Binder composition, comprising basic substances, for producing a lignocellulosic composite, respective process, use and products

Abstract

Described herein is a process for producing a lignocellulosic composite, a binder composition suitable for use in said process, as well as a lignocellulosic composite which can be produced by the process of the invention, and its use. Moreover is described herein a kit for producing a binder composition for use in the production of a lignocellulosic composite and a respective use of such binder composition.

Claims

1. A process for producing a lignocellulosic composite comprising one or more lignocellulosic composite layers, comprising at least the following steps: S1) providing or preparing a mixture, at least comprising: lignocellulosic particles and a binder composition, comprising as components at least: c1) one or more amino acid polymers having two or more primary amino groups, wherein the one or more amino acid polymers comprise or are one or more polylysines, wherein the one or more polylysines have a weight-average molecular weight M.sub.w of 800 g/mol and comprise as monomers integrated in their polymer structure at least 85 mass-% of lysine monomers, based on the total mass of the polymer structure; c2) one or more alpha-hydroxy carbonyl compounds, wherein components c1) and c2) are a binder; and c3) one or more basic substances having a pK.sub.B-value of 3, S2) compacting the mixture from step S1) to receive a compacted mixture, and S3) applying heat and/or pressure to the mixture, so that the binder of the binder composition hardens and a lignocellulosic composite results.

2. The process according to claim 1, wherein the one or more amino acid polymers of component c1) of the binder composition comprise or are one or more polylysines, wherein the one or more polylysines have a weight-average molecular weight M.sub.w of 1000 g/mol; and/or have a weight-average molecular weight M.sub.w of 10000 g/mol; and/or have a weight-average molecular weight M.sub.w in the range of 800 g/molM.sub.w10000 g/mol; and/or comprise as monomers integrated in their polymer structure at least 95 mass-% of lysine monomers, based on the total mass of the polymer structure.

3. The process according to claim 1, wherein the one or at least one of the more alpha-hydroxy carbonyl compounds of component c2) of the binder composition is selected from the group consisting of glycolaldehyde, glyceraldehyde, 1,3-dihydroxyacetone, hydroxyacetone, arabinose, xylose, glucose, mannose, fructose, saccharose and mixtures thereof, and/or the ratio of (i) the total mass of the one or more amino acid polymers of component c1) of the binder composition: (ii) the total mass of the one or more alpha-hydroxy carbonyl compounds of component c2) of the binder composition or used for the preparation of the binder composition is in the range of 60:40 to 90:10.

4. The process according to claim 1, wherein the one or at least one of the more alpha-hydroxy carbonyl compounds is hydroxyacetone.

5. The process according to claim 1, wherein the one or more basic substances having a pK.sub.B-value of 3 are one or more substances having a pK.sub.B-value of 2.5; and the one or at least one of the more basic substances having a pK.sub.B-value of 3 are selected from the group consisting of: alkali metal hydroxides; and earth alkali metal hydroxides; and/or the total amount of component c3), the one or more basic substances having a pK.sub.B-value of 3, is in the range of from 3 to 9 mass-%, relative to the total amount of component c1), the one or more amino acid polymers of the binder composition, and component c2), the one or more alpha-hydroxy carbonyl compounds of the binder composition.

6. The process according to claim 5, wherein the alkali metal hydroxides are selected from the group consisting of LiOH, NaOH, KOH, and mixtures thereof.

7. The process according to claim 1, wherein the binder composition provided or prepared in step S1) further comprises a carrier liquid.

8. The process according to claim 7, wherein component c1), the one or more amino acid polymers, is present in or used for the preparation of the binder composition in a total amount in the range of from 20 to 50 mass-%, relative to the totalized mass of components c1) to c3) and carrier liquid; and/or component c2), the one or more alpha-hydroxy carbonyl compounds, is present in or used for the preparation of the binder composition in a total amount in the range of from 3 to 20 mass-%, relative to the total mass of components c1) to c3) and carrier liquid.

9. The process according to claim 1, wherein in the mixture provided or prepared in step S1) of the process, the total amount of component c1), the one or more amino acid polymers of the binder composition, and of component c2), the one or more alpha-hydroxy carbonyl compounds of the binder composition, is in the range of from 3 to 8 mass %, relative to the total amount of the lignocellulosic particles in an oven-dry state of the mixture.

10. The process according to claim 1, wherein in step S1) components c1) and c3) are premixed with each other and subsequently the resulting pre-mixture is contacted with said lignocellulosic particles.

