Stabilizer for transparent PVC product with good gamma-ray irradiation resistance

Abstract

The invention discloses a stabilizer for a transparent PVC (Polyvinyl Chloride) product with good gamma-ray irradiation resistance. Comprising the following components in parts by weight: 10-20 parts of benzoic acid organic calcium salt, 10-20 parts of benzoic acid organic zinc salt, 10-20 parts of benzoic acid organic magnesium salt, 10-20 parts of benzoic acid organic aluminum salt, 20-30 parts of hydrotalcite, 5-10 parts of borate, 3-10 parts of a pyrimidine auxiliary color retention agent, 3-10 parts of a hindered amine light stabilizer and 5-10 parts of a thioester antioxidant. The hindered amine light stabilizer is a light stabilizer with a hindered amine methyl piperidine structure. The transparent PVC product added with the stabilizer has excellent gamma-ray irradiation resistance, and after the irradiation dose is 25kGy, the yellowness index YI of the transparent PVC product is less than 5.0, which indicates that the transparent PVC product added with the stabilizer does not change color in later application and storage processes after gamma-ray irradiation; the transparency is kept well, the light transmittance after irradiation is greater than 85%, and the transparency requirements of medical and food packaging are met; the mechanical property is well maintained, and the tensile strength retention rate after irradiation is greater than 90%.

Description

Technical Field

[0001] This invention relates to the field of PVC product processing technology, and specifically to a stabilizer for transparent PVC products with good resistance to gamma-ray irradiation. Background Technology

[0002] Polyvinyl chloride (PVC) is a widely used general-purpose plastic. Its transparent products (such as films and sheets) are extensively used in medical infusion bags and food packaging films due to their low cost and good processability. However, after PVC products are sterilized by gamma-ray irradiation (common dose 25-50 kGy), free radical degradation occurs, leading to the breakage of PVC macromolecular chains and the formation of conjugated double bonds. This causes the product to darken in color, increase the yellowness index (YI), and decrease mechanical properties such as tensile strength and elongation at break, affecting its service life. Furthermore, the precipitation of degradation products or stabilizers also reduces the transparency of PVC products. Traditional PVC stabilizers, such as calcium-zinc stabilizers (calcium stearate and zinc stearate systems) and organotin stabilizers, while improving thermal stability, lack sufficient resistance to gamma-ray irradiation and cannot meet the requirements of medical and food packaging. Therefore, developing a stabilizer for transparent PVC products with good resistance to gamma-ray irradiation has become an urgent problem for the industry. Summary of the Invention

[0003] The purpose of this invention is to overcome the deficiencies in the existing technology and provide a stabilizer for transparent PVC products with good resistance to gamma-ray irradiation. This stabilizer is synergistically compounded from benzoic acid organic calcium salts, benzoic acid organic zinc salts, benzoic acid organic magnesium salts, benzoic acid organic aluminum salts, hydrotalcite, borates, pyrimidine auxiliary color-retaining agents, hindered amine light stabilizers, and thioester antioxidants. Transparent PVC products containing this stabilizer exhibit excellent resistance to gamma-ray irradiation; after an irradiation dose of 25 kGy, the yellowness index (γ) of the transparent PVC product is significantly reduced. A value of I < 5.0 indicates that transparent PVC products containing the stabilizer of this invention do not discolor during later application and storage after γ-ray irradiation; transparent PVC products containing the stabilizer of this invention maintain good transparency after irradiation with a dose of 25 kGy of γ-rays, with a light transmittance > 85% after irradiation, meeting the transparency requirements for medical and food packaging; transparent PVC products containing the stabilizer of this invention maintain good mechanical properties after irradiation with a dose of 25 kGy of γ-rays, with a tensile strength retention rate > 90% after irradiation.

[0004] To achieve the above objectives, the technical solution of this invention is to design a stabilizer for transparent PVC products with good resistance to gamma ray irradiation, comprising the following weight components: 10-20 parts of benzoic acid organic calcium salt, 10-20 parts of benzoic acid organic zinc salt, 10-20 parts of benzoic acid organic magnesium salt, 10-20 parts of benzoic acid organic aluminum salt, 20-30 parts of hydrotalcite, 5-10 parts of borate, 3-10 parts of pyrimidine auxiliary color retainer, 3-10 parts of hindered amine light stabilizer, and 5-10 parts of thioester antioxidant, wherein the hindered amine light stabilizer is a light stabilizer with a hindered amine methylpiperidine structure.

