CN1385449A - Method and equipment for producing urea-formaldehyde resin having low content of free formaldehyde - Google Patents
Method and equipment for producing urea-formaldehyde resin having low content of free formaldehyde Download PDFInfo
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- CN1385449A CN1385449A CN 02110285 CN02110285A CN1385449A CN 1385449 A CN1385449 A CN 1385449A CN 02110285 CN02110285 CN 02110285 CN 02110285 A CN02110285 A CN 02110285A CN 1385449 A CN1385449 A CN 1385449A
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Abstract
The production method of ureaformaldehyde resin with low free formaldehyde content includes the following steps: adopting conventional method to produce ureaformaldehyde resin with high free formaldehyde content, adding direct formaldehyde-removing agent ammonia to directly remove formaldehyde, then adding latent formaldehyde-removing agent urea or melamine to make latent formaldehyde removal and adding pH regulating agent to regulate pH value. The free formaldehyde content of urea-formaldehyde resin produced by using said method can be reduced to below 0.1%, and said resin possesses the advantages of high strength, good storage stability and water-proofing property. Its production equipment can be a reactor still whose bottom is equipped with a gas distributor or can include a reactor unit and a special-purpose formaldehyde-removing reaction tank whose bottom is equipped with a gas distributor.
Description
Technical Field
The invention relates to a method and equipment for producing urea-formaldehyde resin, in particular to a method and equipment for producing urea-formaldehyde resin with low content of free formaldehyde.
Background
Urea formaldehyde resins are the most widely used adhesives in the wood industry, with the first place on production. The urea-formaldehyde resin prepared by the conventional production method has high content of freeformaldehyde which accounts for 1-3% of the weight of the urea-formaldehyde resin, and when the urea-formaldehyde resin with high content of free formaldehyde is used for manufacturing artificial boards, a large amount of formaldehyde escapes, so that the environment is seriously polluted, and the health of workers is damaged. After the artificial board is used for decorating houses and manufacturing furniture, formaldehyde smell is generated indoors, and harm is brought to users. For this reason, U.S. Pat. Nos. 2467212, 43-20476 and 48-17877 propose to prepare urea-formaldehyde resins with low formaldehyde molar ratio, the free formaldehyde content in urea-formaldehyde resins can be reduced to below 1%, and when the formaldehyde to urea molar ratio is below 1.25: 1, the free formaldehyde emission of wood-based panels reaches or approaches 30mg/100 g. However, the urea-formaldehyde resin with low molar ratio has poor performance indexes such as bonding strength, storage stability, water solubility and the like, and has high process operation difficulty, high unit glue consumption and high comprehensive cost, thereby seriously restricting the quality of the artificial board.
Disclosure of Invention
The invention aims to provide a production method of urea-formaldehyde resin with high bonding strength, good stability and low free formaldehyde content.
It is another object of the present invention to provide an apparatus for the production method.
The production method of the urea-formaldehyde resin with low free formaldehyde content comprises the following steps of producing the urea-formaldehyde resin with high free formaldehyde content according to a conventional method:
a. directly removing aldehyde, namely adding direct aldehyde removing agent ammonia accounting for 0.05 to 2.5 percent of the weight of the urea-formaldehyde resin into the urea-formaldehyde resin with high content of free formaldehyde at the temperature of lower than 80 ℃ under the stirring condition to directly remove aldehyde, and reducing the content of the free formaldehyde in the urea-formaldehyde resin to 0.1 to 0.01 percent in parts by weight;
b. latent aldehyde removal, namely adding a latent aldehyde removing agent accounting for 0.01-5 percent of the weight of the urea-formaldehyde resin into the urea-formaldehyde resin after direct aldehyde removal under the stirring condition to carry out latent aldehyde removal;
c. and (3) pH adjustment, namely adjusting the pH value of the urea-formaldehyde resin subjected to latent aldehyde removal to 6.5-8.0 by using an alkaline substance pH adjusting agent or an acidic substance pH adjusting agent to obtain a finished product.
The above-mentioned method for adding ammonia as direct formaldehyde-removing agent into urea-formaldehyde resin with high content of free formaldehyde includes two methods: one is to directly and slowly and uniformly introduce ammonia gas, the other is to add ammonium chloride accounting for 0.2 to 3.5 percent of the weight of the urea-formaldehyde resin into the urea-formaldehyde resin under the stirring condition, immediately adjust the pH value of the urea-formaldehyde resin to 6.5 to 9.5 by using 30 to 60 percent of sodium hydroxide, and reduce the content of free formaldehyde in the urea-formaldehyde resin to 0.1 to 0.01 percent according to the parts by weight.
