KR20020093065A - A moldable pellet based on a combination of natural fibers and thermoplastic polymer - Google Patents

Abstract

The moldable material comprises a central portion of the sized natural fiber 1 and may form a continuous natural fiber strand sheathed on the sheath of the thermoplastic 10 or, optionally, may be cut into pellets 14. Also disclosed are methods of making sized natural fiber products, natural fiber containing products, and natural fiber containing products and fiber reinforced composite products.

Description

Formable pellets based on combinations of natural fibers and thermoplastic polymers {A MOLDABLE PELLET BASED ON A COMBINATION OF NATURAL FIBERS AND THERMOPLASTIC POLYMER}

Technical Field

The present invention generally relates to moldable materials suitable for use in modern molding techniques of fiber reinforced composites. The present invention further relates to moldable pellets based on a combination of natural fibers and thermoplastic polymer materials. More particularly, the present invention relates to moldable pellets each comprising a core of natural fibers coated with a sheath of thermoplastic material. The resulting pellets provide a high level of fiber length retention during the molding process and impart a high level of mechanical performance.

Background

Fiber-reinforced plastics or composites known as such are widely known as lightweight, usually non-metallic, extremely powerful materials. Thus, the material is used in a variety of applications where impact resistance, high load bearing capacity and elasticity are required, without the disadvantage of using a material such as metal, which may be too heavy or susceptible to atmospheric degradation such as corrosion. .

Many methods are available for the production of fiber reinforced composites. Typically, the preparation of the composite first forms or shapes a suitable molding medium consisting of a length of fiber reinforcement and a polymeric molding material into the desired shape, and then the shaped material is cured and thereby hardened. Coagulation or curing with fiber reinforced products. Although a number of methods have been developed utilizing different types of molding media and molding and curing methods, they all typically require a combination of fiber reinforcement and polymeric molding material to form a moldable mixture, so that the fiber reinforcement can Can enhance the characteristics. Moreover, all composite manufacturing methods typically share the goal of maximizing the dispersibility of the fiber reinforcement throughout the polymer, thereby making sure that the composite does not contain an area less than the amount of the fiber dispersion, which forms a composite. Performance failures such as explosions or cracks.

While it is desirable to disperse the fiber reinforcement uniformly over the composite matrix, it has often been found to be difficult to achieve the object. Thus, the method of combining the fiber reinforcement and the molding polymer typically requires blending the components, which in turn causes the fiber reinforcement to shear or break in short lengths. Shorter fiber lengths in some ways reduce the physical strength of the composites in that there is less intermingling of certain lengths of fiber reinforcements in the composite matrix, thus reducing load bearing capacity and impact resistance. Therefore, it is preferable that the molding material for producing the composite contains the fiber reinforcement of the maximum length, and it is also preferable that the molding material creates the preservation of the fiber length during the molding process.

One means of increasing the dispersibility of the fiber reinforcement in the composite matrix is to apply a thin layer of sizing to the surface of the fiber reinforcement. Typically, the sizing contains components that chemically modified the surface of the fiber reinforcement to aid dispersibility and to promote bonding and adhesion between the fiber reinforcement and the molding polymer. In this regard, a more stable combination of fiber reinforcement and molding polymer is achieved. In addition, sizing provides some protection to the fiber reinforcement and is not prone to breakage in short lengths. Considerable efforts have been made in the development of sizing agents that are effective in helping dispersibility and reducing the breakdown of fiber reinforcements.

In addition to the need for the development of sizing and molding materials that promote fiber length preservation during molding, there is also a need for fiber reinforced composites that are environmentally friendly and include cost-effective alternatives to conventional fiber reinforcements such as glass fibers. Glass fibers, which are lighter than metal reinforcements and less susceptible to corrosion, have some inherent difficulties in processing. For example, during mechanical processing of glass fibers, dropped fibers or fiber fragments, also known as fluff, can be conveyed by air. The separated fibers or fragments may be finely dispersed in the processing environment or they may be collected on the equipment surface. Additionally, although glass fibers are lighter than metal reinforcements, more weight is added to the composite product than alternative reinforcements such as polymer fibers or natural fibers. Thus, such alternative reinforcements, in particular natural fibers, are extremely preferred choices for use as fiber reinforcements in composite production.

However, attempts to use natural fibers in the manufacture of composites have faced some difficulties. Although conventional molding methods, such as extrusion or compression molding, successfully use glass and even polymer reinforcements in the manufacture of fiber reinforced composites, the routinely required preforming conditions, such as mixing and blending at high temperatures, are the materials used. Place considerable requirements in the Additionally, extrusion, compounding and subsequent molding deteriorate the length and chemical composition and length of the natural fibers, while compression molding becomes an undesirable felt or mat-like product, which cannot be processed in high speed and high power molding processes. Found.

