WO2002068356A1

WO2002068356A1 - Particulate material distributed in-between gathered fibers of a strand and increased loading of sizing resulting therefrom

Info

Publication number: WO2002068356A1
Application number: PCT/US2001/051075
Authority: WO
Inventors: Martin C. Flautt; Ashish P. Diwanji; Leonard J. Adzima; Jeffrey L. Antle; Donald R. Holman; Steven E. Baker
Original assignee: Owens Corning
Priority date: 2000-10-31
Filing date: 2001-10-26
Publication date: 2002-09-06

Abstract

The present invention relates to sized strands with a high sizing loading comprising a plurality of fibrous filaments having a particulate material distributed between the filaments. The present invention also relates to pre-forms and composites made from the sized strands.

Description

PARTICIPATE MATERIAL DISTRIBUTED IN-BETWEEN

GATHERED FIBERS OF A STRAND AND INCREASED

LOADING OF SIZING RESULTING THEREFROM

FIELD OF THE INVENTION

BACKGROUND OF THE INVENTION

Fibers, such as glass fibers, are commonly used as reinforcements for synthetic polymer composites. These fiber reinforced composites are desirable for their combination of light weight and strength and are useful in a variety of applications including automobile components and housings for computers.

Conventional techniques may be used to make fiber reinforced composites and usually involve placing a pre-form in a mold and forming a polymer matrix around the pre-form. Methods for forming pre-forms involve depositing chopped reinforcing fibers on to a porous form, consolidating the fibers by heating, and cooling to form a mat structure. For adequate consolidation, a resin binder is usually incorporated. The term "resin binder" herein refers to a synthetic resin material and/or to precursors thereof. A resin binder is usually added to the chopped fibers before the heating step so that when heated, the resin binder flows across the fibers and acts as a consolidating agent when cooled. When the resin binder is a thermoset, thermoset precursors are added to the chopped fibers before the heating step so that when heated, the thermoset precursors flow across the fibers and act as a consolidating agent when cured. The incorporation of a resin binder in order to produce adequate pre-forms continues to be a significant economic problem in the art.

Incorporating a resin binder into a pre-form typically requires two phases: 1) a strand forming phase and 2) a chemical treatment phase. The strand forming phase involves creating a plurality of fibers by attenuating streams of molten material to create a plurality of fibers, applying a sizing composition to the fibers, and gathering the fibers into a strand. The chemical treatment phase involves chopping the strand, and applying a treatment comprising the resin binder to the strand. Alternatively, the treatment may be applied to the strand first, subsequently followed by chopping the strand. It would be desirable to discover a method for incorporating a resin binder into a pre-form only involving the strand forming phase and eliminating the need for a chemical treatment phase where resin binder is added. Such a method might be achieved by formulating a sizing composition which comprises the resin binder and applying this sizing to a plurality of fibers before they are gathered into a strand. A problem with this proposal is that the fibers bundle tightly when gathered into a strand and leave very little interstitial space in which the resin binder may be adequately loaded. Accordingly, it would be desirable to discover a method for achieving an adequate loading of a resin binder in the strand forming phase thereby eliminating the need for an additional chemical treatment phase.

SUMMARY OF THE INVENTION

An object of the invention is a sized strand comprising gathered fibers, a particulate material distributed in-between the fibers, and a high loading of a sizing composition preferably with a resin binder incorporated into the sizing composition.

Another object of this invention is the application of the sizing composition set forth in the previous paragraph to a plurality of fibers which are gathered to form a sized strand. A high loading of the sizing composition is achieved by addition of a particulate material to the sizing composition. The particulate material becomes distributed in- between the gathered fibers of the strand thereby causing an increase of interstitial space which in turn leads to a higher loading of the sizing composition in the sized strand. Higher loading of a resin binder is attainable by its incorporation into the sizing composition of the present invention. Accordingly, sized strands produced in such a manner have an adequate amount of binder loading so that they may be used to make preforms without the need of an additional chemical treatment in order to add extra resin binder. The present invention is not necessarily limited to increasing the loading of a resin binder but is also useful for increasing the loading of any sizing composition applied during the strand forming process outlined above. Another object of this invention are pre-forms made with the sized strands set forth in the previous paragraph, and reinforced composites made from such pre-forms.