11. The process according to claim 1, wherein the lignocellulosic composite is a lignocellulosic board selected from the group consisting of high-density fiberboard (HDF); medium-density fiberboard (MDF); low-density fiberboard (LDF); wood fiber insulation board; oriented strand board (OSB); chipboard; and natural fiber board; wherein the lignocellulosic board is a single-layer lignocellulosic board or multilayer lignocellulosic board.

12. The process according to claim 1, wherein the process of producing a lignocellulosic composite comprises one, two, three, more than three, or all of the following steps preparing a layer of the mixture provided or prepared in step S1), and in step S2) compacting this layer, preparing a multilayer lignocellulosic composite comprising one or more lignocellulosic composite layers, providing or preparing at least a first and a second individual mixture, and using said first and second individual mixtures for making a first and a second layer of the multilayer lignocellulosic composite, and/or wherein the first and the second individual mixture have the same composition or have different compositions, preparing a multilayer lignocellulosic composite, preparing two or more layers, each layer comprising lignocellulosic particles and a binder, wherein in the two or more layers the lignocellulosic particles and/or the binders are the same or different, compacting, in step S2), the mixture in two stages, wherein in the first stage the mixture is pre-compacted to give a pre-compacted mat, and wherein in the second stage this pre-compacted mat is further compacted; during or after compacting in step S2), hot pressing the mixture, and applying in step S3) a temperature in the range of from 80 to 300 C. and a pressure in the range of from of 0.1 to 10 MPa to the compacted mixture from step S2).

Description

EXAMPLES

(1) The following examples are meant to further explain and illustrate the present invention without limiting its scope.

Materials

(2) The following materials were used in the experiments described below: 1) Dextrose monohydrate, Sigma Aldrich, Spain; 2) L-Lysine solution (50% in water), ADM animal nutrition, USA; 3) Hydroxyacetone (95%), Alfa Aesar (now Thermo Fisher); 4) Sodium hydroxide (97% powder), Sigma Aldrich, USA; 5) Spruce wood chips and fibers (lignocellulosic particles) from Germany, Institut fr Holztechnologie Dresden:

(3) Spruce wood chips were produced in a disc chipper. Spruce trunk sections (length 250 mm) from Germany were pressed with the long side against a rotating steel disc, into which radially and evenly distributed knife boxes were inserted, each of which consisted of a radially arranged cutting knife and several scoring knives positioned at right angles to it.

(4) The cutting knife separated the chip from the round wood and the scoring knives simultaneously limited the chip length. Afterwards the produced chips were collected in a bunker and were subsequently transported to a cross beater mill (with sieve insert) for re-shredding with regard to chip width. Then, the reshredded chips were conveyed to a flash drier and dried at approx. 120 C. The chips were then screened into two useful fractions (B: 2.0 mm2.0 mm and >0.32 mm0.5 mm; C: 4.0 mm4.0 mm and >2.0 mm2.0 mm), a coarse fraction (D: >4.0 mm4.0 mm), which was re-shredded, and a fine fraction (A: 0.32 mm0.5 mm). Fraction B was suitable for use as surface layer chips for three-layered chipboards (surface layer chips), a mixture of 60 wt.-% of fraction B and 40 wt.-% of fraction C was used as chips for single-layered chipboards but was also suitable as core layer chips for three-layered chipboards (core layer chips).

(5) Methods:

(6) 1. Measuring of Residual Particle Moisture Content

(7) The moisture content of the lignocellulosic particles (chips or fibers, see above) before application of the binder was measured according to EN 322:1993 by placing the particles in a drying oven at a temperature of (1032) C. until constant mass was reached. The water content of the particle/binder composition mixtures obtained in step S1) was determined in an analogous manner. For this, a sample of the respective mixture (ca. 20 g) was weighed in moist condition (m.sub.1) and after drying (m.sub.0). The mass m.sub.0 is determined by drying at 103 C. to constant mass. Water content was calculated as follows: water content [in wt. %]=[(m.sub.1m.sub.0)/m.sub.0]100.

(8) 2. Measuring of Press Time Factor

(9) For determining the press time factor, a conventional hot press was used. For the purposes of the present invention, the press time factor was determined as the press time (i.e. the time from closing to opening of the press) divided by the target thickness of the lignocellulosic composite (board). The target thickness refers to the thickness of the lignocellulosic composite at the end of step S3) and was adjusted by the press conditions, i.e. by the distance between the top and bottom press plates, which is adjusted by the automatic distance control of the press.

