Efficient composite formaldehyde reducing agent for wood composite material

Abstract

The invention relates to the technical field of composite formaldehyde reducing agents, in particular to a composite formaldehyde reducing agent in the field of wood composite materials, and the composite formaldehyde reducing agent comprises (i) 50-55% of a physical formaldehyde reducing component selected from nano montmorillonite, activated carbon, nano silicon dioxide and a combination thereof, (ii) 27-35% of a chemical formaldehyde reducing component selected from nano montmorillonite, activated carbon, nano silicon dioxide and a combination thereof, and (iii) 0.5-5% of a water reducing agent. The chemical formaldehyde-reducing component is selected from amine compounds, amino compounds, urea derivatives, urotropine (hexamethylenetetramine), polyhydroxy alcohol and combinations thereof, and (iii) 9.6-15% of other additive components, and the adding percentage of each component is the mass percentage based on the total mass of the composite formaldehyde-reducing agent. The formaldehyde reduction efficiency can be improved, the formaldehyde reduction validity period is prolonged, the formaldehyde reduction validity period covers a short period, a middle period and a long period, and the formaldehyde reduction effect in each stage is continuous and stable.

Description

Technical Field

[0001] The present application relates to the technical field of composite formaldehyde reducing agents, in particular to composite formaldehyde reducing agents in the field of wood composite materials; the present application also relates to a composite adhesive utilizing the composite formaldehyde reducing agent. Background Art

[0002] Urea-formaldehyde resin adhesives are the primary binder for wood composites due to performance and price considerations. However, urea-formaldehyde resins continuously release formaldehyde during and after curing, both during the production and use of wood composites. In research addressing formaldehyde emissions from wood composites bonded with urea-formaldehyde resin adhesives, the use of formaldehyde reducers is a method that can achieve a balance between adhesive performance and price.

[0003] The prior art provides a variety of formaldehyde-reducing agents, such as the one described in patent application CN109401667A, titled "A Formaldehyde-Reducing Agent, Its Preparation Method, and Application in the Production of Low-Formaldehyde-Emitting Fiberboard." The agent comprises 20-40% of a formaldehyde-reducing component, 1-10% of a reinforcing agent, and water. The formaldehyde-reducing component is one or more of urea, sodium metabisulfite, isothiazolinone, acrylamide, and sodium borate, and the reinforcing agent is one or more of disodium hydrogen phosphate, sodium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium acetate, and dimethylethanolamine. During use, MUF resin and the formaldehyde-reducing agent are mixed in a static mixer and pumped along with a curing agent into the discharge valve of a hot mill, where atomized adhesive is sprayed out. The introduction of this formaldehyde-reducing agent can enhance the formaldehyde-binding capacity of melamine-modified urea-formaldehyde resin adhesive systems, raising the environmental rating of the adhesive from E1 to E0 or above.

[0004] Another example is the formaldehyde-reducing agent described in patent application CN101538452B, titled "A Formaldehyde-Reducing Agent for Finished Urea-Formaldehyde Adhesive and Its Application Method." Its composition is 1.24-1.28 parts melamine, 1.78-1.80 parts sodium chloride, and 0.04-0.06 parts sodium dodecylbenzenesulfonate. This formaldehyde-reducing agent can increase the viscosity of the adhesive while reducing formaldehyde emissions, achieving a formaldehyde removal efficiency of over 94%.

[0005] However, the above scheme has the following limitations: in the short term, the formaldehyde-reducing effect cannot be exerted quickly, and in the long term, the formaldehyde-reducing effect cannot be exerted continuously. Summary of the Invention

[0006] The purpose of this application is to provide an improved high-efficiency composite formaldehyde reduction agent suitable for the field of wood composite materials, thereby improving the formaldehyde reduction efficiency and extending the effective period of formaldehyde reduction, covering the short-term, medium-term and long-term formaldehyde reduction period, and maintaining a stable formaldehyde reduction effect at all stages. The following technical solutions are specifically adopted:

[0007] A high-efficiency composite formaldehyde reducing agent for wood composite materials, the composite formaldehyde reducing agent containing:

[0008] (i) 52-55% of a physical formaldehyde-reducing component, wherein the physical formaldehyde-reducing component is selected from nano-montmorillonite, activated carbon, nano-silica, and combinations thereof;

[0009] (ii) 33-35.4% of a chemical formaldehyde-reducing component selected from amine compounds, amino compounds, urea derivatives, urotropine (hexamethylenetetramine), polyhydroxy alcohols, and combinations thereof, and

[0010] (iii) 9.6~15% of other added ingredients,

[0011] The addition percentages of various components are weight percentages based on the total weight of the composite formaldehyde reducing agent.

