Preparation method and application of hyperbranched polysiloxane modified MF resin for impregnated paper

Abstract

The invention discloses a preparation method and application of a hyperbranched polysiloxane-modified impregnated paper MF resin, comprising the following steps: step 1, under a nitrogen atmosphere, heating and stirring at 100 150 DEG C for 0.5 1.5 hours after mixing alcohol with siloxane, then slowly heating for 2 4 hours to 150 200 DEG C, subsequently dialyzing the product to obtain purified terminal epoxy hyperbranched polysiloxane; step 2, mixing 20 40 parts of MF resin with 1 10 parts of terminal epoxy hyperbranched polysiloxane by mass, stirring for 20 40 minutes to obtain hyperbranched polysiloxane-modified impregnated paper MF resin. The present invention can improve the fluidity and permeability of impregnating resin, is beneficial to the impregnation sizing of base paper, and the present invention can also improve the flexibility of impregnated paper.

Description

Technical Field

[0001] The invention relates to the technical field of impregnated paper processing, and in particular to a preparation method and application of a hyperbranched polysiloxane-modified MF resin for impregnated paper. Background Art

[0002] Impregnated paper is an important surface decorative material for furniture, wood floors, and building panels, serving to decorate and protect the substrate. Among them, melamine formaldehyde (MF) impregnated paper dominates due to its excellent bonding strength and water resistance. However, MF impregnated paper is prone to cracking and has difficulty resisting dimensional changes caused by the inherent shrinkage and swelling of the substrate. Furthermore, MF impregnated paper often fails to meet the flame retardant requirements of practical applications, greatly increasing safety risks and the potential for economic losses. Therefore, cracking and poor flame retardant properties have severely restricted the application of MF impregnated paper and have become key issues that need to be urgently addressed in the impregnated paper field.

[0003] The cracks in impregnated paper are mainly caused by the high brittleness of the (MF) resin used in the impregnation process. During the manufacturing process, the base paper is soaked in the MF resin and cured by controlled drying regulation. The fully cured MF resin has a highly cross-linked triazine structure, which restricts the movement of the molecular chain, thereby producing a brittle adhesive layer. In order to solve this problem, researchers have explored many methods, including increasing the chain length, preventing the approach between triazine rings, and reducing the number of cross-linking points of triazine rings in the MF resin. For example, the MF resin was modified by in situ polymerization and microphase separation of dialdehyde starch, which ultimately increased the elongation at break of the impregnated paper by 48.12%.

[0004] Among these modification methods, organosilicon compounds containing Si-O / Si-O-Si with appropriate bond lengths and angles can influence the rotational motion of pendant groups, effectively improving the toughness of MF resins. Furthermore, organosilicon compounds can form a coacervate phase, thereby achieving a flame retardant effect and protecting the organosilicon-modified resin from fire. However, the modified resin is particularly prone to phase separation after the introduction of organosilicon compounds, making subsequent impregnation operations difficult and limiting its large-scale application. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a hyperbranched polysiloxane-modified MF resin for impregnated paper and its application. The present invention can improve the fluidity and permeability of the impregnating resin, facilitate the impregnation and sizing of base paper, and also improve the flexibility of the impregnated paper.

[0006] The technical solution of the present invention is a method for preparing a hyperbranched polysiloxane-modified MF resin for impregnated paper, comprising the following steps:

[0007] Step 1: Under a nitrogen atmosphere, the alcohol and the siloxane are mixed and heated at 100-150° C. with stirring for 0.5-1.5 hours, and then slowly heated to 150-200° C. for 2-4 hours, and then the product is dialyzed to obtain a purified epoxy-terminated hyperbranched polysiloxane;

[0008] Step 2: Mix 20-40 parts of MF resin and 1-10 parts of epoxy-terminated hyperbranched polysiloxane by mass, and stir for 20-40 minutes to obtain a hyperbranched polysiloxane-modified MF resin for impregnated paper.

[0009] In the above-mentioned method for preparing the hyperbranched polysiloxane-modified MF resin for impregnated paper, in step 1, the mass of the alcohol is 50-60 parts; the mass of the siloxane is 35-45 parts.

[0010] In the aforementioned method for preparing the hyperbranched polysiloxane-modified MF resin for impregnated paper, in step 1, the mass of the alcohol is 56 parts; the mass of the siloxane is 39 parts.

[0011] In the aforementioned method for preparing the hyperbranched polysiloxane-modified MF resin for impregnated paper, in step 1, alcohol and siloxane are mixed, heated and stirred at 120° C. for 1 hour, and then slowly heated to 170° C. for 3 hours.