[0005] The preferred technical solution is that the benzoic acid organic calcium salt is one or more of calcium benzoate, calcium p-tert-butylbenzoate, and calcium p-nitroformate.

[0006] Another preferred technical solution is that the benzoic acid organic zinc salt is one or more of zinc benzoate, zinc p-tert-butylbenzoate, and zinc p-nitrobenzene.

[0007] Another preferred technical solution is that the benzoic acid organic magnesium salt is one or more of magnesium benzoate, magnesium p-tert-butylbenzoate, and magnesium p-nitroformate.

[0008] Another preferred technical solution is that the benzoic acid organoaluminum salt is one or more of aluminum benzoate, aluminum p-tert-butylbenzoate, and aluminum p-nitroformate.

[0009] Another preferred technical solution is that the hydrotalcite is a magnesium-aluminum-zinc ternary hydrotalcite with a zinc content of 10%-15%.

[0010] Another preferred technical solution is that the borate is one or more of zinc borate, calcium borate, magnesium borate, and aluminum borate.

[0011] Another preferred technical solution is that the pyrimidine-based auxiliary color retainer is 6-amino-1,3-dimethyluracil.

[0012] A preferred technical solution is that the light stabilizer with the hindered amine-methylpiperidine structure is one or more of the following: benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, sebacate bis(2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) ester of phosphite, and bis(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) ester of 2-ethyl-2-(4-hydroxy-3,5-tertiary butylbenzyl)malonate.

[0013] Another preferred technical solution is that the thioester antioxidant is one or two of dioctadecyl thiodipropionate and dilaurate thiodipropionate.

[0014] The core design concept of this invention is synergistic effect. It involves combining benzoic acid organic calcium salts, benzoic acid organic zinc salts, benzoic acid organic magnesium salts, benzoic acid organic aluminum salts, hydrotalcite, borates, pyrimidine auxiliary color-retaining agents, hindered amine light stabilizers, and thioester antioxidants to form a transparent PVC product stabilizer with good resistance to gamma-ray radiation.

[0015] (1) Benzoic acid organic calcium salts, benzoic acid organic zinc salts, benzoic acid organic magnesium salts, benzoic acid organic aluminum salts, hydrotalcite, and pyrimidine auxiliary color retainers primarily ensure the thermal stability and good initial color of PVC products during heat processing. The main mechanism is that benzoic acid organic zinc salts and aluminum salts have higher metal content than traditional metal soaps such as zinc stearate and aluminum stearate, which can more efficiently replace unstable chloride ions on the PVC chain. Similarly, benzoic acid organic calcium salts and magnesium salts, due to their high metal content, can efficiently replace metal chlorides that catalyze the deHCl removal of the PVC chain, inhibit the formation of conjugated double bonds in the PVC chain, and prevent PVC from yellowing. 6-Amino-1,3-dimethyluridine auxiliary color retainer can synergistically replace unstable chloride ions in the PVC chain with benzoic acid metal salts, allowing PVC to maintain a good initial color. Ternary hydrotalcite has a high metal cation content and a large interlayer spacing, resulting in stronger ion exchange capacity and adsorption, and more efficiently absorbs HCl gas, preventing PVC from degrading and yellowing. The above-mentioned components work synergistically to form a stabilizer for transparent PVC products with good resistance to gamma ray irradiation. This ensures that transparent PVC products have a good initial color after processing and avoids the phenomenon that the yellowish base color will become even more yellow after gamma ray irradiation.

