FIRE RESISTANT COATED POLYESTER MINE GRID AND METHOD FOR PRODUCING IT

Abstract

The invention is drawn to a method of making a fire-resistant mine-grid comprising the following steps: providing a poly(vinyl chloride) (PVC) plastisol, providing a polyester yarn mesh fabric, coating the polyester yarn mesh fabric with the PVC plastisol, heating the coated fabric for about 5 to 20 minutes, more preferably for about 5 to 15 minutes, to a temperature comprised between 110° C. and 150° C., so as to effect gelatinization of the PVC plastisol and form a plasticized PVC coating enveloping the polyester yarns of the mesh fabric,
wherein the PVC plastisol, comprises (a) a poly(vinyl chloride) base resin, (b) from 60 to 140 phr of a primary plasticizer which is tris-(2-chloro-isopropyl)phosphate (TCPP), (c) from 40 to 140 phr of a secondary plasticizer, (d) from 145 to 230 phr of an inorganic filler.

Claims

1. A method of making a fire-resistant wide-meshed grid, the method comprising: coating a polyester yarn mesh fabric with a poly(vinyl chloride) (PVC) plastisol, to obtain a coated fabric; and heating the coated fabric for about 5 to 20 minutes, to a temperature comprised between 110° C. and 150° C., so as to effect gelatinization of the PVC plastisol and form a plasticized PVC coating enveloping the polyester yarns of the mesh fabric, wherein the PVC plastisol, comprises: (a) a poly(vinyl chloride) base resin; (b) from 60 to 140 phr of a primary plasticizer, which is tris-(2-chloro-isopropyl)phosphate (TCPP); (c) from 40 to 140 phr of a secondary plasticizer; and (d) from 145 to 230 phr of an inorganic filler.

2. The method according to claim 1, wherein the secondary plasticizer is selected from the group consisting of chlorinated paraffins, diisononylphthalate, 2,2,4-trimethylpentanediol-1,3-diisobutyrate, and mixtures thereof.

3. The method according to claim 2, wherein the secondary plasticizer is selected from the group consisting of diisononylphthalate, chlorinated paraffins, and a mixture thereof.

4. The method according to claim 1, wherein the PVC plastisol further comprises another primary plasticizer selected from the group consisting of 2-ethylhexyl diphenyl phosphate and butylated triphenyl phosphate ester.

5. The method according to claim 1, wherein the inorganic filler is selected from the group consisting of zinc borate, calcium carbonate, aluminum hydroxide, aluminum phosphinates, hydrotalcite, and mixtures thereof.

6. The method according to claim 1, wherein the inorganic filler comprises at least 60% by weight, with respect to the total weight of inorganic filler, of aluminum hydroxide.

7. The method according to claim 1, wherein the polyester yarn is high tenacity poly(ethylene terephthalate) (PET).

8. The method according to claim 1, wherein the polyester yarn mesh fabric is warp-knitted.

9. The method according to claim 8, wherein the warp-knitted polyester yarn mesh fabric has a mechanical strength of between 100 kN and 1200 kN.

10. The method according to claim 1, wherein the PVC plastisol has a viscosity of between 1500 cp and 4500 cp.

11. The method according to claim 1, wherein the coating of the polyester yarn mesh fabric with PVC plastisol is performed by dip coating.

12. The method according to claim 1, wherein the heating of the coated polyester yarn mesh fabric is performed with hot air.

13. The method according to claim 1, wherein a weight ratio of the PVC plastisol coating to the polyester yarn mesh fabric is comprised between 1.00 and 1.60.

14. The method according to claim 1, wherein the polyester yarn mesh fabric further comprises less than 10% by weight of high strength reinforcing fibers selected from the group consisting of high-tenacity polypropylene, high-tenacity polyamide, aramid fibers, glass fibers, and quartz fibers.

15. A fire-resistant wide-meshed grid, comprising a polyester yarn mesh fabric and a plasticized PVC coating, made according to the method of claim 1.

16. The method according to claim 1, wherein the heating is carried out for about 5 to 15 minutes at a temperature between 120° C. and 140° C.

