A master batch capable of reducing RPET injection pressure and improving RPET transparency

Abstract

The application relates to the technical field of high polymer material modification, and discloses a master batch capable of reducing RPET injection pressure and improving RPET transparency, which comprises 90-96% of low-viscosity special copolyester, 4-8% of small-molecule polyester PET-400 and 0.5-1.8% of hyperbranched polyester, and further comprises 0.1-0.2% of inorganic pigment. By adding a small amount of the master batch in RPET, the injection pressure of the RPET can be obviously reduced, and the transparency and haze of the prepared RPET product can be improved. Energy consumption can be saved, and product properties can be improved.

Description

Technical Field

[0001] This invention relates to the field of polymer material modification technology, specifically to a masterbatch that can reduce RPET injection pressure and improve RPET transparency. Background Technology

[0002] The statements in this section provide only background information relevant to the disclosure of this application and may not constitute prior art.

[0003] With the increasing severity of global climate change and environmental pollution, plastic pollution control has become a focus of international attention. To address this challenge, major economies such as the EU, the US, Japan, and China have successively introduced policies and regulations such as "plastic bans" and "circular economy action plans" to vigorously promote the recycling of plastic products and the application of recycled materials. These initiatives aim to reduce dependence on virgin petroleum-based plastics, decrease carbon emissions, and achieve sustainable development goals. Against this backdrop, recycled polyethylene terephthalate (RPET), as a widely available and high-performance recycled polymer material, is widely used in cosmetic packaging, food and beverage containers, medical consumables, and daily necessities due to its excellent mechanical properties, chemical stability, and processability, making it an important alternative to virgin PET.

[0004] However, RPET undergoes multiple thermal histories, mechanical shearing, and environmental aging during recycling, leading to varying degrees of molecular chain breakage and cross-linking, a significantly wider molecular weight distribution, and unavoidable contamination with trace impurities, additive residues, moisture, and degradation products. These structural and purity changes cause numerous processing challenges for RPET during injection molding: such as decreased melt flowability, requiring higher injection temperatures and pressures to complete mold filling, increasing energy consumption and equipment load; reduced thermal stability, making it more susceptible to thermo-oxidative degradation during high-temperature processing, producing small molecule volatiles such as acetaldehyde, affecting the odor and food safety of the products; uneven crystallization behavior, easily forming microcrystals or stress concentrations during cooling, resulting in optical defects such as fogging and turbidity in transparent products; furthermore, the material's increased sensitivity to heat and light makes products more prone to yellowing during storage or use, severely impacting appearance quality and market competitiveness.

[0005] Currently, to address these issues, manufacturers typically employ techniques such as increasing barrel temperature, injection pressure, and extending holding and cooling times to improve melt flowability and product density. However, this "energy-for-quality" approach not only significantly increases energy consumption, prolongs molding cycles, and reduces production efficiency, but may also exacerbate material thermal degradation, creating a vicious cycle that leads to large batch-to-batch quality fluctuations and low yield rates. Furthermore, over-reliance on process compensation limits the application of RPET in products requiring high transparency and aesthetic appeal.

[0006] Therefore, improving the processing stability and molding efficiency of RPET while ensuring product performance and appearance quality has become a key technological bottleneck in the industrial application of recycled plastics. Currently, the industry urgently needs collaborative innovation across multiple dimensions, including material modification, process optimization, and equipment adaptation, to develop specialized additive systems suitable for the characteristics of RPET, optimize injection molding process windows, and improve mold design. This will enable the efficient, stable, and high-value utilization of recycled materials, truly promoting the development of a circular economy for plastics. Summary of the Invention

[0007] The purpose of this invention is to address the problems of difficult and energy-intensive injection molding of recycled RPET, as well as the high haze and yellowing of the prepared products. This invention provides a masterbatch that can reduce the injection pressure of RPET and improve its transparency. By adding a small amount of RPET, the injection pressure of RPET can be reduced, while the light transmittance of the prepared product is increased and the haze of the product is reduced.

