Recyclable unsaturated polyester thermosetting composite material and preparation method thereof

Abstract

The preparation method comprises the following steps: dropwise adding a (CaCO3) n solution into a disulphide bond-containing polyatomic acid / n-butyl alcohol solution under violent stirring, standing in a dark place, and then violently stirring to prepare a disulphide bond-containing polyatomic acid / (CaCO3) n-butyl alcohol dispersion liquid; and uniformly mixing the prepared disulfide bond-containing polyatomic acid / (CaCO3) n-butyl alcohol dispersion liquid with epoxy unsaturated polyester and a curing agent, and curing at high temperature to obtain the recyclable unsaturated polyester thermosetting composite material. According to the invention, a covalent continuous structure dynamically crosslinked by the epoxy unsaturated polyester resin is constructed through disulfide bonds, and meanwhile, a nacre-like lamellar continuous structure is formed through carboxyl and (CaCO3) n under high pressure, so that the material is endowed with recoverability and excellent mechanical properties. Recycling and reprocessing conditions of the prepared unsaturated polyester thermosetting composite material are simpler and more convenient, the unsaturated polyester thermosetting composite material is suitable for large-scale engineering application, the mechanical property of the reprocessed unsaturated polyester thermosetting composite material is still kept at a higher level, and the material cost is greatly saved.

Description

Technical Field

[0001] The invention relates to the technical field of composite materials, and in particular to a method for preparing a recyclable unsaturated polyester thermosetting composite material and a preparation method thereof. Background Art

[0002] Due to their excellent mechanical properties and processing adaptability, thermosetting plastics are widely used in energy, electrical, automotive manufacturing and other fields. However, the cross-linked polymer network makes unsaturated polyesters insoluble and infusible, difficult to chemically recycle, and cannot be melt-processed. In recent years, many studies have introduced dynamic covalent bonds into thermosetting materials to give thermosetting materials recyclability through dynamic bond exchange.

[0003] For example, the invention patent CN 116285567 B discloses a self-healing and toughened epoxy powder coating, which uses a polyurethane prepolymer terminated with a small molecule diamine containing a borate bond as a dynamic crosslinker. By replacing the traditional curing agent with irreversible permanent crosslinking in the powder coating with a modified curing agent containing a borate dynamic covalent bond, the problem of difficult-to-repair scratches in the powder coating can be effectively improved, thereby extending the service life of the powder coating. Thanks to the interaction between the borate bond, urea bond, and urethane bond hydrogen bonds of the polyurethane crosslinker and the microphase separation of the polyol flexible chain segment, the toughness of the epoxy resin is improved. However, the synthesis process of the crosslinker polyurethane prepolymer in this patent is complicated, the conditions are harsh, and the industrialization difficulty is relatively high.

[0004] For example, invention patent CN 1133136105 B discloses a recyclable unsaturated polyester material based on dynamic disulfide bonds and its preparation method. Castor oil-based unsaturated polyester matrix resin is synthesized by a two-step method, and then it is reacted with 4,4'-dithiodiphenylamine or 4,4'-dithiodibenzoic acid containing reversible dynamic disulfide bonds as a curing agent, and a castor oil-based unsaturated polyester Vitrimer material containing dynamic disulfide bonds is obtained through an epoxy ring-opening reaction. The obtained material has the characteristics of sustainable recycling, chemical recovery and self-repair, but there is no detailed data on its mechanical properties. Summary of the invention

[0005] The main purpose of the present invention is to provide a recyclable polyester composite material containing calcium carbonate and a preparation method thereof, which further improves and maintains the mechanical properties of the recycled product on the basis of the existing thermoplastic processing of thermosetting resins, and solves the problem of decreased mechanical properties of recycled thermosetting resins in actual engineering applications. Compared with the existing technology, it has significant improvement characteristics.

