CN101550323A - E0Preparation method of low-cost UMF resin adhesive for grade plywood - Google Patents

Abstract

The invention discloses a method for preparing a compound₀A preparation method of low-cost UMF resin adhesive for grade plywood. The adhesive has simple preparation method, good reproducibility, low cost and long storage period. The gluing strength and formaldehyde emission of the miscellaneous tree plywood and poplar plywood pressed by the glue meet E₀And (5) the requirements of grade plywood. E of the invention₀The preparation method of the low-cost UMF resin adhesive for the grade plywood adopts a strong acid method process, urea is selected to be added in four batches, melamine is added in three batches, and the urea is added in three batches to play a role in adjusting the molecular mass of the resin, particularly, the urea added for the third time can degrade macromolecular parts in rearranged molecules, reduce the content of ether bonds in the rearranged molecules and reduce the release amount of formaldehyde.

Description

Preparation method of low-cost UMF resin glue for E0 grade plywood

technical field

The present invention relates to a kind of preparation method of resin glue, more specifically relate to a kind of preparation method of low-cost UMF resin glue for E ₀ grade plywood.

Background technique

Urea-formaldehyde resin is widely used in the manufacture of wood-based panels such as particle board, plywood, medium density board and blockboard due to its easy-to-obtain raw materials, low price, simple manufacturing process, and convenient use. It is one of the largest synthetic adhesives on the market. , accounting for more than 70% of the resin glue used in the wood-based panel industry. However, UF resin glue has two major disadvantages of poor water resistance and release of formaldehyde. Formaldehyde is harmful to human health and is considered a possible carcinogen. Improving water resistance and reducing formaldehyde emission are the focus of modification of urea-formaldehyde resin.

Using melamine to improve the water resistance of urea-formaldehyde resin is the most commonly used effective method. Both melamine and urea belong to amine compounds, and melamine has six active groups, which can react with formaldehyde to form methylol urea, which promotes the crosslinking of urea-formaldehyde resin, forms a three-dimensional network structure, and seals many water-absorbing groups at the same time. Sexual groups, greatly improving the water resistance of urea-formaldehyde resin. Patents in this area include CN1834186, CN1616510 and so on.

With the improvement of people's living standards, people pay more and more attention to the quality of life and environmental protection, and the requirements for formaldehyde emission from wood-based panels are becoming more and more stringent. All countries have formulated stricter standards for formaldehyde emission from wood-based panels. European countries have popularized the industrial production of _E1 wood-based panels in the 1990s. In order to meet the market requirements for wood-based panels with low formaldehyde emission, non-formaldehyde-based adhesives such as starch and isocyanate are used for plywood production. Such as CN100999651 provides a kind of preparation method of starch-based wood adhesive with good water resistance, CN1982395 invention discloses cationic amylopectin wood adhesive and preparation method, SY0800410102599.6 proposes a kind of glued wood boards that adopt isocyanate resin spray sizing Although the cost of modified starch glue is low and the formaldehyde emission of the produced board is low, the bonding strength is poor and does not meet the requirements of the national standard. The plywood made of API glue has low formaldehyde emission and the strength can meet the standard, but the cost is expensive. , and benzene organic compounds are produced during the board making process, which is highly toxic and difficult to produce in large quantities. In addition to non-formaldehyde-based adhesives, there are many studies on the optimization of UF resin adhesive formula and process and the post-treatment of boards for the preparation of low-formaldehyde emission plywood. This includes adding various additives and stabilizers during the glue-making process. , Add appropriate formaldehyde collectors when mixing glue, optimize the pressing process or perform post-treatment of formaldehyde removal on the manufactured wood-based panels. CN1632025 invented a catalyst that can reduce the formaldehyde emission of wood-based panels to E ₀ or FC ₀ without changing the production process of formaldehyde resin and wood-based panels. CN1570275 has invented a kind of manufacturing method of environment-friendly grass and wood composite high and medium density fiberboard. The hot-pressed high and medium density fiberboard is passed through the hollow and airtight formaldehyde reduction treatment room, and ammonia gas is introduced into the formaldehyde reduction treatment room, and E ₁ /E ₀ grade environment-friendly high and medium density fiberboard can be prepared through physical and chemical actions. CN1526528 invented a manufacturing method of _E1 / _E0 grade environment-friendly wood-based panels. The free formaldehyde emission is greater than or equal to the plain board of _E2 grade, and then the ammonia gas vacuum method is used to treat the formaldehyde emission of the board. Reach E ₁ /E ₀ level. Although plywood with low formaldehyde emission can be prepared, most of them require post-treatment or the addition of a relatively expensive additive, and the operation process is complicated and the cost is high. The invention is dedicated to the research on the process and formula of urea-formaldehyde resin, without adding any additives, and the pressed plywood can reach _E0 level without any formaldehyde-reducing treatment.

