BINDING RESIN FOR NONWOVEN FABRICS, IN PARTICULAR FOR MANUFACTURING SUPPORTS FOR BITUMINOUS MEMBRANES, A METHOD FOR PREPARING IT, AND A NONWOVEN FABRIC OBTAINED BY USING SAID RESIN

Abstract

There is described a binding resin for nonwoven fabrics, in particular for manufacturing supports for bituminous membranes, consisting of 100% natural, sustainable raw materials. The resin is an aqueous solution consisting of starch, a crosslinking agent of natural origin and a catalyst.

Claims

1-20. (canceled)

21. A bituminous membrane, particularly for covering roofs, comprising a nonwoven support which is impregnated with bitumen, wherein the nonwoven support is manufactured from fibers of synthetic origin, wherein the nonwoven support is further impregnated with a binding resin, and wherein the binding resin is an aqueous starch-based solution consisting of a starch, a crosslinking agent of natural origin, a catalyst and optionally one or more additives.

22. The bituminous membrane according to claim 21, wherein the starch is a native starch.

23. The bituminous membrane according to claim 21, wherein the starch is a modified starch and is modified by a chemical treatment, a physical treatment or an enzymatic treatment.

24. The bituminous membrane according to claim 21, wherein the starch comprises starch molecules subjected to a controlled degradation or a physical treatment.

25. The bituminous membrane according to claim 21, wherein the amount of starch is from 8% to 30% as a percentage by weight in the binding resin.

26. The bituminous membrane according to claim 21, wherein the crosslinking agent is a carboxylic acid having two or more carboxylic groups.

27. The bituminous membrane according to claim 21, wherein the crosslinking agent is selected from the group consisting of citric acid and succinic acid.

28. The bituminous membrane according to claim 21, wherein the amount of crosslinking agent is from 5% to 25% as a percentage by weight of the starch.

29. The nonwoven support according to claim 21, wherein the catalyst is an alkali metal salt of a phosphorus-containing acid.

30. The bituminous membrane according to claim 21, wherein the amount of the one or more additives is between 5 and 25% as compared to the starch weight.

31. The bituminous membrane according to claim 21, wherein the one or more additives is glycerol, and the amount of the glycerol is in the range from 5 to 25% compared to the starch weight.

32. The bituminous membrane according to claim 21, wherein the one or more additives is a hydrophobing agent, and the amount of the hydrophobing agent is from 0.5% to 4% as compared to the starch weight on a dry basis.

33. The bituminous membrane according to claim 21, wherein the amount of starch is from 8% to 30% as a percentage by weight in the binding resin, the crosslinking agent is in an amount from 5% to 25% as a percentage by weight of the starch and the catalyst is in an amount from 40% to 60% as a percentage by weight of the crosslinking agent.

34. The bituminous membrane according to claim 21, wherein the binding resin is 100% of natural origin.

35. The bituminous membrane according to claim 21, wherein the nonwoven support comprises synthetic, metal or glass reinforcing wires or lattice structures.

36. The bituminous membrane according to claim 21, wherein the fibers are derived from polyethylene terephthalate (PET).

37. The bituminous membrane according to claim 21, wherein the nonwoven support has a tensile deformation of 54.3% to 80.9% at ambient temperature.

38. The bituminous membrane according to claim 21, wherein the nonwoven support has a Young module of 46 to 122 MPa at ambient temperature and at 180 C.

39. A building or roof comprising the bituminous membrane of claim 21.

40. A method for producing the bituminous membrane according to claim 21, comprising the steps of: (a) providing a nonwoven support which is manufactured from fibers of synthetic origin, wherein the nonwoven support is impregnated with a binding resin, and the binding resin is an aqueous starch-based solution comprising starch, a crosslinking agent of natural origin and a catalyst; and (b) impregnating the nonwoven support with bitumen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 provides the results of the mechanical tensile test of Test 1 under room temperature.

[0020] FIG. 2 provides the results of the mechanical tensile test of Test 1 under high temperature.

[0021] FIG. 3 provides the results of the mechanical tensile test of Test 2 under room temperature.

[0022] FIG. 4 provides the results of the mechanical tensile test of Test 2 under high temperature.

