CN106753104B - Urea-formaldehyde resin adhesive as well as preparation method and application thereof - Google Patents
Urea-formaldehyde resin adhesive as well as preparation method and application thereof Download PDFInfo
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- CN106753104B CN106753104B CN201611171313.9A CN201611171313A CN106753104B CN 106753104 B CN106753104 B CN 106753104B CN 201611171313 A CN201611171313 A CN 201611171313A CN 106753104 B CN106753104 B CN 106753104B
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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
- C09J161/00—Adhesives based on condensation polymers of aldehydes or ketones; Adhesives based on derivatives of such polymers
- C09J161/20—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
- C09J161/32—Modified amine-aldehyde condensates
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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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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G12/00—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
- C08G12/02—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes
- C08G12/40—Chemically modified polycondensates
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Abstract
The invention provides a urea-formaldehyde resin adhesive which is prepared from the following raw materials in parts by mass: 100 parts of urea, 50-60 parts of formaldehyde, 5-20 parts of water, 0.5-3 parts of a coupling agent, 0.5-2 parts of polyethylene glycol and 0.5-5 parts of lignin. The urea-formaldehyde resin adhesive provided by the invention can reduce the formaldehyde emission and simultaneously can ensure the mechanical property of an adhered product. The urea-formaldehyde resin adhesive provided by the invention is milky, the content of free aldehyde is lower than 0.12%, the solid content is 41-58%, and the viscosity is 17-30S. In addition, the plate prepared by the urea-formaldehyde resin adhesive provided by the invention has the static bending strength of 20.1-28.9 MPa, the elastic modulus of 1689-2635 MPa, the internal bonding strength of 0.39-0.58 MPa, the water absorption thickness expansion rate of 5.1-9.5% and the formaldehyde release amount of 0.11-0.42 mg/L.
Description
Technical Field
The invention relates to the technical field of organic materials, in particular to a urea-formaldehyde resin adhesive and a preparation method and application thereof.
Background
Natural or synthetic, organic or inorganic substances, collectively called adhesives, which are capable of joining two or more articles or materials together by interfacial adhesion and cohesion. With the increasing growth of the artificial board industry, wood composite materials are widely applied to the fields of house construction, home furnishing and the like. For wood composites, the use of adhesives is essential.
However, under the large background that wood composite materials are widely used in house construction, home furnishing and the like, which are closely related to human life, the used adhesives are still mainly 'trialdehyde' adhesives, namely urea-formaldehyde resin adhesives, phenol-formaldehyde resin adhesives and melamine resin adhesives. The products prepared from the trialdehyde glue have the problem of continuous formaldehyde release, and the formaldehyde is a potential carcinogen and threatens the health of human beings.
In order to meet the requirement of environmental protection performance of products, most artificial board factories adopt a urea formaldehyde resin adhesive formula or a modified urea formaldehyde resin formula with low aldehyde urea ratio for production. However, these adjustments have an effect on the mechanical properties of the product to which they are bonded.
Disclosure of Invention
The invention aims to provide a urea-formaldehyde resin adhesive and a preparation method and application thereof. The urea-formaldehyde resin adhesive provided by the invention can reduce the formaldehyde emission and simultaneously can ensure the mechanical property of an adhered product.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a urea-formaldehyde resin adhesive which is prepared from the following raw materials in parts by mass:
preferably, the lignin is one or more of wood grinding lignin, corncob lignin, bamboo lignin and straw lignin.
Preferably, the coupling agent is a polyisocyanate and/or a silicone coupling agent.
The invention also provides a preparation method of the urea-formaldehyde resin adhesive, which comprises the following steps:
mixing formaldehyde, water, a first part of urea, a coupling agent and polyethylene glycol, and then carrying out a first polycondensation reaction to obtain a first polycondensate;
after the pH value of the first condensation polymer is adjusted to 6-6.5, mixing the first condensation polymer with a second part of urea and lignin for a second condensation polymerization reaction to obtain a second condensation polymer;
adjusting the pH value of the second condensation polymer to 7.5-8, and mixing with the residual urea to perform a third condensation polymerization reaction to obtain a third condensation polymer;
and adjusting the pH value of the third condensation polymer to 7-7.5 to obtain the urea-formaldehyde resin adhesive.
