Polyolefin compound

Abstract

The invention belongs to the technical field of high polymer materials, and particularly relates to a polyolefin compound. The polyolefin compound provided by the invention comprises the following components in parts by mass: 100 parts of polyolefin, 10 parts of natural antioxidant and 10 parts of hydrotalcite. 0.05 to 2.0 parts of a natural antioxidant; 0.02 to 3.0 parts of hydrotalcite; in addition, other auxiliaries or modifiers can also be contained. According to the invention, a natural antioxidant is used for replacing a synthetic antioxidant; due to the addition of hydrotalcite, the dispersion of the natural antioxidant is promoted, and the negative effect between the natural antioxidant and the catalyst residue is prevented by absorbing the catalyst residue in polyolefin, so that the antioxidant efficiency of the natural antioxidant is improved; the problems that polyolefin is poor in thermal stability when low content of natural antioxidants are independently used, the cost is high due to high content of the natural antioxidants, the color difference of products is poor, and the requirements of polyolefin processing and application cannot be met are solved. The polyolefin compound has excellent thermal processing stability and long-term stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a polyolefin blend. Background Art

[0002] During the processes of processing, storing, and using polyolefins in the presence of oxygen, oxidation will occur under the action of high temperature, mechanical stress, and other factors, leading to serious deterioration of the appearance and important application properties of the material. Adding antioxidants is the main means to delay oxidation and improve the stability of the material. Currently, the commonly used antioxidants in the polyolefin industry mainly include hindered phenol-based primary antioxidants and phosphite-based secondary antioxidants, and these antioxidants can provide effective thermal-oxidative protection for polyolefin materials. However, there are research reports that these synthetic antioxidants have certain toxicity (Environ Sci Technol 2023, 57, 21550-21557). For example, the hindered phenol antioxidant 3-tert-butyl-4-hydroxyanisole (BHA) has endocrine-disrupting effects and genotoxicity, and it will endanger the development of the brain and nerves when ingested by the human body. In addition, triphenyl phosphate (TPHP), as a phosphite antioxidant, has also been found to cause significant degeneration of axons and nerve endings in the central nervous system. If these synthetic antioxidants and their decomposition products migrate out of the polyolefin materials, they may pose certain hazards to human health and environmental safety. To address these potential risks, there is an urgent need to develop new non-toxic and environmentally friendly antioxidants suitable for polyolefin applications related to the human body. Against this background, natural antioxidants have attracted extensive attention due to their renewable and non-toxic characteristics.

[0003] There are a large number of natural antioxidants in nature, which have been widely used in the fields of food, medicine, feed, cosmetics and so on. Many researchers have tried to use these natural antioxidants in polyolefins. Natural antioxidants such as vitamin E, quercetin, β-carotene, lignin and curcumin have been proven to still play an antioxidant effect in polyolefins. Among various natural antioxidants, vitamin E is a type that has been commercially applied in polyolefins so far. So far, it has been applied to ultra-high molecular weight polyethylene bone joint transplantation materials, as well as active packaging of low-density polyethylene and linear low-density polyethylene. However, even for the relatively mature natural antioxidant vitamin E, there are still some problems in its application in polyolefins. Vitamin E has a good stabilizing effect on polyolefins only when the dosage is relatively high. Considering the relatively high price and certain color of vitamin E, the large use of vitamin E in polyolefins not only increases the production cost, but also makes the polyolefin products seriously discolored, which is not conducive to the application of vitamin E in products sensitive to appearance (such as transparent packaging films). When the dosage of vitamin E is low (<0.2%), its stabilizing effect is limited. For example, some studies have found that at a content of 0.1wt%, the long-term stabilizing efficiency of vitamin E is significantly lower than that of commonly used synthetic antioxidants (J Appl Polym Sci 2005, 98(6), 2427-2439). At present, in order to prepare polyolefin samples with high stability performance, many methods have been tried. It has been found in the literature that the compounding of vitamin E with auxiliary antioxidants such as phosphites can significantly improve the thermal-oxidative stability performance of polyolefin samples (Polym DegradStabil 1999, 64, 145-156); Chinese Patent CN117447768A uses the method of compounding vitamin E and synthetic hindered phenol antioxidants to improve the thermal-oxidative stability performance of polyolefins; these two methods still use synthetic antioxidants with potential toxicity risks, which obviously goes against the original intention of using natural antioxidants. Chinese Patents CN103270101A and CN110448723A use the method of compounding vitamin E with natural auxiliary antioxidants such as sugar alcohols and glutathione to improve the stability performance of polyolefins. However, these all-natural antioxidants have a large polarity difference from polyolefins and are not easily uniformly dispersed in the matrix, which may affect their stabilizing effect. Therefore, it is very urgent but currently quite lacking to develop polyolefin material production technologies that can fully exert the efficacy of natural antioxidants.