(10) The press time factor is given below in units of [sec/mm], i.e. the time from closing to opening of the press in [sec]: target thickness of the pressed board in [mm]. For example, when a 10 mm chipboard is made with a press time of 120 sec, a press time factor of 12 sec/mm results.

(11) 3. Measuring of Densities of Lignocellulosic Composites

(12) The density of lignocellulosic composites (boards) was measured according to EN 323:1993 and is reported herein as the arithmetic average of ten 5050 mm samples of the same lignocellulosic composite (board).

(13) 4. Measuring of Transverse Tensile Strength of Lignocellulosic Composites (Internal Bond Strength)

(14) Transverse tensile strength (internal bond strength) of lignocellulosic composites (boards) was determined according to EN 319:1993 and is reported herein as the arithmetic average of ten 5050 mm samples of the same lignocellulosic composite (board).

(15) 5. Determining the Amount of Binder or Binder Composition

(16) The amount of binder or binder composition in the examples shown below are reported as the total weight of the sum of the respective components of the binder or binder composition in wt.-%, based on the total dry weight of the lignocellulosic particles (wood particles).

(17) 6. Determining the Weight-Average Molecular Weight (M.sub.w) of Polylysines

(18) The weight-average molecular weight (M.sub.w) of polylysines as prepared according to the present examples was determined by generally known size exclusion chromatography under the following conditions: Solvent and eluent: 0.1% (w/w) trifluoroacetate, 0.1 M NaCl in distilled water Flow: 0.8 ml/min Injection volume: 100 l Samples were filtrated with a Sartorius Minisart RC 25 (0.2 m) filter Column material: hydroxylated polymethacrylate (TSKgel G3000PWXL) Column size: inside diameter 7.8 mm, length 30 cm Column temperature: 35 C. Detector: DRI Agilent 1100 UV GAT-LCD 503 [232 nm]

(19) Calibration was done with poly(2-vinylpyridine) standards in the molar mass range from 620 to 2890000 g/mole (from Polymer Standards Service GmbH, Mainz, Germany) and pyridine (79 g/mol).

(20) The upper integration limit was set to 29.01 mL.

(21) The calculation of M.sub.w included the lysine oligomers and polymers as well as the monomer lysine.

Example 1: Synthesis of Polylysines

Example 1a: Poly-L-lysine with M.SUB.w .2100

(22) 2200 g of L-lysine solution was heated under stirring in an oil bath (external temperature 140 C.). Water was distilled off and the oil bath temperature was increased by 10 C. per hour until a temperature of 180 C. was reached. The reaction mixture was stirred for an additional hour at 180 C. (oil bath temperature) and then pressure was slowly reduced to 200 mbar. After reaching the target pressure, distillation was continued for 2 hours. The product was hotly poured out of the reaction vessel, crushed after cooling and dissolved in water to give a 50 wt.-% aqueous solution of poly-L-lysine (the Polylysine Solution 1a hereinafter). The weight-average molecular weight of the resulting poly-L-lysine was 2100 (for determination method see above).

Example 1 b: Poly-L-Lysine with M.SUB.w .3690

(23) The experiment of example 1a as described above was repeated. Different from example 1a, the distillation after reaching the target pressure was continued for 4 hours (instead of for 2 hours). A 50 wt.-% aqueous solution of poly-L-lysine (the Polylysine Solution 1b hereinafter) was finally obtained. The weight-average molecular weight of the resulting poly-L-lysine was 3690 (for determination method see above).

Example 1c: Poly-L-Lysine with M.SUB.w .6270

(24) The experiment of example 1a as described above was repeated. Different from example 1a, the distillation after reaching the target pressure was continued for 4.5 hours (instead of for 2 hours). A 50 wt.-% aqueous solution of poly-L-lysine (the Polylysine Solution 1c hereinafter) was finally obtained. The weight-average molecular weight of the resulting poly-L-lysine was 6270 (for determination method see above).

