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Method for preparing post-crosslinking modified urea-formaldehyde resin adhesive

A cross-linking modification and cross-linking agent technology, which is applied in the wood processing industry, can solve the problems of reducing formaldehyde emission, reducing bonding strength, and limiting the application range of urea-formaldehyde adhesives.

Inactive Publication Date: 2008-11-26
BEIJING UNIV OF CHEM TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] Traditional modified urea-formaldehyde adhesives are mainly researched around reducing the free formaldehyde content in the resin and increasing the bonding strength. These two indicators are contradictory. While reducing the amount of formaldehyde released, it is often at the expense of reducing other properties, especially the bonding strength. Thus limiting the scope of application of urea-formaldehyde adhesives

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0016] Embodiment 1: (formaldehyde, urea, cross-linking agent parts said in the embodiment are all parts by mass)

[0017] 1 Add 80 parts of 40% formaldehyde solution by mass to the reactor, stir, and add sodium hydroxide to adjust the pH value of the solution to 9.2;

[0018] 2 Add 41 parts of urea for the first time, and raise the temperature to 90°C;

[0019] 3 Constant temperature reaction for 20 minutes;

[0020] 4 add formic acid to adjust the pH value of the solution to 4.3;

[0021] 5. Add 21 parts of urea for the second time;

[0022] 6 Add 15 parts of glyoxal, and react at a constant temperature of 105°C for 40 minutes;

[0023] 7 Adjust the pH of the solution to 7.2 with sodium hydroxide.

[0024] The performance comparison between the prepared resin glue and GB / T 14732-93NQTL UF glue is shown in Table 1.

[0025] Table 1 Performance comparison between urea-glyoxal resin glue and GB / T 14732-93NQTL UF glue

[0026] indicators

Embodiment 2

[0028] 1 Add 85 parts of 40% formaldehyde solution by mass to the reactor, stir, and adjust the pH value of the solution to 10.0 with sodium hydroxide;

[0029] 2 Add 37 parts of urea for the first time and heat up to 88°C;

[0030] 3 constant temperature reaction for 18 minutes;

[0031] 4 formic acid to adjust the pH value of the solution to 4;

[0032] 5. Add 24 parts of urea for the second time;

[0033] 6 Add 25 parts of dialdehyde starch and react at a constant temperature of 100°C for 35 minutes;

[0034] 7 sodium hydroxide to adjust the pH of the solution to 7.6.

[0035] The performance comparison between the prepared resin glue and GB / T 14732-93NQTL UF glue is shown in Table 2.

[0036] Table 2 Performance comparison between urea-dialdehyde starch resin glue and GB / T 14732-93NQTL UF glue

[0037] indicators

Embodiment 3

[0039] 1. Add 90 parts of 37% formaldehyde solution into the reactor, stir, and adjust the pH value of the solution to 8 with sodium hydroxide;

[0040] 2 Add 47 parts of urea for the first time and heat up to 86°C;

[0041] 3 constant temperature reaction for 17 minutes;

[0042] 4 formic acid to adjust the pH value of the solution to 6;

[0043] 5. Add 14 parts of urea for the second time;

[0044] 6. Add 0.8 parts of polyvinyl alcohol and react at a constant temperature of 87°C for 15 minutes;

[0045] 7 sodium hydroxide to adjust the pH of the solution to 7.6.

[0046] The performance comparison between the prepared resin glue and GB / T 14732-93NQTL UF glue is shown in Table 3.

[0047] Table 3 Performance comparison between polyvinyl alcohol modified resin glue and GB / T 14732-93NQTL UF glue

[0048] indicators

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Abstract

The invention relates to a preparation method for post-crosslinking modified urea-formaldehyde resin, which is characterized in that under low molar ratio of formaldehyde / carbamide, a cross linker is added in the addition stage or the condensation stage. The method of the invention guarantees the excellent bonding strength of the resin under low free formaldehyde content and low formaldehyde release amount. By detecting, the modified urea-formaldehyde resin prepared by the invention has less than 0.1 percent of free formaldehyde content, less than 1mg / L of formaldehyde release amount of plywood and larger than 2.8MPa of bonding strength and the comprehensive performance is obviously better than the existing urea-formaldehyde resin adhesive.

Description

Technical field: [0001] The invention relates to a preparation method of a urea-formaldehyde resin adhesive, and more particularly relates to a preparation method of a post-crosslinking modified urea-formaldehyde resin adhesive. The prepared adhesive is especially used in the wood processing industry. Background technique: [0002] Urea-formaldehyde resin adhesive is formed by condensation of urea and formaldehyde. Urea-formaldehyde resin adhesive has the advantages of low production cost, sufficient source of raw materials, simple production process, convenient use, colorless adhesive layer after curing, excellent bonding performance, good moisture resistance, and a wide range of uses. So far, in the wood-based panel industry, the cost and price of urea-formaldehyde resin adhesives are unmatched by other adhesives, and its status and function cannot be replaced by other adhesives. [0003] Urea-formaldehyde (UF) resin adhesives still have deficiencies. One of the outstandi...

Claims

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Application Information

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IPC IPC(8): C08G12/40C08K5/3492C08B31/00C08F116/06C08K5/29C08K5/07
Inventor 王海侨喻湘宁李效玉
Owner BEIJING UNIV OF CHEM TECH
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