[0012] In the aforementioned method for preparing the hyperbranched polysiloxane-modified MF resin for impregnated paper, the alcohol is ethylene glycol, 1,4-butanediol or diethylene glycol.

[0013] The preparation method of the aforementioned hyperbranched polysiloxane-modified MF resin for impregnated paper, wherein the siloxane is 3-glycidyloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, tetramethoxysilane, methyltrimethoxysilane, 3-(trimethoxysilyl)propyl methacrylate or 3-glycidyloxypropyltriethoxysilane.

[0014] The aforementioned method for preparing the hyperbranched polysiloxane-modified MF resin for impregnated paper, in step 2, the MF resin is prepared by first dissolving formaldehyde in deionized water, then adjusting the pH of the formaldehyde solution to alkaline using NaOH, then heating the resulting solution to 50-70°C, and slowly adding melamine to the formaldehyde solution, wherein the molar ratio of melamine to formaldehyde is 1:2; finally, heating the mixed solution to 90-100°C and reacting for about 1-2 hours, while maintaining the pH of the solution within the alkaline range, terminating the reaction, and cooling the mixed solution to room temperature to obtain the MF resin.

[0015] In the aforementioned method for preparing the MF resin for impregnated paper modified with a hyperbranched polysiloxane, in step 2, the mass parts of the MF resin are 30 parts, and the mass parts of the epoxy-terminated hyperbranched polysiloxane are 6.5-8.5 parts.

[0016] The invention discloses an application of a hyperbranched polysiloxane-modified MF resin for impregnated paper. The base paper is immersed in the hyperbranched polysiloxane-modified MF resin for impregnated paper for 2-4 minutes, with the resin sizing amount being 70%. After the impregnation, excess resin on the paper surface is removed with a roller, and the paper is then dried in an oven at 110-130°C for 1-3 minutes to obtain a finished impregnated paper.

[0017] In the above application, particleboard is used as the base material, and impregnated paper is used for veneer to make an impregnated paper decorative panel, which is then hot-pressed at a temperature of 150-200°C, a time of 20-50s, and a pressure of 2-5MPa.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention modifies MF resin by using epoxy-terminated hyperbranched polysiloxane. The terminal epoxy groups of the hyperbranched polysiloxane can form hydrogen bonds, covalent bonds, and other structures with the MF resin, effectively improving the interfacial compatibility with the substrate. This reduces the viscosity of the resin, significantly improves its fluidity and permeability, and facilitates sizing operations. Furthermore, the pH of the resin changes from alkaline to neutral, reducing its corrosiveness to impregnated paper and extending its service life.

[0020] 2. The epoxy-terminated hyperbranched polysiloxane of the present invention has a highly branched three-dimensional structure and a large number of intramolecular cavities, which can absorb impact through molecular deformation and cavitation effect, thereby improving the toughness of the resin. Moreover, compared with the traditional Si-O-Si skeleton, the Si-OC skeleton of the epoxy-terminated hyperbranched polysiloxane has harmonious flexibility and rigidity due to its suitable bond length and bond angle. Therefore, the present invention can improve the flexibility of impregnated paper.

[0021] 3. When burning, the epoxy-terminated hyperbranched polysiloxane can form a denser carbon layer to isolate oxygen, thereby improving the flame retardancy of the resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the stress-strain curve of the epoxy-terminated hyperbranched polysiloxane MF resin sample;

[0023] Figure 2 is the elongation at break of the impregnated paper;

[0024] Figure 3 It is a curved diagram of impregnated paper;

[0025] Figure 4 It is a burning diagram of impregnated paper. DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0027] Example 1: Under a nitrogen atmosphere, 50 g of alcohol and 35 g of siloxane were added to a 250 ml four-necked flask, mixed, heated and stirred at 110° C. for 0.5 hour, then slowly heated to 170° C. for 3 hours, and then dialyzed to obtain a purified epoxy-terminated hyperbranched polysiloxane; the alcohol in this step was ethylene glycol; and the siloxane was 3-glycidyloxypropyltrimethoxysilane;

[0028] Step 2: 30 g of MF resin and 2.5 g of epoxy-terminated hyperbranched polysiloxane were mixed in parts by mass, and stirred for 30 minutes to obtain a hyperbranched polysiloxane-modified MF resin for impregnated paper.

