CN107325242B - Preparation method of low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin - Google Patents
Preparation method of low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin Download PDFInfo
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- CN107325242B CN107325242B CN201710524238.8A CN201710524238A CN107325242B CN 107325242 B CN107325242 B CN 107325242B CN 201710524238 A CN201710524238 A CN 201710524238A CN 107325242 B CN107325242 B CN 107325242B
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- 229920001807 Urea-formaldehyde Polymers 0.000 title claims abstract description 65
- GZCGUPFRVQAUEE-SLPGGIOYSA-N aldehydo-D-glucose Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O GZCGUPFRVQAUEE-SLPGGIOYSA-N 0.000 title claims abstract description 56
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 238000002425 crystallisation Methods 0.000 title claims abstract description 13
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims abstract description 31
- 239000004202 carbamide Substances 0.000 claims abstract description 31
- 239000000853 adhesive Substances 0.000 claims abstract description 30
- 230000001070 adhesive effect Effects 0.000 claims abstract description 30
- -1 alkyl quaternary ammonium salt Chemical class 0.000 claims abstract description 26
- 238000000034 method Methods 0.000 claims abstract description 17
- 238000001816 cooling Methods 0.000 claims abstract description 16
- 239000000243 solution Substances 0.000 claims abstract description 14
- 238000010438 heat treatment Methods 0.000 claims abstract description 12
- 239000012670 alkaline solution Substances 0.000 claims abstract description 10
- 238000007599 discharging Methods 0.000 claims abstract description 8
- 238000005070 sampling Methods 0.000 claims abstract description 5
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 71
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 42
- 239000007864 aqueous solution Substances 0.000 claims description 29
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 28
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims description 18
- 239000008098 formaldehyde solution Substances 0.000 claims description 14
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 14
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims description 9
- 235000019253 formic acid Nutrition 0.000 claims description 9
- 238000004321 preservation Methods 0.000 claims description 8
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 5
- XJWSAJYUBXQQDR-UHFFFAOYSA-M dodecyltrimethylammonium bromide Chemical compound [Br-].CCCCCCCCCCCC[N+](C)(C)C XJWSAJYUBXQQDR-UHFFFAOYSA-M 0.000 claims description 3
- SZEMGTQCPRNXEG-UHFFFAOYSA-M trimethyl(octadecyl)azanium;bromide Chemical compound [Br-].CCCCCCCCCCCCCCCCCC[N+](C)(C)C SZEMGTQCPRNXEG-UHFFFAOYSA-M 0.000 claims description 3
- CXRFDZFCGOPDTD-UHFFFAOYSA-M Cetrimide Chemical compound [Br-].CCCCCCCCCCCCCC[N+](C)(C)C CXRFDZFCGOPDTD-UHFFFAOYSA-M 0.000 claims description 2
- PSLWZOIUBRXAQW-UHFFFAOYSA-M dimethyl(dioctadecyl)azanium;bromide Chemical compound [Br-].CCCCCCCCCCCCCCCCCC[N+](C)(C)CCCCCCCCCCCCCCCCCC PSLWZOIUBRXAQW-UHFFFAOYSA-M 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 125000005210 alkyl ammonium group Chemical group 0.000 claims 1
- 239000011120 plywood Substances 0.000 abstract description 7
- 239000011094 fiberboard Substances 0.000 abstract description 4
- 239000002023 wood Substances 0.000 abstract description 4
- HQVFCQRVQFYGRJ-UHFFFAOYSA-N formic acid;hydrate Chemical compound O.OC=O HQVFCQRVQFYGRJ-UHFFFAOYSA-N 0.000 abstract description 2
- 239000003381 stabilizer Substances 0.000 description 5
- 238000003860 storage Methods 0.000 description 5
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonia chloride Chemical compound [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 description 4
- 241000219000 Populus Species 0.000 description 4
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 description 4
- 238000007731 hot pressing Methods 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000004220 aggregation Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 235000019270 ammonium chloride Nutrition 0.000 description 2
- 229910001870 ammonium persulfate Inorganic materials 0.000 description 2
- 239000000084 colloidal system Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- WSFSSNUMVMOOMR-NJFSPNSNSA-N methanone Chemical compound O=[14CH2] WSFSSNUMVMOOMR-NJFSPNSNSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- ODGAOXROABLFNM-UHFFFAOYSA-N polynoxylin Chemical compound O=C.NC(N)=O ODGAOXROABLFNM-UHFFFAOYSA-N 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- GMIMEXBGMYDQTO-UHFFFAOYSA-N C=O.C=O.NC(N)=O Chemical compound C=O.C=O.NC(N)=O GMIMEXBGMYDQTO-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000003292 glue Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000005011 phenolic resin Substances 0.000 description 1
