Formaldehyde-Free MDF Board Two-Step Gluing for Deep Facing
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Solution Overview
Problem
Current formaldehyde-free adhesives for medium-high-density boards, such as MDI adhesives, face challenges like high molecular activity, fast reaction rates, water reactivity, and surface sticking issues, which limit their suitability for deep facing applications.
Innovation Solution
A two-step gluing method is employed, using a lignin adhesive for primary gluing followed by an MDI adhesive after waterproof treatment, along with surface spraying to control water content and improve dimensional stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If MDI adhesive is used for gluing, then formaldehyde-free requirement is met, but surface hardness increases excessively causing inability to meet deep facing requirements
Solution Approach 1:
The gluing process is divided into two distinct steps: first applying lignin adhesive for initial bonding, then applying MDI adhesive after waterproof treatment. This segmentation allows each adhesive to perform its specific function optimally - lignin provides initial glueing with better surface penetration, while MDI provides final bonding strength without causing excessive surface hardness that would prevent deep facing.
Solution Approach 2:
The patent uses a composite adhesive system combining lignin adhesive and MDI adhesive in a sequential application process. This composite approach leverages the complementary properties of both adhesives: lignin's ability to penetrate deep into wood fibers and MDI's high bonding strength, while avoiding the drawbacks of using MDI alone (excessive surface hardness) or formaldehyde-based adhesives (formaldehyde pollution).
2Object-affected harmful factors
If MDI adhesive is used, then formaldehyde-free production is achieved, but reaction speed becomes excessively fast causing manufacturing control difficulties
Solution Approach 1:
The gluing process is divided into two temporal stages: first step uses lignin adhesive with slower reaction characteristics for initial bonding, second step uses MDI adhesive after waterproof treatment for final bonding. This time-based segmentation allows control of reaction speed at each stage, preventing the excessively fast reaction of MDI from causing manufacturing difficulties while still achieving formaldehyde-free production.
Solution Approach 2:
Waterproof treatment is performed as a preliminary action before applying MDI adhesive. This preliminary step modifies the wood surface properties, creating a barrier that moderates the reaction speed of MDI adhesive, preventing excessively fast reaction while maintaining formaldehyde-free production benefits.
3Object-affected harmful factors
If MDI adhesive is used, then formaldehyde-free requirement is satisfied, but water reactivity increases causing sticking problems
Solution Approach 1:
The gluing process is segmented into two steps where lignin adhesive is applied first and allows the wood to absorb moisture and stabilize, then MDI adhesive is applied after waterproof treatment. This segmentation separates the functions: lignin handles initial glueing with better water compatibility, while MDI provides final water-resistant bonding without causing sticking problems.
Solution Approach 2:
Waterproof treatment acts as an intermediary step between the two gluing applications. It modifies the wood surface to be less reactive toward water, thereby reducing the water reactivity issue of MDI adhesive when applied subsequently, while maintaining formaldehyde-free production.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in a formaldehyde-free medium-high-density board capable of deep facing, with enhanced physical and chemical properties, expanded application fields, and compliance with green production standards.
Implementation Method 1
first performing primary gluing by using a lignin adhesive, and then performing secondary gluing by using an MDI adhesive
Implementation Method 2
performing secondary gluing by using an MDI adhesive after waterproof treatment
Implementation Method 3
hot pressing
Implementation Method 4
hot pressing
Implementation Method 5
spraying free water on a surface of a slab after the pre-pressing, so that a water content of fiber of the slab is 8% to 12%
Data Source
AI summary
The present invention relates to a formaldehyde-free medium-high-density board capable of meeting deep facing requirements, and a method for manufacturing same. The method includes: wood chipping, screening, cooking and softening, fiber separating, gluing, drying and sorting, paving, pre-pressing, hot pressing, cooling, sanding, and inspection and warehousing, where the gluing is two-step gluing, including: first performing gluing once by using a lignin adhesive, and then performing secondary gluing by using an MDI adhesive after waterproof treatment. According to the manufacturing method of the present invention, by using biomass adhesives and formaldehyde-free adhesives without adding additives such as a curing agent and an anti-mildew agent, formaldehyde pollution is eliminated from the source by using a two-step gluing method, so that production is formaldehyde-free, and the product is formaldehyde-free. Through the sequential control of the gluing process and the grasp of the gluing type and ratio, surface hardness of the product is improved, and the final product is capable of deep facing to reach 20 to 80 filaments.