Preparation method and application of formaldehyde-free glue for artificial boardTechnical Field
The invention belongs to the technical field of adhesives, and particularly relates to a preparation method and application of an artificial board formaldehyde-free adhesive.
Background
Adhesives play a vital role in the wood industry. The amount of adhesive has become an important indicator for measuring the technical level of the wood industry in a country or region. Along with the development of national economy and the continuous improvement of the living standard of people, the demands of society on wood and wood products are greatly increased. Therefore, the amount of the adhesive used also increases drastically.
With the further implementation of natural forest protection engineering in China, the number of medium and small-sized woods is increasing. Therefore, the production of various artificial boards by using small and medium-sized wood, wood processing residues and forest harvesting residues is an important point of the development of the wood industry in China. Therefore, the artificial board products in China must continuously improve the quality and reduce the cost, and can stand on the place of no failure in the market competition. And the quality level and market competitiveness of the manufactured board product are largely dependent on the production level of the adhesive. The quality of the adhesive has an important influence on the product quality of the artificial board. The cost of the adhesive represents a significant fraction of the overall production cost of the artificial board. The cost of the adhesive cannot be reduced, and the cost of the artificial board cannot be reduced. Therefore, the development of the artificial board adhesive is becoming more and more important.
At present, the main problems in the adhesive industry in China are that (1) the free formaldehyde content in the adhesive is high, so that excessive formaldehyde is released in the artificial board product. Because of the wide use of the artificial board products in the interior decoration and furniture industries of China, the problem has become a social problem affecting human health directly, and has caused a very negative impression in various social circles. In addition, other harmful components in the adhesive, such as phenol, have a significant impact on human health and the environment. If the problems are not properly solved, the sales of artificial board products in China are seriously affected. (2) The adhesive production in China mostly depends on artificial board production enterprises, and the enterprises produce and use the adhesive by themselves. This small-scale agricultural production is not conducive to the development of the adhesive industry. Most artificial board production enterprises in China have relatively small scale and are operated independently, and small factories have little capability to carefully treat the production and quality problems of the adhesive. (3) The adhesive has the advantages of lag production process, unstable quality and poor adaptability to raw materials and adhesive equipment. Due to the inherent quality problems of the adhesive itself, the quality of the manufactured board product can be ensured only by increasing the amount of the adhesive. Excessive use of glue is a major cause of unreduced production cost of the artificial board.
At present, urea-formaldehyde glue, phenolic glue and melamine formaldehyde glue are mainly used in the artificial board industry in China, and are rich in raw material sources, simple in synthesis process and low in cost. It can be seen from the name of the adhesives that these adhesives all contain "aldehyde-containing" adhesives having an aldehyde group structure which releases "free formaldehyde" during drying. When the artificial board using the adhesive is applied to indoor decoration and furniture industry, the released volatile aldehyde substances can cause damage to natural environment and human health, and directly become a social problem affecting human health.
With the pursuit of people for improving living conditions and the improvement of environmental protection consciousness, some polyurethane adhesives and soybean protein adhesives with zero formaldehyde release are also appeared on the market based on the environmental protection. Although the polyurethane adhesive cures at a fast rate, it is costly and also susceptible to ambient temperature and humidity. In addition, the application time of the colloid is very short due to the excessively fast curing speed, the colloid is easy to adhere to the template and the conveyor belt, the requirement on a production line is very high, the dosage of the colloid is difficult to control, and the production cost is increased. The soybean protein adhesive is an adhesive prepared from soybean, which is relatively inexpensive, but contains organic components such as starch and protein, and the presence of these components makes the artificial board susceptible to attack by bacteria and mold in the air, resulting in plaque and mold growth, and also has poor bonding strength, water resistance and weather resistance.