- 229920001568 phenolic resin Polymers 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
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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
- C08G12/04—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
- C08G12/10—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds with acyclic compounds having the moiety X=C(—N<)2 in which X is O, S or —N
- C08G12/12—Ureas; Thioureas
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/16—Nitrogen-containing compounds
- C08K5/17—Amines; Quaternary ammonium compounds
- C08K5/19—Quaternary ammonium compounds
-
- 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
- C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
- C09J11/02—Non-macromolecular additives
- C09J11/06—Non-macromolecular additives organic
-
- 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
- C09J161/22—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds
- C09J161/24—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with acyclic or carbocyclic compounds with urea or thiourea
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Adhesives Or Adhesive Processes (AREA)
- Phenolic Resins Or Amino Resins (AREA)
Abstract
The invention belongs to the field of urea-formaldehyde resin wood adhesives, and particularly relates to a preparation method of low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin. The method comprises the following steps: s1, adding alkyl quaternary ammonium salt into hydroxymethyl urea compound, adjusting pH value of reaction system with formic acid water solution, sampling, observing, adjusting pH value of system with alkaline solution when sampling and dropping into water to be white cloud, adding urea, heating and keeping temperature; s2, cooling the reaction system obtained in the step S1, adding urea, adjusting the pH value of the system by using an alkaline solution, preserving heat, cooling, and discharging to obtain the urea-formaldehyde resin adhesive. The low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin adhesive disclosed by the invention is simple in preparation process and easy to operate. The urea-formaldehyde resin adhesive prepared by the invention is suitable for bonding artificial boards such as plywood, shaving boards, fiber boards and the like.
Description
Technical Field
The invention belongs to the field of urea-formaldehyde resin wood adhesives, and particularly relates to a preparation method of low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin.
Background
The urea-formaldehyde resin has the advantages of abundant and easily-obtained raw materials, low production cost, quick curing, good operability, higher bonding strength and the like, is the variety with the largest consumption in the existing wood adhesives, accounts for more than 80% of the consumption of the wood adhesives, and is mainly used for bonding plywood, shaving boards, medium-density fiber boards and the like. However, the current urea-formaldehyde resin has the defects of formaldehyde release and water resistance in the using process, and the application of the urea-formaldehyde resin is limited. Therefore, the development of the urea-formaldehyde resin adhesive with low formaldehyde release and excellent water resistance is of great significance.
The free formaldehyde content can be effectively controlled by varying the molar ratio of formaldehyde to urea (F/U), the lower the F/U, the lower the free formaldehyde content. Reducing F/U is the most direct and common method for reducing formaldehyde emission from urea-formaldehyde resins, and in addition, urea-formaldehyde resins with low molar ratios of formaldehyde to urea have crystallinity, and Stuligross et al report that urea-formaldehyde resins with low molar ratios of formaldehyde to urea (F/U ═ 1.0) have colloidal characteristics and crystallinity; the crystallinity of urea-formaldehyde resins with different formaldehyde-urea molar ratios is studied by XRD by Park et al, and the study shows that the urea-formaldehyde resins prepared with the formaldehyde-urea molar ratio (F/U ═ 1.2 and F/U ═ 1.0) have crystalline regions after curing, and the crystallinity increases with the increase of curing temperature, curing time and the amount of curing agent. However, with the decrease of F/U, the content of free formaldehyde in the prepared urea-formaldehyde resin is reduced, the reaction activity of the urea-formaldehyde resin is gradually reduced, the formaldehyde emission of the artificial board is also reduced, and the mechanical property of the artificial board is also reduced.
