CN111592842A - Thermosetting artificial board starch adhesive with high starch content and preparation method thereof - Google Patents
Thermosetting artificial board starch adhesive with high starch content and preparation method thereof Download PDFInfo
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- CN111592842A CN111592842A CN202010592418.1A CN202010592418A CN111592842A CN 111592842 A CN111592842 A CN 111592842A CN 202010592418 A CN202010592418 A CN 202010592418A CN 111592842 A CN111592842 A CN 111592842A
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J151/00—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
- C09J151/02—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers grafted on to polysaccharides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27D—WORKING VENEER OR PLYWOOD
- B27D1/00—Joining wood veneer with any material; Forming articles thereby; Preparatory processing of surfaces to be joined, e.g. scoring
- B27D1/04—Joining wood veneer with any material; Forming articles thereby; Preparatory processing of surfaces to be joined, e.g. scoring to produce plywood or articles made therefrom; Plywood sheets
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
- B27N—MANUFACTURE BY DRY PROCESSES OF ARTICLES, WITH OR WITHOUT ORGANIC BINDING AGENTS, MADE FROM PARTICLES OR FIBRES CONSISTING OF WOOD OR OTHER LIGNOCELLULOSIC OR LIKE ORGANIC MATERIAL
- B27N1/00—Pretreatment of moulding material
- B27N1/02—Mixing the material with binding agent
- B27N1/0209—Methods, e.g. characterised by the composition of the agent
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F251/00—Macromolecular compounds obtained by polymerising monomers on to polysaccharides or derivatives thereof
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Abstract
The invention discloses a high-starch-content thermosetting artificial board starch adhesive and a preparation method thereof, belonging to the technical field of adhesive preparation. The invention adopts a gradient heating mode to avoid the phenomena of uneven reaction and the like caused by the formation of caking with overlarge viscosity in the heating process of the high-starch-ratio mixed system, and obviously improves the proportion of the starch. The process greatly shortens the reaction time, reduces the consumption of petroleum monomers, simplifies the complex reaction steps, and most importantly, the proportion of starch in the total solid content is increased to more than 85%, so that the cost of the starch adhesive is greatly reduced, and the green manufacture of the formaldehyde-free artificial board adhesive is realized. The adhesive has good water resistance and strong cohesion, and the properties of the manufactured artificial board exceed the standards of II artificial boards, so the adhesive is suitable for mass production and is widely used for bonding hot-pressing wood decoration, artificial boards and plywood.
Description
Technical Field
The invention relates to a starch adhesive for a thermosetting artificial board with high starch content and a preparation method thereof, belonging to the technical field of adhesive preparation.
Background
Along with the development of building and decoration, the demand of the consumer market in China on wood products is greatly increased. But China occupies less area of the forest, so the artificial board prepared by taking other non-wood plants as raw materials becomes an excellent way for solving the problem of wood shortage. At present, most of artificial boards on the market are produced by a hot pressing process, and adhesives with thermosetting property, namely, a formaldehyde-formaldehyde resin (UF), a phenol-formaldehyde resin (PF) and a melamine-formaldehyde resin (MF), are used, but the adhesives have poor water resistance, cannot be regenerated, release a large amount of formaldehyde in the production and use processes, cause environmental pollution and harm public health. Therefore, there is a need to develop an environmentally friendly natural resource adhesive with good water resistance and good adhesive property.