In view of the deficiencies of the prior art, it is an object of the present invention to form the following moldings in a form that is easily processed without significant fiber length loss during subsequent molding processes, with the advantage of incorporating environmentally and economically desirable natural fibers such as fiber reinforcements. It is to provide a moldable material for use in a composite molding method for generating a material. The method can produce moldable materials suitable for forming composites from natural fibers without any loss of physical properties or processability of the fibers due to prolonged exposure to high heat. The method may also allow for high throughput to ensure fast and cost effective production of moldable natural fiber containing products. There is also a need for natural fiber reinforced moldable materials with good fiber dispersion properties, which will help improve performance. In addition, in that the fiber component is natural and therefore readily biodegradable and renewable, it is formed in a way that has less environmental impact, requires less energy, and solves the problem of glass baffle buildup on processing equipment. There is a need for natural fiber reinforced moldable materials that exclude. Moreover, there is a need for natural fiber reinforced moldable products that are made in such a way as to minimize or eliminate the unpleasant odors normally caused by the degradation of natural fibers during processing to form a moldable material. This need is met with the products and methods of the present invention.

Summary of the Invention

It has now been found that materials suitable for use in the manufacture of fiber reinforced composites can be produced using natural fiber reinforced composites.

Therefore, in one aspect, the present invention is a moldable material comprising a central portion of natural fibers forming a natural fiber strand that is sheathed in a thermoplastic material. The moldable material can be optionally cut into pellets for use in molding the composite.

In another aspect, the present invention includes a multifilament fiber reinforced product comprising a strand of natural fiber reinforcement and a coating of a sizing composition disposed on the surface of the fibers in the strand. The sizing composition comprises a coating component selected from thermoplastic polymers, thermosetting polymers, and hydrocarbon oils or waxes, and further includes at least one component selected from coupling agents, lubricants, and other conventional additives. It may be non-aqueous. Sized natural fiber strands may be sheathed into a thermoplastic material to form a moldable material in accordance with the present invention.

The invention further includes a method of making a moldable natural fiber containing material comprising:

a) providing a multifilament natural fiber strand;

b) The natural fiber strands are sheathed in thermoplastic material.

The present invention additionally encompasses a method of making a fiber reinforced composite article comprising:

a) providing a formable material consisting of natural fiber strands sheathed in a thermoplastic material;

b) heat melting the thermoplastic material;

c) working the material to make the strands into filaments and dispersing the filaments in the thermoplastic material;

d) molding the moldable material to form a product;

e) cool the product to form a fiber reinforced composite product.

The concept of the invention also extends to fiber reinforced products formed according to the method.

The environmental impact and fully reproducible invention overcomes the limitations of the conventional process by minimizing fiber exposure to excessively high temperatures and thus actually eliminating chemical degradation and any associated odors. It also overcomes the limitations caused by poor dispersion of natural fibers in composite molding materials. To some extent, improved dispersion of fibers and improved composite part performance were obtained through the application of a sizing composition on the surface of natural fibers. The present invention also overcomes the limitations that preclude or limit the use of natural fibers as reinforcements in composite molding, especially in mechanical degradation of the fiber structure, during the conversion of natural fiber materials into formable reinforcing materials. In contrast, the present invention provides pellets containing intact long fibers that can be molded to form high quality composites.

Brief description of the drawings

1 shows a process for producing formable pellets composed of natural fiber strand material and thermoplastic facing material according to the invention.

2 is a three-dimensional illustration of pellets formed in accordance with the present invention.

3 is a cross section of a pellet formed according to the invention.

Detailed Description and Examples of the Invention

The present invention uses natural fibers as a main component for forming natural fiber strands, and then acts as a gas for arranging thermoplastic materials to form a moldable material. Thus, in one embodiment, the moldable material of the present invention comprises multifilament natural fiber strands in combination with the thermoplastic material to allow the thermoplastic material to be formed as a sheath around the natural fiber strands. The natural fiber strand may optionally further comprise a sizing that protects the filaments in the strand and improves the miscibility of the filament surface with the thermoplastic material of the sheath. The sheathed resultant strands can be used in continuous form or as cut pieces in forming methods for forming fiber reinforced composites.

As used with the present invention, the term “natural fiber” refers to cellulosic plant fibers that are extracted from any part of the plant, including stems, seeds, leaves, roots or bast. Any natural fiber that meets the requirements of the manufacturing methods described herein can be used in the present invention. Suitable natural fibers include jute, bamboo, cilithia, cotton, vargas, hemp, coir, flax, kenaf, sisal, flax, henequin, or any combination thereof, but It is not limited. The term "substrate" is also used with reference to natural fiber strands in its functioning as the basic element of the present invention, where it is possible to place sizing compositions and / or thermoplastic materials.

