CN111019597B - Vegetable protein-based adhesive and preparation method and application thereof - Google Patents

Abstract

The invention relates to the technical field of adhesives, and discloses a vegetable protein-based adhesive and a preparation method and application thereof. The preparation method comprises: quaternization modification of oxidized defatted vegetable protein meal: taking oxidized defatted vegetable protein meal, 2,3-glycidyl trimethyl ammonium chloride and water and sealing in a container, and carrying out quaternization modification Preparation of polycatechol: take catechol, catalyst and buffer solution in a container, seal and carry out polymerization reaction; prepolymerization reaction: oxidized defatted vegetable protein meal modified by quaternization, polycatechol, The vegetable protein-based adhesive is obtained by prepolymerization of pectin and water. The aldehyde group, quaternary ammonium ion and phenyl group in the vegetable protein-based adhesive can produce phenolic condensation reaction, electrostatic and Hydrophobic effect, to achieve the ultimate purpose of enhancing the bonding strength of plywood.

Description

A kind of vegetable protein-based adhesive and its preparation method and application

technical field

The invention relates to the technical field of adhesives, in particular to a vegetable protein-based adhesive and a preparation method and application thereof.

Background technique

Due to the limited reserves of high-quality wood in my country, plywood and other man-made boards have become the main processing materials for construction, home improvement and transportation industries. Adhesive is one of the indispensable raw materials for the preparation of plywood. Due to the incomplete polymerization of aldehyde small molecules, traditional phenolic and urea-formaldehyde resin adhesives can slowly release formaldehyde and other carcinogenic toxic and harmful gases during the preparation and use process, which poses a great threat to the health of production and users. At present, bio-based adhesives that do not contain small molecular aldehydes such as formaldehyde have become a new development direction in the field of adhesives. During the hot pressing process, due to the hydrogen bonding between protein and natural macromolecules such as cellulose and lignin on the inner and outer surfaces of the veneer, vegetable protein has gradually become the main raw material for the preparation of natural formaldehyde-free adhesives. However, compared with the fossil-based aldehyde resin adhesive itself and the complex and firm cross-linked network system formed by phenolic polymerization, hydrogen bonding and electrostatics formed with the veneer, non-covalent forces such as hydrogen bonding derived from vegetable protein Still weak, its bond strength is still low.

In order to improve the bonding strength, some researchers recently added dopamine-modified polypropylene fibers (Chinese invention patent: a modified vegetable protein adhesive and its preparation method, application number 201810209225.6), sodium hypochlorite (Chinese invention patent: a Soybean protein adhesive for modified materials and preparation method thereof, application number 201611207452.2), thiourea (Chinese invention patent: a vegetable protein adhesive and preparation method and application thereof, application number 201710979162.8) and polyisocyanate (Chinese invention Patent: A vegetable protein adhesive and a method for preparing wood-based panels, application number 201910064132.3) as a reinforcing agent, curing agent, activator and crosslinking agent for vegetable protein-based adhesives. Although these methods have improved the bonding strength of vegetable protein-based adhesives to a certain extent, the introduction of unnatural biomass into the bio-based system may generate new toxic and harmful gases during hot pressing and subsequent use. Will affect the recycling efficiency of plywood. Therefore, in order to overcome the defects caused by non-biomass-based reinforcing agents, curing agents, activators or cross-linking agents, the use of natural biomass or modified biomass to enhance the bonding strength has become a solution in the field of vegetable protein-based adhesives. one of the technical bottlenecks.

SUMMARY OF THE INVENTION

The object of the present invention is to solve the problem of the prior art, and a kind of preparation method of vegetable protein-based adhesive is provided

Another object of the present invention is to provide the vegetable protein-based adhesive prepared by the above method.

Another object of the present invention is to provide the application of the above vegetable protein-based adhesive.

