Non-Weathering, Flame-Proof Composite Material

Abstract

A method for producing a composite material includes using an alkaline binder containing alkali silicate glass; an organic gelling agent and SiO.sub.2 particles; and a biological carrier material. The composite material is particularly stable, flame-proof and also suitable for the exterior.

Claims

1. A process for producing a composite material, comprising: a) providing an alkaline composition comprising at least one alkali metal silicate waterglass, at least one organic gel former; b) adding at least one type of SiO.sub.2 particles; c) combining the composition with at least one biological carrier material, such as fibers, turnings or mats from biological sources; and d) compacting the resultant composite under pressure and elevated temperature in a mold; e) after demolding, drying the composite to obtain the composite material.

2. The process as claimed in claim 1, wherein the organic gel former is a polysaccharide.

3. The process as claimed in claim 1, wherein the alkaline composition comprises at least one alkali metal hydroxide.

4. The process as claimed in claim 1, wherein the organic gel former is selected from comprises xanthan, gum arabic, guaran, galactomannans or mixtures thereof, where the gel former may have been chemically modified.

5. The process as claimed in claim 1, wherein the SiO.sub.2 particles comprise ground sand.

6. A composite material obtained by the process as claimed in claim 1.

7. A precursor composition obtained from step a) of the process as claimed in claim 1.

8. (canceled)

9. A method of producing a composite material, comprising using the precursor composition as claimed in claim 7.

Description

[0115] The working examples are shown in schematic form in the figures. Identical reference numerals in the individual figures denote elements that are the same or have the same function or correspond to one another in terms of their functions. The individual figures show:

[0116] FIG. 1 dependence of the mechanical properties on the binder/fiber weight ratio;

[0117] FIG. 2 dependence of the modulus of elasticity and the 3-point bending strength on the age of the binder/fiber mixture.

PRODUCTION OF THE BINDER

Example 1a: Precursor Composition (Precursor NMC4 210913)

[0118] 13.15 g of potassium hydroxide (85% by weight) is dissolved while stirring in 161.73 g of van Baerle potassium waterglass (SiO.sub.2/K.sub.2O modulus: 2.93:1; density 1.42 g/ml, viscosity 40-50 mPas, about 41.3% by weight of solids). After the solution has been cooled down to room temperature, 2.63 g of guar (galactomannan with galactose/mannose ratio 1:2) is added thereto in small portions while stirring vigorously. On completion of addition of the guar, the solution has slightly elevated viscosity. For further swelling of the guar, the mixture is stirred at low speed at room temperature for at least a further 24 h. In this form, the binder precursor is indefinitely storable.

Example 1b: Activation (NMC4 210913)

[0119] First 142.93 g of ground sand (size distribution: e.g. d(10)=0.547 m; d(50)=3.793 m; d(90)=19.642 m and specific surface area about 4.01 m.sub.2/g) is distributed homogeneously in 177.51 g of high-viscosity binder precursor with a dissolver disk. Thereafter, 7.6 g of fumed silica (primary particle distribution about 200-300 nm) is additionally stirred in homogeneously in small portions. The result is 328.04 g of a milky white binder paste (solids content: about 58.35%). The pot life of the activated binder is about 12 hours.

[0120] Size distribution is determined by laser diffraction. For this purpose, the Mastersizer 2000 from Malvern Panalytics was used. Particle size was determined by laser diffraction both for wet dispersion and for dry dispersion. For automated dry dispersion, a Scirocco 2000 unit was used. For wet dispersion, the automated Hydro 2000 S wet dispersing unit was used. While dry dispersion detected the fines down to about 200 nm, the wet method, by contrast, gave fines over and above 350 nm, but gave better reproducibility over 3 measurements/sample. The size distributions for the dry method gave values of 0.547 m (d10), 3.793 m (d50) and 19.642 m (d90). Values ascertained by the wet method were 0.951 m (d10), 3.722 (d50) and 19.982 (d90). Aqueous dispersion gives more homogeneous data, and dispersion of the sub-u-size particles gives a low result, apparently owing to agglomerate formation in the aqueous solution. The preferred values are based on wet methods.

[0121] Table 2 lists various binder compositions. Betol is a further waterglass. Wollner: Betol K57M: modulus about 1:1; density 1.65 g/ml of solids: about 52%; viscosity about 60 mPas. MFC is used as thixotropic additive on dilution. In the case of KOH, the weight is based on KOH with a KOH content of 85% by weight.

