Method for improving heat resistance of melamine phenolic resin by using phthalonitrile

Abstract

The invention relates to the technical field of high polymer materials, in particular to a method for improving the heat resistance of melamine phenolic resin by using phthalonitrile, which comprises the following steps: uniformly mixing phthalonitrile resin powder and melamine phenolic resin powder at room temperature, and then curing and molding the uniformly mixed powder at 200-280 DEG C to obtain the heat-resistant melamine phenolic resin. The melamine phenolic aldehyde-nitrile group copolymer resin is obtained. According to the method for obtaining the melamine phenolic-nitrile resin with high thermal stability, high wear resistance and high mechanical property through copolymerization, not only can the thermal stability of the resin be greatly improved, but also the mechanical property can be enhanced, and the processing window of the melamine phenolic resin can be widened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high polymer materials, and particularly relates to a method for improving heat resistance of melamine phenolic resin by using phthalonitrile. BACKGROUND

[0002] Phthalonitrile resin is a kind of thermosetting resin containing aromatic heterocyclic cross-linked network structure formed by addition polymerization of phthalonitrile monomers in the presence of heat or catalyst. After curing, the resin can form isodihydroindole, triazine ring, phthalocyanine and dehydrophthalocyanine structures, so that the phthalonitrile resin has excellent thermal performance compared with other thermosetting resins. Phthalonitrile resin is concerned in the fields of aerospace and PCB due to its outstanding thermal performance, high char yield, good mechanical properties and high glass transition temperature, and is expected to be further applied in more fields.

[0003] Melamine phenolic resin is a kind of copolymer resin material obtained by copolymerization of melamine, phenol and formaldehyde as main raw materials. Melamine and formaldehyde first undergo addition reaction to generate hydroxymethyl melamine, and then the hydroxymethyl melamine monomers are subjected to polycondensation to form melamine formaldehyde resin. Melamine phenolic resin has good chemical cross-linking structure and thermal performance. In addition, melamine phenolic resin has certain toughness and good heat resistance, and is suitable for the manufacture of plastics and friction materials. Melamine phenolic resin has many reactive sites and the advantages of phthalonitrile resin structure, which can jointly act to reduce the curing temperature of the copolymer system. However, the heat resistance and mechanical properties still have room for improvement. SUMMARY

[0004] The present application aims to provide a method for improving the heat resistance of melamine phenolic resin by using phthalonitrile, which solves the technical problem that the heat resistance and mechanical properties of melamine phenolic resin and phthalonitrile resin after polymerization still have room for improvement.

[0005] The present application discloses a method for improving the heat resistance of melamine phenolic resin by using phthalonitrile, comprising the following steps: Mixing phthalonitrile resin powder and melamine phenolic resin powder uniformly at room temperature, and then curing and forming the uniformly mixed powder at 200-280 DEG C to obtain melamine phenolic-nitrile-based copolymer resin.

[0006] The method for obtaining melamine phenolic-nitrile-based resin with high thermal stability, high wear resistance and high mechanical properties by copolymerization not only greatly improves the thermal stability of the resin, but also enhances the mechanical properties and widens the processing window of melamine phenolic resin.

[0007] Furthermore, the mixing is performed at 25–80°C and a rotation speed of 300–500 RPM for 30–60 minutes.

[0008] Furthermore, the mass ratio of the phthalonitrile resin powder to the melamine phenolic resin powder is 1:1 to 1:4.

[0009] Furthermore, the mass ratio of the phthalonitrile resin powder to the melamine phenolic resin powder is 1:1 to 1:3.

[0010] Furthermore, the mass ratio of the phthalonitrile resin powder to the melamine phenolic resin powder is 1:3.

[0011] Furthermore, the chemical structural formula of the phthalonitrile resin is as follows: .

[0012] Furthermore, the AR of the phthalonitrile resin is at least one of an aromatic ring, a benzoxazine group, an imidazole group, or an allyl group.

[0013] Furthermore, the AR group of the phthalonitrile resin is a benzoxazine group.