[0016] (2) When transparent PVC products are irradiated with gamma rays, the high-energy gamma rays rapidly penetrate the PVC and generate a large number of free radicals and excited state energy, causing the PVC to discolor. Nano-zinc borate is introduced into the stabilizer because the boron element in it has a strong absorption capacity for neutrons, which can effectively reduce the intensity of neutron radiation. Simultaneously, it interacts with gamma rays to generate boron oxide compounds, which can neutralize the free radicals generated by gamma ray irradiation, reducing the attack of free radicals on PVC chain segments and preventing the formation of conjugated double bonds, thereby reducing the probability of yellowing of irradiated PVC products. The nitroxide free radical structure of the methylpiperidine light stabilizer can quench the excited state energy generated by gamma ray irradiation in the polymer through its mechanism, terminating the irradiation chain degradation reaction of PVC products, thereby further protecting PVC products from light damage and reducing the probability or degree of yellowing. With the irradiation of high-energy gamma rays, the unstable chloride ions in PVC products will react more actively during this process, and the risk of yellowing of PVC products will be greater. Therefore, benzoic acid organic calcium salts, benzoic acid organic zinc salts, benzoic acid organic magnesium salts, benzoic acid organic aluminum salts and 6-amino-1,3-dimethyluridine auxiliary color retainers can replace these chloride ions and prevent the yellowing caused by PVC chain dehydrochlorination.

[0017] (3) The stabilizer selected is a combination of dioctadecyl thiodipropionate and dilauric acid thiodipropionate antioxidants, which can inhibit the phenolic yellowing phenomenon that is easily caused by traditional hindered phenolic antioxidants such as 1076 and 1010 under the action of light and heat, and ensure that transparent PVC products do not change color in the later application and storage after being irradiated by γ-rays.

[0018] The advantages and beneficial effects of this invention are as follows:

[0019] 1. The present invention provides a stabilizer for transparent PVC products with good resistance to gamma ray irradiation. It is composed of benzoic acid organic calcium salt, benzoic acid organic zinc salt, benzoic acid organic magnesium salt, benzoic acid organic aluminum salt, hydrotalcite, borates, pyrimidine auxiliary color retainers, hindered amine light stabilizers, and thioester antioxidants in a synergistic compound. Transparent PVC products with the stabilizer of the present invention exhibit excellent resistance to gamma ray irradiation. After an irradiation dose of 25 kGy, the yellowness index YI of the transparent PVC products is <5.0 (the yellowness index YI of transparent PVC products using traditional PVC stabilizers is 10.23), indicating that the transparent PVC products with the stabilizer of the present invention do not change color after gamma ray irradiation during later application and storage.

[0020] 2. Transparent PVC products containing the stabilizer for transparent PVC products with good resistance to gamma ray irradiation according to the present invention maintain good transparency after irradiation with a gamma ray dose of 25 kGy, with a light transmittance of >85% after irradiation (the light transmittance of transparent PVC products using traditional PVC stabilizers is 70% after irradiation), meeting the transparency requirements for medical and food packaging.

[0021] 3. Transparent PVC products containing the stabilizer of the present invention, which has good resistance to gamma ray irradiation, maintain good mechanical properties after gamma ray irradiation with an irradiation dose of 25 kGy, with a tensile strength retention rate of >90% after irradiation (the tensile strength retention rate of transparent PVC products using traditional PVC stabilizers is 72%). Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0023] The main equipment used in this embodiment is: Bell SRL-Z100 / 200L vertical mixing unit, Collin single screw extruder, Collin twin-roll open mill, Collin flat vulcanizing machine, and Instron tensile testing machine.

[0024] All raw materials used in this embodiment are commercially available, mainly including: calcium benzoate, calcium p-tert-butylbenzoate, zinc benzoate, zinc p-tert-butylbenzoate, magnesium benzoate, magnesium p-tert-butylbenzoate, aluminum p-tert-butylbenzoate, ternary hydrotalcite, 6-amino-1,3-dimethyluracil, benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, dioctadecyl thiodipropionate, PVC type V resin powder, DOTP plasticizer, epoxidized soybean oil (ESBO), etc., and Xiong brand transparent calcium-zinc stabilizer MC 1700P (Bairloch New Material Technology Co., Ltd.).

[0025] Example 1

[0026] A stabilizer for transparent PVC products with good resistance to gamma-ray radiation, comprising the following components by weight:

[0027] 10 parts calcium benzoate, 10 parts zinc benzoate, 10 parts magnesium benzoate, 10 parts aluminum benzoate, 20 parts ternary hydrotalcite (zinc content 15%), 5 parts nano zinc borate, 3 parts 6-amino-1,3-dimethyluracil, 3 parts benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, and 5 parts dioctadecyl thiodipropionate.