Example 1c: Production of a Composite Board Based on Wood Turnings

[0122] 328.04 g of binder paste (NMC4 210913) is mixed vigorously with 160 g of acacia turnings (>1.4 mm-<4 mm fraction). After about 30 minutes, the mixture is introduced homogeneously into a press mold provided with a nonstick coating. The press mold permits the production of a board of dimensions 20201 cm.sup.3. The surface can additionally be upgraded by applying a binder-wood turning blend with a finer screen fraction of the chipped biomass. An illustrative composition is as follows: 72 g of activated binder paste is blended homogeneously with 24.4 g of a wood turning fraction of 1-1.4 mm and 12 g of a wood turning fraction of 500 m to 1 mm, and applied homogeneously to a surface of the coarser wood turning-binder blend introduced into the press mold beforehand. In a hot press, the binder-wood turning blend is compressed and cured under reduced pressure at a temperature of 80 C. for 20 hours. The demolded boards are then dried to constant weight in a drying cabinet at 70 to 90 C. The ratio of binder solids to weight of acacia turnings is 1.2:1.

[0123] The carbonation is undertaken after the composite boards have attained constant weight: [0124] a) in the climate-controlled cabinet at 20 C. and 65% rel. humidity for 3 days with sparging by CO.sub.2 by means of dry ice. For this purpose, the dry ice is replenished after 8 h, 24 h, 32 h, 48 h, 56 h. For the 8-hour period, 5 g of dry ice is introduced, and for the 16-hour period correspondingly 10 g. [0125] b) immersion into propylene carbonate (CO.sub.2 source) and storage in a drying cabinet at 80 C. for 24 h. Thereafter, the composite boards are stored twice in demineralized water at room temperature for about 10 sec. Drying is effected at 80 C. in a drying cabinet overnight. [0126] c) alternatively to propylene carbonate from example b), glycerol carbonate (CO.sub.2 source) is used.

[0127] FIG. 1 shows the dependence of the mechanical properties on the binder/fiber weight ratio (binder here the solids of binder variant NMC4 210121, age of the precursor=1 d (=1 day old)). Thereafter, the precursor was activated with ground sand, and the acacia fibers were incorporated. After 2 hours, the shaping was conducted in a hot press at 80 C. and a pressure of 25 bar for 20 h. Demolding was followed by further curing in a drying cabinet at 80 C. for 24 h. Flexural strengths and transverse tensile strengths are ascertained after natural aging for 50-55 days.

Example 2a: NMC4 210121

[0128] 26.3 g of potassium hydroxide (85% by weight) is dissolved while stirring in 323.46 g of van Baerle potassium waterglass (SiO.sub.2/K.sub.2O modulus: 2.93:1; density 1.42 g/ml, viscosity 40-50 mPas, about 41.3% by weight of solids). After the solution has been cooled to room temperature, 5.26 g of guar (galactomannan with galactose/mannose ratio 1:2) is added thereto in small portions while stirring vigorously. On completion of addition of the guar, the solution shows slightly elevated viscosity. For further swelling of the guar, the mixture is stirred at low speed at room temperature for at least a further 24 h. The binder precursor is indefinitely storable in this form.

[0129] 301.06 g of ground sand is stirred homogeneously into 355.02 g of high-viscosity binder precursor with a dissolver disk. The result is 656.08 g of a cream-colored binder paste (NMC4 210121) (solids content: about 58.35%).

Example 2b:

[0130] 140.6 g of acacia fibers is blended homogeneously with 656.08 g of binder (NMC4 210121). After being left to stand for 2hours, the resulting binder/fiber mixture is introduced into a press mold (cavity: 20020020 mm.sup.3) and compacted by means of a hot press at 80 C. and a pressure of 25 bar to a board of thickness 1 cm and precured under these conditions for 20 h.

[0131] The final curing is effected at 80 C. in a drying cabinet for 24 h.

Example 3: Hemp Web Composite

[0132] 98.2 g of potassium waterglass (van Baerle) is admixed with 8.6 g of KOH while stirring and cooling with an ice bath. Thereafter, 1.6 g of carboxymethylated guar (from Ranie Chemie Produktions-und Vertriebs-GmbH: RAGUM AD type) is added to the mixture in small portions. On completion of addition, the ice bath is removed and the mixture is stirred at room temperature overnight.

[0133] After about 20 h, 89.2 g of silica sol (Levasil 50/50) and then 36.6 g of ground sand are mixed into the precursor while stirring for activation. The result is 234.2 g of activated composition (based on NMC4) having an SiO.sub.2/K.sub.2O modulus of 12.31 and a solids content of about 46.4%. The binder is then worked manually into a hemp web (basis weight 1000 g/m.sup.2) having a weight of 21.6 g. An appropriate excess of binder is needed for homogeneous distribution of the binder in the hemp web having spongelike absorption. The binder prepared beforehand is used in full.