Any arrangement of the majority of natural fiber filaments recruited for forming multifilament strands can be used as gas in the present invention. The filaments may be arranged linearly as a collection of parallel alignments or may be formed as twisted strands consisting of one or more piles. Preferably, the natural fiber filaments are in the form of one strand of twisted strand. However, since different types of natural fibers have different shapes or appearances and varying densities, they can be broad in the number of fibers required to form suitable strands. Thus, the properties of natural fiber strands can be best described and evaluated in terms of indicators such as twist factor and weight per unit length, due to the wide array of dimensional properties of natural fibers.

The twist factor is an evaluation of the average amount of helical twist imparted to a strand along its length. Twist is an important aspect of the present invention because it forms a continuous strand that maintains sufficient structural integrity to act as a gas for the coating process used to apply the sizing composition and / or thermoplastic material to the strand according to the present invention. Natural fibers are discontinuous or basic fibers in that they are naturally present in a relatively short length, typically in the range of about 2 inches (5.08 cm) to about 6 feet (1.83 m). Continuous coating processes, such as the sheathing process of natural fiber strands in thermoplastic materials, require continuous strands. Therefore, in order to use this process properly, the natural fibers must be twisted together to form strands with the least amount of structural defects. However, in addition to increasing the strength of the fiber strands, the amount of twist can also reduce the dispersibility of the natural fibers in subsequent molding processes. In turn, increasing the twist requires more severe processability of the fiber strand, using an increase in shear force or temperature increase applied to the fiber strand to obtain adequate dispersibility. An increase in one of these processability conditions typically degrades the fiber. Thus, since a small number of twists per inch (2.54 cm) is associated with increased ease of fiber dispersibility, a range of typically about 1 twist per 1 inch (2.54 cm) of fiber length to about 1 twist per 4 inch (10.16 cm) Has been found to have sufficient elongation strength to withstand the sizing and strand sheathing process while providing optimum dispersibility.

The main component weight of the natural fiber strand should also be sufficient to facilitate its use in the continuous coating process. Preferably, the weight of the natural fiber strand should range from about 1 g (1.093 g / m) per yard to about 4 g (4.372 g / m) per yard. For example, sisal twines having a weight of about 3 g (3.279 g / m) per yard can be used as natural fiber strands.

Natural fiber strands, which act as a gas for cladding with the thermoplastic material according to the invention, can optionally be sized with a suitable sizing composition before applying the thermoplastic material. The sizing composition may comprise a coating component that provides a uniform film or layer on the surface of the filaments in the strand. The coating component can be selected from thermoplastic polymers, thermoset polymers and hydrocarbon oils or waxes. The fraction of the various forms of coating components in the sizing composition will vary depending on the used. The fraction of coating components will also depend on whether the sizing is an aqueous or non-aqueous formulation.

In one embodiment of the invention, the coating component may be a thermoplastic polymer. Any suitable thermoplastic polymer can be used. The thermoplastic polymer can be added to the aqueous sizing composition in emulsified form or used without conventional emulsification in the non-aqueous sizing composition. Examples of such polymers include maleated polypropylene, hydrocarbons, waxes, wax emulsions and polyurethanes. Preferably, the thermoplastic polymer serving as the coating component is maleated polypropylene, not in emulsified form. Examples of such polymers include Eastman Chemicals Inc. "E-43" available from, having a molecular weight of about 9100 atomic weight units and softening at about 153 ° C (307 ° F). Typically, when the coating component is a thermoplastic polymer, in an aqueous sizing composition at a concentration that provides a fraction of the size of the size of the stranded strand, from about 0.1% to about 10% by weight relative to the total weight of the sized natural fiber strand; Or in a non-aqueous sizing composition that provides a fraction of about 0.1% to about 25% by weight relative to the total weight of the natural fiber strand sized.

The coating component may also be appropriately selected from the group consisting of thermosetting polymers. Examples of such thermosetting polymers include unsaturated polyesters, epoxy resins and polyurethanes. Thermosetting polymers, when used as coating components, may be used in an aqueous sizing composition at a concentration that provides a fraction of the size of the size of the stranded strand from about 0.1% to about 10% by weight relative to the total weight of the sized natural fiber strands; Or in a non-aqueous sizing composition that provides a final fraction of from about 0.1% to about 25% by weight relative to the total weight of the natural fiber strand sized.