In summary, the invention provides a preparation method and application of an aldehyde-free adhesive for an artificial board, the adhesive prepared by the method does not contain aldehyde groups, the artificial board using the adhesive can achieve the effect of zero formaldehyde release, functional monomers are introduced into the aldehyde-free adhesive in the preparation process, so that the aldehyde-free adhesive has certain antibacterial and flame-retardant effects, in addition, a three-stage polymerization mode is adopted in the preparation of the aldehyde-free adhesive, the extremely low monomer residue is controlled, so that the aldehyde-free adhesive has no peculiar smell, and the adhesive is environment-friendly and has excellent comprehensive performance.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to develop a preparation method and application of the formaldehyde-free adhesive for the artificial board, the adhesive prepared by the method does not contain aldehyde groups, the artificial board using the adhesive can achieve the effect of zero formaldehyde release, the formaldehyde-free adhesive is introduced with functional monomers in the preparation process, so that the formaldehyde-free adhesive has certain antibacterial and flame-retardant effects, in addition, a three-stage polymerization mode is adopted in the preparation of the formaldehyde-free adhesive, the extremely low monomer residue is controlled, so that the formaldehyde-free adhesive has no peculiar smell, and the formaldehyde-free adhesive is environment-friendly and has excellent comprehensive performance.
In order to achieve the above purpose, the specific technical scheme of the invention is as follows:
the preparation method of the formaldehyde-free glue for the artificial board comprises the following steps:
(1) Mixing a main monomer, a first initiator, an emulsifier and a solvent, and reacting for 0.5-1h at 20-40 ℃, wherein the main monomer is selected from two or more of ethylene, vinyl chloride, vinyl acetate and vinylidene chloride;
(2) Adding a functional monomer and a second initiator into the reaction system in the step (1), and continuing to react for 2-6 hours at the temperature of 40-75 ℃, wherein the functional monomer comprises one or more of a compound containing double bonds and hydroxyl groups, a compound containing double bonds and carboxyl groups, a compound containing double bonds and epoxy groups, a compound containing double bonds siloxane, vinyl isobutyl ether, isobutoxy methacrylamide and diacetone acrylamide;
(3) And (3) reacting the reaction system in the step (2) for 0.5-1h at 40-60 ℃, adding a terminator to obtain a polymerization emulsion, and using the polymerization emulsion to prepare the formaldehyde-free glue.
Preferably, the double bond and hydroxyl group containing compound contains the following structure:
;
wherein R is an alkyl group containing anhydride group, carboxyl group, amino group, imino group, amide group, alkoxysilane group, silanol group, silyl ether group, hydroxyl group, epoxy group, halogen, mercapto group, episulfide group, unsaturated bond functional group.
Preferably, the double bond and carboxyl group containing compound contains the following structure:
;
Wherein R is an alkyl group containing anhydride groups, carboxyl groups, amino groups, imino groups, alkoxysilane groups, silanol groups, silyl ether groups, hydroxyl groups, epoxy groups, halogens, mercapto groups, episulfide groups, unsaturated bond functional groups.
Preferably, the double bond and epoxy group containing compound contains the following structure:
;
Wherein R is an alkyl group containing anhydride groups, carboxyl groups, amino groups, imino groups, alkoxysilane groups, silanol groups, silyl ether groups, hydroxyl groups, epoxy groups, halogens, mercapto groups, episulfide groups, unsaturated bond functional groups.
Preferably, the double bond siloxane containing compound contains the following structure:
;
wherein R1、R2、R3 is alkyl containing anhydride group, carboxyl group, amino group, imino group, alkoxy silane group, silanol group, silyl ether group, hydroxyl group, epoxy group, halogen, mercapto group, episulfide group and unsaturated bond functional group.
Preferably, the mass ratio of the main monomer to the functional monomer is 1 (0.05-0.5).
Preferably, the polymerization emulsion and the curing cross-linking agent are uniformly mixed to prepare the formaldehyde-free glue.
Preferably, the curing cross-linking agent is composed of one or more of isocyanate containing isocyanate groups, adipic acid dihydrazide, melamine, trimethylol melamine, hexamethoxymethyl melamine, polyol compounds, organic amine compounds, organic silicon compounds containing double bonds, hydroxypropyl methyl cellulose and peroxide compounds.
