Improved use of MDI in engineered wood products

Abstract

A method for forming an engineered wood product, the method comprising grinding a MDI (methylene diphenyl diisocyanate) binder with water in a grinder to form a ground MDI dispersion. The ground MDI dispersion is fed into a wood production machine, where there is lignocellulosic material. The lignocellulosic material is bonded together by the ground MDI dispersion to form an engineered wood product.

Description

Technical Field

[0001] This invention generally relates to adhesives in wood products, and more particularly to improvements in the use of MDI in engineered wood products. Background Technology

[0002] Adhesives used to bond wood are employed in the manufacture of engineered wood products such as oriented strand board (OSB), wood chip plywood, particleboard, veneer, medium-density fiberboard (MDF), high-density fiberboard (HDF), and others. The cost of adhesives constitutes a very large portion of the cost of a process or product. Therefore, there is a strong desire to reduce the cost of adhesives or improve their effectiveness, which will reduce costs and / or consumption and improve the performance of wood products and wood production processes, including faster pressing times.

[0003] Different types of adhesives (i.e., glues, these terms are used interchangeably) all present problems. For example, adhesive formulations that include combinations of urea and formaldehyde structures or combinations of phenol and formaldehyde structures can lead to the release of formaldehyde, a regulated chemical designated as a "known human carcinogen" by the US National Toxicology Program.

[0004] Another adhesive is methylene diphenyl diisocyanate (MDI). MDI resin is used in the production of engineered wood products such as OSB, MDF, particleboard, and lightweight wood fiber insulation. MDI is a versatile and highly effective adhesive that provides a strong bond to wood particles or bundles because it reacts with the wood itself when exposed to intense heat. MDI resin typically forms a chemical bond, rather than the mechanical bond formed in the case of formaldehyde-based resins. MDI bonds by forming a diffuse interphase in which the resin spreads across the surface of the wood and penetrates into cracks, cell cavities, and even cell walls. Summary of the Invention

[0005] This invention aims to provide an improved system and method for using MDI resin in the manufacture of engineered wood products, as described in more detail below. MDI is ground into small particles, such as, but not limited to, less than 200 μm, alternatively less than 100 μm, alternatively less than 50 μm, alternatively less than 10 μm, or alternatively less than 5 μm, to form an MDI dispersion. Surprisingly, grinding has been found to significantly improve the performance and properties of both MDI and the finished engineered wood products, and to reduce process costs.

[0006] Therefore, according to embodiments of the present invention, a method for forming engineered wood products is provided, comprising: grinding an MDI (methylene diphenyl diisocyanate) binder together with water in a grinder to form a ground MDI dispersion; and feeding the ground MDI dispersion into a wood production machine, wherein the wood production machine contains lignocellulose material, wherein the lignocellulose material is mixed and bonded together by the ground MDI dispersion to form an engineered wood product.

[0007] According to an embodiment of the present invention, the MDI binder is ground together with one or more water additives.

[0008] According to an embodiment of the present invention, the MDI binder is milled together with one or more binder additives.

[0009] According to an embodiment of the present invention, the MDI binder is pre-ground in a pre-grinding mill before being ground in a grinding mill.

[0010] According to an embodiment of the invention, the MDI binder and / or water are preheated or precooled before grinding.

[0011] According to an embodiment of the invention, the amount of the milled MDI dispersion in the engineered wood product is approximately 0.5 to 25% by weight based on the final product weight.

[0012] According to an embodiment of the present invention, the controller controls the operating parameters of the method. The controller may be coupled to one or more sensors in a feedback control loop. Attached Figure Description

[0013] The invention will be more fully understood and appreciated from the following specific embodiments, in conjunction with the accompanying drawings, in which:

[0014] Figure 1 This is a simplified block diagram of a system for preparing MDI dispersions for use in the production of engineered wood products, according to a non-limiting embodiment of the present invention. Detailed Implementation

[0015] exist Figure 1In the illustrated embodiment, the MDI binder 10, together with other materials, is milled in a mill 30 (and optionally one or more other mills 32) to form a milled MDI dispersion 12. The milled MDI dispersion 12 may include, but is not limited to, water 14, one or more optional water additives 16 (such as, but not limited to, fire extinguishing agents or bactericides), one or more optional binder additives 18 (such as, but not limited to, fire extinguishing agents or bactericides), surfactants, and other additives 20. The additives may be in liquid or solid form and may be soluble or insoluble. One or more of these components may be pre-milled in one or more pre-mills 34 or added to water or resin prior to milling.

[0016] Therefore, the MDI binder 10 can be pre-ground together with the aforementioned additives. Alternatively, the additives can be pre-ground together with water. The additives can be water-soluble or binder-soluble, or they can be insoluble, and they can be liquid or solid (e.g., powder).

[0017] The milled MDI dispersion 12 is fed into the wood production machine 22, anywhere before the wood product 26 is formed. A non-limiting example is feeding into a mixer, rotary drum mixer, air line, or other type of mixing device, wherein the lignocellulosic material 24 is bound together by the milled MDI dispersion 12 to form the engineered wood product 26.