[0023] FIG. 5 provides the results of the mechanical tensile test of Test 3 under room temperature.

[0024] FIG. 6 provides the results of the mechanical tensile test of Test 3 under high temperature.

[0025] FIG. 7 provides the results of the mechanical tensile test of Test 4 under room temperature.

[0026] FIG. 8 provides the results of the mechanical tensile test of Test 4 under high temperature.

DETAILED DESCRIPTION OF THE INVENTION

Resin Composition

[0027] The resin of the present invention is a starch-based aqueous solution. In addition to starch, the formulation also includes a crosslinker of natural origin, a catalyst and possibly an additive and a hydrophobing agent.

Starch

[0028] The types of starch used in the present invention may comprise native or modified starches. Native starch has a granular structure, is water-insoluble and in this form is only used in some specific applications; for normal applications, it is converted into another form that has a higher water solubility. Native starch may be modified by means of chemical, physical and enzymatic treatments. The treatment technologies are intended to modify the properties of the natural starch to make it more suitable for various applications. For example, the starch may be modified to make it cold soluble and/or to modify its viscosity and/or limit its retrogradation. Therefore, the starch molecules are subjected to a controlled degradation, through thermal or enzymatic treatments, or chemically modified by introducing specific functional groups.

[0029] The type of starch that may be used in the following invention comprises starches extracted from raw materials of plant origin, such as maize, wheat, potatoes, peas and legumes in general, tapioca, etc.

Crosslinking Agent

[0030] The composition of the resin according to the present invention includes the use of a crosslinking agent of natural origin, which is added in order to react with the starch, thus creating covalent bonds. The crosslinking is required to improve the mechanical properties of starch and decrease the water dissolution thereof.

[0031] These compounds typically contain one or more functional groups which react with the hydroxyl groups of the starch molecule, thus promoting the crosslinking thereof. Classes of these crosslinking compounds may include natural polycarboxylic acids such as succinic acid, an inexpensive, non toxic compound which may be manufactured from the fermentation of starch.

[0032] The amount of succinic acid to be added for crosslinking the starch may vary from 5 to 25%, preferably from 10 to 20% (by weight of starch).

Catalyst

[0033] The composition of the resin of the present invention comprises a catalyst that accelerates the crosslinking reaction. In the present invention, an alkali metal salt of a phosphorous-containing acid, such as sodium hypophosphite, has proved to provide the best performance. The amount of catalyst is determined to be from 40 to 60% as compared to the crosslinker weight, preferably from 45 to 55%.

Additive

[0034] The resin composition may also include additives for improving the end product performance. Such additives typically consist of polyols, such as glycerol. A concentration of such additives in the range between 5 and 25% as compared to the starch weight is recommended for improving some plastic properties in the end product, such as elongation to break and flexibility.

Hydrophobing Agent

[0035] Other compounds may be added to the formulation of the natural resin object of the present invention, in order to improve some performance of the end product. The use of large quantities of starch requires the use of a hydrophobing agent to neutralize the affinity of starch with water. A hydrophobing compound is added for limiting the capillarity absorption in the nonwoven fabric fibers, caused by the presence of hydroxyl groups contained in the starch molecule. The water absorption is unfavourable for the applications of nonwoven fabrics in waterproofing in general or for roofing.

[0036] A water repellent compound is generally used as a hydrophobing agent such as to inhibit the action of capillarity absorption in the nonwoven fabric fibers. The best results are obtained by using alkyl ketene dimer (AKD), a fatty acid derivative with two hydrocarbon groups (R1 and R2) containing 8-36 carbon atoms, which may be saturated or unsaturated or branched or linear. The hydrocarbon groups used normally include molecules with 14-18 carbon atoms. When these hydrocarbon groups react with carbohydrates, they impart hydrophobic properties.

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[0037] The hydrophobing compound may be applied to the nonwoven fabric by means of different techniques, including spray atomization on the end product, or added to the formulation and applied by impregnation.

[0038] Generally, the optimal amount of the hydrophobing compound to be added in the impregnation step must be from 0.5 to 4% as compared to the starch weight on a dry basis, preferably of more than 1%.