[0012] By adding physical formaldehyde-reducing ingredients, the composite formaldehyde-reducing agent of the present application can exert a formaldehyde-reducing effect in a short period of time through adsorption and capture, quickly reduce the formaldehyde content of wood composite materials, and control their formaldehyde release; by adding chemical formaldehyde-reducing ingredients, especially the use of amine compounds and amino compounds, the composite formaldehyde-reducing agent of the present application can continuously exert a formaldehyde-reducing effect for a longer period of time through chemical reactions; at the same time, by using uropyrine and urea derivatives, the effective period of the formaldehyde-reducing effect of the composite formaldehyde-reducing agent of the present application can be further extended, making the formaldehyde-reducing effect stable and continuous.

[0013] On the second aspect, the various ingredients mentioned above are safe and harmless, friendly to the human body and the environment, do not contain harmful substances or organic solvents, do not release toxic substances during use, and do not cause secondary pollution.

[0014] Thirdly, the addition of nano-montmorillonite, activated carbon, or nano-silica can improve the mechanical properties of the adhesive, while the addition of uropine can improve the permeability of the adhesive. Therefore, the use of the composite formaldehyde-reducing agent of the present application can improve the performance of the adhesive to a certain extent. Due to the influence of its modification effect, the amount of sizing agent applied can be appropriately reduced. In addition, it can also make urea-formaldehyde resin adhesives suitable for use with some low-grade raw materials.

[0015] Preferably, the physical formaldehyde reducing component is composed of:

[0016] (i.1) 48~50% nano-montmorillonite,

[0017] (i.2) 48-50% activated carbon, and

[0018] (i.3) 1.5~2.5% of nano-silicon dioxide composition,

[0019] The addition percentage of each component is the mass percentage based on the total mass of the physical formaldehyde-reducing component.

[0020] As a preference, nano-montmorillonite is loaded with Fe 3+ Ion modified nano-montmorillonite, with a specific surface area of ​​not less than 250m² / g. 3+ The ion-modified nano-montmorillonite is iron-pillared nano-montmorillonite.

[0021] Here, the use of modified nano-montmorillonite can improve the adsorption efficiency and enable the composite formaldehyde reducer to have a higher treatment efficiency in a high humidity environment.

[0022] Preferably, the other additional components at least include polyacrylic acid (PAA).

[0023] Here, polyacrylic acid (PAA) is selected to form steric hindrance in collaboration with nano-silica, thereby ensuring the dispersion stability of nano-montmorillonite and activated carbon.

[0024] Preferably, the nano-silica is hydrophobic fumed nano-silica with a particle size of 20 to 30 nm.

[0025] Preferably, the chemical formaldehyde-reducing component is composed of:

[0026] (ii.1) 29~31% of amine compounds,

[0027] (ii.2) 32.5~35% amino compounds,

[0028] (ii.3) 14-16.5% urea derivatives,

[0029] (ii.4) 910~12.5% ​​of methenamine (hexamethylenetetramine), and

[0030] (ii.5) 8~10.5% polyhydric alcohol composition,

[0031] The addition percentage of each component is the mass percentage based on the total mass of the chemical formaldehyde-reducing component.

[0032] Preferably, the amine compound is selected from melamine, triethanolamine, and combinations thereof.

[0033] Preferably, the amino compound is dicyandiamide.

[0034] Preferably, the urea derivative is selected from ethylene urea, thiourea, and combinations thereof.