[0004] Hydrotalcite is a type of layered double metal hydroxide substance with a two-dimensional nanostructure, and its chemical composition can be expressed as M 1-x 2+ M x 3+ (OH)2A x / n n- ·yH2O, where M 2+ refers to divalent metal cations, M3+ refers to trivalent metal cations, A n- represents the anion between the lamellae, x is the proportion of trivalent metal cations, and y is the number of water molecules. Common M 2+ ions include Mg 2+ , Zn 2+ , Ni 2+ , Co 2+ , etc. Common M 3+ ions include Al 3+ , Fe 3+ , Cr 3+ , etc. Common anions include CO3 2- , NO 3- , Cl -etc. Different types of hydrotalcites can be obtained by adjusting the cations and anions therein. Hydrotalcite is usually used as a reinforcing agent, an acid scavenger for polyolefins, a heat stabilizer for polyvinyl chloride, etc. We found that the addition of a small amount of hydrotalcite can effectively improve the dispersion of natural antioxidants in polyolefins and contribute to the performance of natural antioxidants. On the other hand, at present, more than 70% of all polyolefin products used in industrial applications are produced by coordination polymerization technology mainly based on Ziegler-Natta (ZN) catalysts, including various linear low-density polyethylene, high-density polyethylene, and all isotactic, syndiotactic polypropylene, polybutene, etc. When applying natural antioxidants to such polyolefins, considering that these polyolefins inevitably contain acidic catalyst residues such as TiCl3 / TiCl4, AlR2Cl, their protective effects become particularly complicated. Research shows that these catalyst residues not only corrode metal processing equipment but also consume antioxidants and reduce the thermal-oxidative stability of materials. In polyolefins stabilized with synthetic antioxidants, acid scavengers are often added industrially to neutralize catalyst residues and protect the antioxidant efficiency of antioxidants. Unlike the variety of antioxidants, the acid scavengers commonly used in the olefin industry mainly include a few substances such as hydrotalcite, zinc stearate, and calcium stearate. It is the application of these acid scavengers that enables synthetic antioxidants to fully exert their stabilizing effects and improve the thermal-oxidative stability of ZN polyolefins. However, the protective effect of acid scavengers is closely related to the antioxidant itself. Therefore, when using natural antioxidants to stabilize ZN polyolefins, whether the acid scavengers developed for traditional synthetic antioxidants can also exhibit good protective effects on natural antioxidants depends on whether they can react preferentially with the catalyst without having adverse effects on natural antioxidants. If the acid scavenger used can neutralize catalyst residues without reacting with natural antioxidants, it can enable natural antioxidants to function efficiently. On the contrary, if the acid scavenger reacts preferentially with natural antioxidants rather than catalyst residues, it may not only fail to protect natural antioxidants but also become a new consumption source of natural antioxidants. If a substance can both promote the dispersion of natural antioxidants in polyolefins and protect natural antioxidants from the damage of catalyst residues, it can be developed into a new technology for efficiently utilizing natural antioxidants to develop high-performance and safer polyolefin materials. However, due to the complexity of this problem, no public literature has clarified the above issues or reported related technologies. Summary of the Invention

[0005] The object of the present invention is to provide a polyolefin blend having excellent thermal processing stability and long-term stability performance.

[0006] The polyolefin blend provided by the present invention has polyolefin as the main body, and its components further include a natural antioxidant and hydrotalcite. By mass, the components are:

[0007] 100 parts of polyolefin, 0.05 - 2.0 parts of natural antioxidant (relative to the amount of polyolefin), 0.02 - 3.0 parts of hydrotalcite (relative to the amount of polyolefin).

[0008] The natural antioxidant is a substance derived from natural sources and having antioxidant function. Specifically, such as vitamin E, quercetin, β-carotene, lignin and curcumin, preferably vitamin E.

[0009] Furthermore, the polyolefin can be a single polyolefin or a mixture of multiple polyolefins in any proportion;

[0010] Furthermore, the polyolefin can be polyethylene, polypropylene or polybutene. Preferably, it is linear low density polyethylene, high density polyethylene, isotactic polypropylene, etc. produced by coordination polymerization using Ziegler-Natta catalyst, metallocene catalyst, etc.

[0011] Furthermore, the hydrotalcite is preferably magnesium-aluminum hydrotalcite, also known as magnesium aluminum carbonate hydroxide hydrate.

[0012] Furthermore, the polyolefin blend may further include one or more other substances. These substances include, but are not limited to, nucleating agents, flame retardants, fillers, light stabilizers, lubricants, antistatic agents, impact modifiers, etc.