Preferably, the temperature of the first polycondensation reaction is 90-95 ℃;
the time of the first polycondensation reaction is 20-40 minutes.
Preferably, the temperature of the second polycondensation reaction is 90-95 ℃;
the time of the second polycondensation reaction is 20-40 minutes.
Preferably, the temperature of the third polycondensation reaction is 80-90 ℃;
the time of the third polycondensation reaction is 20-40 minutes.
Preferably, the mass ratio of the first part of urea to the second part of urea to the residual urea is (50-60): (20-25): (20-25).
The invention also provides an application of the urea-formaldehyde resin adhesive in the technical scheme or the urea-formaldehyde resin adhesive obtained by the preparation method in the technical scheme, and the urea-formaldehyde resin adhesive is used as an adhesive for fiber boards, shaving boards, woodworking boards and bamboo and wood plywood.
The invention provides a urea-formaldehyde resin adhesive which is prepared from the following raw materials in parts by mass: 100 parts of urea, 50-60 parts of formaldehyde, 5-20 parts of water, 0.5-3 parts of a coupling agent, 0.5-2 parts of polyethylene glycol and 0.5-5 parts of lignin. The urea-formaldehyde resin adhesive provided by the invention can reduce the formaldehyde emission and simultaneously can ensure the mechanical property of an adhered product. According to the experimental results of the embodiment, the urea-formaldehyde resin adhesive provided by the invention is milky white, the content of free aldehyde is lower than 0.12%, the solid content is 41-58%, and the viscosity is 17-30S; the plate prepared by the urea-formaldehyde resin adhesive provided by the invention has the static bending strength of 20.1-28.9 MPa, the elastic modulus of 1689-2635 MPa, the internal bonding strength of 0.39-0.58 MPa, the water absorption thickness expansion rate of 5.1-9.5% and the formaldehyde release amount of 0.11-0.42 mg/L.
The invention also provides a preparation method of the urea-formaldehyde resin adhesive, which comprises the following steps: mixing formaldehyde, water, a first part of urea, a coupling agent and polyethylene glycol, and then carrying out a first polycondensation reaction to obtain a first polycondensate; after the pH value of the first condensation polymer is adjusted to 6-6.5, mixing the first condensation polymer with a second part of urea and lignin for a second condensation polymerization reaction to obtain a second condensation polymer; adjusting the pH value of the second condensation polymer to 7.5-8, and mixing with the residual urea to perform a third condensation polymerization reaction to obtain a third condensation polymer; and adjusting the pH value of the third condensation polymer to 7-7.5 to obtain the urea-formaldehyde resin adhesive. The preparation method provided by the invention can fully carry out the reaction of each step, can consume formaldehyde to the maximum extent, and further reduces the content of formaldehyde in the final product.
Detailed Description
The invention provides a urea-formaldehyde resin adhesive which is prepared from the following raw materials in parts by mass:
in the invention, the raw material for preparing the urea-formaldehyde resin adhesive comprises 100 parts of urea based on the amount of the urea. The source of the urea is not particularly required in the present invention, and specifically, commercially available urea may be used. In the present invention, the purity of the urea is preferably 98% or more, more preferably 98.5% or more, and most preferably 99% or more.
Based on 100 parts of urea, the raw material for preparing the urea-formaldehyde resin adhesive comprises 50-60 parts of formaldehyde, preferably 52-58 parts, and more preferably 54-56 parts. In the present invention, the formaldehyde is preferably added in the form of a formaldehyde solution, more preferably an aqueous formaldehyde solution, the mass parts of the formaldehyde being calculated as formaldehyde in the aqueous formaldehyde solution. In the present invention, the mass concentration of the formaldehyde solution is preferably 35 to 40%, more preferably 36 to 39%, and most preferably 37 to 38%.