[0008] The technical solution of the present invention is as follows: This invention provides a masterbatch that can reduce RPET injection molding pressure and improve RPET transparency, comprising the following raw materials by mass fraction: Low viscosity special copolyester 90-96%, small molecule polyester PET-400 4-8% and hyperbranched polyester 0.5-1.8%.

[0009] Selection of low-viscosity special copolyesters: viscosity 0.58-0.65 dl / g, crystallization peak temperature 153℃.

[0010] According to a preferred embodiment, it further includes 0.1-0.2% inorganic pigment.

[0011] The use of inorganic pigments and hyperbranched polyesters: This combination provides both color correction and grain size refinement, significantly improving the transparency and anti-yellowing properties of RPET. The use of small-molecule polyester PET-400: By providing inter-chain lubrication, this reduces injection molding pressure while simultaneously enhancing product transparency.

[0012] According to a preferred embodiment, the low-viscosity special copolyester is G158A or IPA-modified slow-crystallizing PET.

[0013] According to a preferred embodiment, the inorganic pigment is cobalt acetate.

[0014] According to a preferred embodiment, the composition includes 93-96% low-viscosity special copolyester, 4-8% small-molecule polyester PET-400, and 0.5-1% hyperbranched polyester.

[0015] Another aspect of the present invention provides a method for preparing a masterbatch as described above, which can reduce RPET injection molding pressure and improve RPET transparency, comprising the following steps: The aforementioned raw materials are fed into a TSE-75 twin-screw granulator via a loss-in-weight batching system in proportion. The granulation temperature is controlled at 245-270℃ and the screw speed is 300-500 r / min to obtain the final masterbatch.

[0016] According to a preferred embodiment, the granulation temperature is controlled at 260-270℃ and the screw speed is 370-400 r / min.

[0017] According to a preferred embodiment, the granulation temperature is controlled at 265°C and the screw speed is 385 r / min.

[0018] Another aspect of the present invention provides a method for using a masterbatch as described above, which can reduce RPET injection molding pressure and improve RPET transparency, comprising the following steps: The granulated masterbatch is mixed with RPET at a mass ratio of 0.5%-2.5%, and the color plate is obtained by injection molding at an injection temperature of 265-275℃ and a mold cooling temperature of 18-25℃.

[0019] According to a preferred embodiment, the injection temperature is 275°C and the mold cooling temperature is 20°C.

[0020] Compared with existing technologies, the advantages of this invention are: 1. By adding a small amount of the additive prepared in this application to RPET, the injection pressure of RPET can be significantly reduced. According to the test, at the same injection temperature, only 2.5% of the masterbatch prepared in this application needs to be added to reduce the injection pressure of RPET by 10-20 MPa. 2. Regarding improved transparency, this invention effectively regulates the crystallization behavior of RPET during cooling by introducing inorganic pigments and hyperbranched polyester synergistically, inhibiting the formation of large-sized spherulites and promoting the uniform distribution of microcrystalline structures, thereby significantly improving the material's light transmittance. Experimental data shows that after applying the masterbatch of this invention, the light transmittance of RPET injection molded products can be increased by 1-2%, reaching or approaching the level of virgin PET; simultaneously, the haze value is reduced by 3-4%, with a minimum haze of 0.6%. The product surface is clearer and brighter, without obvious turbidity or whitening. This improvement is particularly suitable for cosmetic bottles, high-end beverage bottles, and transparent home storage products with stringent requirements for packaging appearance, significantly enhancing the consumer's visual experience and brand added value.

[0021] 3. Regarding anti-yellowing performance, by adding the masterbatch of this application, the b-value (a parameter indicating the degree of yellowing) of the color chart is reduced by 1.5-3, significantly improving the problems of easy yellowing and rapid appearance deterioration of traditional RPET products. This not only extends the product's shelf life and market life cycle, but also enhances its adaptability to application under light conditions. Detailed Implementation

[0022] The specific embodiments listed in this invention are merely examples, and the invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of this invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of this invention should be covered within its scope. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are commercially available conventional products. To better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Unless otherwise specified, all units used in this specification are International Standard Units (SI), and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors unavoidable in industrial production.

