BE1028461A1 - Dry gluing process for the manufacture of eco-efficient fiberboard or particleboard with a glossy or white color - Google Patents

Abstract

Process for the production of panels of fibers or particles, characterized in that all or part of the glues, additives such as pigments, whitening agents, etc., are added. in the form of a solid powder dispersed on a production line after the drying of the fibers and before the formation of the mat.

Description

Dry gluing process for the manufacture of eco-efficient fiberboard or particleboard in a glossy or white color. The introduction in 1956 of the "dry" process for the manufacture of fibreboard made it possible to increase the speed of production, but also to reduce the volume of waste water to be treated (Williams, 1995}. Nowadays, a line fiberboard production typically consists of 14 successive steps shown in the attached figure:

1. Storage of timber logs: logs can be stored in the open air or ensiled and watered,

2. Debarking of wood logs: the bark is removed by a drum or rotor debarker.

3. Chipping into chips: the debarked logs are cut into chips 5 to 25 mm thick.

4. Platelet storage: The platelets are stored in a silo.

5. Wafer cleaning: The wafers are sorted to eliminate sizes smaller than 2 mm and larger than 50 mm. Then they are washed in water, possibly hot.

6. Pre-heating the chips: Pre-heating to 50-60°C is an optional step whose objective is to soften the chips to facilitate the work of the endless screw which feeds the cooker. The addition of oxidizing or reducing chemical reagents can be carried out in order to reduce the energy consumption of the shredder, to modify the properties of the fibers, including the color and the whiteness of the fibers.

ci by reducing agents, such as sulphites and/or oxidizing agents such as peroxides... (Kibbiewhite et al, 1980; Allison, 1980; Pynnônen et al., 2004).

7. Cooking the wafers: The wafers are treated for 3 to 7 minutes in a pressure cooker at 10 bars of saturated steam at temperatures of 175 to 195°C. The parameters of the cooking step have a significant impact on the final color of the fibers.

8. Defibration: The cooked chips feed a defibrator under a pressure of 8 to 10 bars of saturated steam. An adjustable valve adjusts the pressure and fiber flow at the outlet.

9, Gluing in the blowline: The fibers and the saturated steam pass through a pipe 50 to 120 mm in diameter towards the dryer. The speed of the fibers of the order of 100 m/s and the strong turbulence make it possible to disperse the bundles of fibres. The resin, usually a urea-formaldehyde (UF) glue, and the additives (water repellents, flame retardants, dyes, catalysts, etc.) are injected in aqueous solutions and under pressure into the blowline. An important limitation for solutions to be injected is the viscosity of the liquid, generally less than 150 centipoise. In general, the dry matter present in the solution is at least 50% to limit the water supply.

10.Drying: First, the fibers pass through a flash dryer with a diameter of 1 to 3m, sometimes longer than 100m at a speed of about 30m/s and a temperature above 200 °C. After cycloning, the fibers are exposed to a temperature below 100°C favorable to the polymerization of the resin. A second cycle directs the fibers containing 8 to 12% humidity towards the former.

11. The formation of the mattress: The dry fibers pass through a sieve in order to eliminate the aggregates and form a homogeneous mattress on a conveyor belt whose speed will allow to fix the thickness and the final density of the panel. The company Dieffenbacher Gmbh obtained a patent relating to the addition of a part of the glue and the additives by sprinkling just before the formation of the mattress in order to reduce the need for energy for drying, but also to avoid the pre- hardening of the glue occurring during drying (EP2213431B1}.

12.Pre-pressing: the formed mat undergoes pre-pressing in order to reduce the amount of air between the fibers and to avoid dislocation of the fiber mat during hot pressing.

13. Hot pressing: The mattress is hot pressed between 175 and 190°C continuously or during a cycle of 1 to 5 minutes with a pressure between 0.5 and 10.0 megapascals.

14.The panel is then left to cool and harden.

15,Finish: The panel is finally sanded, cut, and possibly decorated (melamine coating, etc.).

Although wood is intrinsically a source of volatile organic compound emissions, it is undeniable that the use of resins, and the volatile monomers they contain, poses a serious environmental problem, but above all for human health. This is why resins without added formaldehyde, such as those based on phenols, methanodiphenyl diisocyanate,

polyethylene polyamines, etc., are also problematic. In addition, the high temperatures to which its resins are subjected during the traditional production process increase the vapor pressure of its highly reactive products. Finally, hot pressing induces the entrainment of other chemical compounds by water vapor (Wang et al, 2003).

More recently, in addition to toxicity, interest has focused on the entire life cycle of industrial productions. Current resins are all derived from petrochemicals and have difficulty meeting the expectations of sustainability and circular economy sought by our society (Netravali and Pastore, 2015).

During the 1990s, tinted MDF panels were developed and are now widely used in the fields of furniture, children's games, decoration, layout and construction.

