IMPROVED USE OF MDI IN ENGINEERED WOOD PRODUCTS

Abstract

A method for forming an engineered wood product includes grinding an MDI (methylene diphenyl di-isocyanate) binder together with water in a grinder to form a ground MDI dispersion. The ground MDI dispersion is fed into a wood production machine in which are lignocellulosic materials. The lignocellulosic materials are bound together by the ground MDI dispersion to form an engineered wood product.

Claims

1. A method for forming an engineered wood product comprising: grinding an MDI (methylene diphenyl di-isocyanate) binder together with water in a grinder to form a ground MDI dispersion; and feeding said ground MDI dispersion into a wood production machine in which are lignocellulosic materials, wherein said lignocellulosic materials are bound together by said ground MDI dispersion to form an engineered wood product.

2. The method according to claim 1, wherein said MDI binder is ground with one or more water additives.

3. The method according to claim 1, wherein said MDI binder is ground with one or more binder additives.

4. The method according to claim 1, wherein said MDI binder is pre-ground in a pre-grinder before grinding in said grinder.

5. The method according to claim 1, wherein an amount of said ground MDI dispersion in said engineered wood product is about 0.5 to 25 wt % based on final product weight.

6. The method according to claim 1, further comprising using a controller to control an operational parameter of the method.

7. The method according to claim 6, further comprising using a controller to control an operational parameter of the method, said controller being coupled to one or more sensors in a feedback control loop.

8. The method according to claim 1, further comprising cooling said grinder to below room temperature.

9. The method according to claim 1, further comprising heating said grinder to above room temperature.

10. An engineered wood product made by the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawing in which:

[0014] FIG. 1 is a simplified block diagram of a system for preparing an MDI dispersion for use in production of engineered wood products, in accordance with a non-limiting embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0015] In the illustrated embodiment of FIG. 1, MDI binder 10 is ground together with other materials in a grinder 30 (and optionally one or more other grinders 32) to form ground MDI dispersion 12. The ground MDI dispersion 12 may include, without limitation, water 14, one or more optional water additives 16, such as but not limited to, fire extinguishing substances or biocides, one or more optional binder additives 18, such as but not limited to, fire extinguishing substances or biocides, surfactants, and other additives 20. Additives may be in liquid or solid form and may be soluble or non-soluble. One or more of these ingredients may be pre-ground in one or more pre-grinders 34 or added to the water or the resin before grounding.

[0016] Thus, the MDI binder 10 may be pre-ground together with the additives. Alternatively, the additives may be pre-ground with the water. The additives may be water soluble or binder soluble, or may not be soluble, and may be liquid or solid (e.g., powder).

[0017] The ground MDI dispersion 12 is fed into a wood production machine 22, in any place before the formation of the wood product 26. One non limiting example is feeding a blender, a rotary drum blender, a blow line or another type of blending device, in which lignocellulosic materials 24 are bound together by the ground MDI dispersion 12 to form an engineered wood product 26.

[0018] The term “engineered wood product” encompasses wood-containing materials, including, but not limited to, chipboard, fiber board, flake board, laminated-strand lumber, oriented strand board (OSB), medium density fiberboard (MDF), high density fiberboard (HDF), parallel-strand lumber, particle board, plywood, veneer, wafer board and others.

[0019] The term “lignocellulosic material” encompasses pieces of wood used to make engineered wood products and includes, but is not limited to, wood strands, wood particles, wood plies, wood fibers, wood chips and others.

[0020] The term “MDI” or “MDI binder” (used interchangeably) is defined as any resin prepared from methylene diphenyl di-isocyanate, such as but not limited to, 4, 4′-methylene diphenyl di-isocyanate, and includes PMDI.

[0021] The term “grind” encompasses (in all its inflections), grind, crush, mill, disintegrate, pulverize, chop, cut, slice and other methods of reducing size of particles.

[0022] The term “dispersion” encompasses suspension, emulsion, dispersion, solution and others.

[0023] According to a non-limiting embodiment, the amount of ground MDI dispersion 12 in the engineered wood product 26 may be, without limitation, about 1 to 10 wt % based on the final product weight.

[0024] A controller 28 may be coupled to the grinders 30 and 32 (and pre-grinders 34) and to one or more sensors 36 (in a feedback control loop) for controlling every operational parameter of the process, such as but not limited to, temperature, viscosity, density, flow rate, mass flow rate, chemical composition, and others (the sensors 36 being sensors for these parameters). The controller 28 can receive feedback from other elements along the production line, such as from the press, and can transmit operational commands to any element along the production line in accordance with data from the grinding or other process.

[0025] Grinding reduces size of water and/or binder particles and also improves the chemical properties, such as but not limited to, the reactivity of the dispersion in comparison with known reactivity of the prior art. This gives the dispersion much better bonding and performance properties, better distribution of MDI particles, and more long-lasting stability than merely mixing. Grinding reduces the amount of lost water in the process, since the water is trapped in the MDI particles or the MDI particles are trapped in the water, and creates an improved water-binder reaction. The dispersion is used shortly after its creation and well within the pot life of the MDI. The MDI dispersion is broken into small droplet particles. The water is trapped in the MDI droplets and will not react with water external to the droplets.

[0026] It is noted that the invention encompasses both water droplets in the binder and binder droplets in the water.

[0027] In systems that use nozzles, the ground MDI mixture can flow to multiple nozzles and to multiple blenders and is ready for immediate use. The grinding apparatus is external to the wood processing blenders. The ground MDI mixture is suitable for use with atomizers and is not sensitive to blockages or other occlusions in the line. The process is not sensitive to changes in flow rates. The grinders can be cooled or heated to a desired temperature which may be different from room temperature, MDI storage temperature or MDI mixture temperature. Every parameter of the process can be controlled with sensors and feedback to adapt to changing conditions in the process. The MDI spreads more evenly and uniformly in the wood production machine 22. There is better control on the chemical properties such as reactivity of the MDI and thus there is better performance and effectiveness.

[0028] The invention decreases the amount of MDI needed per given area (without limitation, a decrease of about 20% in comparison with the prior art) and increases the effectivity of the MDI and controls its chemical properties such as reactivity.

[0029] The term “about,” as used herein, refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or use solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients used to make the compositions or carry out the methods; and the like. The term “about” also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term “about”, the claims include equivalents to the quantities.