[0035] Preferably, the other added ingredients are:

[0036] (iii.1) 29.5~31.5% polyacrylic acid (PAA),

[0037] (iii.2) 15~16% citric acid,

[0038] (iii.3) 8.5-10% tannin extract, and

[0039] (iii.4) 45~47% inorganic clay composition,

[0040] The addition percentage of each component is the mass percentage based on the total mass of the other added components.

[0041] Preferably, the pH value of the composite formaldehyde reducing agent is 4.8-5.2.

[0042] Preferably, when used, the composite formaldehyde reducing agent is mixed with deionized water, and the addition ratio of the composite formaldehyde reducing agent to deionized water is (90-96):100.

[0043] Another technical purpose of the present application is to provide a composite adhesive utilizing the composite formaldehyde reducing agent, comprising the composite formaldehyde reducing agent and an adhesive.

[0044] Preferably, the ratio of the composite formaldehyde reducing agent to the adhesive is (3~5):100.

[0045] Preferably, the adhesive is a urea-formaldehyde resin adhesive.

[0046] The application of the high-efficiency composite formaldehyde-reducing agent of the present invention can improve the formaldehyde-reducing efficiency and extend the effective period of formaldehyde-reducing. The effective period of formaldehyde-reducing covers the short-term, medium-term and long-term, and the formaldehyde-reducing effect is sustained and stable in each stage.

[0047] At the same time, the use scenarios of wood composite materials cover low humidity and high humidity environments, and the higher the ambient humidity, the greater the dynamic release rate of formaldehyde in the wood composite material, so the formaldehyde reduction performance in a high humidity environment is an issue that should be paid attention to. In this solution, the combination of citric acid and amine compounds can dynamically adjust the pH value to adapt the composite formaldehyde-reducing agent of this application to formaldehyde reduction treatments in various humidity ranges. Specifically, in a low humidity environment, the activity of amino compounds can be increased; in a high humidity environment, the efficiency of the hydroxyl groups on the surface of nano-SiO2 to capture gaseous formaldehyde can be activated. In addition, the combination of modified nano-montmorillonite and activated carbon can maintain formaldehyde adsorption efficiency in a high humidity environment. Thus, it can meet the formaldehyde reduction requirements in an environment with a humidity range of 30~90%RH.

[0048] The composite adhesive using this composite formaldehyde reducing agent also has short-term, medium-term and long-term formaldehyde reducing effects, and the formaldehyde reducing application scenarios cover low-humidity and high-humidity environments. DETAILED DESCRIPTION

[0049] The technical solutions in this application are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of this application, not all of them. The following description of at least one exemplary embodiment is merely illustrative and in no way limits the present application and its application or use. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0050] Example

[0051] A high-efficiency composite formaldehyde reducing agent for wood composite materials, comprising: (i) 52-55% of a physical formaldehyde reducing component, (ii) 33-35.4% of a chemical formaldehyde reducing component, and (iii) 9.6-15% of other added components, wherein the added percentage of each component is a mass percentage based on the total mass of the composite formaldehyde reducing agent.

[0052] The physical formaldehyde-reducing component consists of: (i.1) 48-50% of nano-montmorillonite, (i.2) 48-50% of activated carbon, and (i.3) 1.5-2.5% of nano-silica, wherein the addition percentage of each component is a mass percentage based on the total mass of the physical formaldehyde-reducing component.

[0053] The chemical formaldehyde-reducing component consists of: (ii.1) 29-31% of an amine compound, (ii.2) 32.5-35% of an amino compound, (ii.3) 14-16.5% of a urea derivative, (ii.4) 10-12.5% ​​of hexamethylenetetramine, and (ii.5) 8-10.5% of a polyhydroxy alcohol, wherein the added percentages of each component are weight percentages based on the total weight of the chemical formaldehyde-reducing component. The amine compound is a combination of melamine and triethanolamine, the amino compound is dicyandiamide, and the urea derivative is a combination of ethyleneurea and thiourea.

[0054] Other added ingredients include: (iii.1) 29.5-31.5% of polyacrylic acid (PAA), (iii.2) 15-16% of citric acid, (iii.3) 8.5-10% of tannin extract, and (iii.4) 45-47% of inorganic clay, wherein the addition percentage of each ingredient is a mass percentage based on the total mass of the other added ingredients.