Yet another object of this invention is a sizing composition having the capability of high loading on to a strand wherein the sizing composition comprises a particulate material, a film former, a surfactant, and a liquid carrier. DETAILED DESCRIPTION OF THE INVENTION Gathered Fibers

The sized strand of the present invention comprises a strand composed of gathered fibers or filaments made from fiberizable materials known in the art such as glass, carbon, natural fibers, polymers, or mixtures thereof. Examples of fibrous materials that may be used either alone or in combination with glass or carbon fibers include thermoplastics including polyesters such as DACRON^® (available from E.I. DuPont de Nemours and Company), polyaramids such as KEVLAR^® (available from E.I. DuPont de Nemours and Company), and natural fibers. Preferably, the sized strand comprises reinforcing fibers. Typically, such strands are formed by combining filaments of the reinforcing fibers as they are attenuated from a fiber-forming apparatus such as a bushing or orifice plate, although they may also be made by any method conventionally known in the art. The filaments are coated with the inventive sizing composition set forth herein. After being coated with the sizing composition, the filaments may be gathered to form the sized strand of the present invention. These sized strands may then be formed into yarns or rovings.

Preferably, the diameter of the filaments making up the strands ranges from about 3.5 to about 24 μm, preferably from about 9 to about 16 μm. The preferred filament diameters correspond to U.S. filament designations G, H, and M. Preferably the strand input has a yield of from about 3,700 to about 7,500 yd/lb (7459 to about 15119 m/kg), most preferably about 7,500 yd/lb (15119 m/kg), or approximately 66 TEX (g/km a measurement reflecting the weight and thickness of the strand).

Sizing Compositions The sized strands of the present invention may be made by use of the inventive sizing composition which comprises, as already set forth, the following components: a particulate material, a film former, a surfactant, a resin binder and a liquid carrier. Each component is described in further detail as further embodiments to the present invention.

Particulate Material

The sized strands of the present invention comprises a plurality of gathered fibers and a particulate material distributed in-between the fibers. Any material capable of being distributed in-between a plurality of gathered fibers may be used as the particulate material of the present invention. The particulate material preferably comprises spherical granules. The particulate material is preferably a thermoplastic resin, more preferably a polyolefin, and most preferably polyethylene. An example of a suitable particulate material is a spherical finely divided polyethylene such as MICROTHENE^® FM510 (commercially available from Equistar Limited, LP). The particulate material is preferably present in the sized strand in the amount of 0.20 to 2.0 weight percent based on the sized strand, more preferably from 0.3 to 1.5 weight percent and most preferably from 0.5 to 0.7 weight percent. The average particle size of the particulate material is preferably from 1 to 60 μm, more preferably from 10 to 30 μm, and most preferably from 15 to 20 μm.

The presence of the particulate material in the sized strand may be achieved by applying the inventive sizing composition to a plurality of fibers which are then gathered into a strand. The inventive sizing composition comprises the particulate material in an amount preferably ranging from 1 to 10.0, more preferably from 1.9 to 8.0, and most preferably from 2.5 to 3.7 percent by weight based on the total weight of the sizing composition. The particulate material is preferably insoluble in the liquid carrier of the inventive sizing composition.

Film Former

The sized strand of the present invention further comprises a film former. The film former is preferably present in the sized strand in an amount ranging from 2.6 to 7.5 wt. % solids, more preferably from 3.2 to 5.8 wt. % solids, and most preferably from 3.6 to 4.7 wt. % solids of the sized strand. The presence of the film former in the sized strand may be achieved by applying the inventive sizing composition to a plurality of fibers which are then gathered into a strand. The inventive sizing composition comprises the film former in an amount preferably ranging from 25 to 75, more preferably from 30 to 55, and most preferably from 35 to 45 percent by weight as received based on the total weight of the sizing composition. Any material capable of melting at elevated temperatures (for example greater than 60°C) and forming a tack free film when cooled may be used as the film former in the present invention. Examples of suitable film formers for the present invention are polyvinyl polymers with polyvinyl acetate preferred, and epoxidized polyvinyl acetate most preferred. An example of a preferred epoxidized polyvinyl acetate is DURACET^® 675-01 (commercially available from Franklin International). Surfactant

The sized strand of the present invention further comprises a surfactant. The surfactant is preferably present in the sized strand in an amount ranging from 0.01 to 0.05 wt. %, more preferably from 0.015 to 0.04 wt. %, and most preferably from 0.02 to 0.03 wt. % of the sized strand. The presence of the surfactant in the sized strand may be achieved by applying the inventive sizing composition to a plurality of fibers which are then gathered into a strand. The inventive sizing composition comprises the surfactant in an amount preferably ranging from .05 to 0.26, more preferably from .08 to 0.21, and most preferably from 0.11 to 0.16 percent by weight based on the total 100 of the sizing composition. Any material that reduces the interfacial tension between the particulate material and the liquid carrier of the inventive sizing composition may be used as the surfactant of the present invention. A preferred surfactant comprises molecules which are the reaction product of a substituted phenol polymerized with an alkene oxide. More preferably the surfactant comprises molecules which are the reaction product of an octylphenol polymerized with an ethylene oxide having the formula:

wherein the molecules preferably have an average value of N equal to about 9.5. E Exxaammpplleess ooff ssuucchh aa ssuurrffaacctta-nt include TRITON™ X-100 (commercially available from B. F. Goodrich Company).