The latent aldehyde removing agent can be urea or melamine.
The alkaline substance pH regulator comprises sodium hydroxide and ammonia water, and the acidic substance pH regulator comprises hydrochloric acid, phosphoric acid, ammonium chloride, oxalic acid and citric acid.
The equipment for realizing the production method of the urea-formaldehyde resin with low free formaldehyde content comprises in-kettle production equipment or out-kettle production equipment, wherein the in-kettle production equipment comprises a reaction kettle, the bottom of which is provided with a gas distributor, the gas distributor is communicated with a liquid ammonia storage tank through a pipeline, and the pipeline is connected with a pressure reducing valve with a flowmeter; the production equipment of the out-of-kettle method comprises a reaction kettle unit and a special aldehyde removal reaction tank, wherein a gas distributor is arranged at the bottom of the reaction kettle unit, the gas distributor is communicated with a liquid ammonia storage tank through a pipeline, and a pressure reducing valve with a flow meter is connected to the pipeline.
The gas distributor comprises an annular pipe disc, ammonia gas outlets are uniformly distributed on the top surface of the annular pipe disc, and the aperture of the ammonia gas outlets is 1-20 mm.
The invention is characterized in that the urea-formaldehyde resin with high free formaldehyde content is produced according to the conventional method, then the direct aldehyde removing agent ammonia is added into the urea-formaldehyde resin with high free formaldehyde content for direct aldehyde removal, wherein the ammonia can be ammonia gas or ammonia released by the reaction of ammonium chloride and sodium hydroxide.
Directly adding ammonia gas to react with free formaldehyde to generate hexamethylenetetramine and water:
reacting ammonium chloride with sodium hydroxide to generate ammonia and sodium chloride, and reacting the ammonia with free formaldehyde to generate hexamethylenetetramine and water:
the addition of ammonia eliminates free formaldehyde in the urea-formaldehyde resin, and the generated hexamethylene tetramine does not influence the quality of the urea-formaldehyde resin, and can play a role of a curing agent when the urea-formaldehyde resin is used as an adhesive to prepare a product.
The other important characteristic of the invention is that after the free formaldehyde in the urea-formaldehyde resin is eliminated, the urea or the melamine which is used as the latent aldehyde removing agent is added to eliminate the free formaldehyde generated by the pyrolysis of the urea-formaldehyde resin in the hot pressing process of the artificial board manufacture and the free formaldehyde released by the wood self pyrolysis during the hot pressing of the wood, thereby ensuring that the content of the free formaldehyde in the manufactured artificial board is close to zero and reaches the national standard.
The latent aldehyde removing agent urea reacts with the following reaction in hot pressing:
when the temperature is higher, the reaction is: the urea releases ammonia during hot pressing and is pyrolyzed from urea-formaldehyde resin and woodThe formaldehyde reacts to achieve the aim of eliminating free formaldehyde.
The mechanism of adopting melamine as the latent aldehyde removing agent is as follows: the melamine is crushed into fine powder with the granularity of less than 200 meshes, and is directly added into the urea-formaldehyde resin, the melamine isinsoluble in water and is dispersed in the urea-formaldehyde resin in a suspension state, and the melamine is quickly dissolved under the action of water vapor during hot pressing and reacts with the urea-formaldehyde resin and formaldehyde generated by wood pyrolysis, so that the aim of eliminating free formaldehyde is fulfilled.
The production method of the urea-formaldehyde resin is not only suitable for the urea-formaldehyde resin which is dehydrated and not dehydrated, but also suitable for the urea-formaldehyde resin which is modified and not modified.
The direct aldehyde remover and the latent aldehyde remover are added in the production method of the urea-formaldehyde resin, the advantages are obvious, because the urea-formaldehyde resin has a wider molar ratio range, when the molar ratio is high, the direct aldehyde remover can remove free formaldehyde in the urea-formaldehyde resin, so that the content of the free formaldehyde in the urea-formaldehyde resin is reduced to be below 0.1 percent, the advantages of high strength, good storage stability and good water resistance of the urea-formaldehyde resin can be maintained, and the latent aldehyde remover removes formaldehyde released during pyrolysis of the urea-formaldehyde resin and wood during hot pressing. The formaldehyde content in the urea-formaldehyde resin is very little by removing formaldehyde twice, the free formaldehyde content of the shaving board and the medium-density fiberboard produced by using the urea-formaldehyde resin as the adhesive is reduced to below 9mg/100g, and the free formaldehyde content of the produced multi-layer board and the laminated wood board is reduced to below 1.5 mg/L. The shaving board, the medium density fiberboard, the multilayer board and the block board are used for decorating houses and manufacturing furniture, so that the environment is not polluted, and the body of people is not damaged.
