Environmentally friendly modified urea-formaldehyde resin and preparation method and application thereof

Abstract

The present invention relates to the field of C08L23 / 12, and in particular to an environmentally friendly modified urea-formaldehyde resin and a preparation method and application thereof. The preparation raw materials include, by weight, 8000-12000 parts of formaldehyde, 2500-3000 parts of a first urea, 4000-5000 parts of a second urea, 200-250 parts of a third urea, 50-100 parts of a modifier, 100-200 parts of a triazine-type nitrogen-containing heterocyclic organic compound, 10-15 parts of a first alkali solution, 10-15 parts of a second alkali solution, 5-10 parts of a third alkali solution, 25-35 parts of an acid solution, and 500-800 parts of an auxiliary agent. The urea-formaldehyde resin prepared by the present invention has a free formaldehyde content of less than 0.1% after testing, and is an environmentally friendly resin.

Description

Technical Field

[0001] The present invention relates to the field of C08L23 / 12, and in particular to an environmentally friendly modified urea-formaldehyde resin and a preparation method and application thereof. Background Art

[0002] Urea-formaldehyde resin adhesive is a thermosetting resin obtained by polymerization reaction with formaldehyde and urea as basic raw materials. Urea-formaldehyde resin adhesive is the most widely used adhesive in my country's wood industry. Among wood adhesives, more than 80% of wood-based panels still use urea-formaldehyde adhesive as adhesive. Compared with other adhesives, urea-formaldehyde resin has sufficient raw materials and low prices, and is the lowest price among synthetic resins. Nowadays, various artificial boards, wooden products and furniture have experienced excessive formaldehyde release for a long time, which not only pollutes the environment and harms the health of workers, but also seriously restricts the healthy development of the board industry.

[0003] CN103408712A discloses a method for producing polyvinyl alcohol-modified urea-formaldehyde resin with low formaldehyde residue. The free formaldehyde content is reduced by modifying polyvinyl alcohol, but the viscosity of the urea-formaldehyde resin is significantly increased, which hinders the construction process.

[0004] CN110205067A discloses an environmentally friendly urea-formaldehyde resin adhesive and its preparation method and application. The modified resin has suitable viscosity and low formaldehyde content, but poor water resistance after curing.

[0005] It is difficult for urea-formaldehyde resin in the prior art to simultaneously meet the requirements of low formaldehyde, high viscosity and high water resistance. The market generally uses triazine-type nitrogen-containing heterocyclic organic compounds to modify its water resistance, and they are expensive. Summary of the invention

[0006] The first aspect of the present invention provides an environmentally friendly modified urea-formaldehyde resin. The raw materials for preparing the resin include, by weight: 8000-12000 parts of formaldehyde, 2500-3000 parts of a first urea, 4000-5000 parts of a second urea, 200-250 parts of a third urea, 50-100 parts of a modifier, 100-200 parts of a triazine-type nitrogen-containing heterocyclic organic compound, 10-15 parts of a first alkali solution, 10-15 parts of a second alkali solution, 5-10 parts of a third alkali solution, 25-35 parts of an acid solution, and 500-800 parts of an additive.

[0007] Preferably, in parts by weight, the prepared raw materials include: 8000 parts of formaldehyde, 2900 parts of the first urea, 4875 parts of the second urea, 225 parts of the third urea, 75 parts of the modifier, 150 parts of the triazine-type nitrogen-containing heterocyclic organic compound, 12 parts of the first alkali solution, 12 parts of the second alkali solution, 8 parts of the third alkali solution, 30 parts of acid solution, and 700 parts of the additive.

[0008] As a preferred embodiment, the formaldehyde is a formaldehyde aqueous solution with a mass concentration of 37%.

[0009] As a preferred implementation, the mass content of sulfate in the first urea, the second urea and the third urea is no more than 0.02%.

[0010] The higher the sulfate content in urea, especially when it is higher than 0.02%, the viscosity of the prepared urea-formaldehyde resin will increase significantly and the storage performance will decrease.

[0011] As a preferred implementation, the mass content of biuret in the first urea, the second urea and the third urea is no more than 1%.

[0012] The higher the biuret content in urea, the significantly lower the storage stability of urea-formaldehyde resin.

[0013] The first urea, the second urea and the third urea have the same composition, are all urea, and can be purchased from Luxi Group.

[0014] As a preferred implementation manner, the weight ratio of the formaldehyde to the total weight of the first urea, the second urea and the third urea is (0.9-1.1):1.

[0015] The weight ratio of formaldehyde to urea (F / U) directly affects the bonding properties of the resin. In the prior art, the F / U value is generally maintained at (1.1-1.3):1, which can achieve good storage stability. However, when the F / U value is at a higher level, the hydroxymethyl content in the resin is higher and the free formaldehyde content is higher.