[0028] Example 2

[0029] A stabilizer for transparent PVC products with good resistance to gamma-ray radiation, comprising the following components by weight:

[0030] 15 parts calcium benzoate, 15 parts zinc benzoate, 15 parts magnesium benzoate, 15 parts aluminum benzoate, 25 parts ternary hydrotalcite (zinc content 15%), 7.5 parts nano zinc borate, 6 parts 6-amino-1,3-dimethyluracil, 6 parts benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, and 7.5 parts dioctadecyl thiodipropionate.

[0031] Example 3

[0032] A stabilizer for transparent PVC products with good resistance to gamma-ray radiation, comprising the following components by weight:

[0033] 20 parts calcium benzoate, 20 parts zinc benzoate, 20 parts magnesium benzoate, 20 parts aluminum benzoate, 30 parts ternary hydrotalcite (zinc content 15%), 10 parts nano zinc borate, 10 parts 6-amino-1,3-dimethyluracil, 10 parts benzoic acid (2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, and 10 parts dioctadecyl thiodipropionate.

[0034] Example 4

[0035] A stabilizer for transparent PVC products with good resistance to gamma-ray radiation, comprising the following components by weight:

[0036] 10 parts of calcium p-tert-butylbenzoate, 10 parts of zinc p-tert-butylbenzoate, 10 parts of magnesium p-tert-butylbenzoate, 10 parts of aluminum p-tert-butylbenzoate, 20 parts of ternary hydrotalcite (zinc content 15%), 5 parts of nano zinc borate, 3 parts of 6-amino-1,3-dimethyluracil, 3 parts of sebacic acid bis(2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, and 5 parts of thiodipropionic acid dilaurate.

[0037] Example 5

[0038] A stabilizer for transparent PVC products with good resistance to gamma-ray radiation, comprising the following components by weight:

[0039] 5 parts calcium benzoate, 10 parts p-tert-butylbenzoate, 5 parts zinc benzoate, 10 parts p-tert-butylbenzoate, 5 parts magnesium benzoate, 10 parts p-tert-butylbenzoate, 5 parts aluminum benzoate, 10 parts p-tert-butylbenzoate, 25 parts ternary hydrotalcite (zinc content 12%), 4 parts nano zinc borate, 4 parts nano calcium borate, 6 parts 6-amino-1,3-dimethyluracil, 3 parts benzoate (2,2,6,6-tetramethyl-4-hydroxypiperidine), 3 parts sebacic acid bis(2,2,6,6-tetramethyl-4-hydroxypiperidine), 4 parts dioctadecyl thiodipropionate, 4 parts dilaurate thiodipropionate.

[0040] Example 6

[0041] A stabilizer for transparent PVC products with good resistance to gamma-ray radiation, comprising the following components by weight:

[0042] Calcium benzoate 6 parts, p-tert-butylbenzoate 7 parts, calcium p-nitroformate 7 parts, zinc benzoate 6 parts, p-tert-butylbenzoate 7 parts, zinc p-nitroformate 7 parts, magnesium benzoate 6 parts, p-tert-butylbenzoate 7 parts, magnesium p-nitroformate 7 parts, aluminum benzoate 6 parts, p-tert-butylbenzoate 7 parts, aluminum p-nitroformate 7 parts, ternary hydrotalcite 30 parts (zinc content 10%), nano zinc borate 3 parts, nano magnesium borate 3 parts, nano aluminum borate 4 parts, 6-amino 10 parts of 1,3-dimethyluracil, 3 parts of bis(2,2,6,6-tetramethyl-4-hydroxypiperidine) sebacate, 3 parts of tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) phosphite, 4 parts of bis(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) 2-ethyl-2-(4-hydroxy-3,5-tertiary butylbenzyl)malonate, 5 parts of dioctadecyl thiodipropionate, and 5 parts of dilaurate thiodipropionate.

[0043] Comparative Example 1

[0044] A stabilizer for transparent PVC products, comprising the following components by weight:

[0045] 10 parts of calcium p-tert-butylbenzoate, 10 parts of zinc p-tert-butylbenzoate, 10 parts of magnesium p-tert-butylbenzoate, 10 parts of aluminum p-tert-butylbenzoate, 20 parts of ternary hydrotalcite (zinc content 15%), 3 parts of 6-amino-1,3-dimethyluracil, 3 parts of sebacate bis(2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, and 5 parts of thiodipropionic acid dilaurate.

