CALCIUM CARBONATE FOR PARTICLE BOARDS

Abstract

The present invention relates to a particle board, a process for manufacturing the particle board as well as the use of at least one particulate calcium carbonate-containing material as wood particle replacement in a particle board.

Claims

1. Particle board comprising a) a wood particle base layer having a first side and a reverse side, the wood particle base layer comprising i) wood particles in an amount from 60.0 to 97.5 parts by weight (d/d) and at least one particulate calcium carbonate-containing material in an amount from 2.5 to 40.0 parts by weight (d/d), based on the total dry weight of the wood particles and at least one particulate calcium carbonate-containing material of the wood particle base layer, and b) at least one wood particle surface layer being in contact with the first and/or reverse side of the wood particle base layer, the at least one wood particle surface layer comprising ii) wood particles in an amount from 70.0 to 97.5 parts by weight (d/d) and at least one particulate calcium carbonate-containing material in an amount from 2.5 to 30.0 parts by weight (d/d), based on the total dry weight of the wood particles and the at least one particulate calcium carbonate-containing material of the at least one wood particle surface layer, wherein the sum of the amount of the wood particles and the at least one particulate calcium carbonate-containing material in each of the wood particle base layer and the at least one wood particle surface layer is 100.0 parts by weight (d/d), based on the total dry weight of the wood particles and wherein the at least one particulate calcium carbonate-containing material in the layer is characterized in that the at least one particulate calcium carbonate-containing material has a weight median particle size d.sub.50 from 1.0 m to 1000.0 m.

2. Particle board according to claim 1, wherein the at least one particulate calcium carbonate-containing material is dolomite and/or at least one ground calcium carbonate (GCC), such as marble, chalk, limestone and/or mixtures thereof, and/or at least one precipitated calcium carbonate (PCC), preferably at least one ground calcium carbonate (GCC).

3. Particle board according to claim 1, wherein the at least one particulate calcium carbonate-containing material of the wood particle base layer and/or the at least one wood particle surface layer has a) a weight median particle size d.sub.50 from 15.0 m to 1 000.0 m and preferably from 30.0 m to 1 000.0 m, and/or b) a specific surface area of 5.0 m.sup.2/g, more preferably from 0.1 to 5.0 m.sup.2/g and most preferably of from 0.2 to 1.0 m.sup.2/g as measured by the BET nitrogen method, and/or c) a top cut d.sub.98 from 100.0 to 1 200.0 m, more preferably from 250.0 m to 1 100.0 m and most preferably from 500.0 m to 1 000.0 m.

4. Particle board according to claim 1, wherein the at least one particulate calcium carbonate-containing material of the wood particle base layer and/or the at least one wood particle surface layer consists of calcium carbonate in an amount of 10.0 wt.-%, preferably of 20.0 wt.-%, more preferably of 50.0 wt.-%, even more preferably of 90.0 wt.-%, more preferably of 95.0 wt.-% and most preferably of 97.0 wt.-%, based on the total dry weight of the calcium carbonate-containing material.

5. Particle board according to claim 1, wherein the wood particles of the wood particle base layer and the at least one wood particle surface layer originate from primary wood sources, such as softwood tree species, hardwood tree species, non-wood fibre plants, or secondary wood sources, such as recycled wood, and mixtures thereof.

6. Particle board according to claim 1, wherein the wood particle base layer comprises the wood particles in an amount from 70.0 to 95.0 parts by weight (d/d) and the at least one particulate calcium carbonate-containing material in an amount from 5.0 to 30.0 parts by weight (d/d), based on the total dry weight of the wood particles and the at least one particulate calcium carbonate-containing material of the wood particle base layer, and/or the at least one wood particle surface layer comprises the wood particles in an amount from 75.0 to 95.0 parts by weight (d/d) and at least one particulate calcium carbonate-containing material in an amount from 5.0 to 25.0 parts by weight (d/d), based on the total dry weight of the wood particles and the at least one particulate calcium carbonate-containing material of the at least one wood particle surface layer.

7. Particle board according to claim 1, wherein the wood particles of the wood particle base layer and of the at least one wood particle surface layer are the same or different; and/or the at least one particulate calcium carbonate-containing material of the wood particle base layer and of the at least one wood particle surface layer are the same or different, preferably the at least one particulate calcium carbonate-containing material of the wood particle base layer and of the at least one wood particle surface layer differ in their weight median particle size d.sub.50.