Field of Application of the Invention

[0039] The present invention applies to nonwoven fabrics manufactured from different types of fibers. Such fibers may be of natural, mineral, artificial and synthetic origin. Natural fibers may comprise, for example, cotton, linen, sisal, jute, hemp, coconut. Fibers of synthetic nature may include fibers derived from polyamide, polypropylene, PET, PBT, PTT polymers. Fibers of inorganic origin may comprise glass fibers, ceramic fibers, basalt, carbon, metals, metal oxides. Fibers of artificial nature may be obtained by processing cellulose. The fibers may be cut as a staple or spun in the form of continuous yarns and arranged to form different varieties of nonwoven fabrics, used as supports for bituminous membrane. Nonwoven fabrics may be reinforced during manufacturing by inserting glass, synthetic, metal wires or reinforcing grids. In addition to the reinforcing purpose, the field of application of nonwoven fabrics may also relate to other products used in the field of building, flooring, heat and sound insulation.

Advantages when using the Resin According to the Invention

[0040] One of the main advantages of using a 100% natural resin as an alternative to synthetic resins is linked to the ecological and safety aspect. The total suppression of any formaldehyde-containing or developing compound indeed allows a considerable reduction of polluting emissions and a total safety for workers who manufacture or use such products. In addition, an advantage is obtained in terms of reduction of CO.sub.2 emissions, which may be proved through a Life Cycle Assessment process.

[0041] Using natural, sustainable raw materials also allows a considerable benefit in economic terms, leading to a significant reduction of costs in manufacturing nonwoven fabrics. Synthetic resins typically are very expensive and their price is strongly affected by the oil price and subject to high volatility. Starchthe main compound in the formulation of the resin object of the present inventionis a widely available, low cost compound resulting from raw materials of natural origin, the price of which has a relative stability. Moreover, the crosslinking agent used in the present invention may be a starch derivative, from which it is produced by fermentation, therefore its price has the same stability.

[0042] A further advantage of the present invention relates to the performance of the nonwoven fabric on which it is applied. Indeed, the product impregnated with the 100% natural, sustainable resin object of the present invention, has mechanical properties which are equal to or higher than those obtained by using normal synthetic resins.

Method for Preparing the Resin

[0043] When preparing the natural resin object of the present invention, the various components are added to the dilution water according to the following method: [0044] a. Dosing the dilution water in the total amount determined by the desired solids content. Depending on the applications, the total solids content varies from 10 to 30%. Accordingly, the dilution water represents 70-90% by weight of the formulation. [0045] b. Dosing the starch in the amount from 8% to 30% as a percentage by weight in the resin formulation. [0046] c. Dosing succinic acid in an amount of 5-25% by weight of the starch. [0047] d. Dosing the catalyst in the range between 40 and 60% as compared to the crosslinker weight. [0048] e. Dosing the additive in the range between 5 and 25% as compared to the starch weight.

[0049] The preparation method is described in more detail hereinafter, with reference to experimental tests carried out on specific, non-limiting examples.

Experimental Tests

[0050] Test 1: Pilot Scale Testing of a Resin Consisting of 100% Starch Crosslinked with Succinic Acid.

[0051] The preparation of 500 ml of a mixture with a solids content of 14% and the subsequent assessments of the mechanical and thermal features of a polyester nonwoven fabric impregnated with the same mixture are described. The performance is assessed with the following lab tests, by comparison with the same nonwoven fabric impregnated with the standard synthetic resin consisting of 70% styrene/acrylates30% melamine: [0052] 1. Tensile tests at room temperature according to EN ISO 9073-3-1989; [0053] 2. Tensile tests at high temperature: non-coded method (tensile tests in thermostatic chamber at 180 C., 80 mm distance between the clamps, 100 mm/min deformation speed).

[0054] The starch solution was prepared by dispersing 57.4 g starch, succinic acid and catalyst in water at ambient temperature. The solution was heated to 90 C. and left in isothermal atmosphere for 60 minutes, keeping the system under mechanical stirring. Finally, the system was cooled to 65 C. and the required amount of additive was added.