The urea-formaldehyde resin adhesive prepared by the invention comprises 5-20 parts of water, preferably 10-18 parts of water, and more preferably 12-15 parts of water based on 100 parts of urea. The source of the water is not particularly limited, and the water may be deionized water, distilled water, purified water or tap water.
The raw material for preparing the urea resin adhesive of the present invention comprises 0.5 to 3 parts of a coupling agent, preferably 1 to 2.5 parts, more preferably 1.5 to 2 parts, based on 100 parts of urea, wherein the coupling agent is preferably a polyisocyanate and/or a silicone coupling agent, wherein the polyisocyanate is preferably a diisocyanate and/or a triisocyanate, and wherein the silicone coupling agent is preferably one or more of gamma-aminopropyltriethoxysilane (KH550), gamma-glycidoxypropyltrimethoxysilane (KH560), gamma- (methacryloyloxy) propyltrimethoxysilane (KH570), N- (β -aminoethyl) -gamma-aminopropyltrimethoxysilane (KH792), N- β - (aminoethyl) -gamma-aminopropylmethyldimethoxysilane (DL602), and vinyltrimethoxysilane (DL 171).
Based on 100 parts of urea, the raw material for preparing the urea-formaldehyde resin adhesive comprises 0.5-2 parts of polyethylene glycol, preferably 0.8-1.8 parts, and more preferably 1-1.5 parts. The source of the polyethylene glycol is not particularly required, and the polyethylene glycol can be commercially available. The polyethylene glycol specification of the present invention is not particularly limited, and polyethylene glycol known to those skilled in the art may be used. In the invention, the polyethylene glycol is preferably one or more of polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, polyethylene glycol 800, polyethylene glycol 1000 and polyethylene glycol 1500.
Based on 100 parts of urea, the raw material for preparing the urea-formaldehyde resin adhesive comprises 0.5-5 parts of lignin, preferably 1-4 parts, and more preferably 2-3 parts. In the invention, the lignin is preferably one or more of wood grinding lignin, corncob lignin, bamboo lignin and straw lignin. The source of the lignin is not particularly limited in the present invention, and may be commercially available lignin of the above kind, for example, lignin extracted from paper pulp black liquor. The method for extracting lignin from the papermaking pulp black liquor has no special requirements, and equipment and methods which are well known by the technical personnel in the field are adopted for extraction.
The invention provides a preparation method of the urea-formaldehyde resin adhesive, which comprises the following steps:
mixing formaldehyde, water, a first part of urea, a coupling agent and polyethylene glycol, and then carrying out a first polycondensation reaction to obtain a first polycondensate;
after the pH value of the first condensation polymer is adjusted to 6-6.5, mixing the first condensation polymer with a second part of urea and lignin for a second condensation polymerization reaction to obtain a second condensation polymer;
adjusting the pH value of the second condensation polymer to 7.5-8, and mixing with the residual urea to perform a third condensation polymerization reaction to obtain a third condensation polymer;
and adjusting the pH value of the third condensation polymer to 7-7.5 to obtain the urea-formaldehyde resin adhesive.
The method comprises the steps of mixing formaldehyde, water, a first part of urea, a coupling agent and polyethylene glycol, and then carrying out a first polycondensation reaction to obtain a first polycondensate. In the preferred embodiment of the present invention, formaldehyde is mixed with water prior to mixing with the first portion of urea, the coupling agent, and the polyethylene glycol. The preferred pH of the formaldehyde and water mixture of the present invention is adjusted to a pH of 8.5 to 9, more preferably 8.6 to 8.9, and most preferably 8.7 to 8.8 prior to mixing with the first portion of urea, coupling agent, and polyethylene glycol.
The invention has no special requirement on the substance for adjusting the pH value of the mixture of the formaldehyde and the water, and inorganic alkali liquor which is well known by the technical personnel in the field can be adopted. In the present invention, the inorganic alkali solution is preferably a sodium hydroxide solution and/or a potassium hydroxide solution. The invention has no special requirement on the concentration of the inorganic alkali liquor, and can adjust the pH value of the mixture of formaldehyde and water. According to the invention, the reaction rate of formaldehyde and urea can be slowed down by adjusting the pH value of the mixture of formaldehyde and water to 8.5-9, so that the first polycondensation reaction is carried out more fully.