[0024] The hyperbranched polyester was purchased from Weihua Chenyuan Chemical Co., Ltd. as ET06-48 product; The ordinary PET was purchased from China Resources New Materials Co., Ltd., grade 8816; The low-viscosity special copolyester G158A is a product of Sichuan Yibin Plus Packaging Materials Co., Ltd.

[0025] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0026] Example 1 Low viscosity special copolyester G158A 92.9%; PET-400 6%; inorganic pigment 0.1%; hyperbranched polyester 1%.

[0027] The above-mentioned additives and raw materials are fed into a TSE-75 twin-screw granulator via a loss-in-weight weighing system to produce the final masterbatch. The granulation temperature is 265℃, and the screw speed is 385 r / min.

[0028] After granulation, 0.5% by mass of masterbatch and 99.5% by mass of RPET were used to injection mold a color swatch. The injection temperature was 275℃ and the mold cooling temperature was 20℃. Test results: injection pressure: 30 bar, color swatch light transmittance 87.6%, haze 3%, b-value: 1.5.

[0029] Example 2 Example 2 is a further improvement on Example 1; the difference from Example 1 is that the masterbatch formulation is different.

[0030] Low viscosity special copolyester G158A 95.5%; PET-400 4%; hyperbranched polyester 0.5%.

[0031] After granulation according to the method of Example 1, 2.5% by mass of masterbatch and 97.5% by mass of RPET were used to produce color swatches through the same injection molding process as in Example 1. Test results: Injection pressure of color swatches: 28 bar, light transmittance: 89%, haze: 1%.

[0032] Example 3 Example 3 is a further improvement on Example 1; the difference from Example 1 is that the masterbatch formulation is different.

[0033] Ordinary PET (viscosity 0.8 dl / g): 95.5%; PET-400: 4%; Hyperbranched polyester: 0.5%.

[0034] After granulation according to the method of Example 1, 2.5% by mass of masterbatch and 97.5% by mass of RPET were used to produce color swatches through the same injection molding process as in Example 1. Test results: Injection pressure of color swatches: 40 bar, light transmittance: 86.3%, haze: 5.2%.

[0035] Example 4 Example 4 is a further improvement on Example 1; the difference from Example 1 is that the masterbatch formulation is different.

[0036] Low viscosity special copolyester G158A: 91.5%; small molecule polyester PET-400: 8%; hyperbranched polyester: 0.5%.

[0037] After granulation according to the method of Example 1, 2.5% by mass of masterbatch and 97.5% by mass of RPET were used to produce color swatches through the same injection molding process as in Example 1. Test results: Injection pressure of color swatches: 20 bar, light transmittance: 88%, haze: 2.8%.

[0038] Example 5 Example 5 is a further improvement on Example 1; the difference from Example 1 is that the masterbatch formulation is different.

[0039] Low viscosity special copolyester G158A: 93.5%; small molecule polyester PET-400: 6%; hyperbranched polyester: 0.5%.

[0040] After granulation according to the method of Example 1, 2.5% by mass of masterbatch and 97.5% by mass of RPET were used to produce color swatches through the same injection molding process as in Example 1. Test results: Injection pressure of color swatches: 25 bar, light transmittance 89.7%, haze 0.8%, b-value 1.5.

[0041] Example 6 Example 6 is a further improvement on Example 1; the difference from Example 1 is that the masterbatch formulation is different.

[0042] Low viscosity special copolyester G158A: 92.5%; small molecule polyester PET-400: 6%; hyperbranched polyester: 1.5%.