[0055] The preparation process includes a pre-dispersion stage, a chemical component addition stage, a final mixing and conditioning stage, and an aging stage.

[0056] During the pre-dispersion stage, the temperature was maintained at no more than 40°C. Modified nano-montmorillonite, inorganic clay, and nano-silica were added to a 40% aqueous melamine solution and subjected to high-speed shearing at 3000 rpm for 30-40 minutes. Subsequently, polyacrylic acid (PAA) was added and dispersion continued for 15 minutes until the transmittance reached at least 90% (measured at 650nm). Simultaneously, citric acid and triethanolamine were pre-mixed.

[0057] During the chemical addition phase, dicyandiamide, ethylene urea, and thiourea are added sequentially, stirring at 300 rpm at 40-45°C for 1-1.1 hours to activate the amino groups. Subsequently, a premix of citric acid and triethanolamine is slowly added, while maintaining the temperature below 50°C.

[0058] During the final mixing and conditioning stage, activated carbon, hexamethylenetetramine, and tannin extract were added and stirred at a low speed of 200 rpm for 15 to 20 minutes to avoid demulsification.

[0059] Finally, the mixture was aged for 24 hours to obtain the composite formaldehyde-reducing agent of this embodiment.

[0060] Conventional usage methods include adding the composite formaldehyde reducer to a glue mixing tank at a ratio of (3-5):100 during the mixing process of urea-formaldehyde resin adhesive to achieve mixing; or adding it to the urea-formaldehyde resin adhesive through a curing agent application system at a ratio of (3-5):100 to achieve mixing; or mixing it with deionized water at a ratio of (90-96):100 to prepare a water-based composite formaldehyde reducer, which is then applied to the surface of the wood composite material by spraying, roller coating, or the like.

[0061] A specific method of use involves spraying the composite formaldehyde-reducing agent onto the surface of dried particleboard (with a moisture content of approximately 8%). The amount of spray applied depends on the amount of glue applied, specifically 5-6% of the applied glue. The spraying process can be performed independently or during a cyclonic conveying process. Subsequently, the wood particles are sprayed with a urea-formaldehyde resin adhesive using conventional methods.

[0062] On the one hand, this method can, to a certain extent, allow the cured film-forming adhesive layer to wrap around the wood chips and the solid components of the composite formaldehyde-reducing agent attached to the surface of the wood chips, in particular, it can prevent the loss of the physical formaldehyde-reducing component, while not affecting the contact between the composite formaldehyde-reducing agent and the adhesive. On the other hand, the moisture content of the wood chips will increase to a certain extent after the adhesive is sprayed, and will decrease to a certain extent during the subsequent hot pressing process. During this process, the gaps on the surface of the wood chips will decrease from large to small, thereby mechanically fixing the physical formaldehyde-reducing component in the composite formaldehyde-reducing component, preventing it from losing and affecting the physical formaldehyde-reducing effect.

[0063] Taking the preparation of 100g of the composite formaldehyde reducing agent as an example, the formulas of Examples 1 to 3 are shown in Table 1.

[0064] Table 1

[0065]

[0066] Therefore, the ratio between the physical formaldehyde-reducing components, chemical formaldehyde-reducing components and other added components provided in Example 1 is 52:33:9.6, the ratio between the physical formaldehyde-reducing components, chemical formaldehyde-reducing components and other added components provided in Example 2 is 55:35.4:9.6, and the ratio between the physical formaldehyde-reducing components, chemical formaldehyde-reducing components and other added components provided in Example 3 is 53.5:34.2:12.3.

[0067] Comparative Example 1

[0068] The difference between Control Example 1 and Example 1 is that no physical formaldehyde-reducing component is added, and the ratio between the chemical formaldehyde-reducing component and other added components is maintained at 33:9.6.

[0069] Comparative Example 2

[0070] The difference between Control Example 2 and Example 1 is that no chemical formaldehyde-reducing component is added, and the ratio between the physical formaldehyde-reducing component and other added components is maintained at 52:9.6.

[0071] Comparative Example 3

[0072] The difference between Control Example 3 and Example 1 is that citric acid is not added, and the amounts of other added ingredients are maintained at the same levels as in Example 1.