In alternative embodiments, the coating component may be selected from the group consisting of hydrocarbons, including, for example, liquid hydrocarbon oils and waxes that may be in solid, amorphous or fluid form at room temperature. Hydrocarbon oils are available from Mobil Chemicals, preferably mineral oils such as "WHITEREX 425". Examples of suitable hydrocarbon waxes are Shell Chemical Co. "SHELLWAX 100" available from. In an aqueous sizing composition wherein the hydrocarbon coating component provides a fraction of the size of the size of the stranded strand, from about 0.1% to about 10% by weight relative to the total weight of the sized natural fiber strand; Or in a non-aqueous sizing composition that provides from about 0.1% to about 25% by weight relative to the total weight of the natural fiber strand sized.

Preferably, the coating component used in the aqueous or non-aqueous sizing composition of the present invention is a hydrocarbon oil or wax having a molecular weight ranging from about 250 atomic weight units (amu) to about 4000 amu. The amount of said hydrocarbon coating component incorporated into the aqueous sizing composition prior to application to the natural fiber strands may vary from about 0.5% to about 10% by weight relative to the total weight of the aqueous sizing composition. Preferably, the amount added to the aqueous substrate sizing is from about 1% to about 3% by weight relative to the total weight of the aqueous sizing composition. In the non-aqueous sizing composition according to the present invention, the amount of hydrocarbon coating component may vary from about 0.5% to about 25% by weight, preferably from about 10% to about 15% by weight relative to the total weight of the non-aqueous sizing composition. % to be.

The sizing composition may also include a suitable coupling agent. The coupling agent promotes the connection between the natural fiber strand and the sizing composition, thereby enabling good adhesion of the sizing composition to the strand surface. Examples of such coupling agents include organosilanes, titanates, zirconates, aluminates, zirco-aluminates and chromium methacrylates. Any organosilane coupling agent capable of polymerizing during use in the presence of natural fibers promotes the wetting of the natural fiber surface, which in turn exhibits some adhesion by interacting and adhering molecules on the fiber surface. Eventually, the adhesion effect is observed with the use of the organosilane. In this regard, the organosilane coupling agent also demonstrates thermosetting similar to the thermosetting coating constituents that may be included in the sizing composition of the present invention. Suitable organosilanes that act as coupling agents in the aqueous or non-aqueous sizing compositions of the present invention are gamma-amino propyltriethoxy silanes, which are designated by C.K. Witco Inc. Aminosilane available from. An effective amount of coupling agent is used to provide the coupling effect required to adhere the sizing composition to the surface of the natural fiber strand.

In addition, it may also include one or more conventional additives selected from processing aids, lubricants, viscosity modifiers, surfactants, odor inhibitors, fragrances, fungicides, biocides, and polymeric compatibilizers. One skilled in the art can determine the selection and amount of each such additive in proportion to the desired effect in the sizing composition.

Therefore, if used, the sizing composition can be applied to form a multi fiber reinforced product consisting of strands of natural fiber reinforcement that are permeated or coated with the sizing composition. The sizing composition can be applied by any conventional means, including dip-draw dip baths, rollers, pads or sprayers. The sizing composition may be applied using an in-line applicator in a continuous manner, or may be applied separately off-line. Preferably, depending on the type of natural fiber used, the sizing is applied at a temperature in the range of about 10 ° C (50 ° F) to about 200 ° C (392 ° F). However, the application temperature should generally not exceed 200 ° C. (392 ° F.) during the expansion period, as long as the cellulosic fibers are degraded. The sizing can be applied, for example, to the majority of individual filaments, which can be collected and twisted into strands after treatment with the sizing composition, or instead the sizing composition can be applied to the preformed strands.

In the latter method, in order to substantially coat all of the surfaces of the individual filaments in the strand, the sizing composition should be of a viscosity that permeates or penetrates the flow of the sizing composition through the filaments in the natural fiber strand. For aqueous and non-aqueous sizing compositions, the viscosity can range from about 1 cP (0.001 Pa.s) to about 200 cPs (0.2 Pa.s). The aqueous sizing composition may preferably range in viscosity from about 1 cP (0.001 Pa.s) to about 20 cPs (0.02 Pa.s) at about 60 ° C. (140 ° F.), more preferably depending on the amount of mixed solids. Preferably, the viscosity is from about 1 cP (0.001 Pa.s) to about 10 cPs (0.01 Pa.s) at 60 ° C. (140 ° F.). If the sizing is non-aqueous, the viscosity may range from about 20 cPs (0.02 Pa.s) to about 200 cPs (0.2 Pa.s) at 60 ° C. (140 ° F.), preferably at about 60 ° C. (140 ° F.). 20 cPs (0.02 Pa.s) to about 60 cPs (0.06 Pa.s). This preferred viscosity typically promotes sufficient penetration and coating of the filaments in the natural fiber strand by the sizing composition.