[0134] The binder-soaked web is then preconditioned in an oven preheated to 40 C. for 1 h. Thereafter, the web is precured in a hot press at 85 C. In the course of this, the excess binder is expressed. In order to achieve uniform evaporation of the residual water, the precured web is finally cured between perforated sheets in the hot press at 80 C. under reduced pressure for another 16 h.

[0135] The cured hemp composite weighs 92.65 g. This corresponds to a binder-hemp web ratio of 3.29 parts by weight of cured binder to one part by weight of hemp web.

Example 4: Lightweight Construction Board

[0136] Spray application of the binder to the fibers and subsequent composite production:

[0137] 238 g of fibers finely distributed in a tank and in a thin layer are wetted with the binder NMC4-MFC (table 2) with a spray gun (SATAjet) at a spray pressure of 1.0 bar. Once the fibers have been uniformly and finely wetted, the layer of fibers is turned by 180 and sprayed again until wetting with binder is clearly apparent.

[0138] The total weight of the wetted fibers is 442.6 g. 220.4 g is shut away in a separate vessel.

[0139] The remaining 222.22 g is finely distributed again in the tank and sprayed once more from both sides with binder. The wet weight thereafter is 276.8 g. This binder-fiber mixture too is shut away in a separate vessel until further processing.

[0140] For production of the composite boards, the two fiber-binder mixtures are each introduced into a baking paper-lined press mold (2020about 2 cm.sup.3) and compacted in a hot press to a layer thickness of 1 cm at a pressure of 30 bar and then precured at 85 C. After 1.5 h, the composite is demolded and subjected to further curing in a drying cabinetinserted into a hardening frame at 80 C. for 40 h. The result is boards having a total weight of 169.29 g for sheet 1 and 204.59 g for sheet 2.

[0141] Carbonation was effected by storage under air and by absorption of CO.sub.2 from the air.

[0142] The weight ratios of fibers to binder (cured) are as follows: [0143] Sheet 1: about 2.33 fibers to 1 binder [0144] Sheet 2: about 1.4 fibers to 1 binder

[0145] The sheets were examined by the following methods:

[0146] Bending tests: (EN 310, classification EN 312), modulus of elasticity, maximum tensile stress

[0147] Transverse tensile strength: (EN 319, classification EN 312)

[0148] Dry and after boil test EN 1087-1 (90 min 25 C.->100 C., 120 min @ 100 C.)

[0149] Water retention: (EN 317: thickness swelling, EN 321: moisture resistance via cycling test, EN 1087-1: boil test)

[0150] Depending on the test specimen, it was possible in the bending test to achieve a modulus of elasticity of 2.2 GPa (P2 classification according to EN 312) to 4.4 GPa (P7). The flexural strength was 11 MPa (P1) to 20 MPa (P6).

[0151] In the transverse tensile test according to EN 319, it was possible to achieve a strength of 1.2 MPa to 3.6 MPa (P7). Even after a boil test in water (90 min. 25 C..fwdarw.100 C.; 120 min. 100 C.), a strength of 0.15 MPa to 0.35 MPa was still measured.

[0152] Samples were also stored at 20 C. in water for 24 hours. Sheets of the composite material of the invention with acacia turnings had only an increase in weight of 0% to 4% and an increase in thickness of 0% to 3%.

[0153] By virtue of the use of waterglass and SiO.sub.2 particles, the composite material has good fire resistance. A glass foam is formed at high temperatures, which provides thermal insulation and prevents burning of the material. It was possible to subject a sheet produced to direct flame application at a temperature of above 1000 C. for 1 hour without ignition of or penetration through the board.

[0154] The resultant composite material, when stored in a fieldwithin the movement radius of termites close to a termite nestdid not show any sign of termite infestation, even after 6 months.

[0155] FIG. 2 shows the dependence of the modulus of elasticity and the 3-point flexural strength on the age of the binder/fiber mixture. The binder precursor NMC4 having an age of 23 days was used for the production. After the binder/fiber mixture has aged for 5 to 6 days, a maximum is attained in flexural strength and modulus of elasticity (production parameters: pressed for 1.5 h at 40 bar and 80 C.; 75.1% by weight based on solids in the binder content, NMC4 as precursor).

[0156] Table 3 shows the dependence of the properties of the composites on the age of the storable binder precursors in days (d): 1 d, 4 d, 7 d, 15 d, 16 d, 21 d, 23 d. MFC means additization with microfibrillated cellulose.

[0157] The storage time of the composites produced was between 1.5 and 2 months at room temperature.

[0158] The test specimens were also subjected to accelerated carbonation according to at least one of the above variants.

