Formaldehyde-free environment-friendly shaving board and preparation method thereof

Abstract

The invention discloses a formaldehyde-free environment-friendly shaving board and a preparation method thereof.The shaving board is composed of wood shavings and a functional adhesive, and the core lies in that through molecular design and interface modification of the functional adhesive, the formaldehyde release problem of a traditional shaving board and the performance shortage of an existing formaldehyde-free adhesive are solved; according to the functional adhesive, starch is used as a base material, a modified tackifier, a modified water-resistant agent and the like are used as auxiliary materials, the bonding strength is improved through a cross-linking reaction between hydroxyl of the starch and an isocyanate group in the modified tackifier, the water resistance is enhanced through a hydrophobic barrier formed by a fluorosilane chain segment in the modified water-resistant agent, meanwhile, the hydroxyl is cross-linked with the starch and the modified tackifier, and the water resistance is improved. A dual water-resistant structure is formed, and the purposes of formaldehyde-free environmental protection and performance enhancement are achieved.

Description

Technical Field

[0001] The present invention relates to the field of board materials, and particularly relates to an aldehyde-free and environment-friendly particleboard and a preparation method thereof. Background Art

[0002] Particleboard, as an important man-made board material, is closely related to modern human life. Particleboard is made through processes such as particle preparation, drying and sorting, gluing, paving, pre-pressing, and hot pressing. The particleboard has an extremely high surface flatness, clear and realistic texture, uniform bulk density, and extremely small thickness error. Therefore, it is widely used in furniture, kitchen and bathroom decoration, construction, packaging and other fields.

[0003] In traditional particleboard production, formaldehyde-based adhesives, represented by urea-formaldehyde resin, are the mainstream choice of adhesives. This type of adhesive has a low curing temperature and can produce good bonding effects on particleboards made from various plant materials such as wheat straw and rice husks. However, it cannot be ignored that the formaldehyde emission of formaldehyde-based adhesives exceeds the standard. During the production and use of particleboard, the continuous release of formaldehyde will cause great harm to the human body. Long-term exposure to an environment containing high concentrations of formaldehyde will cause great harm to human health, such as irritating the respiratory tract, triggering allergic reactions, leading to a decrease in immunity, and even increasing the risk of cancer. Therefore, there is an urgent need to improve the environmental performance and quality of products through technological innovation to meet market demand.

[0004] At present, in the field of formaldehyde-free adhesives used in particleboard production, polyurethane adhesives, soy protein adhesives and isocyanate adhesives (MDI) are more typical representatives, but they each have certain limitations. Polyurethane adhesives have the characteristics of fast curing speed, but poor viscosity. Soy protein adhesives have poor bonding strength and water resistance. MDI adhesive itself has poor water resistance, which will cause the board to absorb water and expand.

[0005] Therefore, the development of a new type of tackifying and water-resistant adhesive is of great significance for improving the performance of formaldehyde-free particleboard. Summary of the Invention

[0006] The purpose of the present invention is to provide an aldehyde-free environmentally friendly particleboard and a preparation method thereof.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A formaldehyde-free environmentally friendly particleboard, comprising wood particles and a functional adhesive in a mass ratio of 1:0.2-0.5;

[0009] The functional adhesive comprises the following raw materials in parts by weight: 60-75 parts of starch, 30-40 parts of modified tackifier, 15-20 parts of modified water-resistant agent, 50-60 parts of dimethyl sulfoxide, and 2-4 parts of metal catalyst;

[0010] The functional adhesive preparation steps include:

[0011] Step 1: Add starch to dimethyl sulfoxide, stir evenly, add metal catalyst and modified thickener, stir for 2-4 hours to obtain thickened modified starch liquid;

[0012] Step 2: Add the modified water-resistant agent to the thickened modified starch liquid and stir thoroughly for 2-3 hours to obtain a functional adhesive.

[0013] Furthermore, in step 1, the metal catalyst is dibutyltin dilaurate or stannous octoate.