8. Particle board according to claim 1, wherein the wood particle base layer and/or the at least one wood particle surface layer comprise(s) at least one binder in an amount from 0.05 to 25.0 parts by weight (d/d), based on the total dry weight of the wood particles and the at least one particulate calcium carbonate-containing material, preferably the at least one binder is selected from the group comprising phenol-formaldehyde resin (PF), urea-formaldehyde resin (UF), melamine-formaldehyde resin (MF), melamine-urea-formaldehyde resin (MUF), urea-melamine-formaldehyde resin (UMF), urea-melamine-phenol-formaldehyde resin (UMPF), epoxy resin, methylene diphenyl diisocyanate resin (MDI), polyurethane resin (PU), resorcin resin, starch or carboxymethylcellulose and mixtures thereof, more preferably the at least one binder is selected from the group comprising phenol-formaldehyde resin (PF), urea-formaldehyde resin (UF), melamine-formaldehyde resin (MF), melamine-urea-formaldehyde resin (MUF), urea-melamine-formaldehyde resin (UMF), urea-melamine-phenol-formaldehyde resin (UMPF), epoxy resin, methylene diphenyl diisocyanate resin (MDI), polyurethane resin (PU) and mixtures thereof.

9. Particle board according to claim 1, wherein the wood particle base layer and/or the at least one wood particle surface layer further comprises at least one compound selected from the group comprising waxes, colorants, filler (differing from the at least one particulate calcium carbonate-containing material), dispersants, biocides, hardener and flame retardants.

10. Particle board according to claim 1, wherein the particle board is a three-layer particle board consisting of the wood particle base layer and two wood particle surface layers, preferably one wood particle surface layer is in contact with the first side of the wood particle base layer and the other wood particle surface layer is in contact with the reverse side of the wood particle base layer.

11. Particle board according to claim 1, wherein the particle board has a bending strength of 10 N/mm.sup.2, preferably from 10 to 25 N/mm.sup.2 and most preferably from 10 to 20 N/mm.sup.2; and/or a modulus of elasticity of 1 000 N/mm.sup.2, preferably from 1 600 to 3 500 N/mm.sup.2 and most preferably from 1 600 to 3 200 N/mm.sup.2; and/or internal bond strength of 0.30 N/mm.sup.2, more preferably from 0.35 to 1.0 N/mm.sup.2 and most preferably from 0.35 to 0.9 N/mm.sup.2; and/or a thickness swelling after 24 h water storage of 15%, more preferably from 4.0 to 15.0% and most preferably from 5.0 to 14%.

12. Process for manufacturing a particle board according to claim 1, the process comprising the steps of: a) providing wood particles in dry form, b) providing at least one particulate calcium carbonate-containing material, c) optionally providing at least one binder, d) combining the wood particles of step a) simultaneously or separately in any order with the at least one particulate calcium carbonate-containing material of step b) and the optional at least one binder and/or at least one compound of step c) to form a wood particle-calcium carbonate-containing material mixture which is suitable to form a wood particle base layer mat, e) combining the wood particles of step a) simultaneously or separately in any order with the at least one particulate calcium carbonate-containing material of step b) and the optional at least one binder and/or at least one compound of step c) to form a wood particle-calcium carbonate-containing material mixture which is suitable to form at least one wood particle surface layer mat, d) forming a multi-layer mat of the wood particle-calcium carbonate-containing material mixtures obtained in steps d) and e), and g) pressing the multi-layer mat of step f) in one or more steps into a solid particle board.

13. Process according to claim 12, wherein process steps d) and/or e) is/are carried out in that the wood particles of step a) are combined simultaneously with the at least one particulate calcium carbonate-containing material of step b) and the optional at least one binder and/or at least one compound of step c), or process steps d) and/or e) is/are carried out in that the wood particles of step a) are combined separately with the at least one particulate calcium carbonate-containing material of step b) and the optional at least one binder and/or at least one compound of step c).

14. Process according to claim 12, wherein the wood particles of step a) and/or the at least one particulate calcium carbonate-containing material of step b) is/are provided in dry form.