[0029] In this step, the MF resin is prepared by first dissolving formaldehyde in deionized water, then adjusting the pH of the formaldehyde solution to 8-9 with NaOH, then heating the resulting solution to 60° C., and slowly adding melamine to the formaldehyde solution, wherein the molar ratio of melamine to formaldehyde is 1:2; finally, heating the mixed solution to 90° C. for reaction for about 1-2 hours, while maintaining the pH value of the solution within an alkaline range. In the later stage of the reaction, a suitable amount of the mixed solution is taken with a rubber dropper and then dropwise added to a large amount of water. Once the droplets become misty and clear after a while, the reaction is terminated, and a small amount of urea is added to the mixed solution. The mixed solution is cooled to room temperature to obtain the MF resin.

[0030] Example 2: Under a nitrogen atmosphere, 55 g of alcohol and 40 g of siloxane were mixed in a 250 ml four-necked flask. After mixing, the mixture was heated and stirred at 120° C. for 1 hour, then slowly heated to 180° C. for 3 hours, and then the product was dialyzed to obtain a purified epoxy-terminated hyperbranched polysiloxane; the alcohol in this step was 1,4-butanediol; and the siloxane was γ-methacryloxypropyltrimethoxysilane.

[0031] Step 2: 30 g of MF resin and 4.5 g of epoxy-terminated hyperbranched polysiloxane were mixed by weight and stirred for 30 minutes to obtain a hyperbranched polysiloxane-modified MF resin for impregnated paper. The MF resin preparation method in this example is the same as that in Example 1.

[0032] Example 3: Under a nitrogen atmosphere, 60 g of alcohol and 45 g of siloxane were mixed in a 250 ml four-necked flask, heated and stirred at 150° C. for 0.5 hour, then slowly heated to 190° C. for 3 hours, and then dialyzed to obtain a purified epoxy-terminated hyperbranched polysiloxane; the alcohol in this step was 1,4-diethylene glycol; and the siloxane was tetramethoxysilane;

[0033] Step 2: 30 g of MF resin and 6.5 g of epoxy-terminated hyperbranched polysiloxane were mixed by weight and stirred for 30 minutes to obtain a hyperbranched polysiloxane-modified MF resin for impregnated paper. The MF resin preparation method in this example is the same as that in Example 1.

[0034] Example 4: Under a nitrogen atmosphere, 55 g of alcohol and 45 g of siloxane were mixed in a 250 ml four-necked flask. After mixing, the mixture was heated and stirred at 130° C. for 1.5 hours, then slowly heated to 175° C. for 3 hours, and then the product was dialyzed to obtain a purified epoxy-terminated hyperbranched polysiloxane; the alcohol in this step was 1,4-butanediol; and the siloxane was methyltrimethoxysilane.

[0035] Step 2: 30 g of MF resin and 8.5 g of epoxy-terminated hyperbranched polysiloxane were mixed by weight and stirred for 30 minutes to obtain a hyperbranched polysiloxane-modified MF resin for impregnated paper. The MF resin preparation method in this example is the same as that in Example 1.

[0036] Example 5: Under a nitrogen atmosphere, 50 g of alcohol and 40 g of siloxane were mixed in a 250 ml four-necked flask. After mixing, the mixture was heated with stirring at 120° C. for 1 hour, then slowly heated to 170° C. for 3 hours, and then the product was dialyzed to obtain a purified epoxy-terminated hyperbranched polysiloxane; the alcohol in this step was ethylene glycol; and the siloxane was 3-(trimethoxysilyl)propyl methacrylate.

[0037] Step 2: 30 g of MF resin and 10 g of epoxy-terminated hyperbranched polysiloxane were mixed by weight and stirred for 30 minutes to obtain a hyperbranched polysiloxane-modified MF resin for impregnated paper. The MF resin preparation method in this example is the same as that in Example 1.

[0038] Example 6: Under a nitrogen atmosphere, 56 g of alcohol and 39 g of siloxane were mixed in a 250 ml four-necked flask. After mixing, the mixture was heated with stirring at 120° C. for 1 hour, then slowly heated to 170° C. for 3 hours, and then the product was dialyzed to obtain a purified epoxy-terminated hyperbranched polysiloxane; the alcohol in this step was diethylene glycol; and the siloxane was 3-glycidoxypropyltriethoxysilane.

[0039] Step 2: 30 g of MF resin and 8.5 g of epoxy-terminated hyperbranched polysiloxane were mixed by weight and stirred for 30 minutes to obtain a hyperbranched polysiloxane-modified MF resin for impregnated paper. The MF resin preparation method in this example is the same as that in Example 1.

