Modified adhesive based on waste polystyrene and preparation method thereof

Abstract

The invention relates to a modified adhesive based on waste polystyrene and a preparation method thereof. The invention relates to the field of high-value recovery of waste polystyrene, in particular to a modified adhesive and a preparation method thereof. The prior art has the defects of insufficient performance or complex process and high cost. Rosin and epoxy resin in a specific ratio react with a PS matrix under the condition of no additional catalyst. Key experiments show that the system can synchronously and remarkably improve the thermal stability and rheological property of the adhesive, so that the adhesive keeps stable construction viscosity in a wide temperature range, and excellent final strength and toughness are obtained. By adjusting the proportion of the components, the performance can be flexibly regulated and controlled, the method is simple and convenient, and the cost is low.

Description

Technical Field

[0001] This invention relates to the field of waste polystyrene treatment technology, specifically to a modified adhesive based on waste polystyrene and its preparation method. Background Technology

[0002] Polystyrene (PS), a widely produced general-purpose plastic, is extensively used in electrical appliance housings, packaging containers, and daily consumer goods due to its excellent insulation, ease of processing and molding, and low cost. However, PS material itself has significant performance defects: its molecular chains are highly rigid and brittle, resulting in poor impact resistance and toughness, which severely limits its application in situations requiring good mechanical properties. At the same time, large quantities of discarded PS products are difficult to degrade in the natural environment, causing serious "white pollution" and resource waste problems.

[0003] Currently, the recycling of waste PS faces two major challenges: First, traditional physical recycling (such as melt regranulation) leads to molecular chain breakage and a significant decline in performance, resulting in recycled materials that can only be used at a lower grade, resulting in low economic value. Second, chemical modification aimed at enhancing value is often complex and has limited effectiveness. Common toughening modification methods, such as blending with rubber elastomers, often sacrifice material strength, stiffness, and thermal stability, and suffer from poor compatibility and easy phase separation. While adding small-molecule plasticizers can improve processability, they are prone to migration and volatilization, leading to unstable product performance and potential environmental risks. Therefore, developing a green modification technology that can simultaneously and synergistically improve the toughness, strength, and adhesion properties of PS is a key bottleneck in achieving its high-value recycling.

[0004] Transforming waste polystyrene (PS) into adhesives with specific functionalities is a crucial direction for "upgrading and recycling." However, as a non-polar polymer, PS has low surface energy, poor wettability, and insufficient cohesive strength. When used directly as an adhesive matrix, it generally suffers from weak initial tack, low bond strength, and poor durability. Current technologies, relying solely on physical blending modification, struggle to resolve the conflict between interfacial compatibility and cohesive strength at the molecular level. Therefore, a new technological approach is urgently needed. This approach, through a simple and efficient process, can introduce suitable active components into the PS molecular chain, constructing a strong and resilient adhesive network structure in situ. This would directly transform low-value waste PS into high-performance adhesive products, which has dual significance for promoting a circular economy in plastics and alleviating environmental pressure. Summary of the Invention

[0005] The existing technology has the following problems: modifying waste polystyrene into adhesive materials through conventional physical blending or simple plasticization usually faces challenges such as difficulty in achieving both toughening and reinforcement, poor interfacial compatibility, easy migration and precipitation of small molecule additives, and the need to add multiple tackifying resins and compatibilizers to improve adhesion; resulting in complex formulations and high costs. To address these problems, this invention provides a modified adhesive based on waste polystyrene and its preparation method, characterized in that:

[0006] (1) Add clean, dry waste PS fragments to ethyl acetate, heat and stir at 50°C until PS is completely dissolved to obtain a homogeneous and transparent PS solution;

[0007] (2) Under sealed and continuous stirring conditions, keep the temperature of step (1), first add rosin to the PS solution, stir to dissolve, and through the thermodynamic compatibility between the hydrophobic hydrocarbon skeleton of rosin and the nonpolar benzene ring structure of PS, make the two form a uniform mixture in the molten state. Then add epoxy resin E51 to the reaction system, and stir continuously at a constant temperature. After the reaction is completed, a viscous modified adhesive is obtained.

[0008] (3) After cooling the above viscous adhesive, the modified waste polystyrene adhesive is obtained.

[0009] Preferably, the mass-to-volume ratio of waste PS to ethyl acetate is 0.1g:10mL to 2g:10mL. The mass ratio of waste PS to rosin is 1:1 to 2:1. The mass ratio of rosin to epoxy resin E51 is 0.5:1.

[0010] Preferably, the dissolution temperature is 40~70℃.

