A METHOD OF MANUFACTURING A STIFFENER MATERIAL

Abstract

The present invention provides a method of manufacturing a stiffener material comprising: providing an uncompressed felt layer comprising a primary fibrous material having a density of between 0.08 g/cm3 and 0.16 g/cm3; passing the felt layer through a double belt press; wherein as the felt layer is passed through the double belt press it is maintained under constant pressure whilst first being heated to within 20 C. of a melting point of the primary fibrous material and is subsequently cooled to below the glass temperature of the primary fibrous material to form a compressed material. A stiffener material manufactured according to the method of the present invention is also provided.

Claims

1. A method of manufacturing a stiffener material comprising: providing an uncompressed felt layer comprising a primary fibrous material having a density of between 0.08 g/cm.sup.3 and 0.16 g/cm.sup.3; passing the felt layer through a double belt press; wherein as the felt layer is passed through the double belt press it is maintained under constant pressure whilst first being heated to within 20 C. of a melting point of the primary fibrous material and is subsequently cooled to below the glass temperature of the primary fibrous material to form a compressed material.

2. A method according to claim 1, wherein the primary fibrous material is polyester.

3. A method according to claim 2, wherein the felt layer consists solely of the primary fibrous material.

4. A method according to claim 1, wherein the felt layer comprises a second fibrous material having a lower melting point than the primary fibrous material.

5. A method according to claim 1, wherein the compressed material is coated with a powder adhesive on one or both sides and the compressed material is then passed through a heated double belt press.

6. A method according to claim 5, wherein the compressed material is coated with a powder adhesive on both sides and the compressed material is then passed through a heated double belt press.

7. A method according to claim 5, wherein the compressed material is coated with a powder adhesive on a first side and the compressed material is then passed through a heated double belt press; then the compressed material is coated with a powder adhesive on a second side, opposing the first side, and the compressed material is then passed through a heated double belt press.

8. A method according to claim 5, wherein the heated double belt press is operated at a temperature of less than 150 C and a pressure of less than 20 N/cm.sup.2.

9. A method according to claim 1, wherein the uncompressed felt material is coated with a powder adhesive on one or both sides before the uncompressed felt material is passed through the heated double belt press.

10. A method according to claim 9, wherein the uncompressed felt material is coated with a powder adhesive on both sides before the uncompressed felt material is passed through the heated double belt press.

11. A method according to claim 9, wherein the uncompressed felt material is coated with a powder adhesive on a first side before the uncompressed felt material is passed through the heated double belt press; and then the compressed material is coated with a powder adhesive on a second side, opposing the first side, and is then passed through a heated double belt press.

12. A method according to claim 5, wherein the powder adhesive is one or more of polycaprolactone, ethylene vinyl acetate, polyurethane, polyester, or polyamide powder.

13. A method according to claim 1, wherein the uncompressed felt layer is heated to the melting point of the primary fibrous material as it is passed through the double-belt press.

14. A method according to claim 1, wherein the thickness of the compressed material is between 0.5 mm and 2.5 mm.

15. A method according to claim 1, wherein the density of the compressed material is between 0.4 g/cm.sup.3 and 1.1 g/cm.sup.3.

16. A method according to claim 1, further comprising the subsequent step of forming a laminate material comprising two or more layers of the compressed material.

17. A method according to claim 16, wherein the laminate material is formed by passing the layers through a heated double belt-press.

18. A method according to claim 1, further comprising the subsequent step of forming a sandwich material comprising two layers of the compressed material having a filler material between the two layers of the compressed material.

19. A method according to claim 18, wherein the sandwich material is formed by passing the layers of compressed material and the filler material through a heated double belt press.

20. A method according to claim 17, wherein the laminate material or the sandwich material is coated on at least one side before being passed through the heated double belt-press.

21. A method according to claim 20, wherein the laminate material or sandwich material is coated on both sides before being passed through the double belt press.

22. A method according to claim 20, wherein the laminate material or sandwich material is coated on a first side before being passed through the heated double belt press.

23. A method according to claim 22, wherein the laminate material or sandwich material is subsequently coated on a second side, opposing the first side, and is then passed through a heated double pres.

24. A method according to claim 16, wherein subsequent to forming the laminate material or sandwich material the material is coated on one or both sides and passed through a heated double belt press.

25. A stiffener material made according to the method of claim 1.

Description

DRAWINGS

[0031] FIG. 1 is a schematic of a double belt press suitable for use in the method of the present invention; and

[0032] FIG. 2 is a graph showing the thickness of stiffener materials produced according to the present invention using the double press of FIG. 1;

[0033] FIG. 3 is a graph showing the density of stiffener materials produced according to the method of the present invention using the double press of FIG. 1;

[0034] FIG. 4 is a graph showing of the stiffness of stiffener materials produced according to the method of the present invention using the double press of FIG. 1;

[0035] FIG. 5 is a schematic of a three-step double belt process for forming a coated laminate material;

[0036] FIG. 6 is a schematic of a two-step double belt process for forming a coated laminate material;

[0037] FIG. 7 is a graph showing the weight of stiffener materials produced according to the present invention;

[0038] FIG. 8 is a graph showing the thickness of stiffener materials produced according to the present invention;

[0039] FIG. 9 is two graphs showing the density of stiffener materials produced according to the present invention;

[0040] FIG. 10 is two graphs showing the density of stiffener materials produced according to the present invention; and

[0041] FIG. 11 is two graphs showing the stiffness of stiffener materials according to the present invention.