15. Use of at least one particulate calcium carbonate-containing material as wood particle replacement in a particle board, characterized in that the at least one particulate calcium carbonate-containing material has a weight median particle size d.sub.50 from 1.0 m to 1 000.0 m, preferably from 15.0 m to 1 000.0 m and most preferably from 30.0 m to 1 000.0 m.

Description

EXAMPLES

Measurement Methods

[0228] The following measurement methods are used to evaluate the parameters given in the examples and claims.

Particle Size Distribution (Mass % Particles with a Diameter <X) and Weight Median Diameter (d.sub.50) of a Particulate Calcium Carbonate-Containing Material

[0229] Weight median grain diameter and grain diameter mass distribution of a particulate calcium carbonate-containing material were determined via laser diffraction, i.e. the particle size is determined by measuring the intensity of light scattered as a laser beam passes through a dispersed particulate sample. The measurement was made with a Mastersizer 2000 or a Mastersizer 3000 of Malvern Instruments Ltd. (operating instrument software version 1.04). Alternatively, the measurement can be made with a HELOS particle-size-analyzer of Sympatec, Germany.

[0230] The method and the instruments are known to the skilled person and are commonly used to determine grain size of fillers and pigments. The measurement is carried out in an aqueous solution of 0.1 wt.-% Na.sub.4P.sub.2O.sub.7. The samples are dispersed using a high speed stirrer and supersonics.

Particle Size of Wood Particles

[0231] Particle sizes of wood particles were determined by mechanical vibration sieves and calculation of grading curves. Sieves with differing sieve meshes were setup as a tower starting with the smallest sieve mesh on the bottom and the largest sieve mesh on the top. The wood particles were placed on the top sieve and the sieve tower was fixed in a vibrating machine. The wood particles are thus subjected to fractioning by continuous shaking of the sieve tower within a timer period of 5 min. The balance between the amount of wood particles before being placed on the top sieve and after fractioning was considered as the through fraction in gram. Thus, for each sieve mesh width the percentage of the total amount of wood particles which is fractionized can be calculated. The mesh widths of the sieves were chosen among the following mesh widths (in mm): 0.063-0.1-0.315-0.5-1.0-1.6-2.0-3.15-4.0-6.3-8-12.

[0232] For each analysis at least seven mesh widths were chosen such that the size of the wood particles was sufficiently covered by the chosen mesh widths.

[0233] The particle length and thickness of the wood particles were determined by electron microscopic analysis, such as transmission electron microscope (TEM) or scanning electron microscope (SEM).

Wood Moisture Content

[0234] The wood moisture content is determined in accordance with DIN EN 322. The term equilibrium moisture has to be understood as moisture content of wood or wood based panel at which the wood neither gains nor loses moisture when surrounded by air at a given relative humidity and temperature (definition in wood hand book) The moisture content was determined after 7 days storage in a defined climate of: 65% relative humidity and 20 C. temperature.

BET Specific Surface Area of a Material

[0235] Throughout the present document, the specific surface area (in m.sup.2/g) of the mineral filler is determined using the BET method (using nitrogen as adsorbing gas), which is well known to the skilled man (ISO 9277:1995). The total surface area (in m.sup.2) of the mineral filler is then obtained by multiplication of the specific surface area and the mass (in g) of the mineral filler prior to treatment.

pH of an Aqueous Slurry

[0236] The pH of the aqueous slurry was measured using a standard pH-meter at room temperature, approximately 22 C.

Density

[0237] Density (or raw density) measurements were made in accordance with DIN EN 323.

Thickness Swelling

[0238] Thickness swelling measurements were made after 24 h water exposure in accordance with DIN EN 317.

Internal Bond Strength

[0239] Internal bond strength measurements were made in accordance with DIN EN 319.

Bending Strength and Modulus of Elasticity

[0240] Bending strength and modulus of elasticity were measured in accordance with DIN EN 310.

Solids Content

[0241] The solids content was measured using a Moisture Analyzer of Mettler-Toledo HP43. The method and the instrument are known to the skilled person.

d/d

[0242] The term d/d (dry/dry) refers to the dry amount based on the dry amount of the defined solid material.