[0011] Preferably, the cooling in step (3) is natural cooling at room temperature inside the fume hood.

[0012] Preferably, the size of the waste PS fragments is 1-20cm. 3 .

[0013] Beneficial effects:

[0014] (1) This invention directly uses waste PS as raw material and transforms it into adhesive material with usable value through chemical modification, which effectively reduces "white pollution", conforms to the concept of circular economy and sustainable development, and turns waste into treasure;

[0015] (2) The present invention utilizes the good solubility of ethyl acetate to fully dissolve PS and rosin, so that the two form a homogeneous mixture in the molten state, thereby giving the waste polystyrene a certain viscosity;

[0016] (3) The entire modification process of the present invention is carried out under heating and sealing conditions, and the reaction is driven by the properties of the reactants themselves. This eliminates the initiators or metal catalysts commonly used in traditional grafting modification, simplifies the post-processing steps, reduces production costs, and avoids environmental and toxicity problems that may be caused by catalyst residues.

[0017] (4) This invention creatively utilizes the interaction between the carboxyl groups of rosin acid and the epoxy groups of epoxy resin. The reaction between the carboxyl groups of rosin acid and the epoxy groups introduces the large rosin phenanthrene ring structure into the epoxy network, which can significantly improve the hydrophobicity, rigidity, electrical insulation and dielectric properties of the cured product. It overcomes the defect of performance degradation caused by conventional blending modification and achieves high-performance modification;

[0018] (5) Under heating conditions, the rosin carboxyl groups can undergo ring-opening addition with the epoxy groups of the epoxy resin to form ester bonds, thereby introducing the rosin structure into the polymer network. The epoxy resin is responsible for functionalization (forming ester groups), and the rosin is responsible for microstructure construction (improving physical properties). The two work together to complete the conversion from waste PS to high-performance adhesive materials in one step. The process route is short and efficient. Attached Figure Description

[0019] Figure 1 Figure 1 shows the surface scanning morphology (Figure c) and fracture surface scanning morphology (Figure d) of the modified adhesive obtained in Example 1 of this invention.

[0020] Figure 2 The bonding effect diagrams of the adhesive obtained in Example 1 and the commercially available room temperature curing adhesive for bonding two pine blocks are shown.

[0021] Figure 3 : These are thermogravimetric analysis (TGA) diagrams of the modified adhesives obtained in Example 1 and Comparative Examples 1-4 of this invention.

[0022] Figure 4 : These are temperature-complex viscosity curves of the modified adhesives obtained in Examples 1-3 and Comparative Examples 1-4 of the present invention. Detailed Implementation

[0023] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0024] The epoxy resin E51 used in this embodiment of the invention has an epoxy value of 0.51 eq / 100g, an epoxy equivalent of 198.08 eq / g, and a number-average molecular weight of 168.63 g / mol.

[0025] The rosin used in this embodiment of the invention was purchased from Shenzhen Yoshida Chemical Co., Ltd., and its product number is Aj04.

[0026] The PS waste used in this embodiment of the invention comes from express packaging.

[0027] Example 1

[0028] A method for preparing a modified adhesive based on waste polystyrene is as follows:

[0029] (1) Wash, dry and cut the PS waste into 3-10cm³ pieces;

[0030] (2) Under closed reaction conditions, 2g of PS fragments were added to 10mL of ethyl acetate and stirred until completely dissolved. Then, 1g of rosin was added to the reaction system and stirred at 50℃ for 30 min. After that, 2g of epoxy resin E51 was added to the reaction system and stirred at 50℃ for 3 h. After the reaction was completed, the resulting viscous liquid was transferred to a special mold and placed in a fume hood to cool at room temperature for 24 h to obtain modified waste polystyrene adhesive.

[0031] Example 2

[0032] A method for preparing a modified adhesive based on waste polystyrene is as follows:

[0033] (1) Wash, dry and cut the PS waste into 3-10cm³ pieces;

[0034] (2) Under closed reaction conditions, 0.1g of PS fragments were added to 10mL of ethyl acetate and stirred until completely dissolved. Then, 0.1g of rosin was added to the reaction system and stirred at 50℃ for 30 min. After that, 0.2g of epoxy resin E51 was added to the reaction system and stirred at 50℃ for 3 h. After the reaction was completed, the resulting viscous liquid was transferred to a special mold and placed in a fume hood to cool at room temperature for 24 h to obtain modified waste polystyrene adhesive.

