A compound opening agent for low-density polyethylene film, a high-opening transparent linear low-density polyethylene film with high slip and a preparation method thereof

Abstract

This invention discloses a compound opening agent for low-density polyethylene film, an easy-opening, highly slippery, transparent linear low-density polyethylene film, and its preparation method. The compound opening agent is obtained by compounding silane-modified silica with a cyclic olefin polymer, wherein the mass ratio of silica to cyclic olefin polymer is 1:1 to 6:1. By using two opening agents in combination, this invention significantly reduces the amount of silica used compared to the prior art using silica alone, and at the same amount added, it exhibits better opening properties and transparency compared to the prior art.

Description

Technical Field

[0001] This invention belongs to the field of polyolefin film technology, specifically relating to a compound opening agent for low-density polyethylene film, an easy-opening, highly smooth, transparent linear low-density polyethylene film, and its preparation method. Background Technology

[0002] Linear low-density polyethylene (LLDPE) is the most produced type of PE resin. First appearing in the 1970s, it is a copolymer of ethylene and a small amount of α-olefins (such as 1-butene and 1-octene). It is non-toxic, tasteless, and odorless, with a milky-white appearance. The mechanical properties of LLDPE fall between those of HDPE and LDPE, and its strength, toughness, rigidity, weather resistance, and resistance to environmental stress cracking are superior to LDPE. Due to its excellent mechanical properties and chemical stability, LLDPE has wide applications in industry, agriculture, medical, hygiene, and daily necessities. It is mainly used in food, pharmaceutical, and cultural product packaging, heavy-duty bags, shopping bags, agricultural films, and wire and cable production, among many other fields. It is one of the fastest-growing resin varieties in terms of demand in recent years.

[0003] However, during the blown film process of linear low-density polyethylene (LLDPE), the film layers are prone to adhesion and are difficult to separate. In addition, the pressure of the rollers makes it easy for the films to stick together. The same adhesion problem will be encountered in the production of cast film.

[0004] LLDPE is also commonly used as the surface layer of composite films for packaging food (such as vegetables and similar products), pharmaceuticals, etc., and comes into direct contact with powders, granules, and lumps. To prevent adhesion to the packaged goods, the slip properties of LLDPE are particularly important. For example, reduced film-to-film and film-to-metal friction makes it easier to feed the film into automated conversion and packaging equipment. Films with low slippage are difficult to handle and prone to wrinkling, leading to high conversion losses. Meanwhile, optical properties such as haze and transparency are important performance parameters related to packaging films; for users, it is crucial to be able to see through the packaging for a clear product presentation.

[0005] Adding an opening agent to LLDPE is to prevent the film material from sticking together during production and storage, especially in summer when sticking is very likely to occur. This is to facilitate the production, use, and storage of the film material and to prevent the surface of the LLDPE film material from sticking to the packaged products.

[0006] In the existing technology, the opening agent is either inorganic or organic. Inorganic opening agents include silica, calcium carbonate, clay, kaolin, or talc, as well as synthetic silicates. Based on 100 parts of LLDPE, the dosage of silica, calcium carbonate, clay, kaolin, or talc is generally between 0.05 and 0.2 parts, while the dosage of synthetic silicates is generally between 0.05 and 1.25 parts. Organic opening agents are stearates. Inorganic opening agents can be used alone or in combination, and they can also be used in combination with organic opening agents.

[0007] Patent CN101012322 discloses an antistatic, anti-adhesion, slip-resistant linear low-density polyethylene composition: using LLDPE as a base material, and adding an opening agent, a slip agent, an antistatic agent, and an antioxidant. The opening agent is synthetic silica, prepared by adding it during the granulation stage after mixing the additives with LLDPE as the base material; or by pre-preparing the additives into a masterbatch, metering it into the masterbatch during the granulation stage, and then producing a special material. The proportions of various additives in the masterbatch are: 4-80 parts LLDPE powder, 4-16 parts opening agent, 4-24 parts slip agent, 4-24 parts antistatic agent, 4-16 parts antioxidant, and 4-16 parts zinc stearate. This invention meets the requirements of general production and application; however, the addition of 4-80 parts LLDPE powder during the masterbatch manufacturing process results in a low content of effective components in the masterbatch, requiring a large amount to be added during industrial production, which poses certain difficulties in production.

[0008] Patent CN101052675A discloses a melt-blended polyethylene / cyclic olefin polymer (COP) composition suitable for preparing optically transparent films with a low coefficient of friction, wherein the cyclic olefin polymer is melt-blended into the composition as an opening agent. Based on 100 parts of LLDPE, the amount of opening agent added is 2 to 33 parts. Films made from this composition have a low-friction surface compared to films made from polyethylene resin alone, and also exhibit a haze value comparable to films without an opening agent, but at a higher amount.

[0009] The literature “Development of Special Resins for LLDPE Film” (Synthetic Resins and Plastics, 2009, 26(3): 56-61) introduces that Daqing Petrochemical, while keeping the existing process unchanged, added 0.075 to 0.175 parts of opening agent silica as a basis of 100 parts of LLDPE to improve the opening performance of LLDPE film, but the transparency of the film decreased.

