CN103435755B - A kind of adhesive preparation method of straw making sheet - Google Patents

Abstract

The invention belongs to the technical field of adhesive preparation, and relates to a method for preparing an adhesive that can be used for making boards from crop straw, comprising dissolving diphenylmethane diisocyanate and polyether polyol NJ-330 in acetone, adding dibutyl dilaurate It is prepared by adding hydroxypropyl methacrylate as a catalyst, adding hydroxypropyl methacrylate for capping, adding fluorine-containing acrylate monomer and using azobisisobutyronitrile as an initiator for reaction. The adhesive prepared according to the method of the present invention does not contain free formaldehyde monomer; and the fluorine element is introduced into the isocyanate glue system, because of the lower polarizability of the fluorine atom, strong electronegativity, and smaller van der Waals radius, it can be combined with carbon Atoms combine to form C-F bonds with high bond energy. The surface energy of the main group of fluorocarbons - CF3 is extremely low, which makes the adhesive stable and has good water resistance and mechanical properties after film formation. It is compatible with surface treatment. The straws have a strong bonding effect, and can be made into artificial straw boards through the usual artificial fiberboard production process.

Description

A kind of adhesive preparation method of wheat straw board

technical field

The invention belongs to the technical field of adhesive preparation, and relates to the preparation of adhesive, in particular to an adhesive preparation method which can be used for board making from crop straw.

technical background

As a by-product of agricultural production, wheat straw was first used to make grass-reinforced clay panels for building houses. In 1905, Germany used wheat straw and other crop straw raw materials to mix adhesives for board making research; from 1930 to 1940, the United States also conducted research on using such raw materials to manufacture insulating boards. In the mid-1940s, Britain began to make paper grass boards with straw and wheat straw, and this technology was once transferred to more than 20 countries in the world. In 1970, the United Nations Industrial Development Organization held a seminar with 13 countries participating in non-wood wood-based panels. The production and utilization of wood-based panels has expanded to various straw materials. However, the real research and development of using wheat straw as raw material to produce wood-based panels and large-scale application in production and life has only developed rapidly in recent years.

J. Hague from the Biocomposites Research Center of the University of Wales in the United Kingdom used urea-formaldehyde resin glue, phenolic resin glue and isocyanate glue to conduct in-depth research on the performance of particleboards made of agricultural residues such as wheat straw. The results show that: if these residues are used The strength of the boards manufactured by the method of wood particle board is low, mainly because the waxy and siliceous layers on their surface affect the bonding performance of the adhesive, so the surface should be pretreated and the manufacturing process should be improved. At the same time, the shape of the shavings should also be paid attention to option to increase the internal bonding strength.

The well-known Bayer company in Germany and the former Bison company research center have also explored the field of annual plants as raw materials to produce particleboard. The research results show that although the wheat straw raw material is pretreated with alkali, the conventional urea-formaldehyde adhesive can be used to manufacture the wheat straw board, but the process is not easy to implement and the cost is high, which is not conducive to the general adoption and promotion; when using polyisocyanate glue (PMDI), the wheat straw board The performance of the wood-based panel is better, and the application of the internal release agent can solve the problem of sticking the board, and the process is easy to implement; at the same time, the research also shows that if 100% of the wheat straw is used as the raw material to make the wood-based panel, the amount of glue applied is larger than that of wood. 3%-5% for wood, and 2.5%-3% for wood, which increases the cost of glue.

Journal of Yangzhou University (Natural Science Edition), 2002,5(4):80-82, using discarded straw and phenolic resin as the main raw materials, and preparing composite environmental materials through carbonization of straw→ball milling mixing→press forming→sintering and other processes , the density and electrical conductivity of this material are comparable to wood ceramics, and can be used as magnetron sputtering carbon-based targets and brushes and other plates. However, the adhesive used in this process is phenolic resin, which contains free formaldehyde, which has certain harmful effects on human health.

Forest Products Industry, 2001, 28 (5): 36-38, 42, using MDI as adhesive to prepare wheat straw particleboard, and determine the reasonable amount of MDI applied through experiments. Compared with commonly used adhesives, MDI adhesives have the advantages of short pressurization time, good water resistance and aging resistance of the adhesive layer, but the disadvantage is high cost. MDI adhesives are prone to sticking to the board when producing particle boards, are toxic, and require metering and monitoring. The pumping system must not be contaminated by water.

Contents of the invention

In order to overcome the disadvantages of the above method, the invention discloses a method for preparing an adhesive that can be used for making boards from crop straws.