[0014] Furthermore, the chemical structural formula of the melamine-phenolic resin is as follows: .

[0015] A melamine-phenolic-nitrile copolymer resin was prepared using the method described above.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention utilizes phthalonitrile resin to improve the thermal stability of melamine phenolic resin to a certain extent, while also broadening the processing window; 2. This invention utilizes the ability of phthalonitrile resin to improve the brittleness of melamine phenolic resin to a certain extent; 3. This invention utilizes the ability of phthalonitrile resin to improve the mechanical properties of melamine phenolic resin; 4. The method of this invention also provides new ideas for the synthesis of other polymers with similar reaction mechanisms. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 The viscosity of the copolymer of melamine-phenolic resin before and after modification with phthalonitrile resin is shown as a function of temperature. Figure 2 Thermogravimetric curves of melamine-phenolic resin copolymers before and after modification with different proportions of phthalonitrile resin are shown. Figure 3 A bar chart showing the thermogravimetric analysis (TGA) data of melamine-phenolic resin copolymers modified with different proportions of phthalonitrile resin. Figure 4 Thermochromatograms of melamine-phenolic resin copolymers modified with different proportions of phthalonitrile resin. Figure 5 The thermogravimetric analysis (TGA) curves of phthalonitrile-modified melamine-phenolic resin and melamine-phenolic resin modified with other modifiers show that a 1:3 ratio is superior to common modifiers. Figure 6 Infrared spectra of triamine phenolic resin, phthalonitrile resin, and triamine phenolic-nitrile copolymer resin. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] Example 1 This embodiment discloses a method for improving the heat resistance of melamine phenolic resin using phthalonitrile, comprising the following steps: Step 1: At room temperature, 1 part by weight of phthalonitrile resin containing benzoxazine structure and 3 parts by weight of melamine phenolic resin are initially stirred and mixed.

[0021] Step 2: Place the mixture in a high-speed mixer and stir at 45°C for 30 minutes until the mixture is completely homogeneous.

[0022] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0023] The obtained melamine-phenolic-acrylic copolymer resin had a 5% thermogravimetric temperature of 392.1 ℃ and a char residue of 60.9% at 700 ℃. The improvement in thermal stability was most significant at this ratio.

[0024] Example 2 This embodiment discloses a method for improving the heat resistance of melamine phenolic resin using phthalonitrile, comprising the following steps: Step 1: At room temperature, 1 part by weight of phthalonitrile resin containing benzoxazine structure and 1 part by weight of melamine phenolic resin are initially stirred and mixed.

[0025] Step 2: Place the mixture in a high-speed mixer and stir at 400 RPM at 45 °C for 30 min until the mixture is completely and evenly mixed.

[0026] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0027] The obtained melamine-phenolic-acrylic copolymer resin had a 5% thermal weight loss temperature of 389.8 ℃ and a char residue rate of 67.5% at 700 ℃.

[0028] Example 3 This embodiment discloses a method for improving the heat resistance of melamine phenolic resin using phthalonitrile, comprising the following steps: Step 1: At room temperature, 1 part by weight of phthalonitrile resin containing benzoxazine structure and 1 part by weight of melamine phenolic resin are initially stirred and mixed.

[0029] Step 2: Place the mixture in a high-speed mixer and stir at 45°C for 30 minutes until the mixture is completely homogeneous.

[0030] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0031] The obtained melamine-phenolic-acrylic copolymer resin had a 5% thermal weight loss temperature of 389.8 ℃ and a char residue rate of 67.5% at 700 ℃.

[0032] Example 4 This embodiment discloses a method for improving the heat resistance of melamine phenolic resin using phthalonitrile, comprising the following steps: Step 1: At room temperature, 1 part by weight of phthalonitrile resin containing benzoxazine structure and 1.5 parts by weight of melamine phenolic resin are initially stirred and mixed.

[0033] Step 2: Place the mixture in a high-speed mixer and stir at 45°C for 30 minutes until the mixture is completely homogeneous.