Further preferably, the polyol compound includes one of ethylene glycol, propylene glycol, butylene glycol, pentylene glycol.
Further preferably, the organic amine compound includes one of o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-chloroaniline, m-chloroaniline, p-chloroaniline, N-dimethylethanolamine, N-diethylethanolamine, triethylenediamine, diethylenetriamine, cycloethyleneimine, polyethyleneimine.
It is further preferred that the composition comprises, the organosilicon compound containing double bonds comprises vinyl trichlorosilane, vinyl trimethoxy silane, vinyl triethoxy silane, styryl trimethoxy silane, 3-acryloxypropyl trimethoxy silane, 3-methacryloxypropyl trimethoxy silane 3-methacryloxypropyl triethoxysilane, 3-methacryloxypropyl methyl diethoxysilane, 3-methacryloxypropyl methyl dimethoxysilane one of glycidoxypropyl trimethoxysilane and 3-acryloxypropyl trimethoxysilane.
Preferably, the first initiator and the second initiator are azo-type initiators and/or peroxide initiators.
Preferably, the first initiator and the second initiator are used in an amount of 0.1% to 0.6% of the total monomer amount.
The total monomer amount is the sum of the mass of the main monomer and the functional monomer.
Preferably, the emulsifier is an anionic emulsifier and/or a nonionic emulsifier.
Preferably, the emulsifier is used in an amount of 1% to 8% of the total monomer amount.
Preferably, the terminator is sorbic acid.
Preferably, the terminator is used in an amount of 0.01% to 0.03% of the total monomer amount.
The invention also provides application of the formaldehyde-free glue in the artificial board.
The weight average molecular weight of the polymer emulsion prepared by the method is 1000-500000 daltons, the viscosity is 500-20000 mPa.s, the glass transition temperature (Tg) is-50-70 ℃, and the solid content of the emulsion is controlled to be 20-65%. The invention adopts three-stage polymerization reaction to prepare the alkenyl polymerization emulsion, so that the polymerization emulsion has excellent performance, the content of residual monomers of the polymerization emulsion is as low as 5-100 PPM, the extremely low monomer residues are controlled, the formaldehyde-free glue prepared by the invention has no peculiar smell, the property of the polymerization emulsion is further improved by introducing functional monomers, the polymerization emulsion is more suitable for being used as a wood adhesive, and the emulsion with different properties can be obtained by adopting different monomer combinations and different proportions. The invention adopts emulsion polymerization reaction to prepare polymerization emulsion, the process is simple and mature, the polymerization condition is easy to control, the introduced functional monomer can adjust the performance of the adhesive to obtain the adhesive meeting the design requirement, the curing cross-linking agent of the invention selects a compound with a reactive group to realize self-crosslinking and/or intermolecular crosslinking so as to achieve the aim of drying and curing, and the different proportions of the polymerization emulsion and the curing cross-linking agent can realize different curing speeds, so that the curing speed can be controlled by changing the proportions of the curing cross-linking agent and the emulsion, and the adhesive meets the requirement of field production. According to the invention, the board with excellent performance can be obtained by applying the polymer emulsion to the artificial board in a mode of compounding the polymer emulsion and the curing cross-linking agent.
Compared with the prior art, the invention has the following advantages:
(1) The formaldehyde-free adhesive prepared by the method does not contain formaldehyde, has extremely low residual monomer content and biodegradability, is environment-friendly and can be widely used;
(2) According to the method provided by the invention, after the main monomer is subjected to low-temperature reaction for 0.5-1h, the functional monomer is introduced to perform heating reaction for 2-6h, and then the temperature is reduced to continue the reaction for 0.5-1h, so that the polymer emulsion is prepared, and compared with the polymer emulsion which is easily corroded by bacteria and mould by starch glue and protein glue, the polymer emulsion prepared by the method has certain antibacterial property and flame retardance;
(3) Compared with the existing formaldehyde-free MDI (diphenylmethane diisocyanate) rigid adhesive, the formaldehyde-free adhesive can change the property and the curing time of the adhesive by adjusting the monomer combination and the adding proportion of the curing cross-linking agent, so that the board has good flexibility and bendability, and the problem that the board is easy to burst and crack in the processing process is avoided;
(4) The formaldehyde-free adhesive provided by the method has the advantages of low cost while improving the processability of the plate, and has a wide application prospect.