A method for preparing an adhesive for straw-based boards, comprising dissolving diphenylmethane diisocyanate (MDI) and polyether polyol NJ-330 in acetone, using dibutyltin dilaurate (T-12) as a catalyst , add hydroxypropyl methacrylate (HPMA) for capping, then add fluorine-containing acrylate monomer and use azobisisobutyronitrile (AIBN) as the initiator, the specific steps are as follows:

A. Dissolve diphenylmethane diisocyanate (MDI) and polyether polyol NJ-330 in acetone and heat to 65°C, wherein the amount of NJ-330 is 50-300% of the mass of MDI, preferably 150% The consumption of described acetone is 50～350% of MDI quality, preferred 150%;

B. Add dibutyltin dilaurate (T-12) to the system as a catalyst, the dosage is 0.1% to 0.35% of the mass of MDI, preferably 0.25%, heat up to 90°C and stir for 1 to 5 hours, preferably 3.5 hours ;

C. Cool the system obtained in step B to 50°C, add hydroxypropyl methacrylate (HPMA) for capping, and its dosage is 50-80% of the MDI mass, preferably 60%, after stirring for 3h, cool down to 35°C;

D. Add fluorine-containing acrylate monomer to the system obtained in step C, raise the temperature to 80°C for reaction, add azobisisobutyronitrile (AIBN) initiator, and react for 0.5 to 4.0 hours, preferably 3.0 hours; the fluorine-containing acrylate The amount of the monomer is 50-120% of the amount of HPMA, preferably 100%; the amount of the azobisisobutyronitrile is 0.1-0.4% of the total mass of the fluorine-containing monomer, preferably 0.3%, and the obtained product can be used in wheat straw Adhesives for board making.

The fluorine-containing acrylate monomer of the present invention can be tridecafluorooctyl methacrylate, dodecafluoroheptyl acrylate, dodecafluoroheptyl methacrylate, trifluoroethyl methacrylate, hexafluoroheptyl methacrylate, Either of fluorobutyl or hexafluorobutyl acrylate, preferably hexafluorobutyl methacrylate.

According to the adhesive prepared by the method of the present invention, after testing the water absorption and tensile strength of the adhesive sample after film formation, it is found that the synthesized adhesive has good stability, and has good water resistance and mechanical properties after film formation, which is comparable to The surface-treated straws have a strong bonding effect, and can be made into artificial straw boards through the usual artificial fiber board production process.

Diphenylmethane diisocyanate MDI used in the present invention was purchased from Shanghai Rongrong Chemical Co., Ltd.; polyether polyol (NJ-330, 3000g/mol) was purchased from Jurong Ningwu Chemical Co., Ltd.; Esters were purchased from Sinopharm Chemical Reagent Co., Ltd.; fluorine-containing monomers were purchased from Harbin Xuejia Fluorosilicon Chemical Co., Ltd.; other chemical reagents were purchased from Sinopharm Chemical Reagent Co., Ltd.

Beneficial effect

The special adhesive prepared by the present invention, which can be used for crop straw board making, does not contain free formaldehyde monomer; and the fluorine element is introduced into the isocyanate glue system, due to the structural characteristics of the fluorine atom, such as: the low polarizability of the fluorine atom , strong electronegativity, small van der Waals radius It can combine with carbon atoms to form a high-energy CF bond (540kJ/mol). The main group of fluorocarbons - CF ₃ has a surface energy of only 6mJ/m ² , which is the material with the lowest surface energy known so far. The synthesized adhesive has good stability, and has good water resistance and mechanical properties after film formation.

detailed description

The present invention will be described in detail below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1

Add 20g of diphenylmethane diisocyanate MDI, 10g of polyether polyol NJ-330 and 10g of acetone into a 500mL four-neck flask equipped with a stirrer, reflux condenser, thermometer and feeding device, stir well to dissolve it, Raise the temperature of the system to 65°C, add 0.02g of T-12 catalyst, raise the temperature of the system to 90°C, react for 1h and then cool down to 50°C, add 10g of hydroxypropyl methacrylate (HPMA) for capping, and stir for 3h , cooled to 35°C. Add 5 g of trifluorooctyl methacrylate monomer to the above system, raise the temperature to 80°C for reaction, add 0.05 g of azobisisobutyronitrile AIBN initiator, and react for 0.5 h. Obtain a special adhesive (MGJNJ-1) that can be used for crop straw board making.

Example 2

Add 20g of diphenylmethane diisocyanate MDI, 20g of polyether polyol NJ-330 and 20g of acetone into a 500mL four-necked bottle equipped with a stirrer, reflux condenser, thermometer and feeding device, stir fully to dissolve it, Raise the temperature of the system to 65°C, add 0.03g of T-12 catalyst, raise the temperature of the system to 90°C, react for 3 hours and then cool down to 50°C, add 12g of hydroxypropyl methacrylate (HPMA) for capping, and stir for 3 hours , lower the temperature to 35°C, add 7.5g of dodecafluoroheptyl acrylate monomer to the above system, raise the temperature to 80°C for reaction, add 0.15g of azobisisobutyronitrile AIBN initiator, and react for 1h. Obtain special adhesive (MGJNJ-2) which can be used for crop straw board making.