At present, methods such as a low formaldehyde/urea molar ratio, batch addition of urea, reaction temperature and reaction time are adopted to achieve a good effect of reducing the release of free formaldehyde, but the urea-formaldehyde resin is easily crystallized by using more urea, so that the bonding uniformity of the adhesive is influenced, and the water resistance and bonding strength of the adhesive are also influenced; in addition, the anti-mildew performance of the urea-formaldehyde resin prepared by the prior art needs to be improved.
Disclosure of Invention
In view of the above-mentioned deficiencies of the prior art, the present invention aims to provide a method for preparing a urea-formaldehyde resin with low crystallization, mildew resistance and water resistance.
The purpose of the invention is realized by the following technical scheme: a preparation method of low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin comprises the following steps:
s1, adding alkyl quaternary ammonium salt into hydroxymethyl urea compound, adjusting pH value of reaction system with formic acid water solution, sampling, observing, adjusting pH value of system with alkaline solution when sampling and dropping into water to be white cloud, adding urea, heating and keeping temperature;
s2, cooling the reaction system obtained in the step S1, adding urea, adjusting the pH value of the system by using an alkaline solution, preserving heat, cooling, and discharging to obtain the urea-formaldehyde resin adhesive.
According to the scheme, the preparation method of the hydroxymethyl urea compound comprises the following steps: adding a formaldehyde solution and urea into a reaction vessel in sequence, uniformly mixing, adjusting the pH value of a system by using an alkaline solution, heating and preserving heat, wherein the formaldehyde solution accounts for 100 parts by weight and the urea accounts for 30-37 parts by weight, the mass percentage concentration of the formaldehyde solution is 37%, and the heating and preserving heat are carried out at 65-75 ℃ for 30 minutes, then the temperature is raised to 85-92 ℃ and the temperature is preserved for 30-60 minutes.
According to the scheme, the alkaline solution is a sodium hydroxide aqueous solution or a sodium carbonate aqueous solution system, wherein the pH value is adjusted to be 7.5-9.0 in the preparation method of the hydroxymethyl urea compound, the pH value is adjusted to be 6.0-6.5 in the step S1, and the pH value is adjusted to be 7.5-8.5 in the step S2.
According to the scheme, the mass percent concentration of the sodium hydroxide aqueous solution is 20 percent; the mass percentage concentration of the sodium carbonate aqueous solution is 20%.
According to the scheme, the alkyl quaternary ammonium salt in the step S1 is one or a mixture of dodecyl trimethyl ammonium bromide, tetradecyl trimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium bromide and dioctadecyl dimethyl ammonium bromide.
According to the scheme, the dosage of the alkyl quaternary ammonium salt is 0.5 to 5.0 percent of the weight of the formaldehyde aqueous solution.
According to the scheme, the pH value of the reaction system is adjusted to 4.0-5.5 by the formic acid in the step S1, and the mass percentage concentration of the formic acid solution is 20%.
According to the scheme, the temperature of the heat preservation in the step S1 is 85-92 ℃, and the heat preservation time is 30-45 minutes.
According to the scheme, the temperature of the heat preservation in the step S2 is 65-70 ℃, and the heat preservation time is 30-60 minutes.
The urea-formaldehyde resin adhesive can be applied to the production field of plywood, shaving board and fiber board.
The invention adopts alkyl quaternary ammonium salt as a urea-formaldehyde resin stabilizer to prepare the low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin adhesive, on one hand, the alkyl quaternary ammonium salt stabilizer is introduced in the preparation process of the urea-formaldehyde resin adhesive, so that the aggregation probability of urea-formaldehyde resin colloid particles in the storage process of the urea-formaldehyde resin adhesive is reduced, the crystallinity of the urea-formaldehyde resin is reduced, and the stability of the urea-formaldehyde resin is improved.
Compared with the prior art, the invention has the following advantages and beneficial effects:
according to the invention, alkyl quaternary ammonium salt is used as a urea-formaldehyde resin stabilizer to prepare the urea-formaldehyde resin adhesive with low crystallization, low formaldehyde and mildew resistance, on one hand, the alkyl quaternary ammonium salt stabilizer is introduced in the preparation process of the urea-formaldehyde resin adhesive to reduce the aggregation probability of urea-formaldehyde resin colloid particles in the storage process of the urea-formaldehyde resin adhesive, reduce the crystallinity of the urea-formaldehyde resin and improve the stability of the urea-formaldehyde resin, and in addition, the alkyl quaternary ammonium salt has mildew resistance and can improve the mildew resistance of the urea-formaldehyde resin adhesive, and on the other hand, the alkyl quaternary ammonium salt is used as a stabilizer and can also increase the water resistance of the urea-formaldehyde resin adhesive. The low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin adhesive disclosed by the invention is simple in preparation process and easy to operate. The urea-formaldehyde resin adhesive prepared by the invention is suitable for bonding artificial boards such as plywood, shaving boards, fiber boards and the like.