[0014] Furthermore, in step 2, the preparation method of the viscosity-increasing modifier comprises the following steps:

[0015] Disperse humic acid in dichloromethane and stir evenly, add 3-isocyanatobenzoyl chloride and triethylamine in an ice-water bath, remove from the ice-water bath, and stir at 30-40° C. to prepare a modified tackifier.

[0016] Furthermore, the stirring time is 2-4h, and the stirring speed is 200-400r / min.

[0017] In the above technical solution, under the action of triethylamine, the hydroxyl group in humic acid reacts with the acyl chloride group in 3-isocyanatobenzoyl chloride, introducing an isocyanate group into the humic acid, changing the molecular structure of the humic acid, and preparing a modified thickener.

[0018] Furthermore, the preparation method of the modified water-resistant agent specifically comprises the following steps:

[0019] Step A: Dry calcium carbonate in an oven, cool, disperse calcium carbonate in ethyl acetate, stir evenly, add chloroacetyl chloride and an alkaline catalyst at room temperature, stir for 2-6 hours, and after the reaction is complete, centrifuge and separate the solid product, and dry the product to obtain modified calcium carbonate;

[0020] Step B: Disperse the modified calcium carbonate in tetrahydrofuran, stir evenly, add hydroxyl-terminated methyl-3,3,3-trifluoropropyl (siloxane and polysiloxane) and potassium carbonate, heat to 60-65°C, react for 12-14 hours, cool to room temperature after the reaction is completed, centrifuge, and dry to obtain a modified water-resistant agent.

[0021] Furthermore, in step A, the water content of the dried calcium carbonate is less than 1%.

[0022] Furthermore, in step A, the alkaline catalyst is triethylamine.

[0023] In the above technical solution, under the action of a catalyst, the hydroxyl groups on the surface of calcium carbonate react with the acyl chloride groups in chloroacetyl chloride, and active group chlorine atoms are introduced on the surface of calcium carbonate to obtain modified calcium carbonate, which can undergo further substitution reaction with the terminal hydroxyl groups in the hydroxyl-terminated methyl-3,3,3-trifluoropropyl (siloxane and polysiloxane) structure under the action of a catalyst potassium carbonate to obtain a modified water-resistant agent.

[0024] A method for preparing formaldehyde-free environmentally friendly particleboard comprises the following steps:

[0025] Step S1: screening wood chips and dividing them into surface layer wood chips and core layer wood chips, and pneumatically sorting the dried wood chips to remove impurities to obtain surface layer particleboard and core layer particleboard;

[0026] Step S2: adding functional adhesive to the surface layer wood shavings and the core layer wood shavings respectively, and mixing them thoroughly to obtain surface layer wood shavings and core layer wood shavings;

[0027] Step S3: paving the surface layer wood chips and the core layer wood chips in layers to form a layered paving slab of lower surface layer / core layer / upper surface layer;

[0028] Step S4: After the paving slab is compression-molded, a formaldehyde-free and environmentally friendly particleboard is produced.

[0029] Furthermore, in step S1, the wood chips used for the surface layer are 5-20 mm in length and 0.1-0.5 mm in thickness, and the wood chips used for the core layer are 20-50 mm in length and 1-3 mm in thickness.

[0030] Furthermore, in step S4, the compression pressure is 3-5 MPa.

[0031] Beneficial effects of the present invention:

[0032] (1) The present invention prepares humic acid containing isocyanate groups. The isocyanate groups can react chemically with the hydroxyl groups on the starch molecular chain, and the humic acid and starch are tightly connected through chemical bonds, thereby enhancing the intermolecular force. At the same time, the isocyanate groups in the thickener structure can interact with the hydroxyl groups in the starch structure and the hydroxyl functional groups in the water-resistant modifier structure during the subsequent high-temperature heating and curing process, thereby converting the starch from a linear structure to a three-dimensional network structure. On the one hand, the increase in cross-linking density can enhance the cohesion of starch and improve the bonding performance. On the other hand, the carboxyl groups and phenolic hydroxyl groups in the humic acid molecules in the thickener structure can also provide more hydrogen bond formation sites, further enhancing the bonding strength with the wood particles, thereby improving the integrity of the particleboard.