Calcium Carbonate Content

[0243] For the measurement of the calcium carbonate content in a fibre board product, clean crucibles were placed in a preheated muffle furnace at 560 C. for approximately 1 hour. The crucibles were allowed to cool down in a desiccators for about 20 to 30 min and then weighed accurate to 0.0001 grams. Subsequently, the fibre board product was crushed down and accurately weighed into a crucible. The organic material was slowly burned off in that the crucible with the fibre board product was placed in the cooled muffle furnace (approximately 23-100 C.) and then the temperature was set to 560 C., while the opening on the top of the furnace was kept about three quarters closed to ensure a slow ashing. After approximately 1 hour, the opening on the top of the furnace was completely opened allowing more air in for faster ashing. The samples were left in the furnace until the ash in the crucibles turned white, indicating removal of all carbon from charring. After cooling in a desiccator, the crucible was weighed with the obtained residue. The values given herein are the average of two measurements of independently prepared samples.

[0244] 10.000 grams of the obtained residue were weighed in a flask/beaker and a small amount of demineralized water was added. If the calcium carbonate content of a particulate calcium carbonate-containing material was to be determined, 10.000 grams of the dry sample (dried at 110 C. for 5 hours in an oven) were weighed in a flask/beaker and a small amount of demineralized water was added. Then, 40 mL of hydrochloric acid (25% p.a.) were added to the respective sample and after the CO.sub.2 development stopped, the mixture was boiled for about 5 min. After cooling down, the mixture was filtered through a 0.8 m cellulose-acetate filter and washed thoroughly. Then the filtrate was quantitatively rinsed to a volumetric flask with distilled water and filled up to 1 000.0 ml at 20 C.

[0245] The thus obtained filtrate was then slowly titrated by pipetting 10.00 mL of the obtained filtrate (about 20 C.) into a Memotitrator-beaker and 1.0 g (0.2 g) of triethanolamine puris. and 3.0 g of MgSO.sub.47 H.sub.2O. The mixture was diluted with demineralized water up to 70 mL and then, just before the titration, 10.0 mL of 2N sodium hydroxide and 7 to 9 drops of a HHSNN-methanol solution (0.2 wt.-% of HHSNN (calconcarboxylic acid) in methanol) were added to the mixture. After the pre-dosing, the titrator stirred the mixture for 60 s and then the phototrode voltage was set to 900 to 1150 mV during titration. The calcium carbonate content was displayed in percent.

Materials

[0246] CaCO.sub.3 A: Omyacarb 1 AV, in the form of a powder (97.5 wt. % calcium carbonate content), is a marble form Avenza-Carrara (Italy) deposit and was obtained from Omya and has a weight median particle size d.sub.50 value of 1.7 m.

[0247] CaCO.sub.3 B: Omyacarb 40 GU, in the form of a powder (98 wt. % calcium carbonate content), is a marble from Avenza-Carrara (Italy) deposit and was obtained from Omya. Omyacarb 40 GU has a weight median particle size d.sub.50 value of 26 m.

[0248] CaCO.sub.3 C: Carolith 0.2-0.5 NP, in the form of a bulk material (98 wt. % calcium carbonate content), is a marble from Hausmening (Austria) deposit and was obtained from Omya. Carolith 0.2-0.5 NP has a weight median particle size d.sub.50 value of 340 m.

Test 1

[0249] The present test shows the influence of the replacement of wood particles with a calcium carbonate-containing material with different layouts with respect to the mean particle size and particle size distribution, on mechanical properties of a particle board.

a) Comparative Particle Board

[0250] The comparative particle-board (CE) is characterized in that the board only comprises wood particles, i.e. wood particles are not replaced by a calcium carbonate containing material.

[0251] The wood particles used were from industrial production and included a mixture of wood species (pine, spruce etc.) and had their origin in primary wood sources (round wood) or secondary wood sources (saw mill by products, wood chips, recycled wood etc.). The wood particles are classified in two groups: A) wood particles for the middle layer (ML) and B) wood particles for the surface layer (SL).

[0252] The middle layer (ML) particles had a particle size d.sub.50 of about 9 mm and a particle size d.sub.90 of about 23 mm.

[0253] The surface layer (SL) particles had a particle size d.sub.50 of about 7.5 mm and a particle size d.sub.90 of about 16 mm.