Detailed Description
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings, in which are shown by way of illustration only, and not as an admission of any of the other embodiments of the present invention as defined by the specification. Any equivalent alterations or substitutions by those skilled in the art based on the following embodiments are within the scope of the present invention.
The invention provides a preparation method of an artificial board formaldehyde-free adhesive, which comprises the following steps:
(1) Mixing a main monomer, a first initiator, an emulsifier and a solvent, and reacting for 0.5-1h at 20-40 ℃, wherein the main monomer is selected from two or more of ethylene, vinyl chloride, vinyl acetate and vinylidene chloride;
(2) Adding a functional monomer and a second initiator into the reaction system in the step (1), and continuing to react for 2-6 hours at the temperature of 40-75 ℃, wherein the functional monomer comprises one or more of a compound containing double bonds and hydroxyl groups, a compound containing double bonds and carboxyl groups, a compound containing double bonds and epoxy groups, a compound containing double bonds siloxane, vinyl isobutyl ether, isobutoxy methacrylamide and diacetone acrylamide;
(3) And (3) reacting the reaction system in the step (2) for 0.5-1h at 40-60 ℃, adding a terminator to obtain a polymerization emulsion, and using the polymerization emulsion to prepare the formaldehyde-free glue.
In some examples, the polymeric emulsion is uniformly mixed with a curing cross-linking agent to provide an aldehyde-free gum.
In some examples, the first initiator and the second initiator are azo-based initiators and/or peroxide initiators.
In some examples, the first initiator and the second initiator are used in an amount of 0.1% to 0.6% of the total monomer amount.
In some examples, the emulsifier is an anionic emulsifier and/or a nonionic emulsifier.
In some examples, the emulsifier is used in an amount of 1% to 8% of the total monomer amount.
In some examples, the terminating agent is used in an amount of 0.01% to 0.03% of the total monomer amount.
In the examples described below, the terminator used was sorbic acid, the curing crosslinker used was diphenylmethane diisocyanate, the viscosity of the polymerization emulsion was determined at room temperature using a BROOKFIELD viscometer, the glass transition temperature was determined by DSC, and the solids content was determined according to GB/T27573-2011, unless otherwise specified.
Example 1
The embodiment provides a preparation method of formaldehyde-free glue, which comprises the following steps:
(1) 250g of ethylene and 700g of vinyl acetate are added into 2000g of water, 3g of potassium persulfate, 10g of sodium stearate and 30g of OP-10 emulsifier are added during stirring, and the mixture is reacted for 0.5h at 30 ℃;
(2) 50g of vinyl isobutyl ether and 3g of azo diisobutyl amidine hydrochloride are added into the reaction system in the step (1), and the reaction is continued for 6 hours at 65 ℃;
(3) Reacting the reaction system in the step (2) for 1h at 45 ℃, and adding 0.2g of sorbic acid to obtain a polymerization emulsion with the solid content of 52%, the viscosity of 2000 mPa s, the Tg=5 ℃ and the residual monomer content of 20;
(4) And uniformly mixing the polymerization emulsion and the curing cross-linking agent to obtain the formaldehyde-free adhesive.
Example 2
The embodiment provides a preparation method of formaldehyde-free glue, which comprises the following steps:
(1) 200g of ethylene, 600g of vinyl acetate and 120g of vinyl chloride are added into 2000g of water, 3g of potassium persulfate, 10g of sodium stearate and 30g of OP-10 emulsifier are added during stirring, and the mixture is reacted for 1h at 35 ℃;
(2) 80g of 4-hydroxybutyl acrylate and 3g of azodiisobutyl amidine hydrochloride are added into the reaction system in the step (1), and the reaction is continued for 5 hours at 60 ℃;
(3) Reacting the reaction system in the step (2) for 0.5h at 50 ℃, and adding 0.2g of sorbic acid to obtain a polymerization emulsion with the solid content of 53%, the viscosity of 600 mPa s, the Tg=12 ℃ and the residual monomer content of 10;
(4) And uniformly mixing the polymerization emulsion and the curing cross-linking agent to obtain the formaldehyde-free adhesive.