Drawings
FIG. 1 is a schematic diagram of the reaction mechanism for the preparation of low free formaldehyde urea formaldehyde resin.
FIG. 2 is a polarizing microscope photograph of the film formed by the urea resin of examples 1 to 5, wherein the bright spots are crystal regions.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
The preparation schematic diagram of the low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin is shown in figure 1.
Example 1
(1) 100 parts by weight of an aqueous formaldehyde solution (concentration: 37%) and 30 parts by weight of urea were added to a 500mL flask; adjusting the pH value of the system to 7.5 by using a sodium hydroxide aqueous solution (the concentration is 20%) or a sodium carbonate aqueous solution (the concentration is 20%), preserving the temperature in a 65 ℃ water bath for 30 minutes, slowly heating the water bath temperature to 85 ℃, and preserving the temperature for 30 minutes;
(2) adding 0.5% formaldehyde aqueous solution weight part of hexadecyl trimethyl ammonium bromide into a reaction system, simultaneously adjusting the pH value of the reaction system to 4.0 by using formic acid aqueous solution (the concentration is 20%), measuring the cloud point once every 10 minutes, when a sample is dripped into room-temperature water to be white cloud, adjusting the pH value of the reaction system to 6.0 by using sodium hydroxide aqueous solution (the concentration is 20%) or sodium carbonate aqueous solution (the concentration is 20%), and adding 12 parts by weight of urea; preserving the temperature for 30 minutes;
c. cooling the reaction system to 75 ℃, adding 10 parts by weight of urea, adjusting the pH value to 8.0, preserving the heat at 65 ℃ for 30 minutes, cooling to 45 ℃, and discharging to obtain the urea-formaldehyde resin adhesive.
Example 2
(1) 100 parts by weight of an aqueous formaldehyde solution (concentration: 37%) and 30 parts by weight of urea were added to a 500mL flask; adjusting the pH value of the system to 9.0 by using a sodium hydroxide aqueous solution or a sodium carbonate aqueous solution, keeping the temperature in a water bath at 75 ℃ for 30 minutes, slowly heating the water bath to 92 ℃, and keeping the temperature for 60 minutes;
(2) adding 5.0% formaldehyde aqueous solution weight parts of hexadecyl trimethyl ammonium bromide into a reaction system, simultaneously adjusting the pH value of the reaction system to 5.5 by using formic acid aqueous solution (the concentration is 20%), measuring the cloud point once every 10 minutes, when a sample is dripped into water to form a white cloud, adjusting the pH value of the reaction system to 6.5 by using sodium hydroxide aqueous solution (the concentration is 20%) or sodium carbonate aqueous solution (the concentration is 20%), and adding 18 parts by weight of urea; preserving the temperature for 45 minutes;
(3) cooling the reaction system to 75 ℃, adding 15 parts by weight of urea, adjusting the pH value to 8.5, preserving the heat at 70 ℃ for 60 minutes, cooling to 45 ℃, and discharging to obtain the urea-formaldehyde resin adhesive.
Example 3
(1) A500 mL flask was charged with 100 parts by weight of an aqueous formaldehyde solution (concentration: 37%) and 33 parts by weight of urea; adjusting the pH value of the system to 8.5 by using a sodium hydroxide aqueous solution or a sodium carbonate aqueous solution, keeping the temperature in a 70 ℃ water bath for 30 minutes, slowly heating the water bath to 88 ℃, and keeping the temperature for 40 minutes;
(2) adding cetyl trimethyl ammonium bromide in 2.5 wt% concentration formaldehyde solution into the reaction system, regulating the pH value of the reaction system to 4.5 with formic acid solution (concentration of 20%), measuring the cloud point every 10 min, regulating the pH value of the reaction system to 6.3 with sodium hydroxide solution (concentration of 20%) or sodium carbonate solution (concentration of 20%) when the sample is dropped into water in white cloud, and adding 14 wt% urea; preserving the temperature for 35 minutes;
(3) cooling the reaction system to 75 ℃, adding 12 parts by weight of urea, adjusting the pH value to 8.3, preserving the heat at 67 ℃ for 40 minutes, cooling to 45 ℃, and discharging to obtain the urea-formaldehyde resin adhesive.
