Fiber reinforced building products and method of producing same

• US 4,261,754 A
• Filed: 05/04/1978
• Issued: 04/14/1981
• Est. Priority Date: 05/05/1977
• Status: Expired due to Term

• Current Assignee: Cemfiber A/S
• Original Assignee: Dansk Eternit-Fabrik A/S
• Inventors: Balslev, Jorgen, Krenchel, Herbert E., Ottosen, Jorgen A.
• Primary Examiner(s): Poer, James
• Application Number:
  US05/902,920
• Time in Patent Office: 1,076 Days
• Field of Search: 106/99, 106/90
• US Class Current: 524/8
• CPC Class Codes: B28B 1/52 specially adapted for producing articles from mixtures containing fibres, e.g. asbestos cementby wrapping on to mandrels B28B1/42
• CPC Class Codes: C04B 16/0608 Fibrilles, e.g. fibrillated films
• CPC Class Codes: D01D 5/20 with varying denier along their length
• CPC Class Codes: D01D 5/426 by cutting films
• CPC Class Codes: E04C 2/06 reinforced
• CPC Class Codes: E04C 5/07 Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal metal elements with non-structural coatings E04C5/01

Abstract

A fibrous reinforcing element made from oriented polyolefin material for reinforcing a matrix material such as cement has longitudinally varying cross-sections and frayed surface portions from which fibrils extend. The element has cross-sections which vary along its length, a characteristic which combines with the fibrils of the frayed surface portions to facilitate anchoring of the element in the matrix. The anchoring and strength characteristics make the element particularly useful for constructing cement building products or any product produced from a matrix binding agent. The element is in the form of a fiber made from a polyolefin film which is stretched at least fifteen times and then cut by cutting means along lines at least partially transverse to the direction of orientation. In the preferred embodiment a building product formed from a matrix of Portland cement has dispersed therein, a plurality of fibrous reinforcing elements at least a portion of which are the individual polyolefin fibers described in accordance with the invention. By uniquely providing a combination of the inventive fibers with fibers of other types within the cement matrix, improved anchoring and dispersion of the fibers is achieved, while the improved strength characteristics of the elements contributes to a building product of unusually improved strength.

Claims

1. A method of manufacturing a building product comprising mixing a slurry of an inorganic binding agent as a matrix and a plurality of fibrous reinforcing elements at least a portion of which are flexible, organic oriented polyolefin fibers, each having a weight about from 2 to 35 denier and having cross sections which vary along its length and polyolefin fibrils extending from surface portions thereof, and permitting said slurry to set after forming or moulding.

2. A method of manufacturing a building product according to claim 1, in which the polyolefin fibers are polypropylene fibers.

3. A method of manufacturing a building product according to claim 1 or 2, in which said fibers are dispersed in at least a part of the binding agent, which thereafter is mixed with the remainder of the matrix material.

4. A method of manufacturing a building product according to claim 1, in which the surface of the flexible organic fibers is treated with an inorganic fine grained filler material or the binding agent before mixing with the matrix material.

5. A method of manufacturing a building product according to claims 1, in which the admixing of the fibres to the matrix mass is carried out with the addition of a dispersing agent.

6. A method of manufacturing a building product according to claim 1, in which the product is manufactured in the form of sheets on fiber-sheet-forming machinery having suction equipment for dewatering the green sheets in the forming process.

7. A method of manufacturing a building product according to claim 6 in which the sheets are subjected to a compression during a time interval after forming.

9. A fiber reinforced building product according to claim 1 in which the polypropylene fibers are composed of two sizes of fibers the ratio of the lengths being about 1:

3.

10. A fiber reinforced building product according to claim 1 in which at least part of the fibers is cellulosic fibers.

11. A fiber reinforced building product according to claim 10 in which part of the fibers is inorganic mineral fibers.

12. A fiber reinforced building product according to claim 1 in which the matrix material includes a fine grained inorganic filler material of a size range in which 85 percent is smaller than 1 micron.

13. A method of manufacturing a building product according to claim 2, in which the inorganic binding agent is a hydraulic binding agent.

14. A method of manufacturing a building product according to claim 1, in which the polyolefin fibers are heat stabilized and the hydraulic binding agent is Portland cement.

20. The method according to claim 1 wherein said polyolefin fibers have a tensile strength of at least about 4000 kp/cm².

21. The method according to claim 1 wherein said polyolefin fibers have a modulus of elasticity of at least about 7×

10⁴ kp/cm².

22. The method according to claim 1 wherein said polyolefin fibers have a maximum elongation of up to about 8 percent of the length.

23. The method according to claim 1 wherein said polyolefin fibers are about from 5 to 25 mm in length.

8. A fiber reinforced building product manufactured from a matrix of an inorganic binding agent and a plurality of fibrous reinforcing elements at least a portion of which includes individual filaments of oriented polyolefin fibers cut from polyolefin filaments cut from polyolefin film material which has been stretched at least about 15 times to a thickness of about from 10 to 60 microns, said fibers having cross sections which vary along their length and polyolefin fibrils extending from surface portions thereof, each polyolefin fiber further having a tensile strength of at least about 4000 kp/cm², a modulus of elasticity of at least about 7×

10⁴ kp/cm² and a maximum elongation of up to about 8 percent of the length, said fibers being about from 5 to 25 mm in length.

16. A building product according to claim 8 in which said polyolefin fibers are polypropylene fibers.

15. A method of producing a building product comprising the steps of:

(a) taking polyolefin film material capable of being molecularly oriented by stretching so as to define a direction of orientation;

(b) stretching said orientable film material at least about fifteen times its length to a thickness of about from 10 to 60 microns;

(c) cutting said film material by means of a rotating needle or cutter roller along lines at least partially transverse to the lines of natural weakness caused by the molecular orientation of said material to thereby produce filaments having cross sections which vary along their lengths and frayed surface portions with fibrils of said material extending therefrom;

(d) cutting said filaments into relatively short lengths to produce fibrous reinforcing elements capable of being anchored in a matrix admixture and to maintain surface contact with the admixture to provide fiber reinforcement of a product produced from said admixture;

(e) mixing said polyolefin fibrous reinforcing elements with a plurality of at least one of cellulosic and inorganic mineral fibrous reinforcing elements;

(f) mixing said fibrous reinforcing elements with a hydraulic binding agent;

(g) mixing said hydraulic binding agent and fibrous reinforcing elements in the form of a wet slurry; and

(h) permitting said admixture to set after forming or moulding.

24. The method according to claim 15 further comprising the step of applying heat to said stretched film material to stabilize said material in said stretched condition prior to the step of cutting said material by means of a rotating needle or cutter roller.

17. A fiber reinforced building product manufactured from a matrix slurry of an inorganic binding agent such as Portland cement and a plurality of fibrous reinforcing elements, at least a portion of which are single filaments of oriented polyolefin fibers each having a tensile strength of about from 4000 to 6000 kp/cm², a modulus of elasticity of about from 7 to 10×

10⁴ kp/cm² and a maximum elongation of up to about 8 percent, said polyolefin fibers being between 5 and 25 mm in length and having cross sections which vary along their length and frayed edges with fibrils extending therefrom so as to permit anchoring of said fibers in the matrix slurry.

18. A building product according to claim 17 in which said single filament polyolefin fibers are polypropylene fibers.

19. A building product according to claim 18 in which said single filament fibers are polypropylene fibers of about from 2 to 35 denier cut from polypropylene filaments cut from polypropylene film which has been stretched at least about 15 times its original length to a final thickness of about from 10 to 60 microns.