Example 3
The embodiment provides a preparation method of formaldehyde-free glue, which comprises the following steps:
(1) 200g of ethylene and 700g of vinyl acetate are added into 2000g of water, 3g of potassium persulfate, 10g of sodium stearate and 30g of OP-10 emulsifier are added during stirring, and the mixture is reacted for 0.5h at 40 ℃;
(2) Adding 100g N-methylol acrylamide and 3g of azo-diisobutyl amidine hydrochloride into the reaction system in the step (1), and continuing to react for 3 hours at 70 ℃;
(3) Reacting the reaction system in the step (2) for 1h at 40 ℃, and adding 0.2g of sorbic acid to obtain a polymerization emulsion with 54% of solid content, 3500 mPa s of viscosity, tg=5 ℃ and 10 residual monomer content;
(4) And uniformly mixing the polymerization emulsion and the curing cross-linking agent to obtain the formaldehyde-free adhesive.
Comparative example 1
The preparation method of the formaldehyde-free glue of the comparative example comprises the following steps:
(1) 280g of ethylene, 700g of vinyl acetate and 20g of vinyl isobutyl ether are added into 2000g of water, 3g of potassium persulfate, 3g of azodiisobutyl amidine hydrochloride, 10g of sodium stearate and 30g of OP-10 emulsifier are added during stirring, the mixture is reacted for 7.5 hours at 65 ℃, and 0.2g of sorbic acid is added to obtain a polymerization emulsion with the solid content of 52%, the viscosity of 2300 mPa.s, the Tg=8 ℃ and the residual monomer content of 1500;
(2) And uniformly mixing the polymerization emulsion and the curing cross-linking agent to obtain the formaldehyde-free adhesive.
Comparative example 2
The preparation method of the formaldehyde-free glue of the comparative example comprises the following steps:
(1) 280g of ethylene, 700g of vinyl acetate and 20g of vinyl isobutyl ether are added into 2000g of water, 3g of potassium persulfate, 3g of azodiisobutyl amidine hydrochloride, 10g of sodium stearate and 30g of OP-10 emulsifier are added during stirring, and the mixture is reacted for 6.5 hours at 65 ℃;
(2) Continuously reacting the reaction system for 1h at 40 ℃, and adding 0.2g of sorbic acid to obtain a polymerization emulsion with the solid content of 52%, the viscosity of 2800 mPa s, the Tg=9 ℃ and the residual monomer content of 1200;
(3) And uniformly mixing the polymerization emulsion and the curing cross-linking agent to obtain the formaldehyde-free adhesive.
Comparative example 3
The preparation method of the formaldehyde-free glue of the comparative example comprises the following steps:
(1) 280g of ethylene and 700g of vinyl acetate are added into 2000g of water, 3g of potassium persulfate, 10g of sodium stearate and 30g of OP-10 emulsifier are added during stirring, and the mixture is reacted for 0.5h at 65 ℃;
(2) Adding 20g of vinyl isobutyl ether and 3g of azo diisobutyl amidine hydrochloride into the reaction system in the step (1), and continuing to react for 6 hours at 65 ℃;
(3) Reacting the reaction system in the step (2) for 1h at 65 ℃, and adding 0.2g of sorbic acid to obtain a polymerization emulsion with the solid content of 52%, the viscosity of 2000 mPa s, the Tg=8 ℃ and the residual monomer content of 300;
(4) And uniformly mixing the polymerization emulsion and the curing cross-linking agent to obtain the formaldehyde-free adhesive.
The polymeric emulsions of examples 1-3 and comparative examples 1-3 and the aldehyde-free gum were made into films (25 mm 1 mm) at 110 ℃, and the films were tested for tensile strength and elongation at break. The test results are shown in Table 1.