The starch is a biological macromolecule with abundant natural content, has wide source, low price, environmental protection, regeneration, good cohesiveness and good film-forming property, and is easy to operate when used for preparing the adhesive. Therefore, starch-based wood-based adhesives are a major trend today. At present, hot-pressed artificial boards are widely applied, the production efficiency of the artificial boards is greatly improved, the starch accounts for less than 50 percent of the total solid content of the existing starch adhesives, the starch adhesives greatly depend on non-renewable resources, the cost is high, and the environment-friendly performance is poor. Meanwhile, the adhesive used for bonding at present also requires a better thermosetting property. In addition, the market requirements on artificial boards are more and more strict, and the water resistance of the adhesive is also high. In view of the above performance requirements for adhesives, research teams previously prepared thermosetting starch adhesives which have achieved relatively ideal effects in terms of storage stability, dry strength, etc., but found that the problem of caking due to excessive viscosity and non-uniform reaction occurs when the ratio of starch to solid content is relatively high during the preparation process. Therefore, the problem of caking caused by non-uniform reaction due to excessive system viscosity is necessary to be solved, so that the solid content of the starch is further improved, the dependence on non-renewable petroleum resources is reduced on the original basis, the reaction stability is improved, and the wider application of the adhesive is promoted.
Disclosure of Invention
[ problem ] to
During the preparation of starch adhesives, the problem of caking due to excessive viscosity and non-uniform reaction is found when the starch accounts for a high solid content ratio (more than 75%). The invention aims to ensure that the starch ratio in the starch adhesive is higher, simultaneously, the problem of caking caused by non-uniform reaction is avoided, and the preparation process is more stable.
[ solution ]
According to the invention, control of three key steps of the addition amount of the grafting monomer, the addition amount of the crosslinking monomer, the pre-gelatinization temperature and the manner is greatly researched, so that the starch accounts for 85-90% of the solid content ratio in the starch adhesive prepared by the invention. In the preparation method, a gradient heating mode is adopted to avoid the phenomenon that the reaction is uneven and the artificial board starch adhesive with water resistance conforming to the II-class plywood is formed, and compared with the previous research, the proportion of the starch to the total solid content is increased to more than 85%, so that the cost is reduced.
The reaction mechanism of the invention is as follows: starch milk with better fluidity is obtained by a mode of acidolysis of starch by gradient temperature rise, then a linear polymer is formed by the added grafting monomer to increase the steric hindrance of the starch and the crosslinking monomer, the problems of reaction efficiency reduction and monomer and starch implosion caused by homopolymerization of the crosslinking monomer are reduced, the crosslinking monomer is added after primary grafting is finished to further form the linear polymer into a macromolecular polymer, and the linear polymer is further crosslinked into a macromolecular reticular structure under a hot-pressing process, so that the water resistance and the bonding strength of the starch adhesive are greatly improved. The method effectively avoids the possibility that the initial viscosity of the starch milk is too high and the crosslinking monomer is rapidly copolymerized on the active hydroxyl of the starch to cause the local viscosity to be too high to cause gelation.
In the aspect of key control points, the invention carries out accurate control aiming at the following control points:
the pre-gelatinization temperature is not more than 80 ℃. If the pre-gelatinization temperature is too high, starch can be exposed to too many reaction sites, so that the steric hindrance of starch molecules cannot be effectively increased by the grafting monomers in the pre-emulsion, the starch molecules are easy to gel when the crosslinking monomers are dripped, the pre-gelatinization temperature is too low, the pre-gelatinization effect is incomplete, and the subsequent graft copolymerization reaction is greatly influenced.
Secondly, heating to 60-70 ℃ at the speed of 2-3 ℃/min by adopting a gradient heating means, and adjusting the temperature of the starch milk subjected to acidolysis to 70-80 ℃ at the speed of 1-2 ℃/min. As the proportion of starch to solid content is extremely high, the phenomenon of caking due to overlarge viscosity inevitably occurs in the extremely rapid heating process, and the product adopts gradient heating and heat preservation treatment under the proper temperature condition to ensure uniform and complete gelatinization after being heated.
And the addition amount of the grafting monomer is not more than 6 percent of the using amount of the starch. Too little grafting monomer can form gel due to insufficient hydroxyl sites occupied on the surface of the starch, too much grafting monomer can not greatly improve dry strength and wet strength, can reduce the proportion of solid matters occupied by the starch, and has too much dependence on non-renewable resources.