[0073] Application Example 1

[0074] The composite formaldehyde-reducing agent from Examples 1-3 was added to a urea-formaldehyde resin adhesive (final solids content 60%) in a 4:100 ratio and mixed in a glue mixing tank. Particleboard was prepared according to conventional methods, with an 8% sizing agent application rate. The particleboards prepared in this application example are labeled Samples 1-3.

[0075] Specifically, the above-mentioned prior art method includes the following steps:

[0076] Step 1: After screening and dust removal, wood chips with a thickness of 0.2-0.5 mm and a length of 5-30 mm are obtained, and the moisture content of the wood chips is reduced to 2-4% in a drum dryer. The drying temperature is usually 180-200°C.

[0077] Step 2: Mix wood chips with urea-formaldehyde resin adhesive in a glue mixer, with the glue application amount being 8-10%;

[0078] Step 3: Use fine wood shavings for the two surface layers and coarse wood shavings for the core layer for paving, and perform pre-pressing treatment at a temperature not higher than 50°C;

[0079] Step 4: hot pressing is carried out at a temperature of 180-200°C and a pressure of 4 MPa. The hot pressing time is determined according to the thickness of the plate and is calculated at 25 seconds per millimeter of plate thickness.

[0080] Step 5: After hot pressing, the board is cooled to room temperature (below 40°C) on a cooling rack, sawn into a specification of 1220×2440mm, and the surface is sanded to a thickness tolerance within ±0.2mm.

[0081] Application Example 2

[0082] The composite formaldehyde-reducing agents from Examples 1-3 were added to a urea-formaldehyde resin adhesive (final solids content 60%) at a ratio of 4:100 via a curing agent application system. Particleboard was prepared using the aforementioned prior art method, with an 8% sizing agent application rate. The particleboards prepared in this application example are labeled Samples 4-6.

[0083] Application Example 3

[0084] The composite formaldehyde-reducing agents of Examples 1-3 were mixed with deionized water at a ratio of 94:100 to produce a water-based composite formaldehyde-reducing agent. The agent was then applied by roller coating to the surface of conventional particleboard prepared as described above using the conventional method, with a sizing amount of 9%. The coating amount of the water-based composite formaldehyde-reducing agent was 16 g / m2. The particleboards prepared in this application example are labeled as Samples 7-9.

[0085] Application Example 4

[0086] The composite formaldehyde-reducing agent from Examples 1-3 was sprayed onto the surface of dried particleboard (with a moisture content of approximately 8%). The spraying amount was determined by the applied sizing agent, specifically 6% of the applied sizing agent. To ensure uniform distribution of the composite formaldehyde-reducing agent after spraying, the spraying process was performed separately. Subsequently, the particleboard was sprayed with a urea-formaldehyde resin adhesive according to conventional methods and further processed to obtain particleboard. The particleboards produced in this application example are labeled Samples 10-12.

[0087] Application control example 1

[0088] The particleboard of the prior art is prepared as described above by the method of the prior art, with a sizing amount of 9%, and is marked as control material 1.

[0089] Application control example 2

[0090] The formaldehyde-reducing agents from Control Examples 1-3 were added to the adhesive mixing tank during the mixing process of the urea-formaldehyde resin adhesive (final solids content 60%) at a ratio of 4:100. Particleboard was prepared using the aforementioned prior art method, with an 8% sizing agent application rate. The particleboards prepared in these control examples are designated Control Materials 2-4.

[0091] Application control example 3

[0092] The formaldehyde-reducing agents from Control Examples 1-3 were added to a urea-formaldehyde resin adhesive (final solids content 60%) at a ratio of 4:100 via a curing agent application system. Particleboard was prepared using the aforementioned prior art method, with an application rate of 8%. The particleboards prepared in this application example are designated Control Materials 5-7.

[0093] Application control example 4

[0094] The formaldehyde-reducing agents from Reference Examples 1-3 were mixed with deionized water at a ratio of 94:100 to produce a water-based composite formaldehyde-reducing agent. The agent was then applied to the surface of conventional particleboard prepared using the aforementioned conventional method, using a 9% sizing agent. The coating weight of the water-based composite formaldehyde-reducing agent was 16 g / m². The particleboards prepared in this application example are designated Reference Materials 8-10.