[0013] The preparation method of the polyolefin blend of the present invention is obtained by mixing the components evenly according to the above ratio. The mixing method includes any one of physical mixing, solution blending or melt blending.

[0014] The polyolefin blend provided by the present invention, which contains both natural antioxidant and hydrotalcite, uses natural antioxidant to replace synthetic antioxidant; on the one hand, the addition of hydrotalcite promotes the dispersion of natural antioxidant, and on the other hand, it prevents the negative effect of catalyst residues in the polyolefin on the natural antioxidant by absorbing them, thereby improving the antioxidant efficiency of the natural antioxidant, and solving the problems of poor thermal stability of polyolefin using natural antioxidant alone, high cost caused by using additional additives, poor color of products, and inability to meet the requirements of polyolefin processing applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the test result of melt flow rate (MFR) of samples with different extrusion times in Example 4 and Comparative Example 4 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be further introduced below through examples in combination with the drawings.

[0017] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the technical field to which this application pertains; other test methods and technical means not specifically noted in this application refer to the experimental methods and technical means commonly adopted by those of ordinary skill in the art.

[0018] To better illustrate the content of this application, numerous specific details are given in the following specific embodiments. Those skilled in the art should understand that this application can still be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well-known to those skilled in the art are not described in detail in order to highlight the gist of this application.

[0019] Example 1: Using a Hakke PolyLab OS torque rheometer (Thermo Fisher Scientific, USA), at 180 °C and 80 rpm, 100 parts of high-density polyethylene (produced using a Ziegler-Natta catalyst) (produced by PetroChina Dushanzi Petrochemical Company, grade N3000M), 0.05 parts of vitamin E (Shanghai Bide Pharmaceutical Technology Co., Ltd.), and 0.05 parts of hydrotalcite (Guangdong Chenghe Technology Co., Ltd.) were added to the mixing chamber. After melting and blending for 8 min, it was taken out, cooled, crushed, and pelletized to obtain the polyolefin blend. The oxidation induction time (OIT) and oxidation induction temperature (OOT) of the polyolefin blend were measured using a Q2000 (TA Instruments, USA) differential scanning calorimeter (DSC).

[0020] The specific test conditions are as follows:

[0021] OIT test: During the test, it was heated to 190 °C at 40 °C / min under a nitrogen atmosphere of 50 mL / min and stabilized for 3 min. Then, the gas was switched to air, and this time point was recorded as 0 min. The DSC curve was recorded. The time when the exothermic warp began to appear on the curve was recorded as the oxidation induction time. The longer the oxidation induction time, the better the stability performance of the polyolefin blend.

[0022] OOT test: During the test, it was heated at 10 °C / min under an air atmosphere of 50 mL / min, and the DSC curve was recorded. The temperature when the exothermic warp began to appear on the curve was recorded as the oxidation induction temperature. The higher the oxidation induction temperature, the better the stability performance of the polyolefin blend.

[0023] The results showed that the OIT of the polyolefin blend with 0.05% parts of vitamin E and 0.05% parts of hydrotalcite was 55.7 min, and the OOT was 234.7 °C.

[0024] Example 2, other conditions are the same as in Example 1, and the addition amount of vitamin E in the polyolefin blend is changed to 0.075 parts. The measured OIT is 69.9 min and the OOT is 242.6 °C.

[0025] Example 3, other conditions are the same as in Example 1, and the addition amount of vitamin E in the polyolefin blend is changed to 0.1 parts. The measured OIT is 134.1 min and the OOT is 248.6 °C.

[0026] Example 4, using a twin-screw extruder, at 190 °C and 80 rpm, 100 parts of high-density polyethylene, 0.05 parts of vitamin E and 0.05 parts of hydrotalcite are extruded once, three times, five times, and seven times. The melt flow rate (MFR, 190 °C, 5 kg) of the samples with different extrusion times is tested, and the obtained MFR results are shown in Figure 1 .

[0027] To further prove the beneficial effects of the present invention, the properties and application performance of the polyolefin blend disclosed in the present invention are further clarified through the following comparative examples.

[0028] Comparative Example 1, the sample preparation and detection methods are the same as in Example 1. The OIT of the polyolefin blend containing only 0.05 parts of vitamin E is 13.7 min, and the OOT is 212.4 °C.

[0029] Comparative Example 2, the sample preparation and detection methods are the same as in Example 1. The OIT of the polyolefin blend containing only 0.075 parts of vitamin E is 19.5 min, and the OOT is 228.7 °C.

[0030] Comparative Example 3, the sample preparation and detection methods are the same as in Example 1. The OIT of the polyolefin blend containing only 0.1 parts of vitamin E is 30.7 min, and the OOT is 235.5 °C.