In the invention, the temperature of the first polycondensation reaction is preferably 90-95 ℃, more preferably 91-94 ℃, and most preferably 92-93 ℃; the time of the first polycondensation reaction is preferably 20 to 40 minutes, more preferably 25 to 35 minutes, and most preferably 28 to 33 minutes
In the present invention, it is preferred to raise the temperature from room temperature to the temperature of the first polycondensation reaction. In the invention, the heating rate of heating to the first polycondensation reaction temperature is preferably controlled by the heating time; the temperature rise time is preferably 40 to 45 minutes, more preferably 41 to 44 minutes, and most preferably 42 to 43 minutes.
After the first condensation polymer is obtained, the pH value of the first condensation polymer is adjusted to 6-6.5, and then the first condensation polymer is mixed with a second part of urea and lignin to carry out a second condensation polymerization reaction, so that a second condensation polymer is obtained. The pH value of the first condensation polymer is adjusted to 6-6.5, preferably 6.1-6.4, and more preferably 6.2-6.3. The present invention does not require a substance for adjusting the pH of the first polycondensate, and an inorganic acid or an organic acid known to those skilled in the art may be used. In the present invention, the inorganic acid is preferably hydrochloric acid, sulfuric acid, or nitric acid; the organic acid is preferably formic acid or acetic acid. The present invention does not require any particular concentration of the inorganic acid and the organic acid, and the pH of the first polycondensate may be adjusted.
The pH of the first polycondensate is preferably adjusted in four stages according to the invention: a first stage, a second stage, a third stage, and a fourth stage. In the present invention, the first stage preferably adjusts the pH of the first polycondensate to 5.8 to 6, and specifically may be 5.8, 5.9 or 6. In the present invention, the interval between the first stage and the second stage is preferably 8 to 10 minutes, and specifically may be 8 minutes, 9 minutes, or 10 minutes. In the present invention, the pH of the first polycondensate in the second stage is preferably adjusted to 5.0 to 5.1, and specifically, may be 5.0 or 5.1. In the present invention, the interval between the second stage and the third stage is preferably 8 to 10 minutes, and specifically may be 8 minutes, 9 minutes, or 10 minutes. In the present invention, the third stage preferably adjusts the pH of the first polycondensate to 4.5 to 4.7, and specifically, may be 4.5, 4.6 or 4.7. In the present invention, the interval between the third stage and the fourth stage is preferably controlled by the viscosity of the polycondensate. The invention preferably enters the fourth stage when the viscosity of the first polycondensate is 16-16.5S (25 ℃, coating 4# cup), more preferably 16.1-16.4S, and most preferably 16.2-16.3S. In the present invention, the fourth stage is to adjust the pH of the first condensation polymer to 6 to 6.5, which is not described herein again. The invention controls the pH value of the first condensation polymer by stages to slow down the reaction rate of formaldehyde and urea, so that the second condensation polymerization reaction is carried out more fully. The invention adjusts the pH value step by step to make the reaction proceed mildly and prevent the reaction from being too violent. In addition, the product can be prevented from crystallizing and solidifying, resulting in insufficient reaction.
In the invention, the temperature of the second polycondensation reaction is preferably 90-95 ℃, more preferably 91-94 ℃, and most preferably 92-93 ℃; the time of the second polycondensation reaction is preferably 20 to 40 minutes, more preferably 25 to 35 minutes, and most preferably 28 to 33 minutes.