Contents of the invention

The invention solves the deficiencies and problems existing in the above-mentioned prior art, and provides a preparation method of low-cost UMF resin glue for E ₀ grade plywood. The glue has simple preparation process, good reproducibility, low cost and long storage period. The glue strength and formaldehyde emission of the miscellaneous wood plywood and poplar plywood pressed by this glue meet the requirements of E ₀ grade plywood.

The present invention is achieved through the following technical solutions:

_E0 grade plywood of the present invention uses the preparation method of low-cost UMF resin glue, and step is as follows:

The first step: add formaldehyde aqueous solution and the first batch of urea to the reactor, adjust the pH value to 1.0-3.0, raise the temperature to 80°C-95°C, and react for 40-70min. The molar ratio of formaldehyde to urea is 2.8-3.2: 1;

Second step: adjust the pH value of the intermediate product obtained in the first step to 8.0-9.0, add the first batch of melamine accounting for 2-3% of the formaldehyde mass, and add the second batch of urea at the same time, wherein the cumulative added urea and melamine The molar ratio of the total amount to formaldehyde is 1:2.0-2.2, and the reaction is carried out at 80-95°C for 30-50 minutes;

The third step: adjust the pH value of the intermediate product obtained in the second step to 4.5-5.5, and react at 80-95°C until the system viscosity is 50-150mpa·s;

The fourth step: adjust the pH value of the intermediate product obtained in the third step to 6.5-6.9, add the second batch of melamine with the same quality as the first batch, and add the third batch of urea at the same time, the total amount of urea and melamine added The molar ratio to formaldehyde is 1:1.4~1.6, and the reaction is at 80~90°C for 30~70min;

The fifth step: adjust the pH value of the intermediate product obtained in the fourth step to 8.0-9.0, add the third batch of melamine accounting for 9-11% of the initial formaldehyde mass, and react at 80-90°C for 20-80 minutes;

Step 6: Cool down to 70°C, add the fourth batch of urea, wherein the molar ratio of the total amount of urea and melamine added to formaldehyde is 1:0.9-1.1, continue the reaction for 20-80 minutes, cool and discharge to obtain E ₀ Grade plywood glued with low cost UMF resin.

In the preparation method of low-cost UMF resin glue for E grade ₀ plywood of the present invention, the reagent used for adjusting the pH value is preferably sodium hydroxide, potassium hydroxide, ammonium chloride, formic acid, acetic acid or hydrochloric acid.

In the preparation method of low-cost UMF resin glue for E grade ₀ plywood of the present invention, the mass percent concentration of the formaldehyde solution is preferably 37-40%.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention adopts the strong acid process, the selected urea is added in four batches, and the melamine is added in three batches. The addition of urea in stages can play a role in regulating the molecular weight of the resin, especially the urea added for the third time can not only degrade heavy Exhaust the macromolecular part of the molecule, but also reduce the content of ether bonds and reduce the release of formaldehyde. The first batch of melamine is added in the alkaline stage. The triazine ring of melamine has six active groups, so the reactivity is high, and the acid polycondensation reaction time can be shortened by 1 to 2 hours. The generated methylol melamine enters the main chain skeleton of UMF resin through polycondensation reaction, introduces multifunctional melamine molecules, improves the crosslinking degree of the resin, facilitates its further crosslinking, strengthens the bonding performance of the board, and improves the Glue strength. The methyl ether chain produced by polycondensation of methylol melamine is relatively stable, unlike the methylene ether chain condensed between methylol urea, which is easier to decompose and release formaldehyde. Therefore, adding melamine modification can not only reduce the formaldehyde release of wood-based panels It can also increase the bonding strength.

In the present invention, the molar ratio of F/U is low, a certain quality of melamine is added, and the synthesis process of medium and low temperature is adopted, which further promotes the full reaction of formaldehyde, so the free formaldehyde in the synthesized resin is very low, and it is a low-toxic and environment-friendly urea-formaldehyde resin .

Among the present invention, the used curing agent is a two-component curing agent when the rubber pressing plate is made, mainly composed of NH ₄ Cl and an acid curing agent, and the use of a two-component curing agent is more efficient than traditional single curing agents such as NH ₄ Cl. More advantages, using a composite curing system can not only reduce the pH value of the resin glue, increase the curing speed and cold-press bonding strength, improve the pre-pressing conditions, but also make the low F/U molar ratio UF resin fully cured, and the bonding strength Improvement can reduce the formaldehyde emission of the board. We added NH ₄ Cl, H ₃ PO ₄ , and HCOOH to UMF resins with F/(U+M) molar ratios of 1.05 and 1.00, respectively, to press poplar plywood, and tested the bonding strength and formaldehyde emission. Then add two-component curing agent system composed of NH ₄ Cl, H ₃ PO ₄ , and HCOOH to the two UMF resins respectively, press poplar plywood, and detect the bonding strength and formaldehyde emission. See attached table 3 for the test results.

