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CN-121975480-A - Modified pMDI adhesive, preparation method and application thereof in curing and forming of wooden boards

CN121975480ACN 121975480 ACN121975480 ACN 121975480ACN-121975480-A

Abstract

The invention relates to the technical field of adhesives, in particular to a modified pMDI adhesive, a preparation method and application thereof in curing and forming of wooden boards, comprising the following steps: and heating the pMDI under the nitrogen atmosphere, dripping the modified catalyst into the heated pMDI, obtaining a reaction system after the dripping is completed, keeping the reaction system at a constant temperature, adding the modified lignin into the cooled reaction system in batches, adding the phosphoric acid and the nano silicon dioxide dispersion liquid, and stirring to obtain the modified pMDI adhesive. According to the invention, the curing of the modified pMDI adhesive is accelerated through steam preheating, the activity of the modified catalyst can be activated in the high-temperature and high-humidity environment of the steam preheating, the crosslinking reaction rate of the modified pMDI adhesive is improved, the production efficiency is improved, the excessive brittleness and warp deformation of the plate are avoided, the excellent water resistance of the modified pMDI adhesive can obviously reduce the short-time moisture influence of the steam preheating, and the interface binding force of the adhesive and wood fibers is prevented from being reduced.

Inventors

  • HUANG TENGHUA
  • CHEN SONGWU
  • WANG LIULIU
  • LIU XIAOLING
  • YANG LONG

Assignees

  • 广西壮族自治区林业科学研究院

Dates

Publication Date
20260505
Application Date
20260401

Claims (10)

  1. 1. A method for preparing a modified pMDI adhesive comprising the steps of: s1, heating the pMDI to 40-45 ℃ in a nitrogen atmosphere, starting stirring, dripping the modified catalyst into the heated pMDI, and keeping constant temperature stirring at 40-45 ℃ for 1-1.5h after the dripping is completed to obtain a reaction system; s2, keeping the temperature of the reaction system at 40-45 ℃, stirring for 1-1.5h, and then reducing the temperature of the reaction system to 25-30 ℃; s3, adding modified lignin into the cooled reaction system for 3-4 times at intervals of 10-15min, adding phosphoric acid and nano silicon dioxide dispersion liquid, and stirring for 20-30min to obtain a modified pMDI adhesive; Wherein, the modified catalyst in the step S1 is prepared by the following steps of; s11, adding dibutyl tin dilaurate into absolute ethyl alcohol, uniformly stirring to obtain a mixed system, and dropwise adding glacial acetic acid to adjust the pH value of the mixed system to 5-6; S12, heating the adjusted mixed system to 40-45 ℃, adding the coupling agent modified liquid, and stirring for 1-1.5h at constant temperature to obtain a precursor catalyst; s13, vacuum drying the precursor catalyst at 60-65 ℃ for 1-1.5h, removing absolute ethyl alcohol, and cooling to room temperature to obtain the modified catalyst.
  2. 2. The method of preparing a modified pMDI adhesive according to claim 1, wherein the modified lignin in step S3 is prepared by: S21, adding lignin into absolute ethyl alcohol, uniformly dispersing, adding sodium hydroxide, stirring until the lignin is completely dissolved, and reacting for 1-2 hours at room temperature to obtain a lignin system; S22, heating the lignin system to 50-60 ℃, and dropwise adding propylene oxide to obtain precursor lignin; S23, drying the precursor lignin for 2-3 hours, removing absolute ethyl alcohol and redundant water, grinding, and then sieving with a 100-200 mesh filter screen to obtain the modified lignin.
  3. 3. The method of preparing a modified pMDI adhesive according to claim 1, wherein the coupling agent modification solution in step S12 is prepared by: stirring absolute ethyl alcohol and ethylene glycol at 20-25 ℃ for 15-20min to obtain a mixed solvent, adding a gamma-aminopropyl triethoxysilane coupling agent and a titanate coupling agent, and performing ultrasonic dispersion for 15-20min to obtain a coupling agent modified liquid.
  4. 4. The preparation method of the modified pMDI adhesive according to claim 1, wherein the mass ratio of pMDI to the modified catalyst, modified lignin, phosphoric acid and nano silica in the steps S1 and S3 is 100 (1-3) (5-10) (0.5-1) (2-5).
  5. 5. The preparation method of the modified pMDI adhesive according to claim 1, wherein the mass ratio of dibutyltin dilaurate to absolute ethyl alcohol, glacial acetic acid and coupling agent modification liquid in the steps S11 and S12 is 1 (10-20): 0.05-0.1): 2-4.
  6. 6. The preparation method of the modified pMDI adhesive according to claim 2, wherein the mass ratio of lignin to absolute ethyl alcohol, sodium hydroxide and propylene oxide in the steps S21 and S22 is 1 (15-25): 0.05-0.1): 0.1-0.2.
  7. 7. A method of preparing a modified pMDI adhesive according to claim 3 wherein the ratio of parts by mass of absolute ethanol to ethylene glycol in the preparation of the coupling agent modifying solution is (1.5-2.5), the ratio of parts by mass of gamma-aminopropyl triethoxysilane to titanate coupling agent is (1.5-2.5) 1, and the ratio of parts by mass of the mixed solvent to the sum of the two coupling agents is (1.04-0.08).
  8. 8. The method of preparing a modified pMDI adhesive according to claim 2 wherein the drop rate of the modifying catalyst in step S1 is 0.5-2.0g/min, the drop rate of glacial acetic acid in step S11 is 0.1-0.3g/min, and the drop rate of propylene oxide in step S22 is 0.3-1.0g/min.
  9. 9. A modified pMDI adhesive obtainable according to the preparation method of any of the preceding claims 1-8.
  10. 10. Use of a modified pMDI adhesive of claim 9 for steam pretreatment accelerated cure molding of wood boards.