[0033] (2) The present invention prepares calcium carbonate containing chlorine-based active groups, which reacts chemically with hydroxyl-terminated methyl-3,3,3-trifluoropropylsiloxane to form a strong chemical connection. The hydroxyl-terminated methyl-3,3,3-trifluoropropyl (siloxane and polysiloxane) itself contains fluorosilane segments with extremely low surface energy, which can form a hydrophobic barrier on the surface of the adhesive layer. During the curing process of the adhesive, the hydroxyl groups at the ends of its structure that do not participate in the reaction can also interact with the modified thickener and starch to form a stable chemical bond, tightly connecting the starch molecules with the modified water-resistant agent, and at the same time reacting with the isocyanate groups in it to form a three-dimensional network structure. When water molecules try to penetrate, the cross-linked network forms a physical barrier, greatly slowing down the diffusion rate of water molecules, preventing moisture from invading, and significantly improving the water resistance of the particleboard.

[0034] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 This is the infrared analysis test diagram of the modified water-resistant agent. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0038] Example 1, preparation of adhesive:

[0039] Step 1: Add 60 parts of starch to 50 parts of dimethyl sulfoxide according to parts by weight, stir evenly, add 2 parts of dibutyltin dilaurate, add 3 parts of modified thickener, and stir for 3 hours to prepare a thickened modified starch liquid;

[0040] Step 2: Add 1 part of modified water-resistant agent to the thickened modified starch liquid and stir thoroughly for 2 hours to prepare a functional adhesive.

[0041] The preparation method of the modified tackifier comprises the following steps:

[0042] Disperse 8 g of humic acid in 200 ml of dichloromethane and stir evenly. Add 1 g of 3-isocyanatobenzoyl chloride and 0.5 g of triethylamine in an ice-water bath. After the addition is complete, remove from the ice-water bath and stir at 35°C for 3 h to obtain a modified tackifier.

[0043] The toluene-di-n-butylamine titration method was used to determine the percentage of isocyanate groups in humic acid. 0.5 g of the sample was weighed and evenly dispersed in 20 ml of anhydrous toluene. 10 ml of di-n-butylamine-toluene solution was added with a pipette. After shaking, the sample was allowed to stand at room temperature for 20 min. 40 ml of isopropanol was added and titrated with 0.5 mol / L HCl standard solution using bromocresol green as an indicator. The solution turned from blue to yellow. The amount of hydrochloric acid used was recorded. A blank experiment was performed at the same time. The percentage of isocyanate groups in the sample was calculated according to the formula {[(V1-V0)×C] / m}×4.2, where V0: the volume of HCl standard solution consumed in the blank test, V1: the volume of HCl standard solution consumed in the sample test, C: the molar concentration of the HCl standard solution, and m: the mass of the sample. The test results showed that the percentage of isocyanate groups in the sample was 5.184%.

[0044] The preparation method of the modified water-resistant agent comprises the following steps:

[0045] Step A: Dry 5 g of calcium carbonate in an oven, cool, and disperse the calcium carbonate in 180 ml of ethyl acetate, stir evenly, add 2 g of chloroacetyl chloride and 1 g of triethylamine at room temperature, and stir for 5 h. After the reaction is complete, centrifuge to separate the solid product, and dry the product to obtain modified calcium carbonate;

[0046] Step B: Disperse 3 g of modified calcium carbonate in 100 ml of tetrahydrofuran, stir evenly, add 1 g of hydroxyl-terminated methyl-3,3,3-trifluoropropyl (siloxane and polysiloxane) and 0.5 g of potassium carbonate, heat to 60 ° C, react for 12 hours, and after the reaction is completed, cool to room temperature, centrifuge, and dry to obtain a modified water-resistant agent.