The object of the present invention is achieved through the following technical solutions:

A preparation method of a vegetable protein-based adhesive, comprising:

Quaternization modification of oxidized defatted vegetable protein meal:

Oxidized defatted vegetable protein meal, 2,3-epoxypropyltrimethylammonium chloride and water are sealed in a container, and subjected to quaternization modification reaction; Ammonium modified oxidized defatted vegetable protein meal;

Preparation of polycatechol:

The catechol, the catalyst and the buffer are taken in a container, and the polymerization is carried out after sealing; after the polymerization is completed, the solid catalyst is removed by centrifugation; the supernatant is collected for purification treatment, and then dried to obtain polycatechol;

Prepolymerization:

The vegetable protein-based adhesive is obtained by prepolymerizing the quaternized modified oxidized defatted vegetable protein meal, polycatechol, pectin and water.

Preferably, the oxidative defatted vegetable protein meal is prepared by the following steps:

The defatted vegetable protein meal, NaIO ₄ and NaCl are mixed in water, then sealed and shaded to carry out oxidation reaction; after the oxidation is completed, filter, wash until the pH value of the filtrate reaches 6.5 to 7.0, and collect the solid for drying to obtain oxidized defatted vegetable protein. meal.

Preferably, the mass content of the defatted vegetable protein meal in the water ranges from 2 to 5%, respectively, and the added mass of NaIO and NaCl is 2 to 3 and ₄ to 5 times the mass of the defatted vegetable protein meal, respectively; oxidation temperature, oxidation time and magnetic force The stirring speed ranges were 40-60° C., 12-24 h and 300-500 rpm, respectively.

Preferably, in the quaternization modification of the oxidatively defatted vegetable protein meal, the mass content of the oxidatively defatted vegetable protein meal in water is 5-10%, and the mass of 2,3-epoxypropyltrimethylammonium chloride is 0.5% of the oxidatively defatted vegetable protein meal. 1/4-1/3 of the quality of vegetable protein meal; modification temperature, modification time and magnetic stirring speed range are 60-80°C, 30-40h and 200-400rpm respectively.

Preferably, in the preparation of polycatechol, the ratio of moles of catechol to the volume of the buffer solution ranges from 0.1 to 1 mmol/100ml, and the concentration and pH of the sodium dihydrogen phosphate-disodium hydrogen phosphate buffer solution range from 0.05 to 0.1, respectively. mol/L and 7.5-8.0, the mole number of catalyst is 5-7 times the mole number of added catechol.

Preferably, the catalyst is Ag ₂ O or CuO.

Preferably, the polymerization temperature, polymerization time and magnetic stirring speed range from 22 to 28° C., 24 to 48 h and 80 to 120 rpm, respectively.

Preferably, in the prepolymerization reaction, the mass ratio of the quaternized modified oxidized defatted vegetable protein meal, polycatechol, pectin and water is in the range of (35-40): (2-5): (0.5-1 ): (55～60); the reaction temperature, reaction time and stirring speed of the prepolymerization reaction are respectively 50～75°C, 3～6h and 200～250rpm.

Preferably, the defatted vegetable protein meal is one of defatted corn germ meal or defatted rapeseed meal.

Preferably, the purification treatment is to use a dialysis bag with a minimum molecular weight cut-off of 1000 Da, and use distilled water for dialysis.

A vegetable protein-based adhesive obtained by the above preparation method.

An application of the vegetable protein-based adhesive as an adhesive for the production of original boards and wood-based panels.

Compared with the prior art, the present invention has the following technical effects:

First, the two adjacent hydroxyl groups of carbohydrates in the defatted vegetable protein meal are oxidized to two aldehyde groups, and at the same time, some hydroxyl groups of carbohydrates and proteins in the defatted vegetable protein meal are modified by quaternization, so that part of the hydroxyl groups are derivatized. into quaternary ammonium ions;

Second, the present invention adopts a recyclable solid catalyst (Ag ₂ O or CuO) to catalyze the polymerization of plant-based catechol to form an aromatic polymer containing polyphenyl structure;

Thirdly, the prepolymerization reaction is used to enhance the bonding strength of the vegetable protein-based adhesive itself formed by the modified biomass and the cross-linking agent (pectin).