[0254] Group A particles and Group B particles were processed separately: [0255] A) The obtained wood particles were mixed in a blender with paddle mixer with 8.5 parts by weight (d/d), based on the total dry weight of wood particles, with an urea-formaldehyde binder (Kaurit 350 of BASF AG, Germany), together with 1.5 parts by weight (d/d), based on the total dry weight of wood particles of ammonium nitrate (40% solution) as hardener. [0256] B) The obtained wood particles were mixed in a blender with paddle mixer with 12 parts by weight (d/d), based on the total dry weight of wood particles, with an urea-formaldehyde binder (Kaurit 350 of BASF AG, Germany), together with 0.5 parts by weight (d/d), based on the total dry weight of wood particles of ammonium nitrate (40% solution) as hardener.

[0257] The resin impregnated wood particles were then formed into a mat consisting of three layers with a distribution of [0258] 1. Wood particles from group B) with spread in height of 25% of the total height of the spread wood particle mat [0259] 2. Wood particle from group A) with spread in a height of 50% of the total height of the spread wood particle mat [0260] 3. Wood particles from group B) with spread in height of 25% of the total height of the spread wood particle mat

[0261] The obtained mat was prepressed at room temperature. The prepressed mat was then hot pressed into a solid board of 17.5 mm thickness at a temperature of 220 C.2 C. with a pressing time factor of 15 s/mm. The obtained board was then sanded to a thickness of 17 mm.

b) Inventive Particle Boards

[0262] If not described otherwise, the inventive particle boards were prepared as described for the comparative particle board above.

[0263] In contrast to the comparative particle board, the inventive particle board is characterized in that fibres in an amount of 10 parts by weight (d/d), based on the total dry weight of wood particles in group A) of the comparative sample, respectively, or 10 parts by weight (d/d), based on the total dry weight of wood particles in group B) of the comparative sample, respectively, or 10 parts by weight (d/d), based on the total dry weight of wood particles in group A) and B) of the comparative sample, respectively, were replaced by calcium carbonate containing material in an amount of 10 parts by weight (d/d), based on the total dry weight of wood particles in group A) of the comparative sample, respectively, or 10 parts by weight (d/d), based on the total dry weight of wood particles in group B) of the comparative sample, respectively, or 10 parts by weight (d/d), based on the total dry weight of wood particles in group A) and B) of the comparative sample, respectively. Thus, the wood particle-calcium carbonate-containing material mixture used for preparing the inventive particle board consist of 90.0 parts by weight (d/d) of wood particles and 10 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group A), respectively, or the wood particle-calcium carbonate-containing material mixture used for preparing the inventive particle board consist of 90.0 parts by weight (d/d) of wood particles and 10 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group B), respectively, or the wood particle-calcium carbonate-containing material mixture used for preparing the inventive particle board consist of 90.0 parts by weight (d/d) of wood particles and 10 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in groups A) and B) based on the total dry weight of the wood particles and the at least one particulate calcium carbonate-containing material.

[0264] The details regarding the wood particle replacement content for the comparative and inventive particle boards are summarized in Table 1.

TABLE-US-00001 TABLE 1 Wood particle replacement content for the comparative particle board (CE) and inventive particle boards 1 to 7 (IE1 to IE7) IE 1 IE 2 IE 3 IE 4 IE 5 IE 6 IE 7 10 pbw 10 pbw 10 pbw 10 pbw 10 pbw 10 pbw 10 pbw WPR Reference WPR in SL WPR in ML WPR in SL WPR in ML WPR in SL WPR in ML in SL and ML (CE) by CaCO.sub.3 by CaCO.sub.3 by CaCO.sub.3 by CaCO.sub.3 by CaCO.sub.3 by CaCO.sub.3 by CaCO.sub.3 Wood Particles 100 95 95 95 95 95 95 90 [pbw] CaCO.sub.3 A [pbw] 5 5 CaCO.sub.3 B [pbw] 5 5 10 CaCO.sub.3 C [pbw] 5 5 100 100 100 100 100 100 100 100 SL: surface layer ML: middle layer WPR: wood particle replacement pbw: parts by weight This table reflects the overall replacement of wood particles with respect to the whole particle board

[0265] The results are outlined in FIGS. 1 to 4.