Film Former

The sized strands of the present invention further comprises a second film former. The film former is preferably present in the sized resin in the amount of 0 to 6.0 weight percent based on the sized strand, more preferably from 1.0 to 5.0 weight percent and most preferably from 3.0 to 4.0 weight percent based of the sized strand. The presence of the film former in the sized strand may be achieved by applying the inventive sizing composition to a plurality of fibers which are then gathered into a strand. The inventive sizing composition comprises the film former in an amount preferably ranging from 0 to 60, more preferably from 10 to 50, and most preferably from 30 to 40 percent by weight based on the total 100 of the sizing composition. The film former preferably comprises polymers capable of being cured into a thermoset resin. The preferred film former in EPI-REZ^® 3546 available from Shell Oil Co.

Application of the Sizing Composition

The inventive sizing composition of the present invention may be applied to fibers which are then gathered into strands by any means known in the art. A preferred embodiment is where a molten material is provided by a heated bushing. A plurality of fibers is formed from the molten material, preferably glass, as it exits the bushing from a plurality of orifices with each orifice producing individual fibers. The plurality of fibers are then contacted by a roll applicator which is composed of a rotating roller partially submerged in the inventive sizing composition contained in a reservoir. The sized fibers may then be gathered on a shoe into a strand which is wound on a forming tube. The strand is wound without drying on a forming tube and subsequently dried while on the forming tube.

Pre-form

The sized strands of the present invention and multi-end roving formed therefrom may be incorporated into several reinforcing articles, depending on the desired application. For example, the multi-end rovings may be used to form a woven fabric reinforcement, such as a woven roving or a multi-axial stitched reinforcement. Alternatively, the sized strand and multi-end rovings formed therefrom may also be used, in continuous or chopped form, in various applications requiring an input of reinforcing fiber segments. The sized strand is preferably chopped into segments of about 3 inches (7.62 cm) in length. Most preferably, the chopped segments are from about 1 inch (2.54 cm) to about 3 inches (7.62 cm) in length.

The segments obtained according to the aforementioned procedure are preferably used to make pre-forms using a spray-up process. Such a process is described in U.S. Patent No. 3,170,197. In a particularly preferred embodiment including this method, segments of a multi-end roving comprising the sized strand are blown or spread by conventional means over a shaped pre-form screen and a sufficient level of heat applied to melt and flow the resin binder enough to permit some fusing of the segments. Preferably, suction is applied to promote compacting of the segments as they fuse. The process of fusing allows the layered material to conform to the shape of the pre-form screen, and the material is then set into a solid matted structure or pre-form that may be physically transported if necessary to another location to complete the molding process that forms the final composite product. The pre-form may require cooling before it can be moved.

To make the pre-form, the chopped segments may be laid up on a consolidation screen, and optionally compressed using suction drawn through the screen to form the material into a desired shape that conforms to the contour of the screen. Consolidation may also be accomplished by placing a second screen on top of the pre-form prior to heating.

Reinforced Composite

The pre-form made with the sized strands of this invention may be used in otherwise conventional molding processes, for example liquid resin molding, to make a reinforced composite comprising the pre-form and a polymer matrix. Typically, the preform is placed in a mold cavity into which a moldable polymer matrix material is injected or otherwise added. Any moldable polymer matrix material that is compatible with the thermoset polymer material of the string binder in the pre-form may be used. Typical moldable polymer matrix resins that may be used include vinyl esters, polyesters, urethanes and phenolic thermoplastics. Preferably, the moldable polymer matrix is a reaction product of an isocyanate and a polyol that is compatible with the resin binder that is present in the sized strand. The skilled artisan will be able to identify other moldable matrix resin materials suitable for use with pre-forms made according to this invention without undue experimentation.

EXAMPLES

Various sizings were made by mixing the ingredients as indicated in the table below.

^aAmicure 1400 is micronized dicyandiamide ^bCurezol 2MA-OK is an imidazole

Claims

WHAT IS CLAIMED IS:

1. A fiber strand comprising a plurality of gathered fiber filaments, a particulate material distributed in-between said filaments, and a synthetic resin or precursors thereof.

2. The product of claim 1 wherein the particulate material comprises spherical polymer particles.

3. The product of claim 1 wherein the particulate material comprises a polyolefin polymer.

4. The product of claim 1 wherein the precursors comprise monomers capable of being cured into a thermoset polymer.

5. The product of claim 1 where in the particulate material is a finely divided solid polyolefin.

6. A pre-form made from fibers obtain by chopping the strand of claim 1.

7. A composite article comprising a polymer reinforced by the pre-form of claim 6.