Specifically, in addition to the formation of hydrogen bonds between the hydroxyl groups and amino groups of the degreasing vegetable protein meal, based on the above technical invention, the following enhancement effects can be produced during the prepolymerization reaction: First, some aldehyde groups can interact with polycatechol phenyl structures A polymerization reaction is generated to form a polymeric cross-linked structure similar to formaldehyde and phenol; secondly, part of the quaternary ammonium ions generated by the modification can have electrostatic interactions with the carboxyl groups in the defatted vegetable protein meal and pectin; at the same time, part of the polycatechol The phenyl group can have hydrophobic interaction with the protein alkyl and aryl groups in the defatted vegetable protein meal; finally, under the combined action of non-covalent bonds such as covalent bonds, electrostatic and hydrophobic bonds formed by the phenolic condensation reaction, the hydroxyl groups on the pectin surface and carboxyl groups can form a three-dimensional hydrogen bond network structure with the surface hydroxyl groups of vegetable protein meal and polycatechol, and play the role of cross-linking vegetable protein and polycatechol.

In addition, after the adhesive enters the inner and outer void structure of the veneer by hot pressing, the residual aldehyde groups, quaternary ammonium ions and phenyl groups in the modified vegetable protein-based adhesive can further react with the vacant reaction sites of the lignin phenyl groups on the surface of the veneer fiber. Points, carbohydrate carboxyl groups and lignin hydrophobic groups produce phenolic condensation reaction, electrostatic and hydrophobic interactions, respectively, to achieve the ultimate purpose of enhancing the bonding strength of plywood.

Detailed ways

The specific embodiments of the present invention will be further described below. It should be noted here that the descriptions of these embodiments are used to help the understanding of the present invention, but do not constitute a limitation of the present invention.

A preparation method of vegetable protein-based adhesive, comprising the following steps:

1. Oxidation of defatted vegetable protein meal

First, mix a certain mass of defatted vegetable protein meal, NaIO ₄ and NaCl in a conical flask containing deionized water. The mass content of defatted vegetable protein meal in deionized water ranges from 2 to 5%, respectively _. The quality is 2 to 3 and 4 to 5 times the quality of the degreasing vegetable protein meal, respectively. After adding the magnet, seal the mouth of the triangular bottle with a rubber stopper, and quickly wrap the triangular bottle with tin foil for 2 to 3 layers;

Defatted vegetable protein meal is one of defatted corn germ meal or defatted rapeseed meal.

Next, the triangular flask was placed in a water bath for oxidation treatment, and the oxidation temperature, oxidation time and magnetic stirring speed ranged from 40 to 60° C., 12 to 24 hours, and 300 to 500 rpm, respectively.

Then, after the oxidation is completed, filter the solid-liquid mixture, rinse the solids on the filter paper with deionized water until the pH value of the filtrate reaches 6.5-7.0, collect the solids on the filter paper and freeze-dry to obtain oxidized degreasing vegetable protein meal .

2. Quaternization modification of oxidized defatted vegetable protein meal

Take a certain mass of oxidized defatted vegetable protein meal, 2,3-epoxypropyltrimethylammonium chloride and deionized water in a thick-walled pressure-resistant bottle, add a magnet, and seal it with a polytetrafluoroethylene cap. Wherein, the mass content of the oxidized defatted vegetable protein meal in deionized water is 5-10%, and the mass of the added 2,3-epoxypropyltrimethylammonium chloride is 1/4-1 of the mass of the oxidized defatted vegetable protein meal /3.

Then, the thick-walled pressure bottle was placed in a water bath for quaternization modification, and the modification temperature, modification time and magnetic stirring speed ranged from 60 to 80° C., 30 to 40 h, and 200 to 400 rpm, respectively.

After the modification is completed, the solid-liquid mixture is transferred to a dialysis bag (the minimum molecular weight cut-off is 1000Da), and distilled water is used for dialysis. The solid is collected and freeze-dried, which is the quaternized modified oxidized defatted vegetable protein meal.