In order to realize the production method of the urea-formaldehyde resin, the adopted equipment is only that a gas distributor with simple structure is arranged at the bottom of the reaction kettle or the bottom of the special aldehyde-removing reaction tank, is simple and easy to implement and is convenient for industrial production.
Drawings
The attached drawings show the structure schematic diagram of the equipment adopted for realizing the production method of the urea-formaldehyde resin, wherein:
FIG. 1 is a schematic view of a structure of an in-tank process production apparatus;
FIG. 2 is a schematic view of the structure of an apparatus for producing by the out-of-tank method;
fig. 3 is a schematic diagram of the structure of the gas distributor.
In the figure, 1 is an ammonia pressure reducing valve with a flowmeter, 2 is a liquid ammonia storage tank, 3 is a gas distributor, 4 is an ammonia outlet, 5 is a reaction kettle, 6 is a special aldehyde removing tank, and 7 is a pipe disc.
Detailed Description
Example 1
1) Adding 475 parts of formaldehyde with the concentration of 37% into the reaction kettle, starting a stirrer, and adjusting the pH value of the formaldehyde to 7.5-8.0 by using 30% sodium hydroxide;
2) heating formaldehyde to 40 ℃, adding 139.2 parts of urea, heating the formaldehyde and the urea to 80 ℃ within 30 minutes, keeping the temperature for 1 hour, adding 46.4 parts of second batch of urea, keeping the temperature at 80 ℃ for 30 minutes, immediately adjusting the pH value to 5.0-5.3 by using a 20% ammonium chloride solution, keeping the temperature for 10-90 minutes at 80 ℃, continuously measuring the viscosity, immediately neutralizing the reaction solution by using a 30% sodium hydroxide solution when the viscosity reaches 15-60 seconds, adjusting the pH value to 6.0, and simultaneously cooling to 60 ℃, and starting decompression and dehydration;
3) when the dehydration meets the requirement, cooling the reaction solution by water cooling and adjusting the pH value to 6.6-7.0 by using a sodium hydroxide solution;
4) when the temperature of the reaction liquid is reduced to below 35 ℃, a pressure reducing valve is opened, and 10.2 parts of direct aldehyde removing agent ammonia is introduced within 3 hours under the stirring condition;
5) then 2.7 parts of latent aldehyde removing agent urea is added and stirred to be dissolved;
6) and adjusting the pH value to 7.5 by using 20% ammonium chloride solution to obtain a finished product.
The urea-formaldehyde resin is milk white viscous liquid, the mol ratio of urea to formaldehyde in the formula is 1: 1.9, but the content of free formaldehyde is reduced to 0.09%, and all indexes of a multilayer board and a core-board manufactured by using the urea-formaldehyde resin as an adhesive reach the national standard, wherein the content of the free formaldehyde in the multilayer board is 1.2mg/L, and the content of the core-board is 1.0 mg/L.
Example 2
1) Adding 4000Kg of formaldehyde into a reaction kettle, stirring, adjusting the pH value to 7.8 by using sodium hydroxide, adding 1350Kg of urea, stirring for 5 minutes, ventilating and heating to 80 ℃, stopping gas, naturally heating to 90 ℃, and preserving heat for 30 minutes;
2) adjusting the pHvalue to 5.0 by formic acid, measuring the fog point by water at zero degree, and controlling the reaction time for 60 minutes;
3) adjusting the pH value to 5.4 by using ammonia water, adding 270Kg of urea, controlling the reaction time for 30 minutes, and measuring the fog point by using water at the temperature of 30 ℃;
4) adjusting the pH value to 7.0 by using sodium hydroxide, and cooling to 85 ℃;
5) adding 500Kg of urea, and stirring for 10 minutes;
6) adding 360Kg of urea, stirring for 10 minutes, and then cooling;
7) adjusting the pH value to 7.0 by using sodium hydroxide, and uniformly introducing 16.3Kg of ammonia gas as a direct aldehyde removing agent within 1.5 hours when the temperature is reduced to 35 ℃;
8) adding 53Kg of latent aldehyde removing agent urea, and stirring for dissolving;
9) and adjusting the pH value to 7.8 by using ammonium chloride to obtain a finished product.