17. The method according to claim 1, wherein the PVC plastisol has a viscosity of between 2000 cp and 4000 cp.

18. The method according to claim 1, wherein the PVC plastisol has a viscosity of between 2500 and 3500 cp.

19. The method according to claim 1, wherein a weight ratio of the PVC plastisol coating to the polyester yarn mesh fabric is comprised between 1.05 and 1.40.

20. The method according to claim 1, wherein a weight ratio of the PVC plastisol coating to the polyester yarn mesh fabric is comprised between 1.10 and 1.30.

Description

EXAMPLES

[0049] The uncoated polyester fabric used is a knitted fabric having the following characteristics:

[0050] Stitching yarn count: 666 dtex

[0051] Warp yarn count: 26400 dtex (0 TPM)

[0052] Warp yarn tenacity: 5.8 cN/dtex

[0053] Number of threads per warp strand: 6

[0054] Weft yarn count: 26400 dtex (0 TPM)

[0055] Weft yarn tenacity: 5.8 cN/dtex

[0056] Number of threads per weft strand: 9

[0057] Aperture size (direction warp×weft): 27 mm×26 mm

[0058] Grid size (direction warp×weft): 51 mm×40 mm

[0059] Warp strand width: 14 mm

[0060] Weft strand width: 24 mm

[0061] Stitching pattern: tricot

[0062] For the coating trials 35 cm long, single ribs were cut in the warp and in the weft direction and used.

[0063] To prepare the formulation, all liquid ingredients were first mixed and solid ingredients were then added step by step, under mixing in an overhead shear mixer at 800 rpm. Mixing time was typically fixed to achieve the lowest shear viscosity while ensuring that the temperature did not exceed 38° C.

[0064] All warp single rips and weft single rips were individually dipped in the PVC coating composition and excess was squeezed through a two rubber roll coater with a pressure of 3 bar.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 According to According to According to Comparative the invention the invention the invention Example 4 Base resin PVC 100 100 100 100 Primary plasticizer TCPP 100 120 120 120 Flame-retardant Chlorinated 40 40 40 40 secondary paraffins plasticizer Non flame- Diisononyl- 10 10 10 10 retardant secondary phthalate plasticizer Inorganic Al(OH).sub.3 100 100 100 100 particulate filler CaCO.sub.3 40 100 40 20 Zinc borate 20 20 20 20 Total 160 220 160 140 After flame time 2.50 2.33 3.00 3.17 (sec) Viscosity (cps) 1773 3213 1607 1293 Weft Add-on 1.50 1.58 1.37 1.26 Warp Add-on 1.45 1.64 1.35 1.16

[0065] Table 1 shows that only coating compositions according to the invention, comprising TCPP as primary plasticizer and high amounts of inorganic filler, provide the final coated mesh with a sufficient fire resistance (After flame time of 3.00 sec or less).

[0066] Before coming to the present invention the inventors had tested several PVC plastisol-based coating compositions containing a primary flame retardant plasticizer (2-ethylhexyl diphenyl phosphate, sold as Phosflex® 362 from ICI Chemicals) which did not result in sufficiently low “after flame times”.

[0067] The results of a few of these tests are shown in Table 2 below (Comparative Examples 5-8)

TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Comparative Example 5 Example 6 Example 7 Example 8 Base resin PVC 100 100 100 100 Primary 2-ethylhexyl 60 60 60 60 plasticizer diphenyl phosphate (Phosflex ® 362) Flame- Trimethylpentanediol 0 0 5 25 retardant (TX1B Eastman secondary Chemicals) plasticizer Non flame- Diisononyl- 5 5 5 5 retardant phthalate secondary plasticizer Inorganic Al(OH).sub.3 0 60 40 40 particulate CaCO.sub.3 0 0 0 0 filler Zinc borate 0 6 4 4 Total 0 66 44 44 After flame 37.6 5.67 4.67 3.33 time (sec) Viscosity 4633 13320 3927 2013 (cps) Add-on 1.09 1.72 1.42 1.47