[0046] Comparative Example 2

[0047] A stabilizer for transparent PVC products, comprising the following components by weight:

[0048] 10 parts of calcium p-tert-butylbenzoate, 10 parts of zinc p-tert-butylbenzoate, 10 parts of magnesium p-tert-butylbenzoate, 10 parts of aluminum p-tert-butylbenzoate, 20 parts of ternary hydrotalcite (zinc content 15%), 5 parts of nano zinc borate, 3 parts of 6-amino-1,3-dimethyluridine, and 5 parts of dilaurate thiodipropionate.

[0049] Comparative Example 3

[0050] A stabilizer for transparent PVC products, comprising the following components by weight:

[0051] 10 parts of calcium p-tert-butylbenzoate, 10 parts of zinc p-tert-butylbenzoate, 10 parts of magnesium p-tert-butylbenzoate, 10 parts of aluminum p-tert-butylbenzoate, 20 parts of ternary hydrotalcite (zinc content is 15%), 3 parts of 6-amino-1,3-dimethyluracil, and 5 parts of dilaurate thiodipropionate.

[0052] Comparative Example 4

[0053] A stabilizer for transparent PVC products, comprising the following components by weight:

[0054] 10 parts of calcium p-tert-butylbenzoate, 10 parts of zinc p-tert-butylbenzoate, 10 parts of magnesium p-tert-butylbenzoate, 10 parts of aluminum p-tert-butylbenzoate, 20 parts of ternary hydrotalcite (zinc content 15%), 5 parts of nano zinc borate, 3 parts of sebacic acid bis(2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, and 5 parts of thiodipropionic acid dilaurate.

[0055] Comparative Example 5

[0056] A stabilizer for transparent PVC products, comprising the following components by weight:

[0057] 10 parts of calcium p-tert-butylbenzoate, 10 parts of zinc p-tert-butylbenzoate, 10 parts of magnesium p-tert-butylbenzoate, 10 parts of aluminum p-tert-butylbenzoate, 20 parts of ternary hydrotalcite (zinc content 15%), 5 parts of nano zinc borate, 3 parts of 6-amino-1,3-dimethyluracil, 3 parts of sebacic acid bis(2,2,6,6-tetramethyl-4-hydroxypiperidine) ester, and 5 parts of thiodipropionic acid dilaurate.

[0058] Comparative Example 6

[0059] Bear Brand Transparent Calcium-Zinc Stabilizer MC 1700P (Bairloch New Material Technology Co., Ltd.)

[0060] Table 1. Detailed list of weight components of stabilizers for transparent PVC products in Examples 1-6 and Comparative Examples 1-5.

[0061]

[0062] The raw materials of Examples 1-6 and Comparative Examples 1-5 were weighed according to the weight group distribution ratio in Table 1 and placed in the hopper of the Bell SRL-Z100 / 200L vertical mixer unit. The mixture was stirred at 600 rpm for more than 15 minutes to make the powder uniformly mixed, and PVC product stabilizers numbered S-01 to S-11 were obtained in sequence. The Xiong brand transparent calcium zinc stabilizer MC 1700P in Comparative Example 6 was numbered S-12.

[0063] Application Testing: The transparent PVC product stabilizers numbered S-01 to S-12 were used to prepare transparent PVC product mixtures, and the PVC product mixtures were numbered sequentially as Sample 1 to 12. The formulations are shown in Table 2 below:

[0064] Table 2. Detailed formulation of samples 1-12

[0065]

[0066]

[0067] Weigh the material components corresponding to samples 1 to 12 according to the formula in Table 2, and put the weighed material components into the hopper of the Collin single-screw extruder. Set the temperature of the Collin single-screw extruder to 150℃ in zone 1, 160℃ in zone 2, 165℃ in zone 3, and 165℃ at the extrusion die. Use the Collin single-screw extruder to granulate the material components corresponding to samples 1 to 12 into the corresponding sample 1 to 12 material masterbatches.