[0006] In order to solve the above technical problems, the present invention proposes a recyclable polyester composite material containing calcium carbonate, wherein the composite material uses a disulfide-containing polyacid as a curing agent. Specifically, a covalent continuous structure of a dynamically cross-linked epoxy unsaturated polyester resin is constructed through disulfide bonds, and at the same time, (CaCO3)n is bonded to form a calcium carbonate-containing recyclable polyester composite material under high pressure. Figure 1 More specifically, the above-mentioned disulfide polyacid mainly undergoes two reactions, such as Figure 2 As shown in the figure, one is the disulfide bond carboxylic acid synthesized in situ by mineralization and inorganic bonding; the other is the ring-opening reaction of carboxylic acid and epoxy group. This type of disulfide bond carboxylic acid curing agent can form a continuous structure of nacre-like lamellar layers in the matrix under high pressure, giving the material recyclability and excellent mechanical properties, such as Figure 3 shown.

[0007] The present invention specifically adopts the following technical means:

[0008] The present invention first discloses a method for preparing a recyclable unsaturated polyester thermosetting composite material, comprising:

[0009] 1) dissolving a disulfide bond-containing polyacid in n-butanol to prepare a disulfide bond-containing polyacid / n-butanol solution for later use;

[0010] 2) Dissolve CaCl2·2H2O in n-butanol, add diethylamine, and then introduce CO2 into the solution while stirring to obtain a solution containing (CaCO3)n for later use;

[0011] 3) adding the (CaCO3)n solution dropwise to the disulfide bond-containing polyacid / n-butanol solution under vigorous stirring, allowing to stand in the dark, and then vigorously stirring to obtain a disulfide bond-containing polyacid / (CaCO3)n n-butanol dispersion;

[0012] 4) The disulfide bond-containing polyacid / (CaCO3)n n-butanol dispersion is uniformly mixed with the epoxy unsaturated polyester and the curing agent, and then cured at high temperature to obtain a recyclable unsaturated polyester thermosetting composite material.

[0013] Furthermore, the disulfide bond-containing polyacid in step 1) is selected from one or more of asparagus acid, dithiodiacetic acid, and cystine.

[0014] Furthermore, in step 2), the molar ratio of CaCl2·2H2O to diethylamine is 1:50-200.

[0015] Furthermore, in step 3), the molar ratio of the disulfide bond-containing polyacid to (CaCO3)n is 1:0.1-10.

[0016] Furthermore, in step 4), the disulfide bond polyacid / (CaCO3)n n-butanol dispersion is 5-150 parts; the epoxy unsaturated polyester is 50-150 parts, and the curing agent is 0.1-20 parts.

[0017] Furthermore, the epoxy unsaturated polyester includes: at least one of epoxy vinyl resins 191#, 196#, 901#, and 907#; and the curing agent is at least one of TBPB and TBPO.

[0018] Furthermore, in step 4), the curing temperature is 120-200° C., the curing pressure is 20-200 MPa, and the curing time is 6-15 min.

[0019] The invention also discloses a recyclable unsaturated polyester thermosetting composite material prepared according to any one of the above preparation methods.

[0020] Furthermore, the recyclable unsaturated polyester thermosetting composite material is crushed and recycled and then molded to prepare sheets or other shaped products.

[0021] Furthermore, the molding pressure is 20-150 MPa, the temperature is 80-200° C., and the time is 5-15 min.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) Based on the traditional carboxylic acid or amine curing agent containing dynamic disulfide bonds, a disulfide bond carboxylic acid curing agent is synthesized in situ by mineralization and inorganic bonding. More specifically, the above-mentioned disulfide bond polyacid mainly undergoes two reactions: one is the disulfide bond carboxylic acid synthesized in situ by mineralization and inorganic bonding; the other is the ring-opening reaction between carboxylic acid and epoxy group. This type of disulfide bond carboxylic acid curing agent undergoes epoxy ring-opening reaction while realizing the carboxyl group and inorganic bonding, and can form a nacre-like lamellar continuous structure in the matrix under high pressure, giving the material recyclability and excellent mechanical properties.

[0024] (2) The unsaturated polyester thermosetting composite material has simpler recycling and reprocessing conditions and is suitable for large-scale engineering applications.