Fourthly, the addition amount of the crosslinking monomer is not more than 6 percent of the using amount of the starch. Excessive addition of the cross-linking monomer can excessively cross-link with starch, increase the length of a starch side chain and increase local viscosity, so that the starch and the cross-linking monomer are polymerized to form gel, and the addition of too little cross-linking monomer can reduce the viscosity strength of the starch adhesive.
The invention provides a method for preparing a starch adhesive for a thermosetting artificial board with high starch content, which comprises the following steps:
firstly, the formula of the artificial board starch adhesive comprises: (in parts by mass)
(1) Preparing starch and water into starch milk with the concentration of 20-45% by mass ratio of dry basis of starch, and uniformly stirring;
(2) heating the starch milk to 60-70 ℃ at the speed of 2-3 ℃/min, preserving heat for 10min when the temperature reaches 50 ℃ in the heating process, heating to 60-70 ℃, adding 0.5mol/L hydrochloric acid, carrying out acidolysis for 2-3 h, and adjusting the pH to 4-6; adjusting the temperature of the starch milk subjected to acidolysis to 70-80 ℃ at the rate of 1-2 ℃/min, and pre-gelatinizing for 30-50 min;
(3) adding water into an initiator accounting for 50-70% of the total mass of the initiator to prepare an initiator solution with the mass concentration of 1-2%, preparing a seed emulsion from 15-20% of the initiator solution, a grafting monomer and an emulsifier, and dripping the seed emulsion into the reaction system pre-gelatinized in the step (2) at a constant speed within 20-40 min;
(4) immediately adding the rest initiator solution obtained in the step (3) for further grafting after 10-20 min of preliminary grafting is finished, dropwise adding a crosslinking monomer at a constant speed within 2-2.5 h after 20-30 min, and adding the rest initiator solution with the mass concentration of 1-2% prepared by 30-50% of the total mass of the initiator into the initiator solution after dropwise adding the crosslinking monomer for 1-1.5 h for reaction;
(5) and (4) heating the emulsion subjected to grafting and crosslinking modification in the step (4) to 85-90 ℃, keeping the temperature for 0.5-1 h to remove residual monomers, and cooling to 40-50 ℃ to obtain the starch adhesive.
In one embodiment of the invention, the starch is any one or combination of more of corn starch, waxy corn starch, tapioca starch, wheat starch, and cross-linked starch.
In one embodiment of the invention, the concentrated hydrochloric acid is 12mol/L concentrated hydrochloric acid.
In one embodiment of the present invention, the sodium hydroxide solution is a sodium hydroxide solution having a concentration of 10 mol/L.
In one embodiment of the invention, the initiator is a persulfate.
In one embodiment of the present invention, the grafting monomer is one or a mixture of vinyl acetate, acrylic acid and propylene.
In one embodiment of the invention, the emulsifier is any one or combination of sodium dodecyl sulfate, sodium dodecyl sulfonate, cetyl trimethyl ammonium bromide, octyl phenol polyoxyethylene ether-10 (OP-10) and phosphate ester emulsifier.
In one embodiment of the present invention, the crosslinking monomer is one or more of N-hydroxyacrylamide derivatives having a functional group with copolymerization and condensation properties, such as N- (isobutoxymethyl) -acrylamide, N-dimethylacrylamide, N-isopropoxymethacrylamide, and N-butoxymethylacrylamide, and ensures that no free formaldehyde is generated.
In one embodiment of the present invention, the dropwise addition of the crosslinking monomer in the step (4) is an aqueous solution of a crosslinking monomer with a dropwise addition mass concentration of 10 to 20%.
The invention provides the thermosetting artificial board starch adhesive with high starch content prepared by the method.
The invention provides the application of the prepared high-starch-content thermosetting artificial board starch adhesive in the hot-pressing bonding of artificial boards, plywood and wood blocks and the decoration of wood.