[0266] From FIGS. 1 to 4 it can be gathered that the replacement of wood particles by the calcium carbonate-containing material leads to particle boards having mechanical properties which are maintained or even improved compared to the comparative particle board. In particular, it is shown that a particle board in which 10 parts by weight (d/d) of wood particles were replaced by CaCO.sub.3 C shows clearly less thickness swelling than the comparative particle board. Furthermore, the equilibrium moisture of the particle boards is reduced when the amount of CaCO.sub.3 in the particle boards in increased which thus decreases the overall weight of the particle board. Furthermore the internal bond strength and the bending strength properties can be maintained compared to the comparative sample. All other parameters are the same as for the comparative sample.

Test 2

[0267] This test shows the influence of the replacement of wood particles with a calcium carbonate-containing material with respect to the mean particle size and particle size distribution, on mechanical properties of a particle board.

a) Comparative Particle Board

[0268] The comparative particle-board (CE) is characterized in that the board only comprises wood particles, i.e. wood particles are not replaced by a calcium carbonate containing material.

[0269] The wood particles used were from industrial production and included a mixture of wood species (pine, spruce etc.) and had their origin in primary wood sources (round wood) or secondary wood sources (saw mill by products, wood chips, recycled wood etc.). The wood particles are classified in two groups: A) wood particles for the middle layer and B) wood particles for the surface layer.

[0270] The middle layer (ML) particles had a particle size d.sub.50 of about 9 mm and a particle size d.sub.90 of about 23 mm.

[0271] The surface layer (SL) particles had a particle size d.sub.50 of about 7.5 mm and a particle size d.sub.90 of about 16 mm.

[0272] Group A particles and Group B particles were processed separately: [0273] A) The obtained wood particles were mixed in a blender with paddle mixer with 8.5 parts by weight (d/d), based on the total dry weight of wood particles, with an urea-formaldehyde binder (Kaurit 350 of BASF AG, Germany), together with 1.5 parts by weight (d/d), based on the total dry weight of wood particles of ammonium nitrate (40% solution) as hardener. [0274] B) The obtained wood particles were mixed in a blender with paddle mixer with 12 parts by weight (d/d), based on the total dry weight of wood particles, with an urea-formaldehyde binder (Kaurit 350 of BASF AG, Germany), together with 0.5 parts by weight (d/d), based on the total dry weight of wood particles of ammonium nitrate (40% solution) as hardener.

[0275] The resin impregnated wood particles were then formed into a mat consisting of three layers with a distribution of [0276] 1. Wood particles from group B) with spread in height of 25% of the total height of the spread wood particle mat [0277] 2. Wood particles from group A) with spread in a height of 50% of the total height of the spread wood particle mat [0278] 3. Wood particles from group B) with spread in height of 25% of the total height of the spread wood particle mat

[0279] The obtained mat was prepressed at room temperature. The prepressed mat was then hot pressed into a solid board of 17.5 mm thickness at a temperature of 220 C.2 C. with a pressing time factor of 15 s/mm. The obtained board was then sanded to a thickness of 17 mm.

b) Inventive Particle Boards

[0280] If not described otherwise, the inventive particle boards were prepared as described for the comparative particle board above.