[0018] The term "engineered wood products" covers wood-containing materials, including, but not limited to, wood chip laminates, fiberboard, wood chip plywood, laminated particleboard, oriented strand board (OSB), medium density fiberboard (MDF), high density fiberboard (HDF), parallel particleboard, particleboard, plywood, veneer, wafer board, and others.

[0019] The term "lignocellulosic materials" encompasses wood chips used in the manufacture of engineered wood products, and includes, but is not limited to, wood bundles, wood particles, wood layers, wood fibers, wood chips, etc.

[0020] The term “MDI” or “MDI binder” (which may be used interchangeably) is defined as any resin made from methylene diphenyl diisocyanate, such as, but not limited to, 4,4'-methylene diphenyl diisocyanate, and including PMDI.

[0021] The term “grinding” (in all its variations) encompasses grinding, crushing, milling, breaking down, pulverizing, chopping, cutting, slicing, and other methods of reducing particle size.

[0022] The term "dispersion" encompasses suspensions, emulsions, dispersions, solutions, etc.

[0023] According to a non-limiting embodiment, the amount of milled MDI dispersion 12 in engineered wood product 26 may be, but is not limited to, about 1 to 10 by weight based on the weight of the final product.

[0024] Controller 28 can be coupled to grinders 30 and 32 (and pre-grinding mill 34) and to one or more sensors 36 (in a feedback control loop) for controlling each operating parameter of the process, such as, but not limited to, temperature, viscosity, density, flow rate, mass flow rate, chemical composition, etc. (sensor 36 is a sensor for these parameters). Controller 28 can receive feedback from other components on the production line (such as from presses) and can transmit operating commands to any component on the production line based on data from the grinding process or other processes.

[0025] Milling reduces the size of water and / or binder particles and also improves chemical properties, such as, but not limited to, improved reactivity of the dispersion compared to known reactivity in the prior art. This results in a dispersion with significantly better binding and performance properties, a much better distribution of MDI particles, and much more durable stability than simple mixing. Milling reduces the amount of water lost during the process, as water is trapped within or in the MDI particles, and produces an improved water-binder reaction. The dispersion is used shortly after its formation and throughout the entire useful life of the MDI. The MDI dispersion is broken down into smaller droplet particles. Water is trapped within the MDI droplets and will not react with water outside the droplets.

[0026] It should be noted that this invention covers water droplets in adhesives and adhesive droplets in water.

[0027] In systems using nozzles, the ground MDI mixture can flow to multiple nozzles and multiple mixers, ready for immediate use. The grinding equipment is external to the wood processing mixer. The ground MDI mixture is suitable for use with atomizers and is insensitive to blockages or other obstructions in the pipeline. The process is insensitive to changes in flow rate. The grinder can be cooled or heated to a desired temperature, which may differ from room temperature, MDI storage temperature, or MDI mixture temperature. Each parameter of the process can be controlled using sensors and feedback to accommodate varying conditions in the process. MDI spreads more uniformly and consistently in the wood production machine 22. There is better control over chemical properties such as the reactivity of MDI, and therefore better performance and utility.

[0028] The present invention reduces the amount of MDI required for each given area (by about 20% compared to the prior art, but not limited thereto), increases the utility of MDI, and controls its chemical properties, such as reactivity.

[0029] As used herein, the term "about" refers to a variation in a numerical quantity that can occur, for example, through: typical measurement and liquid handling procedures used in the real world for manufacturing concentrates or using solutions; through unintentional errors in these procedures; through differences in the manufacture, origin, or purity of the ingredients used to manufacture the composition or perform the methods described above; and so on. The term "about" also covers different amounts resulting from different equilibrium conditions of the composition produced from a particular initial mixture. Whether or not modified by the term "about," the claims include quantities equivalent to the stated quantities.

Claims

1. A method for forming engineered wood products, the method comprising: In a grinding mill, an MDI binder is ground together with water to form a ground MDI dispersion, wherein the MDI binder is a resin prepared from methylene diphenyl diisocyanate, and the ground MDI dispersion comprises MDI droplets and water trapped in the MDI droplets. as well as The milled MDI dispersion is fed into a wood production machine containing lignocellulosic material, wherein the lignocellulosic material is bonded together by the milled MDI dispersion to form an engineered wood product.

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

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

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

5. The method according to claim 1, wherein, The amount of the milled MDI dispersion in the engineered wood product is from 0.5% to 25% of the final product weight.

6. The method of claim 1, further comprising using a controller to control the operating parameters of the method.

7. The method of claim 6, further comprising using a controller to control operating parameters of the method, the controller being coupled to one or more sensors in a feedback control loop.

8. The method of claim 1, further comprising cooling the grinding mill to below room temperature.

9. The method according to claim 1, further comprising heating the grinding mill to above room temperature.

10. An engineered wood product, said engineered wood product being prepared by the method of claim 1.

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