[0016] The applicant found that when the weight ratio of formaldehyde to urea is (0.9-1.1):1, the free formaldehyde content of the prepared urea-formaldehyde resin is low, the adhesion is good, and the initial viscosity is extremely high. It is speculated that the reason is that at this ratio, the cross-linking density of the urea-formaldehyde resin is uniform, and the low F / U value results in a lower free formaldehyde content.

[0017] As a preferred embodiment, the viscosity (25°C) of the modifier is 2.3-2.7 mPa.s.

[0018] As a preferred embodiment, the alcoholysis degree of the modifier is 86.5-89%.

[0019] In order to improve the bonding strength of the resin, the modifier is polyvinyl alcohol, purchased from Shanghai Xiangpu International Trading Co., Ltd., model number L-3266.

[0020] As a preferred embodiment, the triazine nitrogen-containing heterocyclic organic compound includes at least one of melamine, triallyl cyanurate, cyanuric chloride and trichloromelamine.

[0021] In order to reduce the content of free formaldehyde, the triazine nitrogen-containing heterocyclic organic compound is melamine.

[0022] As a preferred embodiment, the auxiliary agent is carbohydrate.

[0023] Preferably, the carbohydrate includes at least one of sucrose, glucose, lactose and galactose.

[0024] Preferably, the carbohydrate is sucrose, specifically white granulated sugar.

[0025] The applicant found that adding white sugar into the system can significantly improve the water resistance of urea-formaldehyde resin. The reason may be that the hydrophilic groups in the white sugar are embedded inside the cross-linked layer, and the hydrophilic groups have excellent compatibility with the cross-linked layer, while the hydrophobic groups are evenly exposed on the surface of the cross-linked film, which on the one hand adjusts the viscosity of the resin, and on the other hand enhances the water resistance of the resin.

[0026] As a preferred embodiment, the first alkali solution, the second alkali solution and the third alkali solution are at least one of sodium hydroxide, potassium hydroxide, barium hydroxide and ammonia water.

[0027] Preferably, the first alkali solution, the second alkali solution and the third alkali solution are all sodium hydroxide, specifically, they are all sodium hydroxide aqueous solutions with a mass concentration of 30%.

[0028] As a preferred embodiment, the acid solution includes at least one of formic acid, acetic acid, hydrochloric acid, sulfuric acid, and acetic acid.

[0029] Preferably, the acid solution is formic acid, specifically a formic acid aqueous solution with a mass concentration of 20%.

[0030] A second aspect of the present invention provides a method for preparing an environmentally friendly modified urea-formaldehyde resin, comprising the following steps:

[0031] (1) Adding formaldehyde, modifier and auxiliary agent into the reaction kettle, heating up and keeping warm for 10-20 minutes for the first time, adding the first alkali solution and adjusting the pH value, adding the first urea, heating up and keeping warm for 20-30 minutes for the second time;

[0032] (2) Cooling and adding acid;

[0033] (3) heating for the third time and keeping the temperature for 40-60 min, testing the viscosity for the first time, adding the second alkali solution and adjusting the pH value, adding the triazine-type nitrogen-containing heterocyclic organic compound and the second urea, and testing the viscosity for the second time;

[0034] (4) adding a third alkali solution and adjusting the pH value, adding a third urea, cooling, and discharging the material.

[0035] As a preferred embodiment, the first heating is to heat the temperature to 55-65°C.

[0036] As a preferred embodiment, the second heating is to heat to 90-95°C.

[0037] As a preferred embodiment, the third heating is to heat to 90-94°C.

[0038] As a preferred embodiment, the viscosity value (25°C) of the first viscosity detection is 13-14s per 4 cup.

[0039] As a preferred embodiment, the viscosity value (25°C) of the second viscosity detection is 17-18s per cup of Tu-4.

[0040] As a preferred embodiment, the acid solution is added in two portions: the first portion is 18-22 portions, the pH value is adjusted to 6.5-6.7, and the reaction is performed for 3-5 minutes; the second portion is 8-12 portions, and the pH value is adjusted to 4.0-4.2.

[0041] The third aspect of the present invention provides an application of an environmentally friendly modified urea-formaldehyde resin in the field of wood processing.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The urea-formaldehyde resin prepared by the present invention has a free formaldehyde content of less than 0.1% after testing, and is an environmentally friendly resin.

[0044] 2. The phenolic resin of the present invention achieves a balance between low formaldehyde content and high bonding strength by adding melamine and urea.