[0040] Example 7: Application of a hyperbranched polysiloxane-modified MF resin for impregnated paper. Base paper was immersed in the hyperbranched polysiloxane-modified MF resin for impregnated paper prepared by the preparation method of Examples 1-6 for 3 minutes, with the resin sizing amount being 70%. After impregnation, excess resin on the paper surface was removed with a roller, and then the paper was dried in an oven at 120°C for 2 minutes to obtain a finished impregnated paper.

[0041] Furthermore, the particleboard is used as the base material and the impregnated paper is laminated to produce the MF impregnated paper decorative panel. The decorative panel is hot pressed under the following process conditions: the hot pressing temperature is 150-200°C, the pressing time is 20-50 seconds, and the pressure is 2-5 MPa.

[0042] Comparative Example 1: MF resin prepared according to the method in Example 1.

[0043] Performance testing:

[0044] In order to verify the viscosity and pH value of the hyperbranched polysiloxane-modified MF resin for impregnated paper, the present invention conducted experiments according to the schemes of Comparative Example 1 and Example 6, wherein the mass ratio of MF resin to epoxy-terminated hyperbranched polysiloxane was 30:8.5 (abbreviated as Experiment 4) in addition to the 30:8.5 in the example, 30:2.5 (abbreviated as Experiment 1), 30:4.5 (abbreviated as Experiment 2), and 30:6.5 (abbreviated as Experiment 3) and three comparison groups were set.

[0045] The test was conducted in accordance with the national standards GB / T 1723-1993 and GB / T 9724-2007. The test method is as follows: ① The time it takes for a certain amount of sample to flow out of a hole of a specified diameter at a certain temperature is measured in seconds. ② The specified indicator electrode and reference electrode are immersed in the same test solution, forming a galvanic cell. The electromotive force of this cell is related to the pH value of the solution. The pH value of the solution can be determined by measuring the electromotive force of the galvanic cell. The viscosity and pH value data for each experimental group and comparative example are shown in Table 1.

[0046] Serial number Comparative Example Experiment 1 Experiment 2 Experiment 3 Experiment 4 Viscosity(s) 11 10.5 9.8 9.8 9.3 pH 8.9 6.9 6.8 6.7 6.7

[0047] Table 1

[0048] The viscosity and pH data for Experiments 1-4 in Table 1 show that the fluidity and permeability of the MF impregnating resin significantly improve with increasing epoxy-terminated hyperbranched polysiloxane content, reaching their highest values ​​in Experiment 4. The epoxy-terminated hyperbranched polysiloxane-melamine formaldehyde resin solution is nearly neutral, with an average pH of 6.8. Compared to the alkaline MF resin (pH = 8.9) used in the comparative example, this neutral impregnating resin helps reduce corrosion of the base paper and extend the service life of the impregnated paper.

[0049] Furthermore, the base paper was impregnated with the resins in the comparative example and experiments 1-4 using the same impregnation method as in Example 7, and the mechanical properties of the impregnated paper were tested. Figure 1 This is the stress-strain curve of the epoxy-terminated hyperbranched polysiloxane MF resin sample. Figure 2 is the elongation at break of the impregnated paper; Figure 3 It is the impregnated paper bending diagram. Figure 1-2 As can be seen in the figure, the elongation at break of pure MF impregnated paper is only 1.55%, showing brittle fracture characteristics. After adding end-epoxy hyperbranched polysiloxane, the elongation at break of end-epoxy hyperbranched polysiloxane MF impregnated paper is significantly improved. The elongation at break of end-epoxy hyperbranched polysiloxane MF impregnated paper reaches a maximum of 4.44%, which is 186.5% higher than that of pure MF impregnated paper. This result shows that the introduction of end-epoxy hyperbranched polysiloxane can improve the toughness of MF impregnated paper. The improvement in toughness is caused by the hyperbranched structure that absorbs impact energy and the cavitation effect of the flexible Si-OC skeleton. Although the improvement in toughness is achieved at a marginal compromise in strength, the tensile strength of end-epoxy hyperbranched polysiloxane MF impregnated paper exceeds 10 MPa, meeting the requirements for use.

[0050] In order to intuitively demonstrate the toughness of MF impregnated paper, a paper curling experiment was carried out using a paint film flexibility tester. Figure 3 As shown, pure MF resin-impregnated paper breaks after being bent 90° around a 15 mm reel. However, MF paper impregnated with epoxy-terminated hyperbranched polysiloxane can be bent around a 4 mm reel without cracking. This result indicates that the epoxy-terminated hyperbranched polysiloxane improves the toughness of the MF resin, thereby enhancing the flexibility of the resulting impregnated paper.