Example 4
(1) A500 mL flask was charged with 100 parts by weight of an aqueous formaldehyde solution (concentration: 37%) and 35 parts by weight of urea; adjusting the pH value of the system to 8.0 by using a sodium hydroxide aqueous solution (the concentration is 20%) or a sodium carbonate aqueous solution (the concentration is 20%), preserving the temperature in a 70 ℃ water bath for 30 minutes, slowly heating the water bath to 88 ℃, and preserving the temperature for 50 minutes;
(2) adding 2.5% formaldehyde aqueous solution weight parts of octadecyl trimethyl ammonium bromide into a reaction system, simultaneously adjusting the pH value of the reaction system to 4.5 by using formic acid aqueous solution (the concentration is 20%), measuring the cloud point once every 10 minutes, adjusting the pH value of the reaction system to 6.3 by using sodium hydroxide aqueous solution (the concentration is 20%) or sodium carbonate aqueous solution (the concentration is 20%) when a sample is dripped into water to form a white cloud, and adding 16 parts by weight of urea; preserving the temperature for 40 minutes;
(3) and cooling the reaction system to 75 ℃, adding 12 parts by weight of urea, adjusting the pH value to 8.3, preserving the heat at 68 ℃ for 50 minutes, cooling and discharging to obtain the urea-formaldehyde resin adhesive.
Example 5
(1) A500 mL flask was charged with 100 parts by weight of an aqueous formaldehyde solution (concentration: 37%) and 33 parts by weight of urea; adjusting the pH value of the system to 8.0 by using a sodium hydroxide aqueous solution (the concentration is 20%) or a sodium carbonate aqueous solution (the concentration is 20%), preserving the temperature in a 70 ℃ water bath for 30 minutes, slowly heating the water bath to 90 ℃, and preserving the temperature for 40 minutes;
(2) adding dodecyl trimethyl ammonium bromide in 2.5 wt% concentration formaldehyde solution into the reaction system, regulating the pH value of the reaction system to 4.5 with formic acid solution in 20 wt%, measuring the cloud point every 10 min, regulating the pH value of the reaction system to 6.5 with sodium hydroxide solution in 20 wt% or sodium carbonate solution in 20 wt% when the sample is dropped into water in room temperature in white cloud state, and adding urea in 16 wt%; preserving the temperature for 40 minutes;
(3) cooling the reaction system to 75 ℃, adding 12 parts by weight of urea, adjusting the pH value to 8.0, preserving the heat at 70 ℃ for 50 minutes, cooling and discharging to obtain the urea-formaldehyde resin adhesive.
Examples 1 to 5 were examined for crystallinity using Caikang XPS-550C polarizing microscope, and the sample was a film obtained from the prepared urea resin at 70 ℃; the detection results are shown in FIG. 2: as can be seen from fig. 2, the alkyl quaternary ammonium salt modified urea resin has poor crystallization property;
the basic performances (such as free formaldehyde, solid content and storage stability) of the resin are detected by the alkyl quaternary ammonium salt modified urea-formaldehyde resin prepared in the examples 1-5 according to the method specified in the national standard GB/T14074-2006.
The basic properties of the phenolic resin modified urea-formaldehyde resin prepared by the invention are as follows: the content of free formaldehyde is less than or equal to 0.1 percent, the solid content is 60.0 to 65 percent, and the storage stability is more than 30 days.
The urea-formaldehyde resin prepared in examples 1 to 5 was applied to the bonding of poplar veneers to prepare three-layer poplar plywood. Wherein the thickness of the poplar veneer is 3.0mm, the breadth is 32cm multiplied by 32cm, and the water content is 5 percent. The preparation steps of the adhesive are as follows: the curing agent is a compound solution of ammonium persulfate and ammonium chloride (5 wt% of ammonium persulfate and 15 wt% of ammonium chloride), and the dosage of the curing agent is 6ml/100g of urea-formaldehyde resin; the glue coating amount is 300g/m2(double-sided); hot pressing conditions are as follows: the time of closed-end aging is 30min, the prepressing pressure is 1.0MPa, the prepressing time is 30min, the hot-pressing temperature is 120 ℃, the hot-pressing pressure is 1.5MPa, and the hot-pressing time is 3 min.