In one embodiment of the invention, the artificial board is thermally pressed and bonded by uniformly coating an adhesive on a thin board and then placing the thin board at normal temperature for 5-10min, wherein the thermal pressing pressure is 0.2-0.5MPa and the temperature is controlled at 90-130 ℃.
[ advantageous effects ]:
(1) the invention solves the problem that the adhesive with high starch content is agglomerated due to overlarge viscosity and nonuniform heating in a high-temperature reaction by adopting gradient temperature rise, thereby further increasing the proportion of the adhesive in the total solid content to more than 85 percent, using less non-renewable resources and reducing the cost of the starch adhesive.
(2) The artificial board prepared by the starch adhesive has the property exceeding the requirement of GBT 9846-.
Detailed Description
The present invention is further described below in conjunction with embodiments, it being understood that these examples are for illustrative purposes only and do not limit the scope of the present invention.
The proportion of starch in solid content is calculated by the formula:
placing the prepared product into an aluminum box with weighed mass in advance, drying the product in an oven at 105 ℃ to constant weight, weighing the total mass of the sample and the aluminum box, and calculating the solid content of the sample according to the following formula:
starch solid content (%) ═ m1/(m2-m3)×100
In the formula: m is1Mass of starch added, g
m2The mass of the dried product and the aluminum box, g
m3Mass of aluminum box, g
The effect of the addition of graft monomers on the performance of the adhesives is demonstrated by examples 1, 2 and 3
[ example 1 ]
Formula (mass/g):
the process flow comprises the following steps:
(1) preparing starch and water into starch milk with the concentration of 35% by mass of dry basis of starch, and uniformly stirring;
(2) heating the starch milk in the step (1) at the speed of 2 ℃/min, preserving the heat for 10min when the temperature reaches 50 ℃, continuing to heat to 70 ℃, diluting 8.6g of 12mol/L concentrated hydrochloric acid solution to 0.5mol/L, adding the diluted solution into the starch milk for acidolysis for 2.5h, and then adding 10mol/L sodium hydroxide solution to adjust the pH value to 4; adjusting the temperature of the starch milk subjected to acidolysis to 80 ℃ at the rate of 1 ℃/min, and pre-gelatinizing for 30 min;
(3) dissolving 0.51g of initiator in 40g of water to prepare an initiator solution, mixing the initiator solution accounting for 15 percent of the total mass of the initiator solution with an emulsifier and a grafting monomer to prepare a seed emulsion, cooling the system in the step (2) to 70 ℃ at the speed of 1 ℃/min, and then dropping the seed emulsion into the reaction system pre-gelatinized in the step (2) at a constant speed within 20 min;
(4) after 10min of preliminary grafting is finished, immediately adding the rest initiator solution for further grafting, dripping a crosslinking monomer solution with the mass concentration of 10% within 2h at a constant speed after 20min, and adding 30g of an initiator with the mass concentration of 1% within 1h after dripping the crosslinking monomer;
(5) and (4) heating the emulsion subjected to grafting and crosslinking modification in the step (4) to 85 ℃, keeping the temperature for 0.5h to remove residual monomers, and cooling to 40 ℃ to obtain the starch adhesive.
The product obtained in this example was milky white, glossy and had a very low initial viscosity. The solid content of the starch was calculated by referring to the above "calculation formula of the ratio of starch to solid content", and the ratio of starch to solid content in the product was 88%.
The three-layer plywood is hot-pressed at the temperature of 100 ℃ and the pressure of 0.4MPa, the dry strength of the manufactured three-layer plywood is 1.7MPa, and the wet strength is 1.45MPa (the wet strength is measured after soaking for 3h, if the plywood is cracked within 3h, the wet strength is calculated as 0, the relative wet strength is represented by the cracking time, and the longer the cracking time is, the better the water resistance is), which are all larger than the national standard 0.7 MPa.