[0042] A schematic of a belt press 1 suitable for use in the present invention is shown in FIG. 1. The belt press 1 comprises two counter rotating unperforated belts 2, each mounted about a roller 3 at each end. The belts 2 are controlled to rotate in a suitable direction to pull a material through the belt press and compress the material. Hot plates 4 are provided to heat the material via the belts 2 and hot rollers 5. The hot plates 4 are heated using oil or an electric power unit (not shown). Cooling plates 6 are also provided. Cold water flows into through the cooling plates 6 and associated cold rollers 7 via a centrifugal pump (not shown). The belts 2 are supported by the rollers 3, the hot and cold rollers 5, 7 with pressure being applied to a material along a full length of the belt press with belt distances being adjustable from a central control board.

[0043] The belt press 1 of FIG. 1 was operated in accordance with the present invention on a uncompressed felt material consisting of polyester (PET) fibres to produce a stiffener material having a thickness between 0.5 mm and 2.5 mm. The melting point of the PET fibre is between 245 and 260 C. and the belt press 1 was operated to heat the felt material to between 240 C. and 245 C. The belt press 1 was operated at a pressure of between 50 and 60 N/cm.sup.2. This increased the density of the uncompressed felt material 0.08-0.16 g/cm.sup.3 up to a range of 0.4-1.1 g/cm.sup.3 on the finished product as follows. Details of the uncompressed felt material used are as set out in Table 1 below:

TABLE-US-00001 TABLE 1 Uncompressed felt samples used showing initial density. Weight Gauge Density gsm mm g/cm.sup.3 256 2.7 0.0948 279 2.81 0.099288 530 3.5 0.151429 500 3.4 0.147059 600 3.8 0.157895 550 3.6 0.152778

[0044] Details of the thickness of the stiffener materials produced according to the present invention from the samples set out above are shown in FIG. 2. Details of the density of the stiffener materials are shown in FIG. 3. Details of the DLC (stiffness) in Newtons are shown in FIG. 4. From the data shown in these Figures it can be seen that stiffener materials of thicknesses between 0.5 mm and 2.5 mm, stiffnesses of between 20 and 100 N, weights of between 500 and 750 gsm can be produced using the method of the present invention.

[0045] FIG. 5 shows a three-step process for forming a laminar material according to the present invention. The process uses a double belt press 1 with hot plates 4 and cooling plates 6 substantially in accordance with FIG. 1. In the first step, two 250 gsm sheets of compressed material formed in the manner described immediately above are fed through the double belt press 1 operating at a feed speed of 8 m/min with a pressure of 55 N/cm.sup.2. The double belt press 1 is operated at a temperature of 247 C. This first step acts to form a laminated uncoated stiffener material.

[0046] In the second step a first side of the laminated material is powder coated with a powder adhesive and passed through a double belt press 1 operating at feed speed of 20 m/min, a pressure of 10 N/cm.sup.2, and a temperature of 90 C. This forms a laminated stiffener material that is coated on the first side.

[0047] In the third and final step a second side of the laminated stiffener material is coated with a powder adhesive and the material is passed through a double belt press 1 operating at feed speed of 20 m/min, a pressure of 10 N/cm.sup.2, and a temperature of 90 C. This forms a laminated stiffener material that is coated on both the first side and the second side.

[0048] The double belt press 1 of the first, second and third steps may either be the same double belt press or two, or three separate double belt presses may be used.

[0049] FIG. 6 shows a two-step process for forming a laminar material according to the present invention.

[0050] The process uses a double belt press 1 with hot plates 4 and cooling plates 6 substantially in accordance with FIG. 1. In the first step, two 250 gsm sheets of compressed material formed in the manner described immediately above are fed through the double belt press 1 operating at a feed speed of 8 m/min with a pressure of 55 N/cm.sup.2, at a temperature of 247 C. Before being passed through the double belt press 1 a first side of the uppermost sheet is coated with a powder adhesive. This forms a laminated stiffener material that is coated on the first side.

[0051] In a second and final step a second side of the laminated stiffener material is coated with a powder adhesive and the material is passed through a double belt press 1 operating at feed speed of 20 m/min, a pressure of 10 N/cm.sup.2, and a temperature of 90 C. This forms a laminated stiffener material that is coated on both the first side and the second side.

[0052] The double belt press 1 of the first and second steps may either be the same double belt press or two, or three separate double belt presses may be used.

[0053] The powder adhesive used in the methods of FIGS. 6 and 7 is a caprolactone coating.