[0047] The modified water-resistant agent was made into potassium bromide tablets and subjected to infrared analysis test. The results were as follows: Figure 1 As shown, 3386cm -1 The absorption peak at 2936 cm is the characteristic absorption peak of hydroxyl group. -1 The absorption peak at 3029cm is the characteristic absorption peak of carbon and hydrogen. -1 The absorption peak at 1730 cm is the characteristic absorption peak of unsaturated carbon-carbon double bond. -1 The absorption peak at 1475 cm is the characteristic absorption peak of the ester carbon-oxygen double bond produced by esterification condensation. -1 The absorption peak at 1220 cm is the characteristic absorption peak of carbonate. -1The absorption peak at 1082 cm is the characteristic absorption peak of carbon-fluorine bond. -1 The absorption peak at 1038 cm is the characteristic absorption peak of silicon-oxygen bond. -1 The absorption peak appearing at is the characteristic absorption peak of ether bond.

[0048] Example 2, preparation of adhesive:

[0049] Step 1: Add 70 parts of starch to 56 parts of dimethyl sulfoxide, stir evenly, add 3 parts of dibutyltin dilaurate, add 5.7 parts of modified thickener, and stir for 3 hours to prepare a thickened modified starch liquid;

[0050] Step 2: Add 3.9 parts of modified water-resistant agent to the thickened modified starch liquid and stir thoroughly for 2 hours to prepare a functional adhesive.

[0051] The preparation method of the modified tackifier and the modified water-resistant agent is the same as that in Example 1.

[0052] Example 3, preparation of adhesive:

[0053] Step 1: Add 75 parts of starch to 60 parts of dimethyl sulfoxide, stir evenly, add 4 parts of dibutyltin dilaurate, add 6 parts of modified thickener, stir for 3 hours, and prepare thickened modified starch liquid;

[0054] Step 2: Add 4 parts of modified water-resistant agent to the thickened modified starch liquid and stir thoroughly for 2 hours to prepare a functional adhesive.

[0055] The preparation methods of the modified tackifier and modified water-resistant agent are the same as those in Example 1.

[0056] Comparative Example 1, preparation of adhesive:

[0057] 70 parts of starch were added to 56 parts of dimethyl sulfoxide and stirred evenly to prepare a starch adhesive.

[0058] Comparative Example 2, preparation of adhesive:

[0059] 70 parts of starch were added to 56 parts of dimethyl sulfoxide, stirred evenly, 3 parts of modified water-resistant agent were added, and stirred thoroughly for 2 hours to prepare a functional adhesive.

[0060] The preparation method of the modified water-resistant agent is the same as that of Example 1.

[0061] Comparative Example 3, preparation of adhesive:

[0062] 70 parts of starch were added to 56 parts of dimethyl sulfoxide, stirred evenly, 5 parts of modified thickener and 3 parts of dibutyltin dilaurate were added, and stirred thoroughly for 2 hours to prepare a functional adhesive.

[0063] The preparation method of the modified adhesive is the same as that of Example 1.

[0064] Comparative Example 4, preparation of adhesive:

[0065] Step 1: Add 70 parts of starch to 56 parts of dimethyl sulfoxide, stir evenly, add 3 parts of dibutyltin dilaurate, add 5 parts of modified thickener, and stir for 3 hours to prepare a thickened modified starch liquid;

[0066] Step 2: Add 3 parts of calcium carbonate to the thickened modified starch liquid and stir thoroughly for 2 hours to prepare a functional adhesive.

[0067] The preparation method of the modified tackifier is the same as that in Example 1.

[0068] Test example:

[0069] A. The adhesives prepared in Examples 1 to 3 and Comparative Examples 1 to 4 were evenly coated between PVC / PVC film composite films and dried to form test samples. T-peel strength tests were performed according to standard GB / T 2791-1995.

[0070] B. Soak it in 50℃ water for 24 hours and then observe.

[0071] T-peel strength (kN / m) Water resistance Example 1 0.52 No whitening or shedding Example 2 0.63 No whitening or shedding Example 3 0.51 No whitening or shedding Comparative Example 1 0.41 Whitening and falling off Comparative Example 2 0.43 No whitening or shedding Comparative Example 3 0.49 Whitening and falling off Comparative Example 4 0.46 Partial bleaching

[0072] From the analysis data, it can be seen that the functional adhesives prepared in Examples 1 to 3 have obviously better bonding performance and excellent water resistance, while the functional adhesives prepared without adding the modified tackifier have poor mechanical properties. The functional adhesives prepared without adding the modified water-resistant agent have poor water resistance. The functional adhesives without adding calcium carbonate partially turn white and fall off after being immersed in 50°C water for 24 hours. Therefore, calcium carbonate can enhance the water resistance of the adhesive.