[ example 2 ]
Formula (mass/g):
the process flow comprises the following steps:
(1) preparing starch and water into starch milk with the concentration of 35% by mass of dry basis of starch, and uniformly stirring;
(2) heating the starch milk in the step (1) at the speed of 2 ℃/min, preserving heat for 10min when the temperature reaches 50 ℃, continuing to heat to 70 ℃, preserving heat for 2.5h, diluting 8.6g of 12mol/L concentrated hydrochloric acid solution to 0.5mol/L, adding the diluted solution into the starch milk for acidolysis, and then adding 10mol/L sodium hydroxide solution to adjust the pH value to 4; adjusting the temperature of the starch milk subjected to acidolysis to 80 ℃ at the rate of 1 ℃/min, and pre-gelatinizing for 30 min;
(3) dissolving 0.51g of initiator in 40g of water to prepare an initiator solution, mixing the initiator solution accounting for 15 percent of the total mass of the initiator solution with an emulsifier and a grafting monomer to prepare a seed emulsion, cooling the system in the step (2) to 70 ℃ at the speed of 1 ℃/min, and then dropping the seed emulsion into the reaction system pre-gelatinized in the step (2) at a constant speed within 20 min;
(4) after 10min of preliminary grafting is finished, immediately adding the rest initiator solution for further grafting, dripping a crosslinking monomer solution with the mass concentration of 10% within 2h at a constant speed after 20min, and adding 30g of an initiator with the mass concentration of 1% within 1h after dripping the crosslinking monomer;
(5) and (4) heating the emulsion subjected to grafting and crosslinking modification in the step (4) to 85 ℃, keeping the temperature for 0.5h to remove residual monomers, and cooling to 40 ℃ to obtain the starch adhesive.
The product obtained in this example was milky white, glossy and low in initial viscosity, and the solid content of starch was calculated by referring to the above "calculation formula of the ratio of starch to solid content", and the ratio of starch to solid content in the product was 63%.
The three-layer plywood is hot-pressed at the temperature of 100 ℃ and the pressure of 0.4MPa, the dry strength of the manufactured three-layer plywood is 1.64MPa, and the wet strength is 1.48MPa (the wet strength is measured after soaking for 3h, if the plywood is cracked within 3h, the wet strength is calculated as 0, the relative wet strength is represented by the cracking time, and the longer the cracking time is, the better the water resistance is), which are all larger than the national standard of 0.7 MPa.
[ example 3 ]
Formula (mass/g):
the process flow comprises the following steps:
(1) preparing starch and water into starch milk with the concentration of 35% by mass of dry basis of starch, and uniformly stirring;
(2) heating the starch milk in the step (1) at the speed of 2 ℃/min, preserving heat for 10min when the temperature reaches 50 ℃, continuing to heat to 70 ℃, preserving heat for 2.5h, diluting 8.6g of 12mol/L concentrated hydrochloric acid solution to 0.5mol/L, adding the diluted solution into the starch milk for acidolysis, and then adding 10mol/L sodium hydroxide solution to adjust the pH value to 4; adjusting the temperature of the starch milk subjected to acidolysis to 80 ℃ at the rate of 1 ℃/min, and pre-gelatinizing for 30 min;
(3) dissolving 0.51g of initiator in 40g of water to prepare an initiator solution, mixing the initiator solution accounting for 15 percent of the total mass of the initiator solution with an emulsifier and a grafting monomer to prepare a seed emulsion, cooling the system in the step (2) to 70 ℃ at the speed of 1 ℃/min, and then dropping the seed emulsion into the reaction system pre-gelatinized in the step (2) at a constant speed within 20 min;
(4) after 10min of preliminary grafting is finished, immediately adding the rest initiator solution for further grafting, dripping a crosslinking monomer solution with the mass concentration of 10% within 2h at a constant speed after 20min, and adding 30g of an initiator with the mass concentration of 1% within 1h after dripping the crosslinking monomer;
(5) and (4) heating the emulsion subjected to grafting and crosslinking modification in the step (4) to 85 ℃, keeping the temperature for 0.5h to remove residual monomers, and cooling to 40 ℃ to obtain the starch adhesive.