In the urea-formaldehyde resin, the mol ratio of urea to formaldehyde is 1: 1.2, and the urea-formaldehyde resin is used for an adhesive for manufacturing a medium-density fiberboard, all indexes of the adhesive reach the national standard, and the content of free formaldehyde in the medium-density fiberboard is 8.5mg/100 g.
Example 3
1) Adding 1600Kg of 37 percent formaldehyde into a reaction kettle, adjusting the pH value to 8.0 by using sodium hydroxide, adding 600Kg of urea, ventilating and heating to 60 ℃ within 60 minutes, stopping gas supply, and naturally heating to 90-95 ℃;
2) adjusting the pH value to 4.4 by using ammonium chloride, preserving the temperature for 30 minutes, and continuously measuring theviscosity;
3) after the viscosity is qualified, immediately adjusting the pH value to 8.0 by using sodium hydroxide, cooling to 75 ℃, and adding 150Kg of urea;
4) cooling to 35 ℃, and introducing 24.8Kg of ammonia gas as a direct aldehyde removing agent within 2.3 hours;
5) adding 25.6Kg of latent aldehyde removing agent urea;
6) and adjusting the pH value to 8.0 by using ammonium chloride to obtain a finished product.
The urea-formaldehyde resin has a mol ratio of urea to formaldehyde of 1: 1.53, is used as an adhesive for manufacturing a shaving board, has a free formaldehyde content of 25mg/100g in the shaving board, and meets the E2 grade in the national standard.
The equipment used in the above embodiment can be in-kettle production equipment or out-kettle production equipment, the in-kettle production equipment comprises a reaction kettle 5 with a gas distributor 3 at the bottom, the gas distributor 3 is communicated with a liquid ammonia storage tank 2 through a pipeline, and a pressure reducing valve 1 with a flowmeter is connected to the pipeline, so that the equipment is suitable for self-made production equipment; the production equipment for the extrakettle method comprises a reaction kettle unit and a special aldehyde-removing reaction tank 6, wherein a gas distributor 3 is installed at the bottom of the reaction kettle unit, the gas distributor 3 is communicated with a liquid ammonia storage tank 2 through a pipeline, a pressure reducing valve 1 with a flow meter is connected to the pipeline, and the extrakettle method production equipment mainly solves the defect that the gas distributor is installed at the bottom of the reaction kettle and is relatively troublesome. The gas distributor 3 comprises an annular pipe disc 7, ammonia gas outlets 4 are uniformly distributed on the top surface of the annular pipe disc 7, and the aperture of each ammonia gas outlet 4 is 1-20 mm.
Claims (7)
1. A production method of urea-formaldehyde resin with low free formaldehyde content comprises the following steps of producing urea-formaldehyde resin with high free formaldehyde content according to a conventional method:
a. directly removing aldehyde, namely adding direct aldehyde removing agent ammonia accounting for 0.05 to 2.5 percent of the weight of the urea-formaldehyde resin into the urea-formaldehyde resin with high content of free formaldehyde at the temperature of lower than 80 ℃ under the stirring condition to directly remove aldehyde, and reducing the content of the free formaldehyde in the urea-formaldehyde resin to 0.1 to 0.01 percent in parts by weight;
b. latent aldehyde removal, namely adding a latent aldehyde removing agent accounting for 0.01-5 percent of the weight of the urea-formaldehyde resin into the urea-formaldehyde resin after direct aldehyde removal under the stirring condition to carry out latent aldehyde removal;
c. and (3) pH adjustment, namely adjusting the pH value of the urea-formaldehyde resin subjected to latent aldehyde removal to 6.5-8.0 by using an alkaline substance pH adjusting agent or an acidic substance pH adjusting agent to obtain a finished product.
2. The method for producing urea-formaldehyde resin with low free formaldehyde content as claimed in claim 1, wherein the method of adding the direct formaldehyde remover ammonia is two methods: one is to directly and slowly and uniformly introduce ammonia gas, the other is to add ammonium chloride accounting for 0.2 to 3.5 percent of the weight of the urea-formaldehyde resin into the urea-formaldehyde resin underthe stirring condition, immediately adjust the pH value of the urea-formaldehyde resin to 6.5 to 9.5 by using 30 to 60 percent of sodium hydroxide, and reduce the content of free formaldehyde in the urea-formaldehyde resin to 0.1 to 0.01 percent according to the parts by weight.
3. The method for producing urea-formaldehyde resin with low free formaldehyde content as claimed in claim 1, wherein the latent aldehyde scavenger is urea.
4. The method for producing urea-formaldehyde resin with low free formaldehyde content as claimed in claim 1, wherein the latent aldehyde scavenger is melamine.