[0073] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A formaldehyde-free environmentally friendly particleboard, characterized in that: It is composed of wood shavings and functional adhesive in a mass ratio of 1:0.2-0.5; The functional adhesive comprises the following raw materials in parts by weight: 60-75 parts of starch, 3-6 parts of modified tackifier, 1-4 parts of modified water-resistant agent, 2-4 parts of metal catalyst, and 50-60 parts of dimethyl sulfoxide; The preparation steps of the functional adhesive include: Step 1: Add starch to dimethyl sulfoxide, stir evenly, add metal catalyst and modified thickener, stir for 2-4 hours to obtain thickened modified starch liquid; Step 2: Add the modified water-resistant agent to the thickened modified starch liquid and stir thoroughly for 2-3 hours to obtain a functional adhesive.

2. The formaldehyde-free environmentally friendly particleboard according to claim 1, characterized in that: The metal catalyst is dibutyltin dilaurate or stannous octoate.

3. The formaldehyde-free environmentally friendly particleboard according to claim 1, characterized in that: The modified tackifier preparation method comprises the following steps: Disperse humic acid in dichloromethane and stir evenly, add 3-isocyanatobenzoyl chloride and triethylamine in an ice bath, remove from the ice bath after addition, and stir at a temperature of 30-40° C. to prepare a modified tackifier.

4. The formaldehyde-free environmentally friendly particleboard according to claim 3, characterized in that: The stirring time is 2-4h, and the stirring speed is 200-400r / min.

5. The formaldehyde-free environmentally friendly particleboard according to claim 1, characterized in that: The preparation method of the modified water-resistant agent specifically comprises the following steps: Step A: Dry calcium carbonate in an oven, cool, disperse calcium carbonate in ethyl acetate, stir evenly, add chloroacetyl chloride dropwise at room temperature, add a basic catalyst after the addition is complete, stir for 2-6 hours, and after the reaction is complete, centrifuge and separate the solid product, and dry the product to obtain modified calcium carbonate; Step B: Disperse the modified calcium carbonate in tetrahydrofuran, stir evenly, add hydroxyl-terminated methyl-3,3,3-trifluoropropyl (siloxane and polysiloxane) and potassium carbonate, heat to 60-65°C, react for 12-14 hours, cool to room temperature after the reaction is completed, centrifuge, and dry to obtain a modified water-resistant agent.

6. The formaldehyde-free environmentally friendly particleboard according to claim 5, characterized in that: In step A, the water content of the dried calcium carbonate is less than 1%.

7. The formaldehyde-free environmentally friendly particleboard according to claim 5, characterized in that: In step A, the alkaline catalyst is triethylamine.

8. The method for preparing an aldehyde-free environmentally friendly particleboard according to claim 1, wherein: The following steps are involved: Step S1: screening wood chips and dividing them into surface layer wood chips and core layer wood chips, and pneumatically sorting the dried wood chips to remove impurities to obtain surface layer particleboard and core layer particleboard; Step S2: adding functional adhesive to the surface layer wood shavings and the core layer wood shavings respectively, and mixing them thoroughly to obtain surface layer wood shavings and core layer wood shavings; Step S3: paving the surface layer wood chips and the core layer wood chips in layers to form a layered paving slab of lower surface layer-core layer-upper surface layer; Step S4: After the paving slab is compression-molded, a formaldehyde-free and environmentally friendly particleboard is produced.

9. The method for preparing formaldehyde-free environmentally friendly particleboard according to claim 8, characterized in that: In step S1, the length of the surface layer wood shavings is 5-20 mm, and the thickness is 0.1-0.5 mm; the length of the core layer wood shavings is 20-50 mm, and the thickness is 1-3 mm.

10. The method for preparing formaldehyde-free environmentally friendly particleboard according to claim 8, characterized in that: In step S4, the compression pressure is 3-5 MPa.

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