After the second condensation polymer is obtained, the pH value of the second condensation polymer is adjusted to 7.5-8, and then the second condensation polymer is mixed with the residual urea to carry out a third condensation polymerization reaction, so that a third condensation polymer is obtained. According to the invention, the obtained second condensation polymer is preferably kept still, and the pH value of the second condensation polymer is adjusted to be 7.5-8, more preferably 17.2-17.8S, and most preferably 17.4-17.6S after the viscosity of the second condensation polymer is 17-18S (25 ℃, 4# cup coating). The pH value of the second condensation polymer is adjusted to 7.5-8, preferably 7.6-7.9, and more preferably 7.7-7.8. The invention has no special requirements for the substance for adjusting the pH value of the second polycondensate, and inorganic alkali liquor which is well known to those skilled in the art can be adopted. In the present invention, the inorganic alkali solution described herein is the same as the inorganic alkali solution described in the above technical scheme, and the detailed description thereof is omitted.
In the invention, the temperature of the third polycondensation reaction is preferably 80-90 ℃, more preferably 82-88 ℃, and most preferably 84-86 ℃; the time of the third polycondensation reaction is preferably 20 to 40 minutes, more preferably 25 to 35 minutes, and most preferably 28 to 33 minutes.
In the invention, the mass ratio of the first part of urea to the second part of urea to the residual urea is preferably (50-60): 20-25), more preferably (52-58): 21-24, and most preferably (54-56): 22-23.
After the third condensation polymer is obtained, the pH value of the third condensation polymer is adjusted to 7-7.5, and the urea-formaldehyde resin adhesive is obtained. The pH value of the third condensation polymer is adjusted to 7-7.5, preferably 7.1-7.4, and more preferably 7.2-7.3. The present invention does not require a substance for adjusting the pH of the third polycondensate, and an inorganic acid or an organic acid known to those skilled in the art may be used. In the present invention, the inorganic acid and the organic acid are the same as those described in the above technical solution, and are not described herein again. According to the invention, the pH value of the third condensation polymer is adjusted to 7-7.5, so that the adhesive can be prevented from being solidified to generate a glue block, the viscosity of the adhesive and the use performance of the glue can be improved, and in addition, the storage time can be prolonged.
The invention also provides an application of the urea-formaldehyde resin adhesive in the technical scheme or the urea-formaldehyde resin adhesive obtained by the preparation method in the technical scheme, and the urea-formaldehyde resin adhesive is used as an adhesive for fiber boards, shaving boards, woodworking boards and bamboo and wood plywood.
The urea-formaldehyde resin adhesive provided by the present invention, the preparation method and the application thereof are described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.
In the examples of the present invention, unless otherwise specified, the parts are all parts by mass.
Example 1
139 parts of formaldehyde aqueous solution with the mass fraction of 37% are weighed and added into a reaction kettle at one time, 15 parts of water is added, the pH value is adjusted to 8.5, 55.5 parts of urea with the purity of 98% is added at the first time, then 3 parts of KH550 and 2 parts of polyethylene glycol (400) are added, and the mixture is stirred with steam and heated.
And (3) heating the reaction kettle from the temperature of below 50 ℃, heating for 40 minutes, heating to 90 ℃, and carrying out heat preservation reaction for 30 minutes at the temperature of 90 ℃. After the holding time is up, under the condition that the temperature is kept at 90 ℃, the pH value is firstly adjusted to 5.8, the pH value is adjusted to 5.0 after 10 minutes, and the pH value is adjusted to 4.7 after 8 minutes. And testing the viscosity, adjusting the pH value to 6.2 after the viscosity reaches 16S (25 ℃, coating in a No. 4 cup), adding 21.5 parts of urea with the purity of 98% for the second time, adding 3 parts of wood grinding lignin, reacting for 30 minutes, measuring the viscosity again, and adjusting the pH value to 7.5 after the viscosity reaches 17S (25 ℃, coating in a No. 4 cup).
And after the pH value is adjusted to 7.5, adding 23 parts of urea with the purity of 98% for the third time, preserving the heat for 20 minutes, cooling to 40 ℃, adjusting the pH value to 7.0, and discharging to obtain the urea-formaldehyde resin adhesive.
The obtained urea-formaldehyde resin adhesive is used for producing medium-density fiberboards, the produced products are detected according to national standards of the national quality supervision and quarantine Bureau GB/T14732-2006 Urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde resins for adhesives in the wood industry, GB/T17657-2013 physicochemical property test methods for artificial boards and veneered artificial boards, GB/T18580-.