[0035] Example 3

[0036] A method for preparing a modified adhesive based on waste polystyrene is as follows:

[0037] (1) Wash, dry and cut the PS waste into 3-10cm³ pieces;

[0038] (2) Under closed reaction conditions, 1g of PS fragments were added to 10mL of ethyl acetate and stirred until completely dissolved. Then, 0.6g of rosin was added to the reaction system and stirred at 50℃ for 30 min. After that, 1.2g of epoxy resin E51 was added to the reaction system and stirred at 50℃ for 3 h. After the reaction was completed, the resulting viscous liquid was transferred to a special mold and placed in a fume hood to cool at room temperature for 24 h to obtain modified waste polystyrene adhesive.

[0039] Comparative Example 1 is the same as Example 1, except that the amount of epoxy resin E51 added in Comparative Example 1 is 1g, and the reaction temperature is 40℃.

[0040] Comparative Example 2 is the same as Example 1, except that the amount of rosin added in Comparative Example 2 is 2g and the amount of epoxy resin added is 1g.

[0041] Comparative Example 3 is the same as Example 1, except that epoxy resin E51 was not added in Comparative Example 3.

[0042] Comparative Example 4 is the same as Example 1, except that no rosin was added in Comparative Example 4.

[0043] Comparative Example 5 is the same as Example 1, except that the reaction temperature is room temperature. The epoxy group ring-opening addition reaction cannot occur, and a viscous solid product (the target product) cannot be obtained.

[0044] Comparative Example 6 is the same as Example 1, except that PS waste, ethyl acetate, rosin, and epoxy resin E51 are directly mixed without stepwise mixing. The target product was not obtained, and flocculent matter was generated in the solution.

[0045] Performance testing

[0046] The effect diagram of the modified adhesive obtained in Example 1 bonding the bumps and dents is shown in the attached instruction manual. Figure 1 As shown. Scanning electron microscope (SEM) image of the modified adhesive obtained in Example 1, as shown in the attached instruction manual. Figure 1 Analysis (as shown) reveals that the cured surface exhibits a regular and ordered structure, while the fracture surface displays a typical dimple-like morphology, a clear characteristic of ductile fracture. This result directly confirms that a strong and tough three-dimensional cross-linked network was successfully constructed among the components using the formulation of this invention. This unique microstructure is the fundamental reason for the material's excellent macroscopic properties: the dimple-like characteristics of the fracture surface directly correspond to its excellent impact resistance and fracture toughness; simultaneously, the dense cross-linked network also fundamentally provides excellent thermal stability, which is corroborated by the results of thermogravimetric analysis showing a significant delay in the initial decomposition temperature and a substantial increase in the amount of residual char.

[0047] Thermogravimetric analysis results of the modified adhesives obtained in the embodiments and comparative examples of this invention (see attached specification) Figure 3This indicates that the thermal stability of the adhesive can be precisely controlled by the ratio of epoxy resin to rosin. Epoxy resin is key to constructing the heat-resistant network; increasing its dosage significantly increases the initial decomposition temperature of the material (e.g., about 20°C) and substantially increases the char residue at 700°C (e.g., from 8% to 15%). While rosin contributes to adhesive performance, increasing its dosage causes a certain range of fluctuation in the initial decomposition temperature (e.g., 10-15°C). The thermal stability of the modified adhesives obtained in the embodiments and comparative examples of this invention follows a clear pattern of "Example 1 > Comparative Example 4 > Comparative Example 1 > Comparative Example 2 > Comparative Example 3," demonstrating that through the formulation design of this invention, thermal stability can be designed and optimized on demand while maintaining adhesive performance.

[0048] As attached Figure 4 (Temperature-complex viscosity curve) is shown. Temperature-complex viscosity curve testing was conducted in oscillating mode at 25℃-60℃, with a rate of 2℃ / min, using an Anton-Paar MCR302 rheometer purchased from Anton-Paar GmbH, Austria. Test results show:

[0049] The modified adhesive obtained in Example 1 exhibits good initial tack at room temperature, suitable flowability upon heating, and excellent temperature stability within a temperature range of 25°C to 60°C, showing low temperature dependence and a wider processing window. In contrast, Comparative Examples 1-4, due to component imbalances, exhibit rheological properties that are excessively viscous at low temperatures, excessively thin at high temperatures, and excessively viscous or thin across the entire temperature range, respectively. The absolute viscosity of Example 1 within the 25°C to 60°C range is 2.2 × 10⁻⁶. 5 mPa·s (25℃) ~9.0×10 4 mPa·s (60℃). It exhibits optimal temperature stability (viscosity decreases by only 59% from 25-60℃) and the widest suitable application temperature window (>35℃), with highly linear viscosity-temperature changes (R0). 2 > 0.99. The absolute viscosity values ​​of Comparative Example 1 within the range of 25℃ to 60℃ are 5.8 × 10⁻⁶. 5 mPa·s (25℃) ~8×10 4 mPa·s (60℃). Temperature stability: viscosity decreases by 86.2% from 25-60℃.