[0031] Comparative Example 4, the sample preparation and detection methods are the same as in Example 4. The MFR results of the polyolefin blend containing only 0.05% parts of vitamin E at different extrusion times are as Figure 1 shown.

[0032] The results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1. It can be seen that, compared with Comparative Examples 1-3, the polyolefin blends disclosed in Examples 1-3 of the present invention have higher OIT and OOT values at the same vitamin E content, indicating that they have better thermal oxidation stability.

[0033] Table 1 OIT and OOT test results of different polyolefin blends

[0034] OIT (min, 190℃) OOT (℃) Example 1 55.7 234.7 Example 2 69.9 242.6 Example 3 134.1 248.6 Comparative Example 1 13.7 212.4 Comparative Example 2 19.5 228.7 Comparative Example 3 30.7 235.5 .

[0035] In addition, in Example 4 and Comparative Example 4, a micro twin-screw extruder was used to conduct multiple extrusion experiments on polyolefin composites with and without hydrotalcite. The results are as Figure 1 shown. It can be seen that compared with Comparative Example 4, under the same vitamin E content, the melt flow performance of the polyolefin blend disclosed in Example 4 of the present invention hardly changed during multiple extrusion experiments, and its thermal processing stability was better.

[0036] Example 5: The sample preparation and detection methods were the same as those in Example 1, but the polyolefin matrix was random copolymer polypropylene produced using a Ziegler-Natta catalyst (produced by Xuzhou Haitian Petrochemical Co., Ltd., grade PA14D), the addition amount of vitamin E was 0.1 part, and the addition amount of hydrotalcite was 0.05 part. The measured oxidation induction temperature OOT was 244.1 °C.

[0037] Comparative Example: The sample preparation and detection methods were the same as those in Example 1. The high-density polyethylene in the polyolefin blend was replaced with random copolymer polypropylene, and only 0.1 part of vitamin E was added. The OOT of the prepared polyolefin blend was 233.8 °C.

[0038] Example 6: The sample preparation and detection methods were the same as those in Example 1, but the polyolefin matrix was random copolymer polypropylene produced using a Ziegler-Natta catalyst (produced by Xuzhou Haitian Petrochemical Co., Ltd., grade PA14D). In addition to adding 0.1 part of vitamin E and 0.05 part of hydrotalcite, 0.1 part of a nucleating agent (grade N8000X, produced by Milliken & Company, USA) was also added. The measured oxidation induction temperature OOT was 243.8 °C.

[0039] It can also be seen from the above two examples that under the same vitamin E content, the polypropylene blend simultaneously added with vitamin E and hydrotalcite also has a higher OOT value. When other additives such as a nucleating agent are added, it also has good thermal-oxidative stability.

[0040] Example 7: Others were the same as Example 1. The vitamin E in the polyolefin blend was replaced with quercetin (Shanghai Bide Pharmaceutical Technology Co., Ltd.). The addition amount of quercetin was 0.1 part, and the addition amount of hydrotalcite was 0.05 part. The OOT of the high-density polyethylene blend was measured to be 257.3 °C. This polyolefin blend also showed a relatively high OOT value and had good thermal-oxidative stability.

[0041] The above-disclosed embodiments enable those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art. Therefore, the present invention is not limited to these embodiments shown herein.

Claims

1. A polyolefin blend, characterized in that, Its components include polyolefin, natural antioxidant and hydrotalcite, and the composition is as follows by mass parts: Polyolefin: 100 parts; Natural antioxidant: 0.05 - 2.0 parts; Hydrotalcite: 0.02 - 3.0 parts; The natural antioxidant is a substance derived from natural production and having antioxidant function.

2. The polyolefin blend according to claim 1, wherein The natural antioxidant is selected from vitamin E, quercetin, β - carotene, lignin and curcumin.

3. The polyolefin blend according to claim 1, wherein The polyolefin is a single polyolefin or a mixture of multiple polyolefins in any proportion.

4. The polyolefin blend according to claim 3, characterized in that, The polyolefin is selected from polyethylene, polypropylene and polybutene.

5. The polyolefin blend according to claim 4, wherein The polyolefin is linear low - density polyethylene, high - density polyethylene or isotactic polypropylene produced by coordination polymerization of Ziegler - Natta catalyst or metallocene catalyst.

6. The polyolefin blend according to claim 1, characterized in that, The hydrotalcite is magnesium - aluminum hydrotalcite.

7. The polyolefin blend according to any one of claims 1 to 6, characterized in that, It also includes one or more of the following substances: nucleating agent, flame retardant, filler, light stabilizer, lubricant, antistatic agent, impact modifier.

Images