3. Polymerization of catechol

Take a certain amount of catechol, catalyst and sodium dihydrogen phosphate-disodium hydrogen phosphate buffer in a triangular flask, the ratio of moles of catechol to buffer volume is 0.1～1mmol/100ml, sodium dihydrogen phosphate-phosphoric acid The concentration and pH range of the disodium hydrogen buffer solution are respectively 0.05-0.1 mol/L and 7.5-8.0, and the mole number of catalyst is 5-7 times the mole number of added catechol. Wherein, the catalyst used is Ag ₂ O or CuO.

Then, seal the mouth of the triangular flask with a rubber stopper, and place the sealed triangular flask in a water bath to carry out the polymerization reaction. The polymerization temperature, polymerization time and magnetic stirring speed range are respectively 22～28°C, 24～48h and 80～48°C. 120rpm.

After the polymerization is completed, the solid catalyst is removed by centrifugation, and the centrifugation speed and time are respectively 5000-8000 rpm and 5-10 min, and the supernatant liquid is collected.

The clear liquid obtained by centrifugation is placed in a dialysis bag (with a minimum molecular weight of 1000 Da), and dialyzed with distilled water. When the sodium ion concentration in the dialysis bag is lower than 0.1 mmol/L, the solution in the dialysis bag is collected for freeze-drying, which is the polymerized solution. Catechol.

4. Prepolymerization of vegetable protein-based adhesives

Take a certain quality of quaternized modified oxidized defatted vegetable protein meal, polycatechol, pectin (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., the mass content of galacturonic acid is 74%) and deionized water. In a round-bottomed flask, the round-bottomed flask was equipped with a mechanical stirring device and a thermometer, and the round-bottomed flask was placed in a water bath for pre-reaction.

Among them, the mass ratio ranges of the quaternized modified oxidized degreasing vegetable protein meal, polycatechol, pectin and deionized water are (35-40): (2-5): (0.5-1): ( 55-60); the reaction temperature, reaction time and stirring speed of the mixed solution in the round-bottomed flask are respectively 50-75° C., 3-6 h and 200-250 rpm.

After the pre-reaction is completed, the modified vegetable protein-based adhesive can be used for plywood sizing.

5. Application of modified vegetable protein-based adhesives

First, three-layer plywood is prepared by selecting fast-growing poplar veneer, the moisture content of the veneer is 8-12%, and its three-dimensional dimensions are: length, width and thickness are 350mm, 350mm and 2mm respectively. A poplar veneer is double-sidedly sizing with a modified vegetable protein-based adhesive, and the sizing amount is 320-360 g/m ² , and the veneer is called a core board.

Next, adhere two other un-glued veneers on both sides of the glued core board, and place the bonded three-layer plywood in a dark place for closed aging at room temperature for 30-60min.

At the same time, the aged three-layer board is subjected to hot pressing treatment, and the hot pressing temperature, pressure and time are respectively 1.2-1.3Mpa, 120-130°C and 10-15min.

Finally, the hot-pressed plywood is placed at room temperature for 36-48 hours, and then the produced plywood is tested according to the testing method of GB/T17657-1999 "Experimental Methods for Physical and Chemical Properties of Wood-based Panels and Finished Wood-based Panels".

Examples 1-8 and Comparative Examples 1-5

Table 1 Defatted vegetable protein meal modification and catechol polymerization methods and conditions

Table 2 Comparative Examples and Example Results

Note: When the defatted vegetable protein meal is not modified by one or both of oxidation and quaternization modification, the comparative example uses unmodified defatted vegetable protein meal instead.

It can be seen from Table 2 that the degreasing vegetable protein meal in Comparative Examples 1 to 5 is not oxidized or quaternized, or the catechol is not polymerized, and the adhesive strength of the prepolymerized adhesive obtained by prepolymerization is about the same as the embodiment. about 50%.

The oxidation and quaternization modification process is to oxidize some adjacent two hydroxyl groups of carbohydrates in the defatted vegetable protein meal to two aldehyde groups, and at the same time, the partial hydroxyl groups of the carbohydrates and proteins in the defatted vegetable protein meal are subjected to quaternization modification. It can derivatize some hydroxyl groups into quaternary ammonium ions; some aldehyde groups can react with polycatechol phenyl structure to form a polymerized cross-linked structure similar to formaldehyde and phenol; some quaternary ammonium ions generated by modification can It has electrostatic effect with the carboxyl groups in the defatted vegetable protein meal and pectin, thereby improving the bonding strength of the adhesive. Compared with the experimental effect of Comparative Example 3, it can fully reflect the creativity of the process.