Example 3

Add 20g of diphenylmethane diisocyanate MDI, 30g of polyether polyol NJ-330 and 30g of acetone into a 500mL four-neck flask equipped with a stirrer, reflux condenser, thermometer and feeding device, stir fully to dissolve it, Raise the temperature of the system to 65°C, add 0.04g of T-12 catalyst, raise the temperature of the system to 90°C, react for 2.5h and then cool down to 50°C, add 14g of hydroxypropyl methacrylate (HPMA) for capping, and stir for 3h Afterwards, cool down to 35°C, add 10g of dodecafluoroheptyl methacrylate monomer to the above system, raise the temperature to 80°C for reaction, add 0.02g of azobisisobutyronitrile AIBN initiator, and react for 1.5h. Obtain a special adhesive (MGJNJ-3) that can be used to make boards from crop straw.

Example 4

In a 500mL four-necked bottle equipped with a stirrer, reflux condenser, thermometer and feeding device, add 20g of diphenylmethane diisocyanate MDI, 40g of polyether polyol NJ-330 and 45g of acetone, stir fully to dissolve, Raise the temperature of the system to 65°C, add 0.05g of T-12 catalyst, raise the temperature of the system to 90°C, react for 1.5h and then cool down to 50°C, add 15g of hydroxypropyl methacrylate (HPMA) for capping, and stir for 3h After that, the temperature was lowered to 35°C, 9g of trifluoroethyl methacrylate monomer was added to the above system, the temperature was raised to 80°C for reaction, 0.015g of azobisisobutyronitrile AIBN initiator was added, and the reaction was carried out for 2h. Obtain a special adhesive (MGJNJ-4) that can be used to make boards from crop straw.

Example 5

Add 20g of diphenylmethane diisocyanate MDI, 50g of polyether polyol NJ-330 and 50g of acetone into a 500mL four-neck flask equipped with a stirrer, reflux condenser, thermometer and feeding device, stir well to dissolve it, Raise the temperature of the system to 65°C, add 0.07g of T-12 catalyst, raise the temperature of the system to 90°C, react for 2 hours and then cool down to 50°C, add 13g of hydroxypropyl methacrylate (HPMA) for capping, and stir for 3 hours , lower the temperature to 35°C, add 12g of hexafluorobutyl methacrylate monomer to the above system, raise the temperature to 80°C for reaction, add 0.025g of azobisisobutyronitrile AIBN initiator, and react for 2.5h. A special adhesive (MGJNJ-5) that can be used for making boards from crop straw was obtained.

Example 6

Add 20g of diphenylmethane diisocyanate MDI, 60g of polyether polyol NJ-330 and 70g of acetone into a 500mL four-neck flask equipped with a stirrer, reflux condenser, thermometer and feeding device, stir well to dissolve, Raise the temperature of the system to 65°C, add 0.06g of T-12 catalyst, raise the temperature of the system to 90°C, react for 3 hours and then cool down to 50°C, add 16g of hydroxypropyl methacrylate (HPMA) for capping, and stir for 3 hours , lower the temperature to 35°C, add 10g of hexafluorobutyl acrylate monomer to the above system, raise the temperature to 80°C for reaction, add 0.04g of azobisisobutyronitrile AIBN initiator, and react for 3h. A special adhesive (MGJNJ-6) that can be used for making boards from crop straws was obtained.

Example 7

Add 20g of diphenylmethane diisocyanate MDI, 30g of polyether polyol NJ-330 and 70g of acetone into a 500mL four-neck flask equipped with a stirrer, reflux condenser, thermometer and feeding device, stir fully to dissolve it, Raise the temperature of the system to 65°C, add 0.05g of T-12 catalyst, raise the temperature of the system to 90°C, react for 3.5h and then cool down to 50°C, add 12g of hydroxypropyl methacrylate (HPMA) for capping, and stir for 3h Afterwards, the temperature was lowered to 35°C, 12g of hexafluorobutyl methacrylate monomer was added to the above system, the temperature was raised to 80°C for reaction, 0.036g of azobisisobutyronitrile AIBN initiator was added, and the reaction was carried out for 3h. A special adhesive (MGJNJ-7) that can be used for making boards from crop straws was obtained.

