical brittleness of thermoplastic compositions with wood filler The previously described embodiments of the present invention have many advantages, including providing a reinforcing filler discontinuous lignocellulose fibers for thermoplastic composite compositions that significantly improve the tensile and flexural properties of the compounds This improvement is comparable to that obtained by other mouldable compositions including hardwood, thermomechanical, chemical, more expensive pulp. However, the use of the present invention of lignocellulose fibers Discontinuous thermomechanical pulp is more cost effective than using discontinuous thermo-mechanical chemical lignocellulose pulp with performance similar traction properties. Furthermore, the source of the component materials of the composition can be recycled waste and thermoplastic wood and the processes for manufacturing the fiber fill and the composite are conventional. In this way, the present invention is a significant advance in thermoplastic compound technology in terms of both cost and performance. While the present invention has been described in considerable detail in connection with preferred embodiments thereof, it will be understood, of course, that it is not intended to limit the invention to those embodiments, since modifications may be made by those skilled in the art, particularly to those skilled in the art. the light of the previous teachings. For example, no such combinations of wood fiber sources and thermoplastics are possible within the scope of the description. It is intended to cover all alternatives, equivalent modifications that may be included within the spirit and scope of the invention as defined by the appended claims. Therefore, it is contemplated to cover any of these modifications by the appended claims, since they will include those characteristics that constitute the essential aspects of the improvements within the spirit and actual scope of the invention.

Claims (25)

1. A reinforcing filler of discontinuous lignocellulose fibers for thermoplastic composite compositions, the filler is characterized in that it comprises at least about 20% by weight filler of discontinuous lignocellulose fibers having a length of at least about 15 millimeters and a smaller diameter to 0.5 mm.

2. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the fiber filling is derived from a kind of soft wood tree.

3. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the fiber filling is derived from a kind of hardwood tree.

4. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the fiber is derived from a source of virgin wood.

5. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the dry weight composition of the discontinuous lignocellulose fibers is about 27% lignin, 23% hemicellulose and 45% cellulose.

6. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the diameter of at least about 20% by weight of the discontinuous lignocellulose fibers having a length of at least about 15 millimeters, is at least about 0.1 millimeter.

7. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the diameter of at least about 20% by weight of the discontinuous lignocellulose fibers having a length of at least about 15 millimeters, is between about .1 millimeter and about .5 mm.

8. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the moisture content of the fiber filling is sufficiently low so that blisters do not form in a molded composition including fiber filling.

9. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the moisture content of fiber fill is less than about 5% by weight of the fiber filling.

10. The filling of discontinuous lignocellulose fibers according to claim 1, characterized in that the particle size distribution of the fibers as a total weight percent of the fiber filling that is retained in ASTM sieves, is approximately 20 to approximately 50% retained in an 8 mesh screen, about 20 to about 40% by weight retained in a 16 mesh screen, about 20 to about 30% by weight retained in a 50 mesh screen and about 10% thinner than a 50 mesh screen.

1 1. A process for producing discontinuous lignocellulosic fibers, the process is characterized in that it comprises the steps of: conditioning pieces of wood below about 5.62 to about 7.03 kg / cm2 (about 80 to about 100 psi) of vapor pressure , for a period of approximately 1 to 4 minutes, and mechanically separating the pieces into discrete staple fibers, whereby a significant percentage by weight of the discontinuous lignocellulose fibers has a length exceeding about 15 millimeters and a diameter less than about 0.5 mm.

12. A process for producing discontinuous lignocellulose fibers according to claim 1, characterized in that the step of mechanical separation comprises passing the pieces of wood between a rotating disc and a static disc, the discs are separated by a space of approximately .0072 and .254 millimeters (approximately .003 to approximately .01") and rotate the disc approximately 1,200 RPM.

13. A composition of moldable thermoplastic compound, characterized in that it comprises: from about 20 to about 50% of a filling of discontinuous lignocellulose fibers, the filling of discontinuous lignocellulose fibers comprises at least about 20% by weight of discontinuous lignocellulose fibers having a length of at least about 15%. millimeters and a diameter of less than about .50 millimeter, and of about 50 and 80% by weight of thermoplastic.

14. The moldable thermoplastic composition composition according to claim 13, characterized in that the thermoplastic is selected from polyethylenes, polypropylenes, polyanimides, polyvinylchloride, ABS, polystyrene, polyester and mixtures thereof.

15. The moldable thermoplastic composition composition according to claim 13, characterized in that the thermoplastic is derived from post-consumer or post-industrial waste sources.

16. The moldable thermoplastic composition composition according to claim 13, characterized in that it also comprises up to about 10% of a coupling agent.

17. The moldable thermoplastic composition composition according to claim 16, characterized in that the coupling agent is up to about 5% polypropylene grafted with maleic anhydride and the thermoplastic is from about 45 to about 75% polypropylene.

18. The moldable thermoplastic composition composition according to claim 16, characterized in that the coupling agent is up to about 5% polypropylene grafted with maleic anhydride and the thermoplastic is from about 45 to about 75% polyethylene.

19. The moldable thermoplastic composition composition according to claim 16, characterized in that the coupling agent is up to about 10% ethylene methacrylic or acrylic acid and the thermoplastic is from about 40 to about 70% polyethylenes, polypropylenes, polyanimides, polyvinyl, ABS, polystyrene, polyester or their mixtures.

20. Process for preparing a moldable thermoplastic composition, the process is characterized in that it comprises the steps of: providing about 20% to 50% by weight of the composite composition of a batch of discontinuous lignocellulose fibers, the filling of discontinuous lignocellulose fibers It comprises at least about 20% by weight of discontinuous lignocellulose fibers having a length of at least about 15 millimeters and a diameter of less than .5 millimeters, providing about 50 to about 80% by weight of the thermoplastic composition, mixing the filling of discontinuous lignocellulose fibers and the thermoplastic, extruding the batch of blended lignocellulose and thermoplastic fibers blended through a single screw extruder at an extruder operating temperature of less than about 232 ° C (450 ° F).

21. The process for preparing the moldable thermoplastic composition according to claim 20, characterized in that it further comprises the steps of forming the extruded compound composition in a finished product and cooling the finished product to room temperature.

22. The process for preparing the moldable thermoplastic composition according to claim 20, characterized in that it further comprises the step of providing from about 10% by weight of the composition of a coupling agent composition.

23. The process for preparing the moldable thermoplastic composition according to claim 22, characterized in that the step of providing the coupling agent comprises providing up to about 5% by weight of the composition of polypropylene compound grafted with maleic anhydride and wherein the The step of providing the thermoplastic comprises providing about 45% to about 75% by weight of the polyethylene composition.

24. The process for preparing the moldable thermoplastic composition according to claim 22, characterized in that the step of providing the coupling agent comprises providing up to about 5% by weight of the composition of polyethylene compound grafted with maleic anhydride and wherein the The step of providing the thermoplastic comprises supplying about 45% to about 75% of the polyethylene composition.

25. The process for preparing the moldable thermoplastic composition according to claim 22, characterized in that the step of providing the coupling agent comprises providing up to about 10% by weight of the ethylene-methacrylic or acrylic acid compound composition, and wherein the step of providing the thermoplastic comprises providing about 40% to about 70% by weight of the composition composition of polyethylenes, polypropylenes, polyanimides, polyvinyl chloride, ABS, polystyrene, polyester or mixtures thereof.