As described above, one embodiment of the present invention is a moldable material comprising a strand of continuous natural fiber reinforcement composed of a majority of natural fibers, which is substantially sheathed in the casting of the thermoplastic material. The thermoplastic material is preferably one suitable for use as a molding matrix resin in the formation of fiber reinforced composites. Thermoplastic materials typically have, but are not limited to, polyolefins, polyamides, thermoplastic polyesters, vinyl polymers, polymer modified asphalt, and mixtures thereof, having molecular weights of from about 7000 atomic weight units to hundreds of thousands of atomic weight units. Examples of such thermoplastic materials include polypropylene, polyethylene, polypropylene modified asphalt, recycled polypropylene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polypropylene copolymer polyamides, and mixtures thereof.

The amount and form of the thermoplastic material may be that of the moldable material formed in combination therewith in a conventional molding process to form a fiber reinforced composite article without the addition of any other molding resin. Optionally, the moldable material may be further combined with further conventionally known molding resins during the molding process. Such further molding resins include polyolefins, polyamides or other optional thermoplastic polymers suitable for molding purposes, as will be apparent to those skilled in the art.

The method for producing the molding material of the present invention includes providing a multifilament natural fiber strand and covering the strand with a sheath of thermoplastic material. Prior to sheathing with the thermoplastic material, the natural fiber strands can be optionally sized with the sizing composition described below.

1 illustrates one embodiment of a method of making a formable material using non-aqueous sizing, in accordance with the present invention. 1, one or more ends of the natural fiber strand 1 are released from the collet 2 and passed through one or more rollers 3, after which the natural fiber strand ends 1 are deposited and dip-bathed. (4). The dipbath 4 contains a sizing composition of sufficient viscosity to allow its inhalation or penetration through the filaments of the natural fiber strand ends 1. For example, the sizing composition can include coating components such as hydrocarbon oils, as well as one or more other conventional additives, as described herein. After exiting the deep bath 4, the strand ends 1 are optionally pulled out to provide extension and collection of the ends to form a reinforced end 1a consisting of multiple filaments, with a layer of thermoplastic material applied around them. To form an exterior portion. In an alternative embodiment, when using aqueous sizing, the reinforcing end 1a is passed through one or more ovens (not shown) and then a coating of thermoplastic material is applied.

Particularly preferred methods of applying a thermoplastic material around the continuous fiber material to form the sheath are described in US Pat. 5,972,503. In this method, the natural fiber strands can be pulled or otherwise passed through a suitable coating apparatus. The coating apparatus suitably comprises a means, such as an extruder, to provide a source of molten thermoplastic material for coating the strand. The coated strand is then passed through a die, which controls the amount and thickness of the layer of molten thermoplastic material on the surface of the strand and softens the molten thermoplastic material to form a sheath into which the strand is inserted. A large number of sheathed strands can be formed by pulling or otherwise passing a plurality of coated strands through a corresponding plurality of dies, each die having a pupil sized to form the coating into a thermoplastic sheath of desired thickness. Preferably, the coating device is a wire coater, which is a device or group of devices capable of coating or sheathing one or more strands with thermoplastic material to form a sheath of relatively uniform thickness on each strand. . Preferably, the wire coater also includes a die that forms a uniform desired thickness and / or cross section in the enclosure.

The strand is fed or passed through the coating apparatus using a suitable mechanism such as a puller, which pulls the strand through the wire coater. The puller may be separate or part of the wire coater. The wire coated strand can then be wound around a failure or its equivalent, or else passed through a cutter to fragment into pellets. The cutter can also be adapted to act as a puller or to assist the puller in pulling the strand through the wire coater. The speed of the natural fiber strand through the wire coater die can vary from 100 to 300 feet / minute (0.508 to 1.524 m / s). This rapid yield rate exposes the natural fiber strand to the thermoplastic material, which minimizes the exposure time to a relatively high temperature, but does not raise the temperature of the natural fiber strand itself to the point where no degradation of the fiber occurs. As a result, the natural fiber strands have good thermal history and can form good moldable materials that provide good reinforcements for composite production.

The present technique is shown in FIG. 1, wherein the reinforcing ends 1a formed by collecting the individually sized natural fiber strand ends 1 are pulled out through the wire coater 6 as a coating apparatus. The wire coater 6 mounts a shape die 7, which may be a rounded contour, or any other desired contour, depending on the desired cross-sectional profile of the wire coated strand after exiting the die 7. In the headbox 8 a molten thermoplastic material derived from the melting of a solid thermoplastic raw material such as pellets is fed to the wire coater 6. The molten thermoplastic material is then fed to the extruder 9. From the extruder 9, a stream of molten thermoplastic material is pushed through the nozzle opening (not shown) into the reinforcement end 1a as it passes through the wire coater 6. As the reinforcement end 1a is pulled out through the die 7, the thermoplastic material flows around the reinforcement end 1a, thereby forming a thermoplastic sheathed strand 10, wherein the natural fiber filaments are It is tied together to form a central part surrounded by an outer layer of thermoplastic material. The thermoplastic sheathed strand 10 exits the wire coater 6 and is drawn through the water bath 11 at ambient temperature, which acts as a cooling means. Any suitable alternative cooling means may be used, for example an air drying refrigeration apparatus, or a water sprayer.