[0159] After 2-3 months, the swelling tests were done, and then, after drying and conditioning to constant weight, the boil tests.

TABLE-US-00001 TABLE 1 Grain Grain Grain Specific Chemical size size size surface area Admixture composition pH d.sub.10 d.sub.50 d.sub.90 (BET) Fumed aggregate 99% SiO.sub.2 200 25 m.sup.2/g 0.2-0.3 m (amorphous) Millisil W11 99% SiO.sub.2 7 22 m 55 m 0.8 m.sup.2/g (crystalline) Millisil W12 99% SiO.sub.2 7 16 m 50 m 0.9 m.sup.2/g (crystalline) Sikron SF 800 97.5% SiO.sub.2 7 2 m 6 m 6.0 m.sup.2/g quartz 2% Al.sub.2O.sub.3 (crystalline) Treminex 958-006 60.8% SiO.sub.2 9.5 4 m 32 m 140 m 0.8 m.sup.2/g nepheline 23.0% Al.sub.2O.sub.3 syenite 10.4% Na.sub.2O 4.6% K.sub.2O (amorphous) Treminex 958-700 TST 60.8% SiO.sub.2 9.5 1 m 3 m 9 m 4.0 m.sup.2/g nepheline syenite 23.0% Al.sub.2O.sub.3 (trimethylsilane- 10.4% Na.sub.2O modified) 4.6% K.sub.2O (amorphous) Tremin 939-010 50.0% SiO.sub.2 9.5 L.sub.10 L.sub.50 L.sub.90 0.46 m.sup.2/g wollastonite needles 1% Al.sub.2O.sub.3 22 m 77 m 207 m Average aspect ratio: 45% CaO L/D = 11/1 0.8% MgO Tremin VP939-302 50.0% SiO.sub.2 9.5 L.sub.10 L.sub.50 L.sub.90 1.0 m.sup.2/g wollastonite needles 0.7% Al.sub.2O.sub.3 13 m 46 m 110 m Average aspect ratio: 47% Cao L/D = 8/1 0.3% MgO 1.0% Na.sub.2O + K.sub.2O

TABLE-US-00002 TABLE 2 Molar SiO.sub.2/K.sub.2O Weight modulus Theor. Theor. of Weight Alternative/ after SiO.sub.2 K.sub.2O Theor. potassium Weight Weight of additional Microfibrillated SiO.sub.2 content/g content/g H.sub.2O water- of of ground SiO.sub.2 cellulose Mixture addn. (mol) (mol) content/g glass/g KOH/g guar/g sand/g source/g (MFC)/g NMC4 12.31 4.75 0.61 6.27 4.91 0.43 0.08 1.83 Levasil 0 basis (0.079194) (0.006431) 50 nm/50 (comp.) m.sup.2/g 4.46 NMC4 9.21 195.16 33.28 96.94 161.70 13.15 2.63 150.53 0 0 210121 (3.25271) (0.35326) NMC4 9.23 201.26 34.22 107.46 161.70 + 1.320 2.63 150.53 0 0 210701 (3.35432) (0.36325) Betol 29.77 Betol NMC4 9.21 429.79 73.28 400.76 356.10 28.96 5.79 331.50 0 5.79 MFC (7.16318) (0.77796) 210712 NMC4 9.21 429.79 73.28 313.49 356.10 28.96 5.79 331.50 0 0 210712 (7.16318) (0.77796) dil. NMC4 9.21 1319.31 224.95 655.30 1093.06 88.90 17.78 966.22 Silica fume 0 210913 (21.98844) (2.38801) 200-300 nm 51.38

TABLE-US-00003 TABLE 3 Transverse tensile Solids Proportion Modulus Transverse strength after content of of wood of Flexural tensile boil test/MPa Thickness binder/% fibers/% elasticity/GPa strength/MPa strength/MPa (to EN 1087-1 swelling Mixture by wt. by wt. (to EN 310) (to EN 310) (to EN 319) and EN 319) (to EN 317) NMC4 1d 76.7 23.3 4.1 15.22 3.3 5.18% NMC4 4d 77.2 22.8 3.9 17.88 3.63 0.35 2.18% NMC4 7d 78.7 21.3 3.7 16.08 2.46 0.30 1.44% NMC4 15d 74.4 25.6 3.0 12.61 0.96 0.17 1.55% NMC4 16d 74.3 25.7 2.3 11.03 1.23 0.39 5.73% NMC4 21d 75.0 25.0 2.9 12.34 1.11 0.13 1.47% NMC4 23d 75.1 24.9 3.09 13.74 1.69 0.19 2.14% NMC4 MFC 30.0 70.0 0.18 NMC4 41.7 58.3 0.76 diluted