[0054] FIGS. 7 and 8 show the weight and gauge of samples according to the present invention that are either laminar stiffener materials formed of two 300 gsm sheets or stiffener material formed of a single 500 gsm sheet formed according to the present invention. The stiffener materials are coated on both sides with a 60 gsm caprolactone coating.

[0055] The weight and gauge of coated stiffener materials according to the present invention are set out in Tables 2 and 3 below. The laminar stiffener material is formed according to the two-step process set out above.

TABLE-US-00002 TABLE 2 Weight (g/m2) of coated materials formed in a two-step process Weight (g/m2) 600 gsm 500 gsm 1000 gsm (2 500 1000 gsm (2 500 (2 300 gsm) (single) gsm) Speed 3.2 gsm) Speed 2.7 765 856 1295 1439 705 752 1171 1236 707 715 1138 1201 686 701 1107 1170 692 677 1098 1163 690 659 1108 1165 689 667 1094 1163 697 663 1108 1167 697 655 1134 1188 706 645 1139 1202 718 648 1195 1252 766 640 1300 1340

TABLE-US-00003 TABLE 3 Gauge (mm) of coated materials formed in a two-step process Gauge (mm) 600 gsm (2 500 gsm 1000 gsm (2 500 1000 gsm (2 500 300 gsm) (single) gsm) Speed 3.2 gsm) Speed 2.7 1.15 1.44 1.89 1.89 1.1 1.38 1.9 1.88 1.13 1.36 1.92 1.89 1.14 1.36 1.93 1.93 1.15 1.32 1.94 1.92 1.19 1.31 2.05 1.96 1.16 1.29 2.06 1.94 1.17 1.26 2.06 1.9 1.17 1.22 2 1.9 1.13 1.19 1.94 1.92 1.14 1.11 1.95 1.88 1.14 1.06 1.94 1.87

[0056] FIG. 9 shows the density of various samples of material formed according to the present invention of either 300 gsm or 500 gsm, as compared to the upper and lower specification levels.

[0057] FIG. 10 shows the density of various samples of material formed according to the present invention. The samples being either 500 gsm single layer material, a laminate material formed of two layers of 300 gsm material, or a 1000 gsm laminate material formed of two layers of 500 gsm material. The two 1000 gsm laminate materials were formed at machine speeds of either 2.7 m/min or 3.2 m/min. As can be seen, the 1000 gsm material formed at a higher speed generally had a lower density. All the materials in FIG. 10 have a density of greater than 0.4 g/cm.sup.3. The data from FIG. 10 is shown in Table 4 below.

TABLE-US-00004 TABLE 4 Density (g/cm3) of samples according to the present invention Density (g/cm.sup.3) 1000 1000 gsm (2 500 gsm (2 500 600 gsm (2 500 gsm) gsm) 300 gsm Speed Speed gsm (single) 3.2 2.7 0.6674 0.5887 0.6759 0.734 0.6226 0.5462 0.6036 0.6425 0.607 0.5079 0.5809 0.6536 0.5989 0.5202 0.5745 0.5963 0.5919 0.5081 0.5599 0.6012 0.5749 0.5039 0.5313 0.593 0.5917 0.5142 0.5271 0.6015 0.5849 0.5159 0.5322 0.6046 0.5909 0.5305 0.5713 0.6198 0.6206 0.5334 0.5685 0.6181 0.632 0.572 0.6135 0.6621 0.6747 0.5998 0.6493 0.7077

[0058] FIG. 11 shows the stiffness of various samples of material formed according to the present invention. The samples being either 500 gsm single layer material, laminate material formed of two layers of 300 gsm material, or 1000 gsm laminate material formed of two layers of 500 gsm material. All of these materials were coated on both sides with a 60 gsm CAPA layer. The two 1000 gsm laminate materials were formed at machine speeds of either 2.7 m/min or 3.2 m/min. As can be seen, the 1000 gsm laminate material formed at a higher speed generally had a higher stiffness. The data from FIG. 11 is shown in Table 5 below.

TABLE-US-00005 TABLE 4 Stiffness (N) of laminate materials vs single layer materials DLC (N) 1000 1000 gsm (2 gsm (2 500 500 600 500 gsm) gsm) gsm (2 300 gsm Speed Speed gsm) (single) 3.2 2.7 79.53 73.39 150.95 80.96 58.39 59.37 120.03 62.87 51.43 46.85 111.61 61.56 54.01 47.94 106.4 51.76 49.2 42.68 105.75 56.2 61.86 47.94 107.3 53.95 51.91 41.39 112.8 58.31 59.32 47.04 123 59.82 52.83 41.61 133 67.55 52.09 49.93 117.82 57.93 63.36 51.58 135.67 71.55 69.36 50 171.78 71.66

[0059] Unless otherwise indicated by context the description of the embodiments of the present invention set out above are for illustrative purposes only to explain the present invention. Any feature of the present invention discussed above may be implemented separately form any other feature.