The cooled thermoplastic sheathed strand 10 may be wound and stored for subsequent molding in continuous form, or it may be cut into pellets and packaged for subsequent use in the molding application. Cutting of continuous strands into separate pellets can be carried out via an inline or offline process. In this regard, the equipment may include means such as a cutter for fragmenting the continuous strand into the majority of discrete pellets. In the embodiment shown in FIG. 1, the thermoplastic sheathed end 10 is stretched with one or more rollers 12 and then pulled out through the cutter 13, which causes the strand 10 to be about the same length as the desired size. Fragment Preferably, the thermoplastic sheathed strand 10 is cut into pellets 14 of about 0.25 inches (0.635 cm) to about 2 inches (5.08 cm) in length. Optionally, the thermoplastic sheathed end 10 can be pulled through the wire coater into a puller (not shown) located downstream of the wire coater and below the cutting means. Alternatively, the cutting means itself may be adapted to perform the function of the puller or to assist the puller in pulling the sized natural fiber strands through the wire coater.

The resulting pellets 14 preferably vary from about 0.25 inches (0.635 cm) to about 2 inches (5.08 cm) in length, with the most preferred length being about 0.5 inches (1.27 cm) to about 1 inch (2.54 cm). However, the length of the pellets can be adjusted longer or shorter as required for proper application. Thus, the pellet size can be selected to provide adequate fiber length elongation as well as to provide an optimum aspect ratio for automated handling and processing equipment. As shown in FIG. 1, the pellets 14 may be collected in a container 15 and stored for future packaging or processing, or may be packaged directly by integrating an inline packaging device into a forming operation (not shown).

The pellets formed according to the present invention are typically cylindrical in shape, although the shape can be modified by changing the appearance of the die pulling the wire coated strand after applying the sheath of thermoplastic material. FIG. 2 is approximately cylindrical in shape and includes a tubular sheath 16 of thermoplastic material forming an envelope around a central portion 17 consisting of a majority of natural fiber filaments derived from one or more moving ends. The cross section of this embodiment of the pellets formed with the present invention shows that the central portion 17 of the natural fiber filament is substantially surrounded by the sheath 16, such that the sheath 16 is substantially constant around the center 17. It provides a layer of thermoplastic material that is thick.

The pellets may contain various weight fractions of thermoplastic facing material. In one preferred embodiment, the thermoplastic facing material provides all of the molding resins used to form the composite matrix during molding of the molding material to form the composite article, eliminating the need for compounding with the additional molding resin prior to molding. Accordingly, the thickness of the thermoplastic sheath can be varied to increase or decrease the fraction of thermoplastic material in the moldable material.

The present invention further utilizes a molding method selected from injection molding, compression molding, extrusion-compression molding, extrusion-injection molding, compression-injection molding, or any combination thereof, to provide a fiber reinforced composite article from the moldable material of the present invention. It relates to a method for producing. Preferred methods of making fiber reinforced composite articles include pellets of the invention in a molding process comprising heating and / or extrusion to heat mold the moldable material and to disperse the natural fiber fragments of the pellets across the thermoplastic material. Molding. The mixture of molten thermoplastic material and fibers is then introduced into a suitable mold by conventionally known methods, such as injection or extrusion, or otherwise formed into a product, shaped or cooled. During the cooling process, the mixture of molten thermoplastic material and natural fiber fragments is cured into a hard and elastic composite.

Example

Example 1. Non-aqueous sizing method.

A commercial sisal twine (Ambraco 16000 Untreated Baler Twine) weighing about 3.2 g / yard (3.50 g / m) and about 1 twist / inch (2.54 cm) was used. The number of sisal fibers in the twine was about 120. Samples of non-aqueous size, Sample A-C, were prepared:

A. 1000 g mineral oil (WHITEREX 425).

B. 750 g of mineral oil and 250 g of maleated PP wax (EPOLENE E-43) were combined and heated to about 150 ° C. (302 ° F.) with stirring.

C. 675 g of mineral oil, 225 g of maleated wax and 100 g of stearic acid were combined and heated to about 175 ° C. (347 ° F.) with stirring.

The sisal twine ball was unrolled from the inside and deposited in each size using a dip bath and rewound on a winding machine. Size A was applied at room temperature, but size B and size C were heated in a sizing bath and applied to the sisal at elevated temperature (100 ° C. ± 20 ° C.) (212 ° F. ± 68 ° F.). The amount of sizing selected by the sisal ranged from about 15-20% by weight relative to the total weight of the sized strands (unless otherwise noted, all fractions in the examples described herein were weight percent relative to the total weight of the sized strands). ). The compactly wound package of sized sisal twine is then likely to be wire coated in the next step.