In order to obtain more brilliant colors and with a view to developing a white panel in the mass, the bleaching of the fibers by chemical means, the addition of white pigment and brightening agents have been considered and patented (BASF, EF1817145B1). However, the range of colors that could be developed remains limited: light grey, vanilla, light blue... Indeed, the compounds present in the resins, together with the high pressures and/or temperatures required on the line, and particularly during the cooking/defibration, drying and hot pressing, bring a significant yellow component to the color of the panel (Nicewicz and Kowaluk, 2015). This explains why mass-dyed white has never been put on the market until now.

The present invention provides a solution to several industrial problems concerning panels of fibers and wood particles of the type OSB, MDF, LDF, HDF and other lignocellulosic composites. The invention allows: l. reduce energy consumption during panel production,

2. to reduce the emission of volatile organic compounds,

3. to increase the shine of the panels and to obtain brilliant colors or white in the mass,

4. to increase the durability of the product.

The invention consists in adding all or part of the glues, additives, pigments, bleaching agents, etc. in the form of a solid powder dispersed and distributed by suitable equipment. As described in Figure 2, the equipment incorporates a powder storage system (21), a powder transport and dosing system (22), and finally a powder blowing system (23) to incorporate them into the flow. fiber suspended in the air in the production line {4}. This equipment (16) can be incorporated on a production line from the drying stage (figure 2), to that of the formation of the mat (figure 3), and preferably at the exit of the fibers from the last drying cyclone (figure 4), The invention makes it possible to integrate natural or non-natural polymers, solid pigments and other additives into the glue, and overcomes the limit posed by the too high viscosity for the addition in liquid form to the blowline or to the formation of the mattress (as proposed in patent EP2213431B1). The incorporation of solid powder is carried out for a proportion of 2 to 50% (w/w) of dry fiber, and preferably from 5 to 20%. The invention makes it possible to reduce the quantity of water added to the [lux of fiber after defibration, which makes it possible to reduce the quantity of heat necessary for drying, as a corollary, the invention makes it possible to reduce the temperature of the drying gases for an equivalent fiber flow, the reduction is 5 to 60°C, and preferably 5 to 20°C. The use of glue at a low hardening temperature makes it possible to reduce the pressing temperature to temperatures of the order of 100 to 175° C., and preferably from 105 to 145° C. This temperature reduction reduces on the one hand the emission of volatile organic compounds, and on the other hand, reduces the yellowing of the panels formed, allowing the production of panels of brilliant colors or white in the mass.

Examples Wood fibers coming from a defibrator were mixed in a rotating drum, before forming a mattress, then hot pressed. 40X40 cm panels with a thickness of 9 mm were formed, then tested after 48 hours. Example 1: Composition of the mattress (&4W/W, in percentage of weight of dry matter on the weight of dry fiber): - Glue Milk proteins: 24 - Cross-linker CA1130 - Solenis: 4.4% - Pigments: dioxide of titanium: 4.2%

- Fiber humidity: 10.2% Pressing cycle: - Pressing time: 6 min. - Plate temperature: 140°C, - Maximum pressure/max pressing time. : 9.5 MPa/46 seconds. - Time to reach 100°C at the heart of the panel: 2 min 26 sec.

Tests on the finished panel: - Density (kg/m3): 942 + 23 - Bending (N/mm2)}: 34 + 3.3 - Humidity-24h {x}: 7.79 + 0.34 Example 2: Composition of the mattress (W/W, in percentage of weight of dry matter on the weight of dry fibre): - Glue Milk proteins: 8% - Cross-linker CA1130 - Solenis: 4.4% - Fiber humidity: 10.4 % Pressing cycle: - Pressing duration: 6 min 26 sec. - Tray temperature: 150°C. - Maximum pressure/max pressing time. : 9.1 MPa/106 seconds. - Time to reach 100°C at the heart of the panel: 2 min 40 sec.

Tests on the finished panel: - Density ({kg/m3}: 870 + 27 - Bending (N/mm2}: 35 + 5.1 - Humidity-24h (8): 8.02 + 0.56

Example 3: Composition of the mattress (2W/W, in percentage of weight of dry matter on the weight of dry fibre): - Glue Milk proteins: 15% - Sodium percarbonate catalyst: 0.4% - Fiber humidity: 10 .1% Pressing cycle: - Pressing time: 6 min 5 sec. - Plate temperature: 120°C, - Maximum pressure/max pressing time. : 7.1 MPa/45 seconds. - Time to reach 100°C at the heart of the panel: 2 min 07 sec.