Example 2: Single-Layered Lignocellulosic Composites Poly-L-Lysine/Hydroxyacetone (for Comparison)

Example 2a: Single-Layered Lignocellulosic Composite with Poly-L-Lysine of M.SUB.w .2100/Hydroxyacetone (for Comparison)

(25) In a mixer, 499 g of Polylysine Solution 1a (for preparation see example 1a above) was sprayed onto 5.56 kg (5.40 kg dry weight plus 160 g water from residual particle moisture content) of spruce core layer chips (moisture content 3.0 wt.-%) while mixing. Immediately, 149 g of a hydroxyacetone solution (50 wt.-% in water) was sprayed onto the mixture while mixing. Finally, 90 g of water was sprayed onto the mixture while mixing to adjust the final moisture of the resinated chips. After addition of the water, mixing was continued for 3 min.

(26) The term resinated chips is used herein for the mixture of the chips with the binder composition and additionally added water (and similarly resination).

(27) The binder amount (or proportion of binder in the finished lignocellulosic composite) was calculated as follows:

(28) $[499g0.5\mathrm{of}\mathrm{component}c1)]+[149g0.5\mathrm{of}\mathrm{component}c2)]:5400g\mathrm{lignocellulosic}\mathrm{particles}=6.\%$

(29) The ratio of the binder components was calculated as follows:

(30) $[499g0.5\mathrm{of}\mathrm{component}c1)]:[149g0.5\mathrm{of}\mathrm{component}c2)]=77:23$

(31) The moisture content of the mixture provided or prepared in step S1) was calculated as follows:

(32) $\mathrm{Total}\mathrm{weight}\mathrm{of}\mathrm{water}=499g0.5\left(\mathrm{from}\mathrm{Polylysine}\mathrm{Solution}1a\right)+149g0.5\left(\mathrm{from}\mathrm{hydroxyacetone}\mathrm{solution}\right)+90g\left(\mathrm{from}\mathrm{additional}\mathrm{water}\right)+160g\left(\mathrm{from}\mathrm{chips}\mathrm{moisture}\right)=574g$$\mathrm{Total}\mathrm{weight}\mathrm{of}\mathrm{solids}=499g0.5\left(\mathrm{from}\mathrm{Polylysine}\mathrm{Solution}1a\right)+149g0.5\left(\mathrm{from}\mathrm{hydroxyacetone}\mathrm{solution}\right)+5400g\left(\mathrm{dry}\mathrm{chips}\right)=5724g$$\mathrm{Resulting}\mathrm{moisture}\mathrm{content}=574g/5724g=10.\%$

(33) This water content was checked and confirmed by a method performed analogously to EN 322:1993, resulting in a water content of 10%.

(34) Immediately after resination, 1.10 kg of the mixture were scattered into a 3030 cm mold and pre-pressed under ambient conditions (0.4 N/mm.sup.2). Subsequently, the pre-pressed chip mat thus obtained was removed from the mold, transferred into a hot press and pressed to a thickness of 16 mm to give a chipboard (temperature of the press plates 210 C., max pressure 4 N/mm.sup.2, press time as shown by press time factor in table 1 below) as a single-layered lignocellulosic composite (referred to as SLC 2a C (HA) in table 1).

Example 2b: Single-Layered Lignocellulosic Composite with Poly-L-Lysine of M.SUB.w .3690/Hydroxyacetone (for Comparison)

(35) The experiment of example 2a as described above was repeated. Different from example 2a, 499 g of Polylysine Solution 1b (for preparation see example 1b above) was used. From this experiment, a single-layered lignocellulosic composite (referred to as SLC 2b C (HA) in table 1) resulted.

Example 2c: Single-Layered Lignocellulosic Composite with Poly-L-Lysine of M.SUB.w.=6270/Hydroxyacetone (for Comparison)

(36) The experiment of example 2a as described above was repeated. Different from example 2a, 499 g of Polylysine Solution 1c (for preparation see example 1c above) was used. From this experiment, a single-layered lignocellulosic composite (referred to as SLC 2c C (HA) in table 1) resulted.

Example 3: Single-Layered Lignocellulosic Composite Poly L-Lysines/Hydroxyacetone (According to the Invention)

Example 3a: Single-Layered Lignocellulosic Composite with Poly-L-Lysine of M.SUB.w .2100/Hydroxyacetone (According to the Invention)

(37) 20.0 g sodium hydroxide was added to 499 g of Polylysine Solution 1a and stirred, to give a Polylysine Solution 1a-NaOH.