The sized natural fibers were hung through a crosshead extrusion (wire coated) die with a 3 mm diameter exit hole attached to Killion 2 inches (5.08 cm). The set point temperatures on the extruder were all 225 ° C. (437 ° F.). An extruder was used to supply molten Huntsman P4C6Z-059 (MFI = 35) polypropylene that was dry mixed with the 2% Polybond 3200 polymeric coupling agent around the fiber as it passed through the die. After exiting the die, the coated strands were immediately passed through a 2 m long water bath maintained at 10 ° C. (50 ° F.) and through a Killion 4-24 dual belt puller. In this example the puller speed was set at 100 feet / minute (0.508 m / s) and the extruder output had a weight of 10 g / yard (10.93 g / m) calculated to provide 30% by weight of the (dry) fiber content. Set to obtain strands. In this example the strands were fed directly from the puller to a Conair Jetro 2047 cutter which cuts the strands into pellets of 12 mm length suitable for feeding the injection molding machine.

The pellets from each of Samples A, B and C were pre-dried overnight at 88 ° C. (190 ° F.) and then injection molded to form discs using a Van Dorn 300-RS-25 molding machine. The molding set point temperature was 150 ° C.-171 ° C. (302 ° F.-340 ° F.), screw speed was 60 rpm (6.28 rad / s) and back pressure was 80 psi (551.58 kPa). The die cavity was 3 mm thick and 177 mm diameter. The die temperature was set at 88 ° C. (190 ° F.). Molded disks were evaluated by visual test.

It was observed that all mold discs emit a minimal odor due to the low mold temperature. In addition, sisal fibers retained their natural pale brown color, indicating that minimal levels of degradation no longer occurred during processing.

Disk A (formed from pellets of Sample A) represents the collection of undispersed fiber bundles delivered to the PP matrix; Only about 10% of the fibers were dispersed in the matrix for the visual estimate. Disk B showed a high level of dispersion. It was estimated that less than about 10% of the fiber bundles were not dispersed in the matrix. Disk C exhibited substantially complete fiber dispersion; The bundle was not visible.

Example 2. Aqueous sizing method.

The final amount of size prepared by adding 21.5 g of gamma-aminopropyltriethoxy silane and 100 g of maleated PP emulsion (CHEMCOR 43N40) to deionized water was 8823 g. The mixed solids were calculated to be 0.6 wt%. The amount of 1135 g of sisal twine (same form as in Example 1) was loosened in a 5 gallon (18.93 L) plastic bucket. Loosely spread in the bucket. The aqueous size was poured on top of the sisal hemp and allowed to soak for 10 minutes. The top end of the sisal was found and the twine was moved by hand and the excess size was compressed while moving the twine. The weight of the sized sisal after sizing was 2853 g, indicating that the sisal accounted for about 150% of its weight in the sizing composition. In other experiments, the amount of water selected by sisal when immersed in water is about 150% of the sisal weight. The vessel was placed in a forced air oven at 105 ° C. (221 ° F.) and water was removed after drying for about 30 hours. The amount of dried sizing composition on the dried sisal was about 0.9% by weight. The sisal was then wire coated as described in Example 1.

Applicant's invention is contemplated as including many other embodiments that are not described in detail herein, and therefore the above disclosure should not be understood as being limited to the above embodiments or preferred embodiments.

Claims (33)