[0051] Furthermore, the impregnated paper was burned to test the flame retardant properties. Figure 4 It is a burning diagram of impregnated paper. Figure 4 It can be seen that during the 15-second combustion process, the unmodified MF-impregnated paper exhibited a longer flame length and a faster burning rate, due to the poor flame retardancy of the MF impregnated resin. The addition of epoxy-terminated hyperbranched polysiloxane significantly reduced the flame length and burning rate of the epoxy-terminated hyperbranched polysiloxane-impregnated MF paper. The impregnated paper in Experiment 4 burned more slowly and did not produce a flame. These results demonstrate that epoxy-terminated hyperbranched polysiloxane improves the flame retardancy of MF-impregnated paper.

[0052] In summary, the present invention modifies MF resin by using epoxy-terminated hyperbranched polysiloxane, thereby reducing the viscosity of the resin, significantly improving its fluidity and permeability, and facilitating sizing operations. Furthermore, the pH of the resin is changed from alkaline to neutral, which can reduce its corrosiveness to impregnated paper and extend its service life. Furthermore, the present invention can improve the flexibility and flame retardancy of the impregnated paper.

Claims

1. A method for preparing a hyperbranched polysiloxane-modified MF resin for impregnated paper, characterized in that: The steps include: Step 1: Under a nitrogen atmosphere, the alcohol and siloxane are mixed and heated at 100-150° C. with stirring for 0.5-1.5 hours, and then slowly heated to 150-200° C. for 2-4 hours, and then the product is dialyzed to obtain a purified epoxy-terminated hyperbranched polysiloxane; Step 2: Mix 20-40 parts by mass of MF resin and 1-10 parts of epoxy-terminated hyperbranched polysiloxane, and stir for 20-40 minutes to obtain a hyperbranched polysiloxane-modified MF resin for impregnated paper; The alcohol is ethylene glycol, 1,4-butanediol or diethylene glycol; The siloxane is 3-glycidyloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, tetramethoxysilane, methyltrimethoxysilane, 3-(trimethoxysilyl)propyl methacrylate or 3-glycidyloxypropyltriethoxysilane.

2. The method for preparing hyperbranched polysiloxane-modified impregnated paper MF resin according to claim 1, wherein: In step 1, the mass of the alcohol is 50-60 parts; the mass of the siloxane is 35-45 parts.

3. The method for preparing hyperbranched polysiloxane-modified impregnated paper MF resin according to claim 2, wherein: In step 1, the mass of the alcohol is 56 parts; the mass of the siloxane is 39 parts.

4. The method for preparing hyperbranched polysiloxane-modified impregnated paper MF resin according to claim 1, wherein: In step 1, the alcohol and siloxane are mixed and heated at 120° C. with stirring for 1 hour, and then slowly heated to 170° C. for 3 hours.

5. The method for preparing the hyperbranched polysiloxane-modified MF resin for impregnated paper according to claim 1, wherein: In step 2, the MF resin is prepared by first dissolving formaldehyde in deionized water, then adjusting the pH of the formaldehyde solution to alkaline with NaOH, heating the resulting solution to 50-70°C, and slowly adding melamine to the formaldehyde solution, wherein the molar ratio of melamine to formaldehyde is 1:2; finally, heating the mixed solution to 90-100°C for 1-2 hours, while maintaining the pH value of the solution within the alkaline range, terminating the reaction, and cooling the mixed solution to room temperature to obtain the MF resin.

6. The method for preparing the hyperbranched polysiloxane-modified MF resin for impregnated paper according to claim 1, wherein: In step 2, the mass parts of the MF resin are 30 parts, and the mass parts of the epoxy-terminated hyperbranched polysiloxane are 6.5-8.5 parts.

7. Application of the hyperbranched polysiloxane modified MF resin for impregnated paper obtained by the preparation method according to claim 1, characterized in that: The base paper is immersed in the hyperbranched polysiloxane modified MF resin for impregnated paper for 2-4 minutes, with the resin sizing amount being 70%. After impregnation, excess resin on the paper surface is removed with a roller, and then dried in an oven at 110-130°C for 1-3 minutes to obtain the finished impregnated paper.

8. The use according to claim 7, characterized in that: The particleboard is used as the base material and veneered with impregnated paper to make an impregnated paper decorative panel, which is then hot-pressed at a temperature of 150-200 °C, a time of 20-50 s, and a pressure of 2-5 MPa.

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