TABLE 1 test results of various properties of urea-formaldehyde resin adhesive and fiberboard (15mm board)
As can be seen from Table 1, the urea-formaldehyde resin adhesive of this example has a low free aldehyde content of 0.12% or less. The produced fiber board has strong static bending strength, high internal bonding strength and high elastic modulus which are all higher than standard values; the water absorption thickness expansion rate and the formaldehyde emission are low, and the requirements of E0-grade standard are met.
Example 2
Weighing 150 parts of formaldehyde with the mass fraction of 37%, adding the formaldehyde into a reaction kettle at one time, adding 5 parts of water, adjusting the pH value to 8.8, adding 55.5 parts of urea with the purity of 98% at the first time, adding 2 parts of KH560 and 1.5 parts of polyethylene glycol (400), and stirring and heating by opening steam.
And (3) heating the reaction kettle from the temperature of below 50 ℃, heating for 45 minutes, heating to 95 ℃, and carrying out heat preservation reaction for 30 minutes at the temperature of 95 ℃. After the holding time is up, under the condition that the temperature is kept at 95 ℃, the pH value is firstly adjusted to 6.0, the pH value is adjusted to 5.1 after 10 minutes, and the pH value is adjusted to 4.5 after 10 minutes. And testing the viscosity, adjusting the pH value to 6.5 after the viscosity reaches 16.5S (coating the No. 4 cup at 25 ℃), adding 21.5 parts of urea with the purity of 98% for the second time, adding 3 parts of corncob lignin, reacting for 30 minutes, measuring the viscosity again, and adjusting the pH value to 7.8 after the viscosity reaches 18S (coating the No. 4 cup at 25 ℃).
And after the pH value is adjusted to 7.8, adding 23 parts of urea with the purity of 98% for the third time, preserving the heat for 20 minutes, cooling to 40 ℃, adjusting the pH value to 7.5, and discharging to obtain the urea-formaldehyde resin adhesive.
The obtained urea-formaldehyde resin adhesive is used for producing shaving boards, the produced products are detected according to national standards of the national quality supervision and quarantine Bureau GB/T14732-2006 Urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde resins for adhesives in the wood industry, GB/T17657-2013 physicochemical property test methods for artificial boards and veneered artificial boards, GB/T18580 + 2008 Formaldehyde release limit in artificial boards and products thereof for interior decoration materials and GB/T4897.3-2003 shaving boards, and the performance detection results are shown in Table 2.
TABLE 2 test results of various properties of urea-formaldehyde resin adhesive and particle board (15mm board)
As can be seen from Table 2, the urea-formaldehyde resin adhesive of this example has a low free aldehyde content of 0.15% or less. The produced shaving board has strong static bending strength, high internal bonding strength and high elastic modulus which are all higher than standard values; the water absorption thickness expansion rate and the formaldehyde emission are low, and the requirements of E0-grade standard are met.
Example 3
Weighing 150 parts of formaldehyde with the mass fraction of 37%, adding the formaldehyde into a reaction kettle at one time, adding 10 parts of water, adjusting the pH value to be 8.6, adding 55.5 parts of urea with the purity of 98% at the first time, adding 0.5 part of KH570 and 0.5 part of polyethylene glycol (400), and stirring and heating by using steam.
And (3) heating the reaction kettle from the temperature of below 50 ℃, heating for 45 minutes, heating to 93 ℃, and carrying out heat preservation reaction for 30 minutes at the temperature of 93 ℃. After the holding time is up, under the condition that the temperature is kept at 93 ℃, the pH value is firstly adjusted to 6.0, the pH value is adjusted to 5.1 after 10 minutes, and the pH value is adjusted to 4.5 after 10 minutes. And testing the viscosity, after the viscosity reaches 16.5S (25 ℃, coating 4# cup), adjusting the pH value to 6.5, adding 21.5 parts of urea with the purity of 98% for the second time, adding 0.5 part of straw lignin, reacting for 30 minutes, testing the viscosity again, and after the viscosity reaches 18S (25 ℃, coating 4# cup), adjusting the pH value to 7.8.