[0025] (3) The mechanical properties of the unsaturated polyester thermosetting composite material after reprocessing still remain at a high level, greatly saving material costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a continuous structure of nacre-like lamellar layers as described in the embodiment of the present invention;

[0027] Figure 2 It is the dynamic cross-linked molecular structure described in the embodiment of the present invention;

[0028] Figure 3 These are photos of samples before and after reprocessing as described in Example 3 of the present invention. DETAILED DESCRIPTION

[0029] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0030] The embodiment of the present invention provides: a recyclable unsaturated polyester thermosetting composite material and a preparation method thereof. The specific implementation method is as follows:

[0031] Embodiment 1:

[0032] Preparation of disulfide bond-containing polyacid / (CaCO3)n mixed molecule solution curing agent:

[0033] First, 0.64 parts of disulfide bond-containing polyacid were completely dissolved in 100 parts of n-butanol by weight to form a disulfide bond-containing polyacid / n-butanol solution.

[0034] Next, dissolve 0.05 parts of CaCl2·2H2O in 100 parts of n-butanol and add 0.25 parts of diethylamine to prepare a mixed solution. Then, add 100 ml of -1 The solution became turbid after a few minutes. Finally, CO2 was bubbled for 10 min and stirred for 30 min to obtain a (CaCO3)n / n-butanol solution.

[0035] Then, under vigorous stirring, 100 parts of freshly prepared (CaCO3)n / n-butanol solution were added dropwise to 100 parts of disulfide-bond-containing polyacid / n-butanol solution, and allowed to stand at 25°C for 30 min, avoiding strong light exposure.

[0036] Finally, after 8 hours of vigorous stirring, a disulfide bond-containing polyacid / (CaCO3)n n-butanol dispersion was obtained.

[0037] Preparation of recyclable unsaturated polyester thermosetting composites:

[0038] 100 parts of epoxy vinyl resin 191#, 80 parts of disulfide bond polyacid / (CaCO3)n n-butanol dispersion, and 1 part of curing agent TBPO were mixed evenly by weight, and then cured at 140°C and 110 MPa for 15 minutes. The epoxy unsaturated polyester resin undergoes epoxy ring opening and dynamically crosslinks with the disulfide bonds in the disulfide bond-containing polyacid to obtain a recyclable unsaturated polyester thermosetting composite material.

[0039] Embodiment 2:

[0040] The unsaturated polyester thermosetting composite material prepared in Example 1 was crushed, and then put into a hot pressing mold cavity, and compacted again at 150° C. and 120 MPa for 10 min to obtain a reprocessed unsaturated polyester thermosetting composite material.

[0041] Embodiment 3:

[0042] The unsaturated polyester thermosetting composite material prepared in Example 2 was crushed, then put into a hot pressing mold cavity, and compacted again at 150° C. and 120 MPa for 10 min to obtain a reprocessed unsaturated polyester thermosetting composite material.

[0043] Comparative Example 1:

[0044] By weight, 2.56 parts of disulfide-containing polyacid were heated at 120°C to obtain a low-viscosity transparent liquid. After mixing it with 1.86 parts of amorphous CaCO3 nanoparticles, the mixture was vigorously stirred at 120°C for 60 minutes until the CaCO3 nanoparticles and the disulfide-containing polyacid were uniformly mixed, and then cooled to room temperature to obtain a disulfide-containing polyacid-CaCO3 nanocomposite material.

[0045] Take 100 parts of epoxy vinyl resin 191#, 80 parts of disulfide bond-containing polyacid-CaCO3, and 1 part of curing agent TBPO by weight. Mix the disulfide bond-containing polyacid-CaCO3 and epoxy unsaturated polyester and other components evenly, and cure them at 140°C and 110MPa for 15 minutes to obtain an unsaturated polyester thermosetting composite material.