The preparation process of the invention is simple and the reproducibility is good. The polymerization degree of the synthesized resin is moderate, the viscosity of the resin is low, and the polycondensate contains less amino groups and imino groups, the stability of the resin is good, and the storage period is long. It can be placed for 7 to 10 days after being pressed with the synthesized resin, without any post-treatment for reducing aldehydes, and the operation is simple. Moreover, the added mass of melamine in the present invention is less than 9.0% of the total mass of UMF resin, and the cost is relatively low.

Detailed ways

The present invention is illustrated below through specific examples, but the present invention is not limited to these examples.

Example 1

In the first step, add 320g of 37% formaldehyde aqueous solution and 73g of the first batch of urea to a 500ml flask, adjust the pH value to 2.0 with 20% ammonium chloride solution, raise the temperature to 95°C, and react for 40min.

In the second step, adjust the pH value to 8.5 with 15% NaOH solution, add the first batch of melamine 8g and the second batch of urea 30g, and react at 95°C for 30min.

In the third step, use 20% ammonium chloride solution to adjust the pH value to 5.0, and react at 95°C to the required viscosity of 81mpa·s.

The fourth step is to adjust the pH value to 6.8 with 20% ammonium chloride solution, and add the second batch of melamine 8g and the third batch of urea 37g. React at 90°C for 40 minutes.

The fifth step is to adjust the pH value to 8.5 with 15% NaOH solution, add the third batch of melamine 33g, and react at 90°C for 20min.

The sixth step is to lower the temperature to 70°C, add the fourth batch of urea 51g, continue the reaction for 50min, and cool and discharge. The properties were tested separately, and the results are listed in Attached Table 1, and 1% NH ₄ Cl and 0.5% H ₃ PO ₄ were used as the curing agent to press the plate, and the test results are shown in Attached Table 2.

Example 2

In the first step, add 320g of 40% formaldehyde aqueous solution and 79g of the first batch of urea to a 500ml flask, adjust the pH value to 1.0 with 20% ammonium chloride solution, raise the temperature to 80°C, and react for 70min.

In the second step, adjust the pH value to 8.0 with 15% NaOH solution, add the first batch of melamine 8g and the second batch of urea 31g, and react at 80°C for 50min.

In the third step, use 20% ammonium chloride solution to adjust the pH value to 5.5, and react at 80°C to the required viscosity of 74mpa·s.

The fourth step is to adjust the pH value to 6.5 with 20% ammonium chloride solution, and add the second batch of melamine 8g and the third batch of urea 40g. React at 80°C for 70 minutes.

The fifth step is to adjust the pH value to 8.0 with 15% NaOH solution, add the third batch of melamine 33g, and react at 80°C for 80min.

The sixth step is to lower the temperature to 70°C, add the fourth batch of urea 60g, continue the reaction for 80min, and cool and discharge. The properties were tested separately, and the results are listed in Attached Table 1, and 1% NH ₄ Cl and 0.5% H ₃ PO ₄ were used as the curing agent to press the plate, and the test results are shown in Attached Table 2.

Example 3

In the first step, add 320g of 38.5% formaldehyde aqueous solution and 84g of the first batch of urea to a 500ml flask, adjust the pH value to 3.0 with 20% ammonium chloride solution, raise the temperature to 85°C, and react for 50min.

In the second step, adjust the pH value to 8.5 with 15% NaOH solution, add the first batch of melamine 8g and the second batch of urea 30g, and react at 85°C for 40min.

In the third step, adjust the pH value to 4.5 with 20% ammonium chloride solution, and react at 85°C to the desired viscosity of 95mpa·s.

The fourth step is to adjust the pH value to 6.9 with 20% ammonium chloride solution, add the second batch of melamine 8g and the third batch of urea 30g. React at 85°C for 30 minutes.

The fifth step is to adjust the pH value to 9.0 with 15% NaOH solution, add the third batch of melamine 33g, and react at 85°C for 50min.

The sixth step is to lower the temperature to 70°C, add the fourth batch of urea 78g, continue the reaction for 50min, and cool and discharge. The properties were tested separately, and the results are listed in Attached Table 1, and 1% NH ₄ Cl and 0.5% H ₃ PO ₄ were used as the curing agent to press the plate, and the test results are shown in Attached Table 2.

Example 4

In the first step, add 320g of 38.5% formaldehyde aqueous solution and 80g of the first batch of urea to a 500ml flask, adjust the pH value to 2.0 with 20% ammonium chloride solution, raise the temperature to 85°C, and react for 55min.

In the second step, adjust the pH value to 8.5 with 15% NaOH solution, add the first batch of melamine 8g and the second batch of urea 34g, and react at 85°C for 40min.

