Molded or extruded synthetic railroad ties, beams and structural members

[57] ABSTRACT

This invention relates to railroad ties and the like, such as beams and structural members, and particularly to articles of recycled wood and to the process of making the same.

Claims, 3 Drawing Figures

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U.S. Patent sept. 30,1975

3,908,902

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3,908,902

MOLDED OR EXTRUDED SYNTHETIC RAILROAD TIES, BEAMS AND STRUCTURAL MEMBERS This invention relates to railroad ties, beams and structural members made from waste wood.

Railroad ties have been made of wood for many years, the ties being placed on rock ballast and having the steel rails carried thereon and fastened thereto, such as by spikes or the like. Wood deteriorates in spite of being impregnated with a preservative, such as creosote. The ties are of such a size that wood must be obtained from large size trees without defects, such as splits, and suitable lumber or wood is becoming scarce. Other types of material, such as concrete or metal, have not been satisfactory because of weight and improper resiliency. Also, concrete is subject to cracking because of water freezing. Due to the aforementioned scarcity of lumber, beams and similar structural members of high strength also have been expensive and difficult to obtain. It is known to make thin particle board from wood chips and thermosetting resins, such as in U.S. Pat. No. 3,463,746.

One of the objects of the invention is to provide an improved railroad tie, structural member, or the like, which is relatively inexpensive and yet will perform satisfactorily in service and the method of making the same.

In one aspect of the invention, recycled comminuted railroad ties, as well as waste wood, such as wood chips or bark, can be mixed with thermoplastic polyester resin and catalyst and subjected to high pressure and heat to form a railroad tie, structural beam or the like. The term “structural beam” is meant to include load bearing members for buildings or other structural use. The mixture also can include fire retardants and reinforcing means, such as wood slabs as obtained in lumber milling operations. The waste wood has its moisture content controlled so as to have a moisture retention of at least 30 percent by weight. The ties and beams have a relatively high density in the range of 50 to 70 lbs. per cu. ft. and with a high strength.

Other objects, advantages and features of the present invention will become apparent from the accompanying description and drawings, which are merely exemplary.

IN THE DRAWINGS

FIG. 1 is a fragmentary perspective view of a tie with rails thereon;

FIG. 2 is a schematic view of one manner of making a tie; and

FIG. 3 is a fragmentary perspective sectional view of a tie showing the chips therein.

Referring to FIG. 1, a railroad tie 10 is normally partially embedded or laid on crushed rock ballast 11. Rails 12, 13 are laid on top of tie 10 and can be held in place in various known manners, such as by spikes 14, 15.

Old or used railroad ties can be cut or comminuted or made into wood chips for use in producing the tie of the present invention. If the tie has creosote therein and it is deemed necessary, the creosote can be removed in any known manner, such as acetone or the like.

Other waste wood products, such as bark resulting from lumber milling or chips produced in milling, can be used as will appear hereafter. Merely by way of ex2 ample, the chips can be % to % inch in length and the comminuted tie fibers can be % inch long.

The recycled tie chips or fibers and/or the waste wood is mixed with thermoplastic polyester resin and then placed in a mold and pressed under heat and pressure.

Alternatively, the mixture can be extruded as shown in FIG. 2. The waste wood to be extruded along with the resin and additives are placed in hopper 16 and extruded through dies 17 by screw 18 to a receiving station 19. Heat is applied as is known in the extrusion art. The finished tie 20 or structural member is sized as desired. Other suitable catalysts can be used, including those which do not require external heat for action.

The waste wood should be dried or treated before molding or extrusion so that it has a moisture retention of at least approximately 30 percent by weight and preferably about 35 percent.

As one specific example, a tie or beam can be produced which is composed of:

Percentage by Weight

Waste wood 50%

Polyester resin, GR 117 25%

Aluminum hydrate, Alcoa 331 23%

Benzyl peroxide powder catalyst 1%

Dimethyl aniline catalyst 1%

The thermoplastic resin is that furnished by W. R. Grace Co. under the identification of GR 117. Greater flexibility in the ties and beams was obtained by using a polyester resin furnished by W. R. Grace under the identification of GR 14010.

Aluminum hydrate can be added to the mix together with the catalyst for the polyester resin.

The structural member can have a composition in accordance with the following approximate ranges:

Percentage by Weight

Waste wood 38% - 65%

Aluminum hydrate 25% - 23%

Polyester resin GR 117 or GR 14010 35% - 10%

Dimethyl aniline 1% — 1%

Catalyst.

Benzyl peroxide powder 1% — 1% mixed with

When placed in a mold, a pressure of 300 to 800 p.s.i. can be applied for 15 to 30 minutes at 250°F. to 300°F. A density of 50 to 70 lbs. per cu. ft. is obtained.

As a reinforcing means, slabs of wood also could be included in the mix. As an example, ties are normally 8 feet 6 inches to 9 feet 0 inch in length and are approximately 6 inches X 8 inches or 7 inches X 9 inches in cross section. The slabs can extend longitudinally in the member to within about 2 inches of each end, there being a single slab, more than one slab, or overlapping slabs.

It should be apparent that changes in details of construction and arrangement of parts may be made without departing from the spirit of the invention except as defined in the appended claims.