Description

Modified pMDI adhesive, preparation method and application thereof in curing and forming of wooden boards Technical Field The invention relates to the technical field of adhesives, in particular to a modified pMDI adhesive, a preparation method and application thereof in curing and forming of wooden boards. Background The production of artificial board (fiber board, shaving board and oriented shaving board) mainly includes the main procedures of wood unit preparation, drying, sizing, paving and forming, hot-pressing and post-treatment, in all procedures, the hot-pressing is a technological process of making adhesive fully solidified under the condition of a certain time, pressure and temperature, and making smaller wood units firmly adhere together, and also is a process of implementing artificial board from "dividing" to "combining", and the hot-pressing process is the procedure with highest energy consumption in artificial board production process, and determines key and core of artificial board production efficiency, and the hot-pressing efficiency mainly depends on curing rate of adhesive used, so that the selection of adhesive is one of factors affecting hot-pressing process. The core of the technology is that the rapid and uniform temperature and humidity regulation and control of the inside of the wood plate are realized through steam preheating, the adaptive thermodynamic conditions are provided for the crosslinking and curing of the adhesive, the interface bonding state of wood fibers is optimized, and finally the aims of shortening the curing period and improving the molding quality are realized. However, the interface binding force between the adhesive and the wood fiber is still easy to be reduced due to short-time moisture contact caused by steam preheating, the conventional pMDI curing rate is low, and the rapid curing cannot be realized by fully utilizing the thermodynamic condition of the steam preheating, so that the plate molding efficiency and the interface binding quality are difficult to be compatible, and therefore, aiming at the problems in the background technology, a modified pMDI adhesive, a preparation method and application thereof in curing and molding of the wood plate are provided by a person skilled in the art. Disclosure of Invention Aiming at the defects of the prior art, the invention aims to provide a modified pMDI adhesive, a preparation method and application thereof in curing and forming of wood boards, so as to solve the problems in the prior art. In order to achieve the above purpose, the present invention provides the following technical solutions: a method of preparing a modified pMDI adhesive comprising the steps of: s1, heating the pMDI to 40-45 ℃ in a nitrogen atmosphere, starting stirring, dripping the modified catalyst into the heated pMDI, and keeping constant temperature stirring at 40-45 ℃ for 1-1.5h after the dripping is completed to obtain a reaction system; s2, keeping the temperature of the reaction system at 40-45 ℃, stirring for 1-1.5h, and then reducing the temperature of the reaction system to 25-30 ℃; s3, adding modified lignin into the cooled reaction system for 3-4 times at intervals of 10-15min, adding phosphoric acid and nano silicon dioxide dispersion liquid, and stirring for 20-30min to obtain a modified pMDI adhesive; Wherein, the modified catalyst in the step S1 is prepared by the following steps of; s11, adding dibutyl tin dilaurate into absolute ethyl alcohol, uniformly stirring to obtain a mixed system, and dropwise adding glacial acetic acid to adjust the pH value of the mixed system to 5-6; S12, heating the adjusted mixed system to 40-45 ℃, adding the coupling agent modified liquid, and stirring for 1-1.5h at constant temperature to obtain a precursor catalyst; s13, vacuum drying the precursor catalyst at 60-65 ℃ for 1-1.5h, removing absolute ethyl alcohol, and cooling to room temperature to obtain the modified catalyst. Further, the modified lignin in the step S3 is prepared by the following steps: S21, adding lignin into absolute ethyl alcohol, uniformly dispersing, adding sodium hydroxide, stirring until the lignin is completely dissolved, and reacting for 1-2 hours at room temperature to obtain a lignin system; S22, heating the lignin system to 50-60 ℃, and dropwise adding propylene oxide to obtain precursor lignin; S23, drying the precursor lignin for 2-3 hours, removing absolute ethyl alcohol and redundant water, grinding, and then sieving with a 100-200 mesh filter screen to obtain the modified lignin. Further, the coupling agent modified liquid in the step S12 is prepared by the following steps: stirring absolute ethyl alcohol and ethylene glycol at 20-25 ℃ for 15-20min to obtain a mixed solvent, adding a gamma-aminopropyl triethoxysilane coupling agent and a titanate coupling agent, and performing ultrasonic dispersion for 15-20min to obtain a coupling agent modified liquid. Further, the mass part ratio of pMDI to the modified