[0034] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0035] The obtained melamine-phenolic-acrylic copolymer resin had a 5% thermal weight loss temperature of 384.5 ℃ and a char residue rate of 62.8% at 700 ℃.

[0036] Example 5 This embodiment discloses a method for improving the heat resistance of melamine phenolic resin using phthalonitrile, comprising the following steps: Step 1: At room temperature, 1 part by weight of phthalonitrile resin containing benzoxazine structure and 2 parts by weight of melamine phenolic resin are initially stirred and mixed.

[0037] Step 2: Place the mixture in a high-speed mixer and stir at 45°C for 30 minutes until the mixture is completely homogeneous.

[0038] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0039] The obtained melamine-phenolic-acrylic copolymer resin had a 5% thermal weight loss temperature of 354.9 ℃ and a char residue rate of 62.0% at 700 ℃.

[0040] Comparative Example 1 Step 1: At room temperature, 1 part by weight of phthalonitrile resin containing benzoxazine structure and 5 parts by weight of melamine phenolic resin are initially stirred and mixed.

[0041] Step 2: Place the mixture in a high-speed mixer and stir at 45°C for 30 minutes until the mixture is completely homogeneous.

[0042] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0043] The obtained melamine-phenolic-acrylic copolymer resin had a 5% thermal weight loss temperature of 362.4 ℃ and a char residue rate of 59.6% at 700 ℃.

[0044] Comparative Example 2 Step 1: At room temperature, 1 part by weight of phthalonitrile resin containing benzoxazine structure and 10 parts by weight of melamine phenolic resin are initially stirred and mixed.

[0045] Step 2: Place the mixture in a high-speed mixer and stir at 45°C for 30 minutes until the mixture is completely homogeneous.

[0046] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0047] The obtained melamine-phenolic-acrylic copolymer resin had a 5% thermal weight loss temperature of 367.1 ℃ and a char residue rate of 57.7% at 700 ℃.

[0048] Comparative Example 3 Step 1: At room temperature, mix 1 part by weight of E51 epoxy resin and 3 parts by weight of melamine phenolic resin by initial stirring.

[0049] Step 2: Place the mixture in a high-speed mixer and stir at 45°C for 30 minutes until the mixture is completely homogeneous.

[0050] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0051] The obtained epoxy-modified melamine-phenolic polyresin had a 5% thermal weight loss temperature of 349.4 °C and a char residue of 52.5% at 700 °C. These performance characteristics are significantly lower than those of Example 1 (1:3 ratio).

[0052] Comparative Example 4 Step 1: At room temperature, mix 1 part by weight of KH550 silane coupling agent and 3 parts by weight of melamine phenolic resin by initial stirring.

[0053] Step 2: Place the mixture in a high-speed mixer and stir at 45°C for 30 minutes until the mixture is completely homogeneous.

[0054] Step 3: The blend obtained in Step 2 is cured into a copolymer at 240 °C.

[0055] The obtained silane coupling agent modified melamine phenolic resin had a 5% thermal weight loss temperature of 293.9 °C and a char residue of 39.7% at 700 °C. These performances were significantly lower than those of Example 1 (1:3 ratio).

[0056] Figure 1 The graphs show the viscosity versus temperature curves for Examples 1 and 2. The melamine phenolic resin modified with phthalonitrile resin has a lower curing temperature and a higher viscosity (under the same temperature conditions). This indicates that the phthalonitrile-modified melamine phenolic resin has stronger intermolecular forces and better mechanical and thermal properties.

[0057] Figure 2 The thermogravimetric curves are for Examples 1, 2, 3, 4, and 5, and Comparative Examples 1 and 2. Figure 3 Data derived from the thermogravimetric curves of Examples 1, 2, 3, 4, and 5, and Comparative Examples 1 and 2. Figure 2 , 3 It can be seen that the thermal properties of melamine phenolic resin modified with phthalonitrile resin are better than those of melamine phenolic resin without phthalonitrile resin modification. The 5% thermal weight loss temperature of melamine phenolic resin modified with phthalonitrile resin is higher than 354.9 ℃, and its char residue rate at 700 ℃ is higher than 57.7%, which increases with the increase of phthalonitrile resin content.