[0095] The formaldehyde emission of particleboards 1-12 and 1-10 was tested using the desiccant method in accordance with Section 4.40 of GB / T 17657-2022, Test Methods for Physical and Chemical Properties of Wood-Based Panels and Finished Wood-Based Panels. The results are shown in Table 2.

[0096] Table 2 (Unit: mg / L)

[0097]

[0098] The formaldehyde removal efficiency of particleboards of samples 1 to 12 was compared in dry and humid environments. The results are shown in Table 3.

[0099] Table 3

[0100]

[0101] The mechanical properties of particleboards of test materials 1 to 12 and control material 1 were compared. The test method was carried out in accordance with GB / T 17657-2022 "Test methods for physical and chemical properties of wood-based panels and veneered wood-based panels". The results are shown in Table 4.

[0102] Table 4

[0103]

[0104] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A high-efficiency composite formaldehyde reducing agent for wood composite materials, characterized in that: The composite formaldehyde reducing agent contains: (i) 52-55% of a physical formaldehyde-reducing component, wherein the physical formaldehyde-reducing component is selected from nano-montmorillonite, activated carbon, nano-silica, and combinations thereof; (ii) 33-35.4% of a chemical formaldehyde-reducing component selected from amine compounds, amino compounds, urea derivatives, urotropine (hexamethylenetetramine), polyhydroxy alcohols, and combinations thereof, and (iii) the balance is other added ingredients, The addition percentages of various components are weight percentages based on the total weight of the composite formaldehyde reducing agent.

2. The high-efficiency composite formaldehyde reducing agent for wood composite materials according to claim 1, characterized in that: The physical formaldehyde reduction component consists of: (i.1) 48~50% nano-montmorillonite, (i.2) 48-50% activated carbon, and (i.3) 1.5~2.5% of nano-silicon dioxide composition, The addition percentage of each component is the mass percentage based on the total mass of the physical formaldehyde-reducing component.

3. The high-efficiency composite formaldehyde reducing agent for wood composite materials according to claim 2, characterized in that: The other additional components include at least polyacrylic acid (PAA).

4. The high-efficiency composite formaldehyde reducing agent for wood composite materials according to claim 1, characterized in that: The chemical formaldehyde-reducing component consists of: (ii.1) 29~31% of amine compounds, (ii.2) 32.5~35% amino compounds, (ii.3) 14-16.5% urea derivatives, (ii.4) 10-12.5% ​​hexamethylenetetramine, and (ii.5) 8~10.5% polyhydric alcohol composition, The addition percentage of each component is the mass percentage based on the total mass of the chemical formaldehyde-reducing component.

5. The high-efficiency composite formaldehyde reducing agent for wood composite materials according to claim 4, characterized in that: The amine compound is selected from melamine, triethanolamine, and combinations thereof.

6. The high-efficiency composite formaldehyde reducing agent for wood composite materials according to claim 4, characterized in that: The amino compound is dicyandiamide.

7. The high-efficiency composite formaldehyde reducing agent for wood composite materials according to claim 4, characterized in that: The urea derivative is selected from the group consisting of ethylene urea, thiourea, and combinations thereof.

8. The high-efficiency composite formaldehyde reducing agent for wood composite materials according to claim 1, characterized in that: The other added ingredients are: (iii.1) 29.5~31.5% polyacrylic acid (PAA), (iii.2) 15~16% citric acid, (iii.3) 8.5-10% tannin extract, and (iii.4) 45~47% inorganic clay composition, The addition percentage of each component is the mass percentage based on the total mass of the other added components.

9. The high-efficiency composite formaldehyde reducing agent for wood composite materials according to claim 1, characterized in that: Used to prepare a composite adhesive, the composite adhesive includes the mixed composite formaldehyde reducing agent and adhesive.

10. The composite adhesive according to claim 9, characterized in that: In the composite adhesive, the ratio of the composite formaldehyde reducing agent to the adhesive is (3-5):100.

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