[0068] Samples 1 to 12 were processed into sheets 1 to 12 using a Collin two-roll open mill. The front and rear roll temperatures of the open mill were 175℃ and 170℃, respectively, and the rotation speeds were 20r / min and 18r / min, respectively, for a time of 5min. Sheets 1 to 12 were then pressed into sample sheets 1 to 12 with a size of 15cm×15cm and a thickness of 1mm using a Collin flat vulcanizing machine.

[0069] According to GB 16352-1996 "Standard for Sterilization by Gamma Ray Radiation of Disposable Medical Products", samples 1-12 were subjected to gamma ray irradiation tests with an irradiation dose of 25 kGy; according to GB / T 2410-2008 "Determination of Light Transmittance and Haze of Transparent Plastics", the transparency of samples 1-12 before and after gamma ray irradiation was tested; according to GBT1040.2-2006 "Determination of Tensile Properties of Plastics", the tensile mechanical properties of samples 1-12 before and after gamma ray irradiation were tested.

[0070] Table 3. Detailed color changes of samples 1-12 before and after gamma-ray irradiation test.

[0071]

[0072] Note: YI is the yellowness index.

[0073] The data in Table 3 show that the initial colors of samples 1-9 and sample 11 before γ-ray irradiation were not significantly different, while sample 10 (using the transparent PVC product stabilizer in Comparative Example 4) had a yellowish initial color before γ-ray irradiation. This indicates that pyrimidine-based auxiliary color retainers (6-amino-1,3-dimethyluracil) can effectively improve the yellowness index (YI) of transparent PVC products. Samples 1-6 (using the transparent PVC product stabilizers with good γ-ray irradiation resistance in Examples 1-6) maintained a yellowness index (YI) below 5.0 after γ-ray irradiation, while sample 12 (using the Xiong brand transparent calcium-zinc stabilizer MC in Comparative Example 6)... The yellowness index (YI) of sample 1700P reached 10.23 after γ-ray irradiation, indicating severe yellowing. This demonstrates that the stabilizer for transparent PVC products with good γ-ray irradiation resistance of this invention can effectively resist γ-ray irradiation in transparent PVC products. Comparing the yellowness index (YI) of samples 4 and 7-11, it can be seen that the yellowness index (YI) of samples 7-11 increased significantly after γ-ray irradiation. This indicates that the stabilizer for transparent PVC products with good γ-ray irradiation resistance of this invention, which is synergistically compounded with benzoic acid organic calcium salt, benzoic acid organic zinc salt, benzoic acid organic magnesium salt, benzoic acid organic aluminum salt, hydrotalcite, borates, pyrimidine auxiliary color retaining agents, hindered amine light stabilizers, and thioester antioxidants in a certain proportion, has a synergistic γ-ray irradiation resistance effect in transparent PVC products. However, the stabilizer for transparent PVC products lacking one or more of these components exhibits a correspondingly weakened γ-ray irradiation resistance effect.

[0074] Table 4 shows the transparency (haze value) test results of samples 1-12 before and after gamma-ray irradiation.

[0075]

[0076] As can be seen from the data in Table 4, the transmittance of samples 1-12 before γ-ray irradiation was ≥88%. Among them, the transmittance of samples 7-12 (using the transparent PVC product stabilizers in Comparative Examples 1-6) after γ-ray irradiation was <80%, especially sample 12 (using the Xiong brand transparent calcium-zinc stabilizer MC 1700P in Comparative Example 6), whose transmittance was only 70% after γ-ray irradiation. This is because the color of samples 7-12 turned yellow significantly after γ-ray irradiation, resulting in a decrease in transparency and a severe reduction in transmittance. On the other hand, the transmittance of samples 1-6 (using the transparent PVC product stabilizers with good γ-ray irradiation resistance in Examples 1-6) did not decrease much after γ-ray irradiation, and the transmittance of samples 1-6 was ≥87% after γ-ray irradiation. This indicates that the transparent PVC products using the transparent PVC product stabilizers with good γ-ray irradiation resistance of the present invention maintain good transparency after γ-ray irradiation.

[0077] Table 5 shows the tensile properties of samples 1-12 before and after gamma-ray irradiation.