The embodiments of the present invention have been described above in detail, but the present invention is not limited to the described embodiments. For those skilled in the art, without departing from the principle and spirit of the present invention, various changes, modifications, substitutions and alterations can be made to these embodiments, which still fall within the protection scope of the present invention.

Claims (6)

1. A preparation method of a vegetable protein-based adhesive is characterized by comprising the following steps:

quaternization modification of the oxidized and degreased vegetable protein meal:

taking oxidized degreased plant protein meal, 2, 3-epoxypropyl trimethyl ammonium chloride and water, sealing in a container, and carrying out quaternization modification reaction; after modification, carrying out purification treatment, and drying to obtain quaternized modified oxidized defatted plant protein meal;

the oxidative degreasing plant protein meal is prepared by the following steps:

mixing defatted plant protein meal and NaIO₄Mixing with NaCl in water, sealing and shading to perform oxidation reaction; after the oxidation is finished, filtering, washing until the pH value of the filtrate reaches 6.5-7.0, collecting solids, and drying to obtain oxidized and degreased vegetable protein meal;

in the quaternization modification of the oxidized and degreased vegetable protein meal, the mass content of the oxidized and degreased vegetable protein meal in water is 5-10%, and the mass of the 2, 3-epoxypropyltrimethylammonium chloride is 1/4-1/3 of the mass of the oxidized and degreased vegetable protein meal; the modification temperature, the modification time and the magnetic stirring speed range are respectively 60-80 ℃, 30-40 h and 200-400 rpm;

preparation of poly-catechol:

placing catechol, a catalyst and a buffer solution in a container, sealing and then carrying out polymerization reaction; after the polymerization is finished, centrifuging to remove the solid catalyst; collecting supernatant, purifying, and drying to obtain poly-catechol;

in the preparation of the poly-catechol, the molar ratio of the catechol to the volume of the buffer solution is 0.1-1 mmol/100ml, the concentration and the pH range of the sodium dihydrogen phosphate-disodium hydrogen phosphate buffer solution are 0.05-0.1 mol/L and 7.5-8.0 respectively, and the molar number of the catalyst is 5-7 times of the molar number of the added catechol, wherein the catalyst is Ag₂O or CuO; the polymerization temperature, the polymerization time and the magnetic stirring speed range are respectively 22-28 ℃, 24-48 h and 80-120 rpm;

and (3) prepolymerization:

carrying out prepolymerization reaction on oxidized degreased vegetable protein meal modified by quaternization, poly catechol, pectin and water to obtain vegetable protein-based adhesive;

in the prepolymerization reaction, the mass ratio of the oxidized defatted vegetable protein meal modified by quaternization, the poly catechol, the pectin and the water is (35-40): (2-5): (0.5-1): (55-60); the reaction temperature, the reaction time and the stirring speed of the prepolymerization reaction are respectively 50-75 ℃, 3-6 h and 200-250 rpm.

2. The method for preparing the vegetable protein-based adhesive according to claim 1, wherein the mass content of the defatted vegetable protein meal in water is 2-5%, respectively, and the NaIO content is₄Adding NaCl with the mass being 2-3 times and 4-5 times of the mass of the degreased vegetable protein meal respectively; the oxidation temperature, the oxidation time and the magnetic stirring speed range are respectively 40-60 ℃, 12-24 h and 300-500 rpm.

3. The method of claim 1, wherein the defatted vegetable protein meal is one of defatted corn germ meal or defatted canola seed meal.

4. The method of claim 1, wherein the purification process comprises dialyzing the mixture with distilled water using a dialysis bag with a minimum molecular weight cut-off of 1000 Da.

5. A vegetable protein-based adhesive obtained by the production method according to any one of claims 1 to 4.

6. Use of the vegetable protein-based adhesive according to claim 5 as an adhesive for producing original wood boards and artificial boards.