Tests on the finished panel: - Density (kg/m3): 833 + 14 - Bending {N/mm2}: 32 x 2.8 - Humidity-2dh (4): 7.16 + 0.26 Example 4: Composition of mattress (#W/#W, in percentage of weight of dry matter on the weight of dry fiber): - Glue Soy protein: 15% - Sodium percarbonate catalyst: 0.6% - Linseed oil: 25 - Humidity of fibres: 9.3% Pressing cycle: - Pressing time: 7 min 30 sec. - Tray temperature: 105°C. - Maximum pressure/max pressing time. : 7.2 MPa/75 seconds. - Time to reach 100°C at the heart of the panel: 3 min 25 sec.

Tests on the finished panel:

- Density (kg/m3): 1002 + 33 - Elasticity (N/mm2): 3076 + 56 - Humidity-24h (2): 7.89 + 0.44 - Swelling-24h ({(#): 10.88 + 0.24 - CIELAB color: L*=75; ax=2.6; b*=7.5 Example 5: Composition of the mattress (3W/W, in percentage of weight of dry matter on the weight of dry fiber) : - Glue Milk proteins: 19% - Fiber humidity: 10.23 Pressing cycle: - Pressing time: 6 min 55 sec - Plate temperature: 115°C - Maximum pressure/max pressing time: 11.9 MPa/48 seconds - Time to reach 100°C at the core of the panel: 2 min 22 sec.

Tests on the finished panel: - Density (kg/m3): 1097 x 71 - Elasticity (N/mm2): 32204 246 - Humidity-24h (%): 10.44 + 5.56 - In summary, the invention consists adding all or part of the glues, additives, pigments, bleaching agents, etc. in the form of a solid powder dispersed and distributed by suitable equipment on a production line from the drying stage to that of the formation of the mattress, and preferentially at the exit of the fibers from the last drying cyclone. - The equipment includes a powder storage system, a powder transport and dosing system, and finally a powder blowing system to incorporate them into the airborne fiber flow.

- The incorporation of solid powder is carried out for a proportion of 2 to 50% (w/w) of dry fiber, and preferably from 5 to 20%, - The invention makes it possible to reduce the temperature of the drying gases for a flow equivalent fiber, the reduction is 5 to 60°C, and preferably 5 to 20°C.

- The use of glue with a low hardening temperature makes it possible to reduce the temperature of the press to temperatures of the order of 100 to 175°C, and preferably from 105 to 145°C.

- The previous characteristics combined allow, on the one hand, the production of panels of brilliant colors or white in the mass.

Scientific Bibliography Williams, W. The panel pioneers: an historical perspective. Wood Based Panels International 17 (September): 6 {1995}. Kibblewhite, E.F. Brookes, Diane and Allison, R.W. Effect of ozone on the fiber characteristics of thermomechanical pulp. Tappi. 63(4}):135 (1980). Allison, R.W. Low Energy Fulping Through Ozone Modification. Appita J. 34(3):197/-204 (1980).

Pynnônen T., Hiltunen E., Paltakari J., Laine J.E. and Paulapuro H. Good bonding for low-energy HT-CTMP by press drying, Pulp & Paper Canada T 57 105:3 (2004).

Wang, W. and Gardner, D.

Investigation of volatile organic compound press emissions during particleboard production.

For.

production

J., 49(3), 65-72.A. (1999). Netravali N. and Pastore C.

Mr.

Sustainable Composites: Fibers, Resins and Applications.

Destech Publications Incorporated, (2014). Nicewicz and Kowaluk, Changes of surface brightness of MDF boards.

Ann.

WULS - SGGW, For. and Wood Technol. 92, (2015)

Patents Dieffenbacher, EP2213431B1 BASF, EP16517/145B1

Claims (6)

Claims 1. Process for producing fiber or particle boards characterized in that all or part of the glues, additives such as pigments, bleaching agents, etc. are added. in the form of a solid powder dispersed on a production line after the fibers have dried and before the formation of the mat. 2. Process according to claim 1, in which the dispersion takes place between the formation of the drying paste and the formation of the mat, and preferably at the exit of the fibers from the last drying cyclone. 3. Method according to any one of the preceding claims, in which equipment is used integrating a powder storage system, a powder transport and dosing system, and finally a powder blowing system to incorporate them into the fiber flow. suspended in the air. 4. Method according to any one of the preceding claims, in which the incorporation of solid powder is carried out for a proportion of 2 to 505 {w/w) of dry fiber, and preferably from 5 to 208. 5, Process according to any one of the preceding claims, in which the temperature of the drying gases varies from 6. A method according to any preceding claim wherein! an adhesive with a low hardening temperature is used, making it possible to reduce the temperature of the press to temperatures of the order of 100 to 175°C, and preferably from 105 to 145°C. 7. A method according to any preceding claim wherein the glue used is a protein box glue, e.g. milk or soy protein. 8, Frocédé according to any of the preceding claims for the production of panels of brilliant colors or white in the mass. 9, a fiberboard obtained by a process of any preceding claim. 10, Panel according to the preceding claim characterized in that it is a mass-dyed white MDF panel.