In the third step, use 20% ammonium chloride solution to adjust the pH value to 5.0, and react at 85°C to the required viscosity of 107mpa·s.

The fourth step is to adjust the pH value to 6.7 with 20% ammonium chloride solution, add the second batch of melamine 8g and the third batch of urea 45g. React at 85°C for 60 minutes.

The fifth step is to adjust the pH value to 8.5 with 15% NaOH solution, add the third batch of melamine 33g, and react at 85°C for 60min.

The sixth step is to lower the temperature to 70°C, add the fourth batch of urea 70g, continue the reaction for 20-80min, and cool and discharge. The properties were tested separately, and the results are listed in Attached Table 1, and 1% NH ₄ Cl and 0.5% H ₃ PO ₄ were used as the curing agent to press the plate, and the test results are shown in Attached Table 2.

Example 5

The glue prepared in Example 1 was used, and 1% NH ₄ Cl was used as the curing agent to press the plate. The test results are shown in Attached Table 2.

Example 6

The glue prepared in Example 2 was used, and 1% NH ₄ Cl was used as the curing agent to press the plate. The test results are shown in Attached Table 2.

Attached Table 1 Technical indicators of UMF resin glue for grade E ₀ plywood

Formaldehyde% Viscosity mpa s % of solids Curing time S Shelf life days Example 1 0.13 81 56.4 227 ＞20 Example 2 0.10 74 56.0 233 ＞20 Example 3 0.09 95 56.7 249 ＞20 Example 4 0.07 107 56.9 252 ＞20

Detection of UMF resin glue: solid content is tested according to 3.5 of GB/T14074-2006; viscosity is tested according to 3.3 of GB/T14074-2006; curing time is tested according to 3.7 of GB/T14074-2006; free formaldehyde is tested according to 3.7 of GB/T14074-2006 3.16 of GB/T14074-2006 shall be tested.

Attached Table 2 Test results of UMF resin glued boards for grade E ₀ plywood

The strength of plywood in Attached Table 2 is the test results of 14 specimens, which are the average glued strength, and the denominator is the lowest strength to the highest strength.

Attached Table 3 Test results of UMF resin glue pressing poplar plywood with different curing agent systems

The pressed poplar plywood was placed at room temperature for 5-7 days before testing. The bonding strength is tested according to the provisions of 4.15 in GB/T17657-1999; the amount of formaldehyde released is tested according to the provisions of 4.12 of the dryer method in GB/T17657-1999.

Claims (3)

1, a kind of E ₀Level plywood is characterized in that step is as follows with the preparation method of low-cost UMF Resin adhesive:

The first step: formalin, first urea are added reactor, and adjust pH to 1.0～3.0 are warming up to 80 ℃～95 ℃, reaction 40～70min, and described formaldehyde and urea mol ratio are 2.8～3.2: 1;

Second step: the pH value of the intermediate product that the first step is obtained transfers to 8.0～9.0, add the trimeric cyanamide that first accounts for formaldehyde quality 2～3%, add second batch of urea simultaneously, wherein adding up the urea of adding and the total amount of trimeric cyanamide and the mol ratio of formaldehyde is 1: 2.0～2.2, reacts 30～50min down at 80～95 ℃;

The 3rd step: the pH value of second intermediate product that obtain of step is transferred to 4.5～5.5, under 80～95 ℃, react to system viscosity be 50～150mpas;

The 4th step: the 3rd pH value that goes on foot the intermediate product that obtains is transferred to 6.5～6.9, add second batch of trimeric cyanamide with first same quality, add the 3rd batch of urea simultaneously, the urea that accumulative total adds and the total amount of trimeric cyanamide and the mol ratio of formaldehyde are 1: 1.4～1.6, react 30～70min under 80～90 ℃ of conditions;

The 5th step: the 4th pH value that goes on foot the intermediate product that obtains is transferred to 8.0～9.0, add the 3rd batch of trimeric cyanamide that accounts for initial formaldehyde quality 9～11%, react 20～80min down at 80～90 ℃;

The 6th step: be cooled to 70 ℃, add the 4th batch of urea, wherein adding up the urea of adding and the total amount of trimeric cyanamide and the mol ratio of formaldehyde is 1: 0.9～1.1, continues reaction 20～80min, and cooling discharging promptly obtains E ₀Level plywood is with low-cost UMF Resin adhesive.

2, E according to claim 1 ₀Level plywood is with the preparation method of low-cost UMF Resin adhesive, and agents useful for same is sodium hydroxide, potassium hydroxide, ammonium chloride, formic acid, acetate or hydrochloric acid when it is characterized in that described adjusting pH value.

3, E according to claim 1 ₀Level plywood is 37～40% with the preparation method of low-cost UMF Resin adhesive, the mass percentage concentration that it is characterized in that described formalin.