TABLE 1 film Properties of the polymeric emulsions and aldehyde-free gums of examples 1-3 and comparative examples 1-3
Application example 1
The application example is the application of the formaldehyde-free glue prepared in the embodiment 1 in the P2 particle board, and the steps are as follows:
s1, uniformly mixing 38g of polymerization emulsion and 5g of curing cross-linking agent, and fully and uniformly stirring with 1080g of surface fine wood chip;
S2, uniformly mixing 84g of the polymerization emulsion and 10g of the curing cross-linking agent, and fully and uniformly stirring with 1616g of core layer coarse wood dust;
and S3, pressing the wood chips mixed by the above into a board with the breadth of 520 x 18mm by adopting a vertical automatic oil pressure forming machine produced by Jiangsu tin-free yangming rubber machinery Co-Ltd, and curing for 72h.
Application example 2
The application example is the application of the formaldehyde-free glue prepared in the embodiment 2 in the P6 shaving board, and the steps are as follows:
S1, uniformly mixing 76g of polymerization emulsion and 7g of curing cross-linking agent, and fully and uniformly stirring with 1080g of surface fine wood chip;
s2, uniformly mixing 129g of polymerization emulsion and 10g of curing cross-linking agent, and fully and uniformly stirring with 1616g of core layer coarse wood dust;
and S3, pressing the wood chips mixed by the above into a board with the breadth of 520 x 18mm by adopting a vertical automatic oil pressure forming machine produced by Jiangsu tin-free yangming rubber machinery Co-Ltd, and curing for 72h.
Application example 3
The application example is the application of the formaldehyde-free glue prepared in the embodiment 3 in the P10 shaving board, and the steps are as follows:
S1, uniformly mixing 216g of polymerization emulsion and 21g of curing cross-linking agent, and fully and uniformly stirring with 1080g of surface fine wood chip;
s2, uniformly mixing 281g of polymerization emulsion and 14g of curing cross-linking agent, and fully and uniformly stirring with 1616g of core layer coarse wood dust;
and S3, pressing the wood chips mixed by the above into a board with the breadth of 520 x 18mm by adopting a vertical automatic oil pressure forming machine produced by Jiangsu tin-free yangming rubber machinery Co-Ltd, and curing for 72h.
Application example 4
The application example is the application of the formaldehyde-free glue prepared in the example 1 in the plywood, and the steps are as follows:
40g of the polymerization emulsion and 4g of the curing crosslinking agent are fully and uniformly stirred for standby.
And (3) drawing a marking line (15X 25 mm) on one end of each wood sheet (25X 80 mm), then gluing the marking line area (the glue gluing amount is 150g/m2), pressing the two glued wood sheets by using a carpenter clamp, putting the wood sheets into a standard curing chamber with the temperature of 20 ℃ and the relative humidity of 60%, and curing for 7 days.
Application example 5
The application example is the application of the formaldehyde-free glue prepared in the example 2 in the plywood, and the steps are basically the same as those of the application example 4.
Application example 6
The application example is the application of the formaldehyde-free glue prepared in the example 3 in the plywood, and the steps are basically the same as those of the application example 4.
Comparative application example 1
The procedure of the comparative example was essentially the same as that of example 1, except that the polymeric emulsion used in the comparative example was the polymeric emulsion prepared in comparative example 1.
Three plates were pressed using the same formulation as in application examples 1-3 and comparative application example 1, and various properties were measured according to GB/T4897-2015 particle board, each block was divided into three samples for testing 9 times, the best and worst values were removed, and the average of the remaining 7 values was taken. The results are shown in Table 2. The plywood sheets of application examples 4 to 6 were tested for properties according to the D4 standard in Classification of thermoplastic Wood Adhesives for non-structural use EN204 and the results are shown in Table 3.
TABLE 2 particle Board Performance results for application examples 1-3 and comparative application example 1
TABLE 3 Property results of plywood of application examples 4-6
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.