A moldable material comprising a majority of natural fiber strands including a wrapped fiber, and a sheath of thermoplastic material. The method of claim 1, wherein the natural fibers are made of jute, cotton, vargas, hemp, coir, linen, bamboo, cilantro, kenaf, sisal, henequin, manila hemp, flax and mixtures thereof. Formable material selected from the group. 2. The moldable material of claim 1, wherein the thermoplastic material is selected from the group consisting of polyolefins, polyamides, thermoplastic polyesters, vinyl polymers, polymer modified asphalt, and mixtures thereof. 4. The thermoplastic material of claim 3 wherein the thermoplastic material is comprised of polypropylene, polyethylene, polypropylene modified asphalt, recycled polypropylene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polypropylene copolymer, polyamide, and mixtures thereof. Formable material selected from the group. The formable material of claim 1 further comprising a sizing on the surface of the natural fiber strand. 6. The moldable material of claim 5, wherein the sizing comprises a thermoplastic polymer, a thermoset polymer or a hydrocarbon as coating component. The multifilament fiber reinforced product of claim 1 in the form of pellets from about 0.25 inches (0.635 cm) to about 2 inches (5.08 cm) in length. Natural fiber strands composed of a majority of natural fiber filaments formed from one or more strands; And a coating of a sizing composition disposed on the surface of the filament. The method of claim 8, wherein the natural fiber is selected from the group consisting of jute, cotton, vargas, hemp, coir, linen, bamboo, cilantro, kenaf, sisal, henequin, manila hemp, flax, and mixtures thereof. Multifilament fiber reinforced product. 9. The natural fiber reinforcement of claim 8, wherein the natural fiber reinforcement has a twist factor of about 1 twist per 1 inch (2.54 cm) of strand length to about 1 twist per 4 inches (10.16 cm), and from about 1 g to 1 yard of strand length. A multi strand filament fiber reinforced product having a weight of about 4 g per yard. The multifilament fiber reinforced product of claim 8, wherein the sizing composition comprises a coating component selected from the group consisting of thermoplastic polymers, thermoset polymers, hydrocarbon oils, and waxes. 12. The multifilament fiber reinforced product of claim 11, wherein the sizing composition comprises a hydrocarbon oil or a wax. 13. The multifilament fiber reinforced product of claim 12, wherein the sizing composition comprises a hydrocarbon oil or wax having a molecular weight ranging from about 250 amu to about 4000 amu. 13. The multifilament fiber reinforced product of claim 12, wherein the viscosity of the sizing composition is from about 1 cP (0.001 Pa.s) to about 200 cPs (0.2 Pa.s) at a temperature of about 60 ° C (140 ° F). 9. The multifilament fiber reinforced product of claim 8, wherein the sizing composition further comprises a coupling agent selected from the group consisting of organosilanes, titanates, zirconates, aluminates, zirco-aluminates and chromium methacrylates. The multifilament fiber reinforcement of claim 8, wherein the sizing composition further comprises at least one compound selected from the group consisting of processing aids, lubricants, viscosity modifiers, surfactants, odor inhibitors, fragrances, fungicides, biocides, and polymeric compatibilizers. product. Process for producing a moldable natural fiber-containing material comprising: a) providing a multifilament natural fiber strand; b) Sheathing the natural fiber strands to the sheath of the thermoplastic material. 17. The method of claim 16, wherein the sheathing of the natural fiber strands is a wire coating to form thermoplastic sheathed composite strands. 18. The method of claim 17, further comprising cutting the thermoplastic clad natural fiber strand into pellets. 18. The method of claim 17, wherein the molecular weight of the thermoplastic material used to sheath the natural fiber strand is at least 7000 amu. 18. The method of claim 17, wherein the thermoplastic material is selected from the group consisting of polyolefins, polyamides, thermoplastic polyesters, vinyl polymers, polymer modified asphalt, and mixtures thereof. 22. The method of claim 21 wherein the thermoplastic material is comprised of polypropylene, polyethylene, polypropylene modified asphalt, recycled polypropylene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polypropylene copolymers, polyamides, and mixtures thereof. Selected from the group. 18. The method of claim 17, wherein the natural fiber strands are sheathed with thermoplastic material after sizing with a sizing composition. The method of claim 23, wherein the sizing composition comprises a coating component selected from the group consisting of thermoplastic polymers, thermoset polymers, hydrocarbon oils, and waxes. The method of claim 24, wherein the sizing composition comprises a hydrocarbon oil or wax that is solid at room temperature. The method of claim 25, wherein the viscosity of the sizing composition is between about 1 cP (0.001 Pa.s) and about 200 cPs (0.2 Pa.s) at a temperature of about 60 ° C. (140 ° F.). The method of claim 25, wherein the hydrocarbon oil or wax has a molecular weight ranging from about 250 amu to about 4000 amu. A method of making a fiber reinforced composite product comprising: a) providing a formable material consisting of natural fiber strands sheathed in a thermoplastic material; b) heat melting the thermoplastic material; c) working the material to make the strands into filaments and dispersing the filaments in the thermoplastic material; d) molding the moldable material to form a product; e) Cool and harden the product. 29. The method of claim 28, wherein the formable material is in pellet form. 30. The method of claim 29, wherein forming the pellets further comprises combining the pellets with the resinous matrix material. 27. The method of claim 26, wherein the thermoplastic material is selected from the group consisting of polyolefins, polyamides, thermoplastic polyesters, vinyl polymers, polymer modified asphalt, and mixtures thereof. 32. The thermoplastic material of claim 31, wherein the thermoplastic material is comprised of polypropylene, polyethylene, polypropylene modified asphalt, recycled polypropylene, polyvinyl chloride, polyethylene terephthalate, polybutylene terephthalate, polypropylene copolymer, polyamide, and mixtures thereof. Selected from the group. A fiber reinforced composite product made by the method of claim 26.