5. The method of claim 1, wherein the alkaline substance pH adjuster comprises sodium hydroxide and ammonia water, and the acidic substance pH adjuster comprises hydrochloric acid, phosphoric acid, ammonium chloride, oxalic acid, and citric acid.
6. The apparatus for producing the urea resin with low free formaldehyde content according to claim 1, which comprises an in-kettle production apparatus or an out-kettle production apparatus, wherein the in-kettle production apparatus comprises a reaction kettle (5) with a gas distributor (3) installed at the bottom, the gas distributor (3) is communicated with a liquid ammonia storage tank (2) through a pipeline, and a pressure reducing valve (1) with a flow meter is connected to the pipeline; the production equipment of the out-of-kettle method comprises a reaction kettle unit and a special aldehyde removal reaction tank (6) with a gas distributor (3) arranged at the bottom, wherein the gas distributor (3) is communicated with a liquid ammonia storage tank (2) through a pipeline, and a pressure reducing valve (1) with a flow meter is connected on the pipeline.
7. The apparatus for producing urea resin having a low free formaldehyde content according to claim 6, wherein the gas distributor (3) comprises an annular pipe plate (7), the top surface of the annular pipe plate (7) is uniformly provided with the ammonia gas outlet holes (4), and the diameter of the ammonia gas outlet holes (4) is 1-20 mm.
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| Application Number | Priority Date | Filing Date | Title |
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| CNB021102856A CN1171921C (en) | 2002-04-20 | 2002-04-20 | Method and equipment for producing urea-formaldehyde resin having low content of free formaldehyde |
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| CNB021102856A CN1171921C (en) | 2002-04-20 | 2002-04-20 | Method and equipment for producing urea-formaldehyde resin having low content of free formaldehyde |
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| CN1171921C CN1171921C (en) | 2004-10-20 |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1331910C (en) * | 2005-04-19 | 2007-08-15 | 湖南大学 | Method for removing free formaldehyde in amino resin modified by hydroxylic acrylic ester |
| CN100427522C (en) * | 2006-01-26 | 2008-10-22 | 中北大学 | Method and device for removing free formaldehyde in urea-formaldehyde resin |
| CN102277113A (en) * | 2011-06-01 | 2011-12-14 | 山东光华板材有限公司 | Modification binder for 3-methylacryloyl propane diamine distillation raffinate and preparation method |
| CN103007898A (en) * | 2012-12-31 | 2013-04-03 | 吕新民 | Preparation method and use method of modified bentonite environment-friendly formaldehyde removing agent |
| CN107815159A (en) * | 2017-10-24 | 2018-03-20 | 兰州科天水性科技有限公司 | A kind of compound formaldehyde elimination agent of water-based banksia rose plate environment-friendly type and its preparation and application |
| CN110359117A (en) * | 2019-07-30 | 2019-10-22 | 中原工学院 | A kind of preparation method of ureaformaldehyde fiber |
-
2002
- 2002-04-20 CN CNB021102856A patent/CN1171921C/en not_active Expired - Fee Related
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1331910C (en) * | 2005-04-19 | 2007-08-15 | 湖南大学 | Method for removing free formaldehyde in amino resin modified by hydroxylic acrylic ester |
| CN100427522C (en) * | 2006-01-26 | 2008-10-22 | 中北大学 | Method and device for removing free formaldehyde in urea-formaldehyde resin |
| CN102277113A (en) * | 2011-06-01 | 2011-12-14 | 山东光华板材有限公司 | Modification binder for 3-methylacryloyl propane diamine distillation raffinate and preparation method |
| CN103007898A (en) * | 2012-12-31 | 2013-04-03 | 吕新民 | Preparation method and use method of modified bentonite environment-friendly formaldehyde removing agent |
| CN103007898B (en) * | 2012-12-31 | 2014-11-05 | 吕新民 | Preparation method and use method of modified bentonite environment-friendly formaldehyde removing agent |
| CN107815159A (en) * | 2017-10-24 | 2018-03-20 | 兰州科天水性科技有限公司 | A kind of compound formaldehyde elimination agent of water-based banksia rose plate environment-friendly type and its preparation and application |
| CN110359117A (en) * | 2019-07-30 | 2019-10-22 | 中原工学院 | A kind of preparation method of ureaformaldehyde fiber |
| CN110359117B (en) * | 2019-07-30 | 2022-01-21 | 中原工学院 | Preparation method of urea-formaldehyde fiber |
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| CN1171921C (en) | 2004-10-20 |
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