The mildew-proof grade is detected according to JC/T2039-.
The detection results are as follows: examples 2, 3, and 4 were 0-grade, and examples 1 and 5 were 1-grade.
The basic properties of the obtained three-layer poplar plywood, such as water resistance, formaldehyde emission and bonding strength, are detected according to the method specified in GB/T9846-2004.
The detection results are as follows: the water resistance meets the requirements of II-class water-resistant plywood; the formaldehyde release amount is less than or equal to 0.05 mg/L; the bonding strength is more than or equal to 0.4 MPa.
The above results show that: the urea-formaldehyde resin prepared by the invention has the characteristics of low crystallinity, good storage stability, excellent mildew resistance and water resistance, has higher bonding strength when being applied to the preparation of adhesives, and meets the requirement of environmental protection.
The above description is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various modifications and changes without departing from the inventive concept of the present invention, and these modifications and changes are within the protection scope of the present invention.
Claims (9)
1. A preparation method of low-crystallization, mildew-proof and water-resistant urea-formaldehyde resin comprises the following steps:
s1, adding alkyl quaternary ammonium salt into hydroxymethyl urea compound, adjusting the pH value of the reaction system to 4.0-5.5 by formic acid aqueous solution, sampling and observing, adjusting the pH value of the system to 6.0-6.5 by alkaline solution when the sample is dropped into water to be white cloud, adding urea, heating and preserving heat;
s2, cooling the reaction system obtained in the step S1, adding urea, adjusting the pH value of the system to 7.5-8.5 by using an alkaline solution, preserving heat, cooling, and discharging to obtain the urea-formaldehyde resin adhesive.
2. The method of preparing a low crystalline, mold and water resistant urea-formaldehyde resin as claimed in claim 1, wherein the methylol urea compound is prepared by: adding a formaldehyde solution and urea into a reaction vessel in sequence, uniformly mixing, adjusting the pH value of a system by using an alkaline solution, heating and preserving heat, wherein the formaldehyde solution accounts for 100 parts by weight and the urea accounts for 30-37 parts by weight, the mass percentage concentration of the formaldehyde solution is 37%, and the heating and preserving heat are carried out at 65-75 ℃ for 30 minutes, then the temperature is raised to 85-92 ℃ and the temperature is preserved for 30-60 minutes.
3. The method of claim 2, wherein the alkaline solution is an aqueous sodium hydroxide solution or an aqueous sodium carbonate solution, and the hydroxymethyl urea compound is prepared at a pH of 7.5 to 9.0.
4. The method of preparing a low crystalline, mold and water resistant urea-formaldehyde resin as claimed in claim 3, wherein the concentration of the aqueous sodium hydroxide solution is 20% by mass; the mass percentage concentration of the sodium carbonate aqueous solution is 20%.
5. The method of claim 1, wherein the quaternary alkyl ammonium salt in step S1 is one or more selected from the group consisting of dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, and dioctadecyldimethylammonium bromide.
6. The method for preparing a low-crystalline, mold-proof and water-resistant urea-formaldehyde resin as claimed in claim 2, wherein the amount of said alkyl quaternary ammonium salt is 0.5-5.0% by weight of the aqueous formaldehyde solution.
7. The method for preparing a low-crystalline, mold-proof and water-resistant urea-formaldehyde resin as claimed in claim 1, wherein the formic acid solution of step S1 has a concentration of 20% by mass.
8. The method of preparing a low crystalline, mold and water resistant urea-formaldehyde resin as claimed in claim 1, wherein the temperature of the heat preservation in step S1 is 85 ℃ to 92 ℃ and the heat preservation time is 30 to 45 minutes.
9. The method for preparing a low-crystalline, mold-proof, and water-resistant urea-formaldehyde resin according to claim 1, wherein the temperature of the heat preservation in step S2 is 65 ℃ to 70 ℃ and the heat preservation time is 30 to 60 minutes.
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