TABLE-US-00001 INGREDIENTS % [w/w] [g] Starch 11.5%. 57.4 Succinic acid 1.6% 8.0 Glycerol 1.6% 8.0 Sodium hypophosphite 0.8% 4.0 Water 84.5% 422.6

[0055] Samples (33 cm44 cm) of PET nonwoven fabric reinforced with glass wires 60 TEX were impregnated in a bath containing the 100% starch-based prepared solution with a solids content of 14%. The samples were impregnated to reach a final add-on of 21% on a dry basis following oven drying. The resin applied on the nonwoven fabric samples was oven dried and crosslinked at 200 C. for 3 minutes and 45 seconds. 10 specimens were obtained from the samples produced, which were subjected to mechanical tensile tests with Instron dynamometer: [0056] 5 50300 mm specimens for cold tests (room temperature) [0057] 5 50180 mm specimens for hot tests (180 C.)

[0058] The tensile test results are shown in FIG. 1 and FIG. 2, which show the curve (Pr7) obtained from the average of 5 specimens. The tables below (Tab. 1 and Tab. 2) summarize the main mechanical properties measured in the lab tests.

TABLE-US-00002 TABLE 1 Cold mechanical properties. Comparison of sample Pr7 to STD STD Pr7 Weight [g/m.sup.2] 148 174 Breaking load NW (N/50 mm) 151 326 Tensile deformation NW [%] 23.0% 65.0% Load at 2% [N/50 mm] 229 168 Tenacity - L [N/50 mm/g*m.sup.2] 0.102 0.187 Young module [MPa] 111 100

TABLE-US-00003 TABLE 2 Hot mechanical properties. Comparison of sample Pr7 to STD STD Pr7 Weight [g/m.sup.2] 148 169 Wire breaking load (N/50 mm) 91 86 Wire tensile deformation [%] 2.0% 2.18% Deformation @ 50N [%] 1.10% 1.27% Deformation @ 80N [%] 1.57% 1.96% Deformation @ 100N [%] \ \ Young module [MPa] 52 100
Test 2: Pilot Scale Testing of Resin Consisting of 100% Starch Crosslinked with Succinic Acid.

[0059] The preparation of 500 ml of a mixture with a solids content of 14% and the subsequent assessments of the mechanical and thermal features of a polyester nonwoven fabric impregnated with the same mixture through lab tests are described.

[0060] The process of Example #1 was repeated with the exception of the thermal treatment of the solution. The starch solution was prepared by dispersing 57.4 g starch in water at ambient temperature. The relative required amount of succinic acid, catalyst and additive was dissolved in the starch solution. Finally, the amount of water required to achieve the desired concentration was added.

[0061] The mechanical test results are shown in the following figures (FIG. 3 and FIG. 4), which show the curve (Pr4) obtained from the average of 5 specimens. The tables below (Tab. 3 and Tab. 4) summarize the main mechanical properties measured in the lab tests.

TABLE-US-00004 TABLE 3 Cold mechanical properties. Comparison of 100% starch + citric to STD STD Pr4 Weight [g/m.sup.2] 148 142 Breaking load NW (N/50 mm) 151 195 Tensile deformation NW [%] 23.0% 80.9% Load at 2% [N/50 mm] 229 136 Tenacity - L [N/50 mm/g*m.sup.2] 0.102 0.137 Young module [MPa] 111 47

TABLE-US-00005 TABLE 4 Hot mechanical properties. Comparison of sample Pr4 to STD STD Pr4 Weight [g/m.sup.2] 148 134 Wire breaking load (N/50 mm) 91 96 Wire tensile deformation [%] 2.0% 2.63% Deformation @ 50N [%] 1.10% 1.23% Deformation @ 80N [%] 1.57% 1.90% Deformation @ 100N [%] \ 2.64% Young module [a] 52 46
Test 3: Pilot Scale Test of Resin Consisting of 100% Starch Crosslinked with Succinic Acid.

[0062] The preparation of 500 ml of a mixture with a solids content equal to 14% and the subsequent assessments of the mechanical and thermal features of a polyester nonwoven fabric impregnated with the same mixture through lab tests are described.

[0063] The process of Example #2 was repeated with the exception of the succinic acid content increased from 8.0 g to 10.6 g (20% as compared to the starch weight on a dry basis). Accordingly, the catalyst amount was increased to 5.3 g.