[0046] The products obtained in the above Examples 1-3 and Comparative Example 1 were subjected to mechanical property tests in accordance with GB / T 1040-2018 Determination of tensile properties of plastics:

[0047] The test results are shown in Table 1:

[0048] Table 1:

[0049] Example 1 Example 2 Example 3 Comparative Example 1 Tensile strength(MPa) ≥60 ≥60 ≥60 ≥40 Tensile modulus(GPa) ≥1.4 ≥1.4 ≥1.4 ≥0.5 Elongation at break (%) ≥30 ≥30 ≥30 ≥10 Compression strength (MPa, 60% strain) ≥100 ≥100 ≥100 ≥40 Compression modulus (GPa, 60% strain) ≥3 ≥3 ≥3 ≥1

[0050] It can be seen that the composite materials obtained in Examples 1 to 3 of the present invention maintain their mechanical properties after being reprocessed several times, and their mechanical properties are much higher than those of the existing dynamically bonded cross-linked recyclable thermosetting resin composite materials.

[0051] In contrast, Comparative Example 1 does not use disulfide-containing polyacids to bond with (CaCO3)n, but uses CaCO3 nanoparticles instead. During the material preparation process, the organic phase or inorganic phase is nucleated separately, and the inorganic-organic interface bonding is poor. This leads to a difference in macroscopic force: when the composite materials of Examples 1 to 3 are subjected to stress, the stress is transmitted along the covalent ion bicontinuous network. In contrast, high stress accumulates at the organic-inorganic interface of the composite material of Comparative Example 1, where the material usually breaks and fails.

[0052] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a recyclable unsaturated polyester thermosetting composite material, comprising: 1) dissolving a disulfide bond-containing polyacid in n-butanol to prepare a disulfide bond-containing polyacid / n-butanol solution for later use; 2) Dissolve CaCl2·2H2O in n-butanol, add diethylamine, and then introduce CO2 into the solution while stirring to obtain a solution containing (CaCO3)n for later use; 3) adding the (CaCO3)n solution dropwise to the disulfide bond-containing polyacid / n-butanol solution under vigorous stirring, allowing to stand in the dark, and then vigorously stirring to obtain a disulfide bond-containing polyacid / (CaCO3)n n-butanol dispersion; 4) The disulfide bond-containing polyacid / (CaCO3)n n-butanol dispersion is uniformly mixed with the epoxy unsaturated polyester and the curing agent, and then cured at high temperature to obtain a recyclable unsaturated polyester thermosetting composite material.

2. The preparation method according to claim 1, wherein: In step 1), the disulfide bond-containing polyacid is selected from one or more of asparagus acid, dithiodiacetic acid, and cystine.

3. The preparation method according to claim 1, wherein: Step 2) The molar ratio of CaCl2·2H2O to diethylamine is 1:50-200.

4. The preparation method according to claim 1, wherein: Step 3) The molar ratio of the disulfide bond-containing polyacid to (CaCO3)n is 1:0.1-10.

5. The preparation method according to claim 1, wherein: Step 4) The disulfide bond polyacid / (CaCO3)n n-butanol dispersion is 5-150 parts; the epoxy unsaturated polyester is 50-150 parts, and the curing agent is 0.1-20 parts.

6. The preparation method according to claim 5, wherein: The epoxy unsaturated polyester comprises: at least one of epoxy vinyl resin 191#, 196#, 901#, and 907#; The curing agent is at least one of TBPB and TBPO.

7. The preparation method according to claim 1, wherein: Step 4) The curing temperature is 120-200° C., the curing pressure is 20-200 MPa, and the curing time is 6-15 min.

8. A recyclable unsaturated polyester thermosetting composite material prepared according to the preparation method according to any one of claims 1 to 7.

9. A recyclable unsaturated polyester thermosetting composite material according to claim 8, wherein: The recyclable unsaturated polyester thermosetting composite material is crushed and recycled and then molded to prepare sheets or products in other shapes.

10. The recyclable unsaturated polyester thermosetting composite material according to claim 9, wherein: The molding pressure is 20-150 MPa, the temperature is 80-200° C., and the time is 5-15 minutes.

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