The product obtained in this example was milky white, glossy and low in initial viscosity, and the solid content of starch was calculated by referring to the above "calculation formula of the ratio of starch to solid content", and the ratio of starch to solid content in the product was 48%.
The three-layer plywood is hot pressed at 100 ℃ and 0.4MPa, the dry strength of the manufactured three-layer plywood is 1.7MPa, and the wet strength is 1.59MPa (the wet strength is measured after soaking for 3h, if the glue is broken within 3h, the wet strength is calculated as 0, the relative wet strength is represented by the glue breaking time, and the longer the glue breaking time is, the better the water resistance is relatively), which is greater than the national standard of 0.7 MPa.
The effect of the addition amount of the grafting monomer on the performance of the adhesive is demonstrated by examples 1, 2, 3 and 4, and it can be seen from the above data through significant analysis that the influence of the addition amount of the grafting monomer on the dry strength and the wet strength of the adhesive is not great. The addition of too much graft monomer not only increases the length of the dropwise addition but also increases the consumption of non-renewable resources. Therefore, 2-6 g of grafting monomer is selected, and the proportion of starch in solid adhesive is greatly improved.
Comparative example 1
Formula (mass/g):
the process flow comprises the following steps:
(1) preparing starch and water into starch milk with the concentration of 35% by mass of dry basis of starch, and uniformly stirring;
(2) heating the starch milk in the step (1) at the speed of 2 ℃/min, preserving heat for 10min when the temperature reaches 50 ℃, continuing to heat to 70 ℃, preserving heat for 2.5h, diluting 8.6g of 12mol/L concentrated hydrochloric acid solution to 0.5mol/L, adding the diluted solution into the starch milk for acidolysis, and then adding 10mol/L sodium hydroxide solution to adjust the pH value to 4; adjusting the temperature of the starch milk subjected to acidolysis to 80 ℃ at the rate of 1 ℃/min, and pre-gelatinizing for 30 min;
(3) dissolving 0.51g of initiator in 40g of water to prepare an initiator solution, mixing the initiator solution accounting for 15 percent of the total mass of the initiator solution with an emulsifier and a grafting monomer to prepare a seed emulsion, cooling the system in the step (2) to 70 ℃ at the speed of 1 ℃/min, and then dropping the seed emulsion into the reaction system pre-gelatinized in the step (2) at a constant speed within 20 min;
(4) after 10min of preliminary grafting is finished, immediately adding the rest initiator solution for further grafting, dripping a crosslinking monomer solution with the mass concentration of 10% within 2h at a constant speed after 20min, and adding 30g of an initiator with the mass concentration of 1% within 1h after dripping the crosslinking monomer;
(5) and (4) heating the emulsion subjected to grafting and crosslinking modification in the step (4) to 85 ℃, keeping the temperature for 0.5h to remove residual monomers, and cooling to 40 ℃ to obtain the starch adhesive.
The product obtained by the comparative example is milky white, matt and high in initial viscosity, the solid content of the starch is calculated by referring to the formula for calculating the proportion of the starch to the solid content, the ratio of the starch to the solid content in the product is 90%, but the adhesive is very uneven and has milky white lumps, so that great difficulty is brought to gluing, and the product has no commercial utilization value.