And after the pH value is adjusted to 7.8, adding 23 parts of urea with the purity of 98% for the third time, preserving the heat for 30 minutes, cooling to 40 ℃, adjusting the pH value to 7.5, and discharging to obtain the urea-formaldehyde resin adhesive.
The obtained urea-formaldehyde resin adhesive is used for producing the core-board, the produced product is detected according to the physical and chemical performance test method of artificial boards and veneered artificial boards of the national quality supervision and quarantine administration GB/T14732-2006 Urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde resins for wood industry adhesive, GB/T17657-2013 Standard of core-board, GB/T5849 Ampere 2006 Standard of core-board, GB/T18580-2008 Formaldehyde release limit in artificial boards and products for interior decoration materials and the quality monitoring spot check scheme of the national forestry administration 2015 forest products, and the performance detection result is shown in Table 3.
Table 3: urea-formaldehyde resin adhesive and detection result of various performances of core-board
As can be seen from Table 3, the urea-formaldehyde resin adhesive of this example has a low free aldehyde content of 0.15% or less. The transverse static bending strength and the surface bonding strength of the produced core-board are high and higher than standard values, the formaldehyde emission is low, and the core-board meets the requirements of E0-level standards.
Example 4
152 parts of formaldehyde with the mass fraction of 37% are weighed and added into a reaction kettle at one time, 20 parts of water is added, the pH value is adjusted to be 8.8, 55.5 parts of urea with the purity of 98% is added at the first time, 1 part of DL602 and 1 part of polyethylene glycol (400) are added, and steam is started to stir and heat.
And (3) heating the reaction kettle from the temperature of below 50 ℃, heating to 93 ℃ after 43 minutes, and carrying out heat preservation reaction for 30 minutes at the temperature of 93 ℃. After the holding time is up, the pH value is adjusted to 6.0 firstly under the condition that the temperature is kept at 93 ℃, the pH value is adjusted to 1 after 10 minutes, and the pH value is adjusted to 4.5 after 8 minutes. And testing the viscosity, adjusting the pH value to 6.5 after the viscosity reaches 16.5S (coating in a No. 4 cup at 25 ℃), adding 21.5 parts of urea with the purity of 98% for the second time, adding 5 parts of bamboo lignin, reacting for 30 minutes, measuring the viscosity again, and adjusting the pH value to 7.5 after the viscosity reaches 18S (coating in a No. 4 cup at 25 ℃).
And after the pH value is adjusted to 7.5, adding 23 parts of urea with the purity of 98% for the third time, preserving the heat for 25 minutes, cooling to 40 ℃, adjusting the pH value to 7.0, and discharging to obtain the urea-formaldehyde resin adhesive.
The obtained urea-formaldehyde resin adhesive is used for producing bamboo and wood plywood, the produced products are detected according to the physical and chemical performance test methods of artificial boards and veneered artificial boards of the general Bureau of quality supervision and quarantine GB/T14732-2006 Urea, phenol-formaldehyde and melamine-formaldehyde resins for adhesives in the wood industry, GBT17657-2013, GB/T9846.1-GB/T9846.12-2004 national Standard for plywood and GB/T18580-2008 Formaldehyde emission limit for Artificial boards for interior decoration materials and products thereof, and the performance detection results are shown in Table 4.
Table 4: urea-formaldehyde resin adhesive and detection results of various properties of bamboo and wood plywood
As can be seen from Table 4, the urea-formaldehyde resin adhesive of this example has a low free aldehyde content of 0.13% or less. The produced bamboo and wood plywood has low formaldehyde emission and meets the standard requirement of E0 level.