[0043] After granulation according to the method of Example 1, 2.5% by mass of masterbatch and 97.5% by mass of RPET were used to produce color swatches through the same injection molding process as in Example 1. Test results: Injection pressure of color swatches: 20 bar, light transmittance 87.9%, haze 3.7, b-value 1.8.

[0044] Example 7 Example 7 is a further improvement on Example 1; the difference from Example 1 is that the masterbatch formulation is different.

[0045] Low viscosity special copolyester G158A: 93.4%; small molecule polyester PET-400: 6%; hyperbranched polyester: 0.5%; cobalt acetate: 0.1%.

[0046] After granulation according to the method of Example 1, 2.5% by mass of masterbatch and 97.5% by mass of RPET were used to produce color swatches through the same injection molding process as in Example 1. Test results: Injection pressure of color swatches: 25 bar, light transmittance: 90%, haze: 0.6, b-value: -2.

[0047] Example 8 Example 8 is a further improvement on Example 1; the difference from Example 1 is that the masterbatch formulation is different.

[0048] Low viscosity special copolyester G158A: 93.3%; small molecule polyester PET-400: 6%; hyperbranched polyester: 0.5%; cobalt acetate: 0.2%.

[0049] After granulation according to the method of Example 1, 2.5% by mass of masterbatch and 97.5% by mass of RPET were used to produce color swatches through the same injection molding process as in Example 1. Test results: Color swatch injection pressure: 24 (bar), light transmittance 90%, haze 0.6, b-value -3.

[0050] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A masterbatch that can reduce RPET injection molding pressure and improve RPET transparency, characterized in that, Raw materials including the following mass fractions: Low viscosity special copolyester 90-96%, small molecule polyester PET-400 4-8% and hyperbranched polyester 0.5-1.8%.

2. The masterbatch according to claim 1, which can reduce RPET injection molding pressure and improve RPET transparency, is characterized in that, It also includes 0.1-0.2% inorganic pigments.

3. The masterbatch according to claim 1, which can reduce RPET injection molding pressure and improve RPET transparency, is characterized in that, The viscosity of the low-viscosity special copolyester is 0.58-0.65 dl / g, and the low-viscosity special copolyester is G158A.

4. The masterbatch according to claim 2, which can reduce RPET injection molding pressure and improve RPET transparency, is characterized in that, The inorganic pigment is cobalt acetate.

5. The masterbatch according to claim 1, which can reduce RPET injection molding pressure and improve RPET transparency, is characterized in that, Raw materials including the following mass fractions: Low viscosity special copolyester 93-96%, small molecule polyester PET-400 4-8% and hyperbranched polyester 0.5-1%.

6. A method for preparing a masterbatch that can reduce RPET injection molding pressure and improve RPET transparency according to any one of claims 1-5, characterized in that, Includes the following steps: The raw materials are added to a TSE-75 twin-screw granulator in proportion, the granulation temperature is controlled at 245-270℃, and the screw speed is 300-500 r / min to obtain the final masterbatch.

7. The method for preparing a masterbatch that can reduce RPET injection molding pressure and improve RPET transparency according to claim 6, characterized in that, Granulation temperature is controlled at 260-270℃, and screw speed is 370-400 r / min.

8. The method for preparing a masterbatch that can reduce RPET injection molding pressure and improve RPET transparency according to claim 7, characterized in that, The granulation temperature is controlled at 265℃ and the screw speed is 385 r / min.

9. A method for using a masterbatch according to any one of claims 1-5 that can reduce RPET injection molding pressure and improve RPET transparency, characterized in that, Includes the following steps: The granulated masterbatch is mixed with RPET at a mass ratio of 0.5%-2.5%, and the mixture is then injected to obtain a color sample. The injection temperature is 265-275℃, and the mold cooling temperature is 18-25℃.

10. A method for using a masterbatch according to claim 9, which can reduce RPET injection molding pressure and improve RPET transparency, characterized in that, Injection temperature 275℃, mold cooling temperature 20℃.