Comparative example 2
The formulation was the same as in example 1;
the process flow comprises the following steps:
(1) preparing starch and water into starch milk with the concentration of 35% by mass of dry basis of starch, and uniformly stirring;
(2) heating the starch milk in the step (1) to 70 ℃ at the speed of 2 ℃/min, diluting 8.6g of 12mol/L concentrated hydrochloric acid solution to 0.5mol/L, adding the starch milk for acidolysis, carrying out acidolysis for 2.5h, then adding 10mol/L sodium hydroxide solution to adjust the pH to 4, adjusting the temperature of the starch milk after acidolysis to 80 ℃ at the speed of 1 ℃/min, and pregelatinizing for 30 min;
(3) dissolving 0.51g of initiator in 40g of water to prepare an initiator solution, mixing the initiator solution accounting for 15 percent of the total mass of the initiator solution with an emulsifier and a grafting monomer to prepare a seed emulsion, cooling the system in the step (2) to 70 ℃ at the speed of 1 ℃/min, and then dropping the seed emulsion into the reaction system pre-gelatinized in the step (2) at a constant speed within 20 min;
(4) after 10min of preliminary grafting is finished, immediately adding the rest initiator solution for further grafting, dripping a crosslinking monomer solution with the mass concentration of 10% within 2h at a constant speed after 20min, and adding 30g of an initiator with the mass concentration of 1% within 1h after dripping the crosslinking monomer;
(5) and (4) heating the emulsion subjected to grafting and crosslinking modification in the step (4) to 85 ℃, keeping the temperature for 0.5h to remove residual monomers, and cooling to 40 ℃ to obtain the starch adhesive.
The formed adhesive has high viscosity, the edge part loses fluidity to form gel, and the central area also forms partial agglomeration due to non-uniform reaction, so that the adhesive has no use value.
Comparative example 3
The formulation was the same as in example 1;
the process flow comprises the following steps:
(1) preparing starch and water into starch milk with the concentration of 35% by mass of dry basis of starch, and uniformly stirring;
(2) heating the starch milk in the step (1) at a speed of 5 ℃/min, keeping the temperature for 10min when the temperature reaches 50 ℃ in the heating process, continuing to heat to 70 ℃, diluting 8.6g of 12mol/L concentrated hydrochloric acid solution to 0.5mol/L, adding the diluted solution into the starch milk for acidolysis for 2.5h, and then adding 10mol/L sodium hydroxide solution to adjust the pH value to 4; adjusting the temperature of the starch milk subjected to acidolysis to 80 ℃ at the speed of 10 ℃/min, and pre-gelatinizing for 30 min;
(3) dissolving 0.51g of initiator in 40g of water to prepare an initiator solution, mixing the initiator solution accounting for 15 percent of the total mass of the initiator solution with an emulsifier and a grafting monomer to prepare a seed emulsion, cooling the system in the step (2) to 70 ℃ at the speed of 1 ℃/min, and then dropping the seed emulsion into the reaction system pre-gelatinized in the step (2) at a constant speed within 20 min;
(4) after 10min of preliminary grafting is finished, immediately adding the rest initiator solution for further grafting, dripping a crosslinking monomer solution with the mass concentration of 10% within 2h at a constant speed after 20min, and adding 30g of an initiator with the mass concentration of 1% within 1h after dripping the crosslinking monomer;
(5) and (4) heating the emulsion subjected to grafting and crosslinking modification in the step (4) to 85 ℃, keeping the temperature for 0.5h to remove residual monomers, and cooling to 40 ℃ to obtain the starch adhesive.
In the comparative example, due to the fact that the temperature rising rate is too high, the formed adhesive is high in viscosity, the edge part loses fluidity to form gel, a large amount of blocks are formed in the central area due to uneven reaction, and the use value is low.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A method for preparing a thermosetting artificial board starch adhesive with high starch content is characterized by comprising the following steps:
firstly, the formula of the artificial board starch adhesive comprises: (in parts by mass)
(1) Preparing starch and water into starch milk with the concentration of 20-45% by mass ratio of dry basis of starch, and uniformly stirring;
(2) heating the starch milk to 60-70 ℃ at the speed of 2-3 ℃/min, preserving heat for 10min when the temperature reaches 50 ℃ in the heating process, heating to 60-70 ℃, adding 0.5mol/L hydrochloric acid, carrying out acidolysis for 2-3 h, and adjusting the pH to 4-6; adjusting the temperature of the starch milk subjected to acidolysis to 70-80 ℃ at the rate of 1-2 ℃/min, and pre-gelatinizing for 30-50 min;
(3) adding water into an initiator accounting for 50-70% of the total mass of the initiator to prepare an initiator solution with the mass concentration of 1-2%, taking 15-20% of the initiator solution by mass, grafting a monomer and an emulsifier to prepare a seed emulsion, and dripping the seed emulsion into the reaction system pre-gelatinized in the step (2) at a constant speed within 20-40 min for reaction;
(4) immediately adding the rest initiator solution obtained in the step (3) for further grafting after 10-20 min of preliminary grafting is finished, dropwise adding a crosslinking monomer at a constant speed within 2-2.5 h after 20-30 min, and adding the rest initiator solution with the mass concentration of 1-2% prepared by 30-50% of the total mass of the initiator into the initiator solution after dropwise adding the crosslinking monomer for 1-1.5 h for reaction;
(5) and (4) heating the emulsion subjected to grafting and crosslinking modification in the step (4) to 85-90 ℃, keeping the temperature for 0.5-1 h to remove residual monomers, and cooling to 40-50 ℃ to obtain the starch adhesive.
