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Method for synthesizing urea-formaldehyde resin containing micro free formaldehyde for E0-level artificial boards

A technology of free formaldehyde and urea-formaldehyde resin, used in aldehyde/ketone condensation polymer adhesives, adhesive types, adhesives, etc., can solve the problems of brittle adhesive layer, increase cost, low bonding strength, etc. degree, the effect of reducing formaldehyde

Active Publication Date: 2012-07-25
CHANGZHOU UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, these methods have not solved the problem of long-term release of formaldehyde during the use of wood-based panels due to resin structure factors.
In particular, the addition of a large number of modifiers greatly increases the cost of the product, making it difficult to market
[0004] Due to the structural characteristics of the urea-formaldehyde resin itself, the molecule contains a methylol group, which is hydrophilic and easy to hydrolyze under acidic conditions; the methylol group and -NH in the urea-formaldehyde resin molecule 2 It is easy to cross-link, so the urea-formaldehyde resin has problems such as internal stress generated after curing, which makes the adhesive layer brittle, easy to crack, poor in water resistance and aging resistance, easy to gel, and poor in stability.
Especially for low molar ratio urea-formaldehyde glue, due to the presence of free-NH 2 Multiple, crosslinkable groups -CH 2 The low number of OH causes more quality problems such as low bonding strength, water resistance, poor operability of plywood production process, etc.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0017] Add 100g of formaldehyde solution into the reaction kettle at one time, adjust the pH to 6.5~7.0 with 20% sodium hydroxide solution, heat to 50~53°C, add the first batch of urea 60g, raise the temperature to 85~88°C, and keep it warm for 15min; pH to 3.0~3.5, polymerize at 65~75°C; adjust pH to 6.5~7.0, add the second batch of urea 40g, acidify with formic acid to pH 4.0~4.4, stir at the same temperature for 15min; Three batches of urea 20g, stirred at 65~75°C for 5min; then adjusted the pH to 4.0~4.4 with formic acid, stirred at 65~75°C for 15min; Material, the product free formaldehyde content is less than 0.05% environment-friendly urea-formaldehyde resin glue.

[0018] The produced urea-formaldehyde resin has the following typical characteristics:

[0019] Solid content 62%

[0020] Viscosity 280 mPa·s

[0021] pH 7.8

[0022] Specific gravity 1.25g / ml

[0023] Free formaldehyde 0.05%

[0024] Storage period 80 days

Embodiment 2

[0026] Apply the urea-formaldehyde resin in Example 1 on the glued surface of the wood-based panel, the amount of glue applied is 280-300g / m2 (single side), and the two pieces of test materials are combined parallel and parallel to the grain, using 0.78-1.18MPa (8- 12kgf / cm2), after pre-pressing at room temperature (not lower than 20°C) for 0.5-1.0h, hot-pressing at a temperature of 100-110°C for 5min, and molding to obtain wood-based panels. Its main performance is as follows.

[0027] Moisture content 8%

[0028] Free formaldehyde emission 0.1mg / L

[0029] Bonding strength 0.8MPa

[0030] The quality index of the urea-formaldehyde resin produced by the present invention meets the requirements of the national standard GB / T 14732-2006, and reaches the level of imported products; the free formaldehyde content in the product is ≤0.05% (wt.), and the formaldehyde release amount after the product is applied is limited The value reaches the technical requirements of E0 grade woo...

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Abstract

The invention provides a method for synthesizing urea-formaldehyde resin containing micro free formaldehyde for E0-level artificial boards and relates to the technical field of urea-formaldehyde resin adhesives. The method has the following advantages: urea and a 37% formaldehyde aqueous solution are used as raw materials and the weak base-weak acid-weak base three-level pH quasi-steady-state control polymerization process is adopted to produce the urea-formaldehyde resin products; the content of free formaldehyde is less than 0.05%; the artificial board products prepared by using the resin have formaldehyde release not more than 0.1mg / L, meet GB / T14732-2006 and do no harm to users; and meanwhile, the resin meets the requirements in moisture content, bonding strength and the like and reaches the E0 level.

Description

technical field [0001] The invention relates to a method for synthesizing micro-free formaldehyde urea-formaldehyde resin for E0 grade wood-based panels, and relates to the technical field of urea-formaldehyde resin glue. It can be used to form industrial products with ultra-low free formaldehyde emission. The urea-formaldehyde resin adhesive produced by this method has the advantages of high bonding strength, fast curing, good operability, low cost, and abundant sources of raw materials. It is widely used in adhesive production. Background technique [0002] Urea-formaldehyde resin has high bonding strength, good cold water resistance, moderate hot water resistance, rapid curing, light color of the cured adhesive layer, will not pollute the surface of the glued board, and has good miscibility with water. It is easy to adjust the appropriate viscosity and concentration; in addition, urea-formaldehyde resin also has the advantages of high initial viscosity, good operability...

Claims

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Application Information

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IPC IPC(8): C08G12/12C09J161/24
Inventor 张跃严生虎刘建武沈介发
Owner CHANGZHOU UNIV
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