[0045] 3. The present invention creatively adds white sugar, which unexpectedly improves the water resistance of urea-formaldehyde resin. DETAILED DESCRIPTION

[0046] Example 1

[0047] The first aspect of the present embodiment provides an environmentally friendly modified urea-formaldehyde resin. The preparation raw materials include, by weight: 8000 parts of formaldehyde, 2900 parts of a first urea, 4875 parts of a second urea, 225 parts of a third urea, 75 parts of a modifier, 150 parts of a triazine-type nitrogen-containing heterocyclic organic compound, 12 parts of a first alkali solution, 12 parts of a second alkali solution, 8 parts of a third alkali solution, 30 parts of an acid solution, and 700 parts of an additive.

[0048] The formaldehyde is a formaldehyde aqueous solution with a mass concentration of 37%.

[0049] The mass content of sulfate in the first urea, the second urea and the third urea is no more than 0.02%, and the mass content of biuret is no more than 1%;

[0050] The first urea, the second urea and the third urea have the same composition, are all urea, and can be purchased from Luxi Group.

[0051] The modifier is polyvinyl alcohol, with a viscosity (25° C.) of 2.3-2.7 mPa.s and a degree of alcoholysis of 86.5-89%, purchased from Shanghai Xiangpu International Trade Co., Ltd., model number L-3266.

[0052] The triazine nitrogen-containing heterocyclic organic compound is melamine.

[0053] The auxiliary agent is white granulated sugar, which is commercially available.

[0054] The first alkali solution, the second alkali solution and the third alkali solution are all sodium hydroxide aqueous solutions with a mass concentration of 30%.

[0055] The acid solution is a formic acid aqueous solution with a mass concentration of 20%.

[0056] The second aspect of the present embodiment provides a method for preparing an environmentally friendly modified urea-formaldehyde resin, comprising the following steps:

[0057] (1) Add formaldehyde, modifier and auxiliary agent into the reactor, heat to 60°C for the first time and keep warm for 15 minutes, continue to add the first alkali solution and adjust the pH value to 8.5, add the first urea, heat to 92°C for the second time and keep warm for 25 minutes;

[0058] (2) Cooling to 88°C, adding acid solution twice, adding 20 parts in the first time, adjusting the pH value to 6.6, and reacting for 4 minutes; adding 10 parts in the second time, adjusting the pH value to 4.1;

[0059] (3) The temperature was raised to 94°C for the third time and kept warm for 50 min. The first viscosity test at 25°C was 13-14 seconds for coating 4 cups. The second alkali solution was added and the pH value was adjusted. The triazine-type nitrogen-containing heterocyclic organic compound and the second urea were added. The second viscosity test at 25°C was 17-18 seconds for coating 4 cups.

[0060] (4) Add the third alkali solution and adjust the pH value to 8.8, add the third urea, cool to 55° C., adjust the pH value to 8.8, cool to 40° C., and discharge.

[0061] The third aspect of this embodiment provides an application of an environmentally friendly modified urea-formaldehyde resin in the field of wood processing.

[0062] Comparative Example 1

[0063] The first aspect of this comparative example provides an environmentally friendly modified urea-formaldehyde resin, and the specific implementation manner is the same as that of Example 1, except that the first urea is 3700 parts, the second urea is 3475 parts, and the third urea is 475 parts.

[0064] The second aspect of this comparative example provides a method for preparing an environmentally friendly modified urea-formaldehyde resin, and the specific implementation method is the same as that of Example 1.

[0065] The third aspect of this comparative example provides an application of an environmentally friendly modified urea-formaldehyde resin in the field of wood processing.

[0066] Comparative Example 2

[0067] The first aspect of this comparative example provides an environmentally friendly modified urea-formaldehyde resin, and the specific implementation method is the same as that of Example 1, except that the triazine nitrogen-containing heterocyclic organic compound is replaced by 0 parts.

[0068] The second aspect of this comparative example provides a method for preparing an environmentally friendly modified urea-formaldehyde resin, and the specific implementation method is the same as that of Example 1.

[0069] The third aspect of this comparative example provides an application of an environmentally friendly modified urea-formaldehyde resin in the field of wood processing.

[0070] Comparative Example 3

[0071] The first aspect of this comparative example provides an environmentally friendly modified urea-formaldehyde resin, and the specific implementation method is the same as that of Example 1, except that the auxiliary agent is replaced with 0 parts.

[0072] The second aspect of this comparative example provides a method for preparing an environmentally friendly modified urea-formaldehyde resin, and the specific implementation method is the same as that of Example 1.

[0073] The third aspect of this comparative example provides an application of an environmentally friendly modified urea-formaldehyde resin in the field of wood processing.

[0074] Comparative Example 4

[0075] The first aspect of this comparative example provides an environmentally friendly modified urea-formaldehyde resin, and the specific implementation method is the same as that of Example 1, except that the modifier is polyvinyl alcohol with a viscosity of 23-28 mPa.s, purchased from Dongguan Hengye Additive Co., Ltd., model number C805.

