METHOD FOR THE PRODUCTION OF LIGNOCELLULOSE MATERIALS

Abstract

The present invention relates to a process for the production of lignocellulose materials via mixing A) of lignocellulose-containing particles or fibers, B) with organic isocyanate having at least two isocyanate groups or a mixture of these, and optionally with C) binders selected from the group of the phenol-formaldehyde resins, the aminoplastic resins, the protein-based binders, and other polymer-based binders, and mixtures of these, D) additives or a mixture of these, and E) plastics particles or a mixture of these, with the steps of: i.) scattering of the resultant mixture to give a mat, ii.) precompaction and heating of the mat during or after the precompaction process, and iii.) then hot pressing,
wherein, in the step ii.), operations are carried out at elevated temperature during and/or after the precompaction process, and a value of at least 4 cm is achieved for the resultant mat in the push-off test.

Claims

1-20. (canceled)

21. A process for the production of isocyanate-bound lignocellulose materials, the process comprising: A) lignocellulose-containing particles or fibers, B) organic isocyanate having at least two isocyanate groups or a mixture of these, C) optionally binders selected from the group of the phenol-formaldehyde resins, the aminoplastic resins, the protein-based binders, and other polymer-based binders, and mixtures of these, D) optionally additives or a mixture of these, and E) optionally plastics particles or a mixture of these, to form a mixture i.) scattering the resultant mixture to give a mat, ii.) precompacting and heating the mat during or after the precompaction process, and iii.) hot pressing, wherein, in the step ii.), operations are carried out at elevated temperature of from 55 to 90 C. during and/or after the precompaction process, the mat, at the juncture at which the final heating temperature is reached in the center of the mat, the mat has a height of from 27.5 to 60% of the height of the mat immediately after the scattering of the mat, and a value of at least 4 cm is achieved for the resultant mat in the push-off test.

22. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein from 65 to 99% by weight of one or more lignocellulose-containing particles or fibers (component A) are mixed with B) from 1 to 10% by weight of one or more organic isocyanates having at least two isocyanate groups, or a mixture of these (component B), C) from 0 to 5% by weight of binders selected from the group of the phenol-formaldehyde resins, the aminoplastic resins, the protein-based binders, and other polymer-based binders, and mixtures of these (component C), D) from 0 to 10% by weight of additives or a mixture of these (component D), E) from 0 to 10% by weight of plastics particles or a mixture of these (component E), in any desired sequence.

23. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein the isocyanate-containing lignocellulose materials are medium-density fiberboard, high-density fiberboard, particleboard, or oriented strand boards.

24. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein the isocyanate-containing lignocellulose materials are single- or multilayer particle- or fiberboard.

25. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein the isocyanate-containing lignocellulose materials are single- or multilayer particleboard.

26. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein the isocyanate-containing lignocellulose materials are three-layer particleboard.

27. The process for the production of isocyanate-bound lignocellulose materials according to claim 26, wherein the underside and/or upper side of the mat is brought into contact, before or during the step ii.), with water or an aqueous solution, emulsion, or suspension of a component F).

28. The process for the production of isocyanate-bound lignocellulose materials according to claim 26, wherein the underside and upper side are brought into contact with water or an aqueous solution, emulsion, or suspension of a component F).

29. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein, in step ii.), operations are carried out at elevated temperature of from 60 to 80 C. during and/or after the precompaction process.

30. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein, in step ii.), operations are carried out at elevated temperature of from 65 to 80 C. during and/or after the precompaction process.

31. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein in the step ii.) during and/or after the precompaction process the temperature in the center of the mat is at least 55 C.

32. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein in the step ii.) during and/or after the precompaction process the temperature in the center of the mat is at least 60 C.

33. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein in the step ii.) during and/or after the precompaction process the temperature in the center of the mat is at least 65 C.

34. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein in the step ii.) during and/or after the precompaction process the temperature in the center of the mat is at most 90 C.

35. The process for the production of isocyanate-bound lignocellu lose materials according to claim 21, wherein in the step ii.) during or after the precompaction of the mat, at the juncture at which the final heating temperature is achieved in the center of the mat, the height of the mat is from 30 to 50% of the height of the mat immediately after the scatiering of the mat.

36. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein in the step ii.) the heat is introduced within a period of 60 seconds to reach the temperature according to any of claim 27.

37. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein the density of the isocyanate-containing lignocellulose materials is from 300 to 1200 kg/m.sup.3.

38. Wall paneling, infill, shuttering, floors, partitions, shelving, or internal layers for doors comprising isocyanate-bound lignocellulose materials produced according to claim 21.

39. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein from 80 to 98.5% by weight of one or more lignocellulose-containing particles or fibers (component A) are mixed with B) from 1.5 to 5% by weight of one or more organic isocyanates having at least two isocyanate groups, or a mixture of these (component B), C) from 0 to 4% by weight of binders selected from the group of the phenol-formaldehyde resins, the aminoplastic resins, the protein-based binders, and other polymer-based binders, and mixtures of these (component C), D) from 0.5 to 8% by weight of additives or a mixture of these (component D), E) from 0 to 8% by weight of plastics particles or a mixture of these (component E), in any desired sequence.

40. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein from 85 to 98.25% by weight of one or more lignocellulose-containing particles or fibers (component A) are mixed with B) from 1.75 to 4% by weight of one or more organic isocyanates having at least two isocyanate groups, or a mixture of these (component B), C) from 0 to 3% by weight of binders selected from the group of the phenol-formaldehyde resins, the aminoplastic resins, the protein-based binders, and other polymer-based binders, and mixtures of these (component C), D) from 1 to 6% by weight of additives or a mixture of these (component D), E) from 0.5 to 6% by weight of plastics particles or a mixture of these (component E), in any desired sequence.

41. The process for the production of isocyanate-bound lignocellulose materials according to claim 21, wherein from 90 to 98% by weight of one or more lignocellulose-containing particles or fibers (component A) are mixed with B) from 2 to 3.5% by weight of one or more organic isocyanates having at least two isocyanate groups, or a mixture of these (component B), C) from 0 to 2% by weight of binders selected from the group of the phenol-formaldehyde resins, the aminoplastic resins, the protein-based binders, and other polymer-based binders, and mixtures of these (component C), D) from 2 to 5% by weight of additives or a mixture of these (component D), E) from 1 to 5% by weight of plastics particles or a mixture of these (component E), in any desired sequence.

Description

EXAMPLES

[0180] 1a) Material mixture for the outer layers (mixture 1)

[0181] 99 g of Lupranat M20 S (BASF Polyurethanes GmbH) and 225 g of water were added successively to 3392 g of outer layer particles (moisture content 2.8%) and mixed in a paddle mixer.

1b) Material mixture for the middle layers (mixture 2)

[0182] 99 g of Lupranat M20 S (BASF Polyurethanes GmbH) and 168 g of water were added successively to 3458 g of middle layer particles (moisture content 4.8%) and mixed in a paddle mixer.

2) Production of the Particle Mats

[0183] A mat composed of three layers was scattered into a scattering frame. The lowermost layer (outer layer) of mixture 1, the middle layer (core) of mixture 2, and the upper layer (outer layer) of mixture 1 in a mass ratio of 16.5:67:16.5 (total weight of the mat 2370 g). The scattered mat was precompressed in the scattering frame in a downstroke press at room temperature 60 seconds at a specific pressure of 10 bar. This precompressed the mat to a thickness of 40 mm. Subsequently, the scattering frame was removed. To monitor the temperature profile in the middle of the board (middle layer temperature), an optical sensor was introduced into a horizontal hole in the center of the middle layer in the narrow face of the mat. Subsequently, the mat was provided with separation fabrics on the upper and lower sides and compressed to a thickness d in an HLOP 170 high-frequency press from Hoefer Presstechnik GmbH and then heated by applying a high-frequency alternating field (27.12 MHz) to a middle layer temperature of T within a time t. The anode current was chosen such that the target temperature T was attained within the time t. After the attainment of the target temperature, the high-frequency press was opened. In this way, two or three identical particle mats were produced in each case. The first mat was used to conduct a push-off test (3.1); the second was used in order to produce a particleboard after automatic transfer into a hot press during which a gap was surmounted (3.2), and the third was produced and used in the cases where it was not possible to surmount that gap without damage. The third mat was then transferred into a hot press without automatic transfer, in order to produce a particleboard (3.2).

3.1 Push-Off Test

[0184] The mat was placed on a test table in such a way that one end of the mat was flushed with the table edge. The mat was then pushed at a constant advance rate of 15 cm/min over the table edge until gravity caused break-off of the mat. A ruler accompanying the material was used to measure the length of the projecting mat prior to break-off. The values were rounded upward or downward to the nearest cm.

3.2 Production of the Particleboards

[0185] The mat was pushed by means of an automatic transfer system with an advance rate of 9 m/min into an HLOP 350 hot press from Hoefer Presstechnik GmbH, In the course of this, the self-supporting mat had to surmount a gap of 7 cm. The stability of the mat was assessed according to the following criteria:

TABLE-US-00001 Mat assessment (gap) Criteria 1 Mat surmounts the gap and remains stable 2 Slight material loss when surmounting the gap, no deformation 3 Slight deformation of the mat and slight material loss when surmounting the gap 4 Mat is completely destroyed and cannot surmount the gap

[0186] The mats of assessment levels 1 and 2, after being transferred automatically into the hot press, were pressed at a temperature of 220 C. to a thickness of 16 mm (pressing time 123 s). The transverse tensile strengths of the three-layer particieboards thus produced were determined according to EN 319, and the densities to EN 1058.

[0187] The mats of assessment levels 3 and 4 were subsequently produced once again and pressed without automatic transfer (i.e. without guiding the mat across the 7 cm gap) in the hot press at a temperature of 220 C. to a thickness of 16 mm (pressing time 123 s). The transverse tensile strength of the three-layer particleboards thus produced was determined according to EN 319, and the densities according to EN 1058.

4. Test Results

[0188]

TABLE-US-00002 Test Reference.sup.a) 1 2 3 4 5 6 7 8 9 Thickness d [mm] 39 33 26 26 26 26 26 26 26 Time t [s] 90 83 90 65 47 39 36 19 42 Temperature T 81 68 74 74 77 76 77 55 90 [ C.] Mat assessment 4 4 2 1 1 1 1 1 3 1 (gap) Push-off test [cm] 1 2 4 6 6 >7 >7 >7 4 >7 Density of 673 689 690 682 693 663 655 646 650 682 particleboard [kg/m.sup.3] Transverse 0.53 0.59 0.72 0.70 0.66 0.58 0.62 0.45 0.69 0.22 tensile strength of particleboard [N/mm.sup.2] .sup.a)without compaction and heating in the high-frequency press