Example 8

Add 20g of diphenylmethane diisocyanate MDI, 40g of polyether polyol NJ-330 and 60g of acetone into a 500mL four-necked flask equipped with a stirrer, reflux condenser, thermometer and feeding device, stir fully to dissolve it, Raise the temperature of the system to 65°C, add 0.06g of T-12 catalyst, raise the temperature of the system to 90°C, react for 4 hours and then cool down to 50°C, add 12g of hydroxypropyl methacrylate (HPMA) for capping, and stir for 3 hours , lower the temperature to 35°C, add 10g of hexafluorobutyl methacrylate monomer to the above system, raise the temperature to 80°C for reaction, add 0.04g of azobisisobutyronitrile AIBN initiator, and react for 4h. Obtain a special adhesive (MGJNJ-8) that can be used for crop straw board making.

experimental method

The water absorption and tensile strength of the special adhesive sample after film formation were measured, and the results are shown in the table below.

sample Tensile strength (MPa) Water absorption (%) MGJNJ-1 4.01 12.67 MGJNJ-2 4.90 10.26 MGJNJ-3 4.98 9.98 MGJNJ-4 5.16 10.29 MGJNJ-5 5.23 8.67 MGJNJ-6 5.47 9.40 MGJNJ-7 6.36 7.59 MGJNJ-8 5.77 9.59

The results show that the adhesive obtained by the present invention has good stability, has good water resistance and mechanical properties after film formation, and has a strong bonding effect with the surface-treated straw, and can pass through conventional man-made fiberboards. Production process, made of artificial straw board.

The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by the description of the present invention, or directly or indirectly used in other related technical fields, shall be the same as The theory is included in the patent protection scope of the present invention.

Claims (8)

1. A method for preparing an adhesive for straw-based boards, comprising dissolving diphenylmethane diisocyanate MDI and polyether polyol NJ-330 in acetone, taking dibutyltin dilaurate T-12 as a catalyst, adding Hydroxypropyl methacrylate HPMA is capped, then add fluorine-containing acrylate monomer and use azobisisobutyronitrile AIBN as initiator, it is characterized in that, the specific steps are as follows: A. Dissolve diphenylmethane diisocyanate MDI and polyether polyol NJ-330 in acetone and heat to 65°C, wherein the amount of NJ-330 is 50-300% of the mass of MDI, and the amount of acetone 50~350% of MDI quality; B. Add dibutyltin dilaurate T-12 to the system as a catalyst, the dosage is 0.1%~0.35% of the mass of MDI, heat up to 90°C and stir for 1~5h; C. Cool the system obtained in step B to 50°C, add hydroxypropyl methacrylate HPMA to end-cap, the amount of which is 50-80% of the mass of MDI, after stirring for 3 hours, cool down to 35°C; D. Add fluorine-containing acrylate monomer to the system obtained in step C, heat up to 80°C for reaction, add azobisisobutyronitrile AIBN initiator, and react for 0.5~4.0h; the amount of the fluorine-containing acrylate monomer is HPMA The amount of azobisisobutyronitrile is 0.1% to 0.4% of the total mass of the fluorine-containing monomer, and the adhesive that can be used for straw board making is obtained. 2. the adhesive preparation method of straw board according to claim 1, is characterized in that, the consumption of NJ-330 described in step A is 150% of MDI quality, and the consumption of described acetone is 150% of MDI quality . 3. The method for preparing an adhesive for straw-based boards according to claim 1, wherein the amount of dibutyltin dilaurate T-12 in step B is 0.25% of the MDI mass, and the temperature is raised to 90°C Stir for 3.5h. 4. The method for preparing the adhesive of straw-based board according to claim 1, characterized in that, the amount of hydroxypropyl methacrylate HPMA described in step C is 60% of the MDI quality, and after stirring for 3 hours, the temperature is lowered to 35 ℃. 5. The method for preparing the adhesive of straw-based board according to claim 1, characterized in that, the azobisisobutyronitrile AIBN initiator described in step D reacts for 3.0 h; the fluorine-containing acrylate monomer The amount used is 100% of the amount of HPMA, and the amount of azobisisobutyronitrile is 0.3% of the total mass of the fluorine-containing monomers to prepare an adhesive that can be used for making boards from straw. 6. The method for preparing an adhesive for straw-based boards according to claim 1 or 5, wherein the fluorine-containing acrylate monomer can be trifluorooctyl methacrylate, dodecafluoroheptyl acrylate , dodecafluoroheptyl methacrylate, trifluoroethyl methacrylate, hexafluorobutyl methacrylate or hexafluorobutyl acrylate. 7. The method for preparing an adhesive for making boards from straw according to claim 1 or 5, characterized in that the fluorine-containing acrylate monomer is hexafluorobutyl methacrylate. 8. The adhesive for board made from straw prepared according to any one of the aforementioned methods.