[0058] Figure 4 The differential scanning calorimetry (DSC) curves for Examples 1, 2, 3, 4, and 5, and Comparative Examples 1 and 2, are obtained from... Figure 3It can be seen that as the content of phthalonitrile resin increases, the exothermic peak becomes less obvious and the enthalpy value of the main peak decreases. This indicates that the addition of phthalonitrile can reduce curing shrinkage and internal stress, thereby improving the interfacial bonding strength of the composite material.

[0059] Figure 5 The thermogravimetric curves for Example 1 and Comparative Examples 3 and 4 are provided by [the relevant source]. Figure 5 It can be seen that the phthalonitrile-modified system with a 1:3 ratio is significantly better than the epoxy resin and silane coupling agent-modified system in terms of thermal stability.

[0060] Figure 6 The infrared spectra of Examples 1 and 2, and the phthalonitrile resin are shown below. Figure 4 It can be seen that the triamine phenol-nitrile copolymer resin at 2230 cm -1 The peak phase of the nitrile group was significantly lower than that of phthalonitrile resin, and the peak phase of the triamine phenolic-nitrile copolymer resin was 1008 cm⁻¹. -1 The hydroxymethyl group was significantly reduced compared to that of the triamine phenolic resin, indicating that the nitrile group and hydroxymethyl group in the triamine phenolic-nitrile resin underwent a copolymerization reaction, which provides a basis for improving its thermal properties.

[0061] The above are the embodiments listed in this example. However, this example is not limited to the optional embodiments described above. Those skilled in the art can arbitrarily combine the above methods to obtain other various embodiments. Anyone can derive other various forms of embodiments based on the inspiration of this example. The above specific embodiments should not be construed as limiting the scope of protection of this example. The scope of protection of this example should be determined by the claims, and the specification can be used to interpret the claims.

Claims

1. A method for improving the heat resistance of melamine phenolic resin using phthalonitrile, characterized by: The method comprises the following steps: The phthalonitrile resin powder and the melamine phenolic resin powder are mixed uniformly at room temperature, and then the mixed powder is cured and formed at 200-280°C to obtain a melamine phenolic-nitrile copolymer resin.

2. The method for improving the heat resistance of melamine phenolic resin by using phthalonitrile according to claim 1, characterized in that: The mixing is performed at 25-80°C for 30-60 minutes at a rotation speed of 300-500 RPM.

3. The method for improving the heat resistance of melamine phenolic resin by using phthalonitrile according to claim 1, characterized in that: The mass ratio of the phthalonitrile resin powder to the melamine phenolic resin powder is 1:1-1:

4.

4. The method for improving the heat resistance of melamine phenolic resin by using phthalonitrile according to claim 3, characterized in that: The mass ratio of the phthalonitrile resin powder to the melamine phenolic resin powder is 1:1-1:

3.

5. The method for improving the heat resistance of melamine phenolic resin by using phthalonitrile according to claim 4, characterized in that: The mass ratio of the phthalonitrile resin powder to the melamine phenolic resin powder is 1:

3.

6. The method for improving the heat resistance of melamine phenolic resin by using phthalonitrile according to claim 1, characterized in that: The chemical structural formula of the phthalonitrile resin is: 。 7. The method for improving the heat resistance of melamine phenolic resin by using phthalonitrile according to claim 6, characterized in that: The AR of the phthalonitrile resin is at least one of an aromatic ring, a benzoxazine group, an imidazole group, or an allyl group.

8. The method for improving the heat resistance of melamine phenolic resin by using phthalonitrile according to claim 7, characterized in that: The AR of the phthalonitrile resin is a benzoxazine group.

9. The method for improving the heat resistance of melamine phenolic resin by using phthalonitrile according to claim 1, characterized in that: The chemical structural formula of the melamine phenolic resin is: 。 10. A melamine-phenolic-nitrile-based copolymer resin characterized by: A melamine phenolic resin with improved heat resistance prepared by the method of any one of claims 1-9.

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