[0078]

[0079]

[0080] As can be seen from the data in Table 5, the tensile strengths of samples 1-12 before γ-ray irradiation were not significantly different. Among them, the tensile strength retention rate of samples 7-12 (using the transparent PVC product stabilizers in Comparative Examples 1-6) after γ-ray irradiation was all <85%, indicating that the PVC molecular chains of samples 7-12 were severely broken after γ-ray irradiation, which destroyed the original molecular structure and led to a decrease in the mechanical tensile properties of the transparent PVC products. On the other hand, the tensile strength retention rate of samples 1-6 (using the transparent PVC product stabilizers with good γ-ray irradiation resistance in Examples 1-6) after γ-ray irradiation was all ≥91%, indicating that the transparent PVC products using the transparent PVC product stabilizers with good γ-ray irradiation resistance of the present invention had a good tensile property retention rate after γ-ray irradiation.

[0081] This invention discloses a stabilizer for transparent PVC products with excellent resistance to gamma-ray irradiation. It is composed of benzoic acid organic calcium salts, benzoic acid organic zinc salts, benzoic acid organic magnesium salts, benzoic acid organic aluminum salts, hydrotalcite, borates, pyrimidine auxiliary color-retaining agents, hindered amine light stabilizers, and thioester antioxidants in a synergistic compound. Transparent PVC products containing this stabilizer exhibit excellent resistance to gamma-ray irradiation. After irradiation at a dose of 25 kGy, the yellowness index (YI) of the transparent PVC products is <5.0, indicating that the transparent PVC products containing this stabilizer do not discolor during later application and storage after gamma-ray irradiation. Transparent PVC products containing this stabilizer maintain good transparency after irradiation at a dose of 25 kGy, with a light transmittance >85%, meeting the transparency requirements for medical and food packaging. Transparent PVC products containing this stabilizer also maintain good mechanical properties after irradiation at a dose of 25 kGy, with a tensile strength retention rate >90%.

[0082] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A stabilizer for transparent PVC products with good resistance to gamma-ray radiation, characterized in that, It comprises the following components by weight: 10-20 parts of benzoic acid organic calcium salt, 10-20 parts of benzoic acid organic zinc salt, 10-20 parts of benzoic acid organic magnesium salt, 10-20 parts of benzoic acid organic aluminum salt, 20-30 parts of hydrotalcite, 5-10 parts of borates, 3-10 parts of pyrimidine auxiliary color retainer, 3-10 parts of hindered amine light stabilizer, and 5-10 parts of thioester antioxidant, wherein the hindered amine light stabilizer is a light stabilizer with a hindered amine methylpiperidine structure.

2. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The benzoic acid organic calcium salts mentioned are one or more of calcium benzoate, calcium p-tert-butylbenzoate, and calcium p-nitroformate.

3. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The benzoic acid organic zinc salt is one or more of zinc benzoate, zinc p-tert-butylbenzoate, and zinc p-nitrobenzene.

4. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The benzoic acid-based organic magnesium salt is one or more of magnesium benzoate, magnesium p-tert-butylbenzoate, and magnesium p-nitroformate.

5. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The benzoic acid organoaluminum salts mentioned are one or more of aluminum benzoate, aluminum p-tert-butylbenzoate, and aluminum p-nitroformate.

6. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The hydrotalcite mentioned is a magnesium-aluminum-zinc ternary hydrotalcite with a zinc content of 10%-15%.

7. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The borates mentioned are one or more of zinc borate, calcium borate, magnesium borate, and aluminum borate.

8. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The pyrimidine-based auxiliary color-retaining agent is 6-amino-1,3-dimethyluracil.

9. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The hindered amine-methylpiperidine light stabilizer is one or more of the following: (2,2,6,6-tetramethyl-4-hydroxypiperidine) benzoate, bis(2,2,6,6-tetramethyl-4-hydroxypiperidine) sebacate, tris(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) phosphite, and bis(1,2,2,6,6-pentamethyl-4-hydroxypiperidine) 2-ethyl-2-(4-hydroxy-3,5-tertiary butylbenzyl)malonate.

10. The stabilizer for transparent PVC products with good resistance to gamma-ray radiation as described in claim 1, characterized in that, The thioester antioxidant is one or both of dioctadecyl thiodipropionate and dilaurate thiodipropionate.

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