The urea-formaldehyde resin adhesive is prepared from the following raw materials in parts by mass: 100 parts of urea, 50-60 parts of formaldehyde, 5-20 parts of water, 0.5-3 parts of a coupling agent, 0.5-2 parts of polyethylene glycol and 0.5-5 parts of lignin. The urea-formaldehyde resin adhesive provided by the invention can reduce the formaldehyde emission and simultaneously can ensure the mechanical property of an adhered product. According to the experimental results of the embodiment, the urea-formaldehyde resin adhesive provided by the invention is milky white, the content of free aldehyde is lower than 0.12%, the solid content is 41-58%, and the viscosity is 17-30S. In addition, the plate prepared by the urea-formaldehyde resin adhesive provided by the invention has the static bending strength of 20.1-28.9 MPa, the elastic modulus of 1689-2635 MPa, the internal bonding strength of 0.39-0.58 MPa, the water absorption thickness expansion rate of 5.1-9.5% and the formaldehyde release amount of 0.11-0.42 mg/L.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (7)
1. The urea-formaldehyde resin adhesive is prepared from the following raw materials in parts by mass:
the lignin is one or more of wood grinding lignin, corncob lignin, bamboo lignin and straw lignin;
the coupling agent is polyisocyanate and/or organosilicon coupling agent.
2. A method for preparing the urea formaldehyde resin adhesive of claim 1, comprising the steps of:
mixing formaldehyde, water, a first part of urea, a coupling agent and polyethylene glycol, and then carrying out a first polycondensation reaction to obtain a first polycondensate;
after the pH value of the first condensation polymer is adjusted to 6-6.5, mixing the first condensation polymer with a second part of urea and lignin for a second condensation polymerization reaction to obtain a second condensation polymer;
adjusting the pH value of the second condensation polymer to 7.5-8, and mixing with the residual urea to perform a third condensation polymerization reaction to obtain a third condensation polymer;
and adjusting the pH value of the third condensation polymer to 7-7.5 to obtain the urea-formaldehyde resin adhesive.
3. The method according to claim 2, wherein the temperature of the first polycondensation reaction is 90 to 95 ℃;
the time of the first polycondensation reaction is 20-40 minutes.
4. The method according to claim 2, wherein the temperature of the second polycondensation reaction is 90 to 95 ℃;
the time of the second polycondensation reaction is 20-40 minutes.
5. The method according to claim 2, wherein the temperature of the third polycondensation reaction is 80 to 90 ℃;
the time of the third polycondensation reaction is 20-40 minutes.
6. The method according to any one of claims 2 to 5, wherein the mass ratio of the first part of urea to the second part of urea to the remaining part of urea is (50-60): (20-25): (20-25).
7. The application of the urea-formaldehyde resin adhesive of claim 1 or the urea-formaldehyde resin adhesive prepared by the preparation method of any one of claims 2 to 6 is characterized in that the urea-formaldehyde resin adhesive is used as an adhesive for fiber boards, shaving boards, blockboards and bamboo and wood veneers.
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| CN107619650A (en) * | 2017-10-04 | 2018-01-23 | 镇江市星耀智能装备有限公司 | A kind of adhesive for water resistant sheet material |
| CN117511314A (en) * | 2023-10-26 | 2024-02-06 | 广州福诚美化工有限公司 | High-glossiness water-based paint and preparation process thereof |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1069509A (en) * | 1991-08-15 | 1993-03-03 | 鞠纯衡 | Lignin modified uric-aldehyde resin and production method thereof |
| CN103725233A (en) * | 2013-11-26 | 2014-04-16 | 沃太能源南通有限公司 | Preparation method of lignin-based urea-formaldehyde resin adhesive with low formaldehyde release |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4194997A (en) * | 1975-05-05 | 1980-03-25 | Edler Folke J | Sulfite spent liquor-urea formaldehyde resin adhesive product |
| US9109123B2 (en) * | 2013-03-14 | 2015-08-18 | Georgia-Pacific Chemicals Llc | Urea mixtures and methods for making and using same |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1069509A (en) * | 1991-08-15 | 1993-03-03 | 鞠纯衡 | Lignin modified uric-aldehyde resin and production method thereof |
| CN103725233A (en) * | 2013-11-26 | 2014-04-16 | 沃太能源南通有限公司 | Preparation method of lignin-based urea-formaldehyde resin adhesive with low formaldehyde release |
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