[0064] The mechanical test results are shown in the following figures (FIG. 5 and FIG. 6), which show the curve (Pr6) obtained from the average of 5 specimens. The tables below (Tab. 5 and Tab. 6) summarize the main mechanical properties measured in the laboratory tests.

TABLE-US-00006 TABLE 5 Cold mechanical properties. Comparison of sample Pr6 to STD STD Pr6 Weight [g/m.sup.2] 148 174 Breaking load NW (N/50 mm) 151 310 Tensile deformation NW [%] 23.0% 54.3% Load at 2% [N/50 mm] 229 217 Tenacity - L [N/50 mm/g*m.sup.2] 0.102 0.177 Young module [MPa] 111 122

TABLE-US-00007 TABLE 6 Hot mechanical properties. Comparison of sample Pr6 to STD STD Pr6 Weight [g/m.sup.2] 148 172 Wire breaking load (N/50 mm) 91 90 Wire tensile deformation [%] 2.0% 2.21% Deformation @ 50N [%] 1.10% 1.37% Deformation @ 80N [%] 1.57% 2.03% Deformation @ 100N [%] \ 2.01% Young module [MPa] 52 97
Test 4: Pilot Scale Testing of Resin Consisting of 100% Starch Crosslinked with Citric Acid.

[0065] The preparation of 500 ml of a mixture with a solids content of 14% and the subsequent assessments of the mechanical and thermal features of a polyester nonwoven fabric impregnated with the same mixture through lab tests are described.

[0066] The process of Example #2 was repeated with the exception of 8.2 g succinic acid replaced with 8.2 citric acid.

[0067] The mechanical test results are shown in the following figures (FIG. 7 and FIG. 8), which show the curve (Pr3) obtained from the average of 5 specimens. The tables below (Tab. 7 and Tab. 8) summarize the main mechanical properties measured in the laboratory tests.

TABLE-US-00008 TABLE 7 Cold mechanical properties. Comparison of sample Pr3 to STD STD Pr3 Weight [g/m.sup.2] 148 118 Breaking load NW (N/50 mm) 151 170 Tensile deformation NW [%] 23.0% 61.5% Load at 2% [N/50 mm] 229 175 Tenacity - L [N/50 mm/g*m.sup.2] 0.102 0.145 Young module [MPa] 111 71

TABLE-US-00009 TABLE 8 Hot mechanical properties. Comparison of sample Pr3 to STD STD Pr3 Weight [g/m.sup.2] 148 133 Wire breaking load (N/50 mm) 91 86 Wire tensile deformation [%] 2.0% 2.29% Deformation @ 50N [%] 1.10% 1.14% Deformation @ 80N [%] 1.57% 1.94% Deformation @ 100N [%] \ 2.92% Young module [MPa] 52 47

[0068] Tensile tests at ambient temperature (FIGS. 1, 3, 5, 7) show better performance for the product impregnated with 100% natural resin for both the load and the elongation at break, and for the tenacity. Using a percentage of succinic acid of 20% as compared to the starch weight (Example #3), the mechanical properties at ambient temperature are particularly improved and the Young Modulus also has a 10% increase.

[0069] From the tensile tests at 180 C. (FIGS. 2, 4, 6, 8), no substantial differences between the two products are noted in the low deformation range (0-5%). At deformations higher than 5%, the load for the product impregnated with the 100% natural resin shows an increasing trend with the elongation, whereas for the standard product it remains almost constant.

Test 5

[0070] Samples (20 cm300 cm) of the same nonwoven fabric as that of test #4, with initial weight from 70 to 80 g, were subjected to capillarity tests upon the addition of an AKD solution with a solids content of 15%. The AKD solution was added to the nonwoven fabric by spray atomization so as to reach a final add-on of 20% on a dry basis following the oven drying of the samples at 120 C. for 30 minutes.

[0071] The samples were immersed in water containing a drop of dye (methylene blue) to an initial level of 20 mm and analyzed after 2 and 24 hours by comparison with similar nonwoven fabric samples not treated with AKD.

[0072] The test showed that the addition of the hydrophobing agent has decreased the capillarity absorption by 75%.