[0281] In contrast to the comparative particle board, the inventive particle board is characterized in that fibres in an amount of 20 parts by weight (d/d), 30 parts by weight (d/d), 40 parts by weight (d/d), based on the total dry weight of wood particles in wood particle group A) of the comparative sample, respectively, or 20 parts by weight (d/d), 30 parts by weight (d/d), 40 parts by weight (d/d), based on the total dry weight of wood particles in wood particle group B) of the comparative sample, respectively, or 10 parts by weight (d/d), 20 parts by weight (d/d), 30 parts by weight (d/d), based on the total dry weight of wood particles in group A) and B) of the comparative sample, respectively, were replaced by calcium carbonate containing material in an amount of 20 parts by weight (d/d), 30 parts by weight (d/d), 40 parts by weight (d/d), based on the total dry weight of wood particles in group A) of the comparative sample, respectively, or 20 parts by weight (d/d), 30 parts by weight (d/d), 40 parts by weight (d/d), based on the total dry weight of wood particles in group B) of the comparative sample, respectively, or 10 parts by weight (d/d), 20 parts by weight (d/d), 30 parts by weight (d/d), based on the total dry weight of wood particles in group A) and B) of the comparative sample, respectively. Thus, the wood particle-calcium carbonate-containing material mixture used for preparing the inventive particle board consist of 80.0 parts by weight (d/d) of wood particles and 20 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group A), respectively, 70.0 parts by weight (d/d) of wood particles and 30 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group A), respectively, 60 parts by weight (d/d) of wood particles and 40 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group A), respectively, or the wood particle-calcium carbonate-containing material mixture used for preparing the inventive particle board consist of 80.0 parts by weight (d/d) of wood particles and 20 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group B), respectively, 70.0 parts by weight (d/d) of wood particles and 30 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group B), respectively, 60 parts by weight (d/d) of wood particles and 40 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group B) respectively, or 90.0 parts by weight (d/d) of wood particles and 10 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group A) and B), respectively, 80.0 parts by weight (d/d) of wood particles and 20 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group A) and B), respectively, 70 parts by weight (d/d) of wood particles and 30 parts by weight (d/d) of the calcium carbonate-containing material, based on the total dry weight of the wood particles in group A) and B), based on the total dry weight of the wood particles and the at least one particulate calcium carbonate-containing material.

[0282] The calcium carbonate used was calcium carbonate C.

[0283] The details regarding the wood particle replacement content for the comparative and inventive particle boards are summarized in Table 2.

TABLE-US-00002 TABLE 2 Wood particle replacement content for the comparative particle board (CE) and inventive particle boards 8 to 16 (IE8 to IE16) IE 8 IE 9 IE 10 IE 11 IE 12 IE 13 IE 14 IE 15 IE 16 20 pbw 30 pbw 40 pbw 20 pbw 30 pbw 40 pbw 10 pbw 20 pbw 30 pbw WPR in WPR in WPR in WPR in WPR in WPR in WPR in SL WPR in SL WPR in SL Reference SL by SL by SL by ML by ML by ML by and ML by and ML by and ML by (CE) CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 CaCO.sub.3 Wood Particles [pbw] 100 90 85 80 90 85 80 90 80 70 CaCO.sub.3 C [pbw] 10 15 20 10 15 20 10 20 30 100 100 100 100 100 100 100 100 100 100 SL: surface layer ML: middle layer WPR: wood particle replacement pbw: parts by weight This table reflects the overall replacement of wood particles with respect to the whole panel

[0284] The results for the density and the equilibrium moisture are outlined in FIGS. 5 and 6.

[0285] From the obtained results it can be gathered that the replacement of wood particles by the calcium carbonate-containing material leads to particle boards having mechanical properties which are maintained or even improved compared to the comparative sample. In particular, the equilibrium moisture of the particle boards is reduced when the amount of CaCO.sub.3 in the particle boards in increased which thus decreases the overall weight of the particle board. Furthermore, it is shown that a particle board in which 20 to 40 parts by weight (d/d) of wood particles of group B) were replaced by CaCO.sub.3 C shows comparable internal bond values compared to the comparative sample. Furthermore, the bending strength, modulus of elasticity as well as thickness swelling can be maintained compared to the comparative sample and are well within the classifications of the European standard requirements according to DIN EN 312. All other parameters are the same as for the comparative sample.

[0286] Table 3 outlines the theoretically achieved classifications following European standard DIN EN 312.

TABLE-US-00003 TABLE 3 Theoretically achieved classifications following European standard DIN EN 312 Sample P1 P2 P3 P4 P5 P6 Reference (CE) x x x x x x 10% WPR Group B) CaCO.sub.3 C x x x x x x 20% WPR Group B) CaCO.sub.3 C x x x 30% WPR Group B) CaCO.sub.3 C x x 40% WPR Group B) CaCO.sub.3 C 10% WPR Group A) CaCO.sub.3 C x x x x x x 20% WPR Group A) CaCO.sub.3 C x x x x 30% WPR Group A) CaCO.sub.3 C x x 40% WPR Group A) CaCO.sub.3 C x 10% WPR Group A) + B) CaCO.sub.3 C x x x 20% WPR Group A) + B) CaCO.sub.3 C x x 30% WPR Group A) + B) CaCO.sub.3 C Specification achieved: X = Yes; = No