2. The method of claim 1, wherein the starch is any one or more of corn starch, waxy corn starch, tapioca starch, wheat starch, and cross-linked starch.
3. The method of claim 1, wherein the initiator is a persulfate.
4. The method of claim 1, wherein the grafting monomer is one or more of vinyl acetate, acrylic acid and propylene.
5. The method of claim 1, wherein the emulsifier is any one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, cetyl trimethyl ammonium bromide, octyl phenol polyoxyethylene ether-10 (OP-10), and phosphate ester emulsifier.
6. The method according to claim 1, wherein the crosslinking monomer is one or more of N- (isobutoxymethyl) -acrylamide, N-dimethylacrylamide, N-isopropoxymethacrylamide and N-butoxymethacrylamide.
7. The method according to claim 1, wherein the concentrated hydrochloric acid is 12mol/L concentrated hydrochloric acid, and the sodium hydroxide solution is 10mol/L sodium hydroxide solution.
8. The method according to claim 1, wherein the dropwise addition of the crosslinking monomer in the step (5) is an aqueous solution of the crosslinking monomer with an dropwise addition mass concentration of 10-20%.
9. The high-starch-content thermosetting artificial board starch adhesive prepared by the method according to any one of claims 1 to 8.
10. The high starch content thermosetting artificial board starch adhesive of claim 9 is used for hot-pressing adhesion of artificial boards, plywood and wood blocks, and decoration of wood.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114106749A (en) * | 2021-12-24 | 2022-03-01 | 江南大学 | Low-viscosity thermosetting particle board starch adhesive and preparation method thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009263450A (en) * | 2008-04-23 | 2009-11-12 | Henkel Japan Ltd | Adhesive for label |
| CN105820780A (en) * | 2016-06-07 | 2016-08-03 | 江南大学 | Wood starch adhesive based on pre-emulsification technology and preparing method of wood starch adhesive |
| CN111205794A (en) * | 2020-02-26 | 2020-05-29 | 江南大学 | Starch adhesive for thermosetting artificial board and preparation method thereof |
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2020
- 2020-06-24 CN CN202010592418.1A patent/CN111592842A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2009263450A (en) * | 2008-04-23 | 2009-11-12 | Henkel Japan Ltd | Adhesive for label |
| CN105820780A (en) * | 2016-06-07 | 2016-08-03 | 江南大学 | Wood starch adhesive based on pre-emulsification technology and preparing method of wood starch adhesive |
| CN111205794A (en) * | 2020-02-26 | 2020-05-29 | 江南大学 | Starch adhesive for thermosetting artificial board and preparation method thereof |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114106749A (en) * | 2021-12-24 | 2022-03-01 | 江南大学 | Low-viscosity thermosetting particle board starch adhesive and preparation method thereof |
| CN114106749B (en) * | 2021-12-24 | 2022-08-02 | 江南大学 | Low-viscosity thermosetting type shaving board starch adhesive and preparation method thereof |
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