[0076] The second aspect of this comparative example provides a method for preparing an environmentally friendly modified urea-formaldehyde resin, and the specific implementation method is the same as that of Example 1.

[0077] The third aspect of this comparative example provides an application of an environmentally friendly modified urea-formaldehyde resin in the field of wood processing.

[0078] Performance Testing

[0079] The test was carried out with reference to GB / T 14732-2017 "Urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde resins for adhesives in the wood industry" and GB / T14074-2017 "Test methods for adhesives and resins for the wood industry". The quality indicators are shown in Table 1.

[0080] Table 1

[0081]

[0082] Refer to GB / T 17657-2013 "Test methods for physical and chemical properties of wood-based panels and veneer wood-based panels", class II bonding strength, class I immersion peeling and formaldehyde emission were determined by the dryer method, using 40×40×2mm eucalyptus veneers, a total of five layers, double-sided coating of the modified urea-formaldehyde resin of the embodiment and the comparative example, the coating amount is 360g / m 2 , add 25% of commercial flour by weight of the modified urea-formaldehyde resin, and after coating, laminate it and heat press it at 125℃ for 10 minutes with a pressure of 10kg / cm 2, The test results are shown in Table 2.

[0083] Table 2

[0084]

Claims

1. An environmentally friendly modified urea-formaldehyde resin, characterized in that: The raw materials for preparation include, by weight: 8000 parts of formaldehyde, 2900 parts of the first urea, 4875 parts of the second urea, 225 parts of the third urea, 75 parts of the modifier, 150 parts of the triazine nitrogen-containing heterocyclic organic compound, 12 parts of the first alkali solution, 12 parts of the second alkali solution, 8 parts of the third alkali solution, 30 parts of acid solution, and 700 parts of the auxiliary agent; The formaldehyde is a formaldehyde aqueous solution with a mass concentration of 37%; The mass content of sulfate in the first urea, the second urea and the third urea is no more than 0.02%, and the mass content of biuret is no more than 1%; The first urea, the second urea and the third urea have the same composition, which are urea; The modifier is polyvinyl alcohol, with a viscosity of 2.3-2.7 mPa.s at 25°C and a degree of alcoholysis of 86.5-89%. The triazine nitrogen-containing heterocyclic organic compound is melamine; The auxiliary agent is white sugar; The first alkali solution, the second alkali solution and the third alkali solution are all sodium hydroxide aqueous solutions with a mass concentration of 30%; The acid solution is a formic acid aqueous solution with a mass concentration of 20%; The method for preparing the environmentally friendly modified urea-formaldehyde resin comprises the following steps: (1) Add formaldehyde, modifier and additive into the reactor, heat it to 60°C for the first time and keep it warm for 15 minutes, continue to add the first alkali solution and adjust the pH value to 8.5, add the first urea, heat it to 92°C for the second time and keep it warm for 25 minutes; (2) Cool down to 88°C, add acid solution twice, add 20 parts in the first time, adjust the pH value to 6.6, and react for 4 minutes; add 10 parts in the second time, and adjust the pH value to 4.1; (3) The temperature was raised to 94°C for the third time and kept warm for 50 minutes. The first viscosity test at 25°C was 13-14 seconds for coating 4 cups. The second alkali solution was added and the pH value was adjusted. The triazine-type nitrogen-containing heterocyclic organic compound and the second urea were added. The second viscosity test at 25°C was 17-18 seconds for coating 4 cups. (4) Add the third alkali solution and adjust the pH value to 8.8, add the third urea, cool to 55°C, adjust the pH value to 8.8, cool to 40°C, and discharge.

2. A method for preparing an environmentally friendly modified urea-formaldehyde resin according to claim 1, characterized in that: The steps include: (1) Add formaldehyde, modifier and additive into the reactor, heat it to 60°C for the first time and keep it warm for 15 minutes, continue to add the first alkali solution and adjust the pH value to 8.5, add the first urea, heat it to 92°C for the second time and keep it warm for 25 minutes; (2) Cool down to 88°C, add acid solution twice, add 20 parts in the first time, adjust the pH value to 6.6, and react for 4 minutes; add 10 parts in the second time, and adjust the pH value to 4.1; (3) The temperature was raised to 94°C for the third time and kept warm for 50 minutes. The first viscosity test at 25°C was 13-14 seconds for coating 4 cups. The second alkali solution was added and the pH value was adjusted. The triazine-type nitrogen-containing heterocyclic organic compound and the second urea were added. The second viscosity test at 25°C was 17-18 seconds for coating 4 cups. (4) Add the third alkali solution and adjust the pH value to 8.8, add the third urea, cool to 55°C, adjust the pH value to 8.8, cool to 40°C, and discharge.

3. Use of the environmentally friendly modified urea-formaldehyde resin according to claim 1 in the field of wood processing.

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