[0050] The modified adhesive obtained in Comparative Example 2 has an absolute viscosity range of 7.5 × 10⁻⁶ m / s in the temperature range of 25°C to 60°C. 5 mPa·s (25℃) ~10×10 4 mPa·s (60℃), viscosity-temperature change is highly linear R 2 >0.99. Temperature stability: viscosity decreases by 86.7% between 25-60℃.

[0051] The modified adhesive obtained in Comparative Example 3 has an absolute viscosity range of 0.2 × 10⁻⁶ within the temperature range of 25°C to 60°C. 5 mPa·s (25℃) ~7×10 4 mPa·s (60℃), viscosity-temperature change is highly linear R 2 >0.99. Temperature stability: viscosity increases by 250% at 25-60℃.

[0052] The modified adhesive obtained in Comparative Example 4 has an absolute viscosity range of 4.2 × 10⁻⁶ m / s in the temperature range of 25°C to 60°C. 5 mPa·s (25℃) ~5×10 4 mPa·s (60℃), viscosity-temperature change is highly linear R 2 >0.99. Temperature stability: viscosity decreases by 88.1% from 25-60℃.

[0053] Two pine blocks, each measuring 4cm × 4cm × 4cm, were bonded together using the adhesive obtained in Example 1 and a conventional commercially available adhesive (white glue, brand name: Vivo). The contact area of ​​the pine blocks was 4cm × 4cm, and the basis weight of the adhesive on the contact surface was 0.4kg / m². 2 The test results are as shown in the attached instruction manual. Figure 2 As shown, the left side is a bonding effect diagram of a commercially available room-temperature curing adhesive, and the right side is a bonding effect diagram of the adhesive obtained in Example 1.

[0054] Comparative data demonstrates that the modified adhesive obtained in Example 1 of this invention successfully achieves the optimal balance between flowability, cohesion, and process stability, providing a key basis for its reliability and wide applicability in practical applications.

[0055] The bonding effects of conventional commercially available adhesives (white glue, brand name Vivo) and the adhesive obtained in Example 1 of this invention were tested according to the following methods:

[0056] Based on a single-sided application rate of 0.5 kg / m 2 Two 4mm thick 304 stainless steel sheets of the same size and thickness were bonded together and placed at a constant temperature of 40°C for 24 hours. The shear strength between the sheets was then tested according to standard GB 7124-2008 (Fe-Fe). The test results showed that the shear strength of the adhesive obtained in Example 1 was 8.53 MPa, while the shear strength of a conventional commercially available adhesive was 8.55 MPa.

[0057] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A modified adhesive based on waste polystyrene, characterized in that, The preparation method includes the following steps: (1) Add clean, dry waste PS fragments to ethyl acetate, heat and stir at 50°C until PS is completely dissolved to obtain a homogeneous and transparent PS solution; (2) Under sealed and continuous stirring conditions, keep the temperature of step (1), first add rosin to the PS solution, stir until it is completely dissolved and mixed, then add epoxy resin E51, and stir continuously at constant temperature to make the components evenly mixed and pre-reacted to obtain a viscous modified adhesive. (3) Cool the modified adhesive obtained in step (2) to obtain the modified adhesive based on waste polystyrene.

2. The modified adhesive based on waste polystyrene according to claim 1, characterized in that, The mass-to-volume ratio of the waste PS to ethyl acetate is 0.1g:10mL to 2g:10mL.

3. The modified adhesive based on waste polystyrene according to claim 2, characterized in that, The mass ratio of waste PS to rosin is 1:1 to 2:

1.

4. The modified adhesive based on waste polystyrene according to claim 3, characterized in that, The mass ratio of rosin to epoxy resin E51 is 0.5:

1.

5. A modified adhesive based on waste polystyrene according to any one of claims 1-4, characterized in that, The reaction temperature in step (2) is 40~70℃.

6. A modified adhesive based on waste polystyrene according to any one of claims 1-4, characterized in that, The reaction time described in step (2) is 1 to 3 hours.

7. A modified adhesive based on waste polystyrene according to any one of claims 1-4, characterized in that, The size of discarded PS fragments is 3-10cm. 3 .

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