(38) In a mixer, 519 g of Polylysine solution 1a-NaOH was sprayed onto 5.56 kg (5.40 kg dry weight plus 160 g water from residual particle moisture content) of spruce core layer chips (moisture content 3.0 wt.-%) while mixing. Immediately, 149 g of a hydroxyacetone solution (50 wt.-% in water) was sprayed onto the mixture while mixing. Finally, 90 g of water was sprayed onto the mixture while mixing, to adjust the final moisture of the resinated chips. After addition of the water mixing was continued for 3 min.

(39) From the binder composition as prepared above, a single-layer lignocellulosic composite (referred to as SLC 3a I (HA) in table 1) was prepared as described in example 2a.

Example 3b: Single-Layered Lignocellulosic Composite with Poly-L-Lysine of M.SUB.w .3690/Hydroxyacetone (According to the Invention)

(40) The experiment of example 3a as described above was repeated. Different from example 3a, 499 g of Polylysine Solution 1b (for preparation see example 1b above) was used (instead of Polylysine Solution 1a). From this experiment, a single-layered lignocellulosic composite (referred to as SLC 3b C (HA) in table 1) resulted.

Example 3c: Single-Layered Lignocellulosic Composite with Poly-L-Lysine of M.SUB.w .6270/Hydroxyacetone (According to the Invention)

(41) The experiment of example 3a as described above was repeated. Different from example 3a, 499 g of Polylysine Solution 1c (for preparation see example 1c above) was used (instead of Polylysine Solution 1a). From this experiment, a single-layered lignocellulosic composite (referred to as SLC 3c C (HA) in table 1) resulted.

Example 4: Single-Layered Lignocellulosic Composite Polylysine/Dextrose (for Comparison)

(42) In a mixer, 499 g of Polylysine Solution 1a (50 wt.-% in water) was sprayed onto 5.56 kg (5.40 kg dry weight plus 160 g water from residual particle moisture content) of spruce core layer chips (moisture content 3.0 wt. %) while mixing. Immediately, 149 g of a dextrose solution (50 wt.-% in water) was sprayed onto the mixture while mixing. Finally, 90 g of water was sprayed onto the mixture while mixing to adjust the final moisture of the resinated chips. After addition of the water, mixing was continued for 3 min.

(43) From the binder composition as prepared above, a single-layer lignocellulosic composite (referred to as SLC 4 C (DEX) in table 1) was prepared as described in example 2.

Example 5: Single-Layered Lignocellulosic Composite Polylysine/Dextrose (According to the Invention)

(44) In a mixer, 519 g of Polylysine Solution 1a-NaOH (for preparation see example 3 above) was sprayed onto 5.56 kg (5.40 kg dry weight plus 160 g water from residual particle moisture content) of spruce core layer chips (moisture content 3.0 wt.-%) while mixing. Immediately, 149 g of a dextrose solution (50 wt.-% in water) was sprayed onto the mixture while mixing. Finally, 90 g of water was sprayed onto the mixture while mixing to adjust the final moisture of the resinated chips. After addition of the water, mixing was continued for 3 min.

(45) From the binder composition as prepared above, a single-layer lignocellulosic composite (referred to as SLC 5 I (DEX)) was prepared as described in example 2.

Example 6: Determining Parameters of Lignocellulosic Composites

(46) For the single-layer lignocellulosic composites prepared according to examples 2 to 5, certain board parameters were determined and are shown in table 1 below:

(47) TABLE-US-00001 TABLE 1 Parameters of lignocellulosic composites Press Internal NaOH amount time Board bond Lignocellulosic (solid/solid of factor density strength composite binder) [wt.-%] [s/mm] [kg/m.sup.3] [N/mm.sup.2] SLC 2a C (HA) 0 6 694 0.67 0 8 702 0.81 SLC 2b C (HA) 0 6 693 0.60 SLC 2c C (HA) 0 6 643 0.51 SLC 3a I (HA) 6 6 696 0.86 6 8 698 0.94 SLC 3b I (HA) 6 6 704 0.81 SLC 3c I (HA) 6 6 661 0.62 SLC 4 C (DEX) 0 8 No board No board 0 12 629 0.1 SLC 5 I (DEX) 6 8 651 0.12 6 12 671 0.32 No board in table 1 above means that the resulting material after pressing was not a sound chipboard and showed fractures, blows and/or bursts.

(48) From the data shown in table 1 above it can i.a. be seen that the presence of a basic substance having a pK.sub.B-value of 3 (NaOH) in the binder composition used in the process of the present invention results in an increased internal bond strength of a lignocellulosic composite produced in said process.