[0010] The literature “Development of special resin for linear low-density polyethylene film” (Refining and Chemical Industry, 2010, (1): 19-21) states that the SiO2 dosage range should be 75-175 μg / g, the optimal dosage of the lubricant is 30-90 μg / g, the developed resin has a haze of 14%, and the opening performance is easy to peel off. Therefore, specific data on the friction performance of the film are not mentioned, and the haze is relatively high.

[0011] In the literature “Research and Application of Easy-to-Open, High-Transparency Linear Low-Density Polyethylene” (Elastomers, 2010, 20(5): 60-63), the opening agent is a mixture of inorganic opening agent dicalcium phosphate and organic opening agent stearamide. The ratio of organic opening agent to inorganic opening agent is 3-2 (mass ratio). The best compounding effect is achieved when the amount added is 0.10%. However, in order to increase transparency, a transparency enhancer was added during the experiment. After the transparency enhancer was added, it was easy to produce an odor, which is not good for the packaging film.

[0012] The literature “Application of slip agents and anti-stick opening agents in plastic films” (Plastic Additives, 2017, (3): 19-22) details the application and function of slip agents, anti-stick and opening agents in plastic films, including amide slip agents, non-migratory slip and anti-stick agents, inorganic anti-stick and opening agents, and organic anti-stick and opening agents, but does not provide specific performance data.

[0013] The market demand for LLDPE, which combines good openness and slip properties with high transparency, is approximately 300,000 tons per year.

[0014] Existing literature mainly focuses on improving the opening and slip properties of films, primarily using opening agents and slip agents. While improving opening and slip properties, this can reduce the product's transparency and toughness. There is also literature that uses transparent nucleating agents to increase transparency, but this invisibly increases the amount of additives required, raising production costs. Furthermore, the addition of nucleating agents can easily generate odors, which is detrimental to packaging films. Summary of the Invention

[0015] The purpose of this invention is to provide a compound opening agent for low-density polyethylene film, an easy-opening, highly slippery, transparent linear low-density polyethylene film, and a method for preparing the same, so as to solve the problems of excessive opening agent dosage, poor friction performance, and easy film adhesion in the prior art.

[0016] To achieve the above objectives, the present invention provides a compound opening agent for low-density polyethylene film, which is obtained by compounding silane-modified silica with a cyclic olefin polymer, wherein the mass ratio of silica to cyclic olefin polymer is 1:1 to 6:1, preferably 4:1.

[0017] The compound opening agent for low-density polyethylene film of the present invention is prepared by mixing silica, cyclic olefin polymer and silane coupling agent, and stirring at 80-100°C to obtain the compound opening agent. In the present invention, the stirring time is not specifically limited, as long as the materials are fully mixed, preferably for 10-25 minutes.

[0018] The compound opening agent for low-density polyethylene film of the present invention has a mass ratio of silica to silane coupling agent of 100:1 to 3.

[0019] The compound opening agent for low-density polyethylene film of the present invention has a silica particle size of 900-2000 mesh.

[0020] The compound opening agent for low-density polyethylene film of the present invention is wherein the cyclic olefin polymer is a polymer of monocyclic or polycyclic olefins, such as a polymer of cycloene, dicyclic olefin, tricyclic olefin or tetracyclic olefin.

[0021] The compound opening agent for low-density polyethylene film of the present invention is wherein the monocyclic or polycyclic olefin is a monosubstituted or polysubstituted cyclic olefin.

[0022] The compound opening agent for low-density polyethylene film of the present invention comprises a cyclic olefin polymer that is a copolymer of monocyclic or polycyclic olefins and acyclic olefins; the acyclic olefin is one or more of ethylene, propylene and butene; and the cyclic olefin is norbornene.

[0023] To achieve the above objectives, the present invention also provides an easy-opening, highly slippery, transparent linear low-density polyethylene film, prepared from the following raw materials: 100 parts by weight of linear low-density polyethylene, 0.025 to 0.055 parts by weight of the aforementioned compound opening agent, 0.05 to 0.20 parts by weight of slip agent, and 0.05 to 0.20 parts by weight of antioxidant, wherein the slip agent is erucamide, and the cyclic olefin polymer has a melt flow rate of 11 g / 10 min to 30 g / 10 min at 230°C and 2.16 kg.

[0024] The easy-opening, highly smooth, transparent linear low-density polyethylene film of this invention has a density of 0.915–0.921 g / cm³. 3 Measured according to ISO 1183-2:2004.

[0025] The easy-opening, high-smooth, transparent linear low-density polyethylene film of the present invention uses an antioxidant that is a hindered phenolic antioxidant or a mixture of a hindered phenolic antioxidant and a phosphite antioxidant. The hindered phenolic antioxidant is a commonly used substance in the art, such as 1010 or 1076; the phosphite antioxidant is a commonly used substance in the art, such as 168.

[0026] To achieve the above objectives, the present invention also provides a method for preparing the aforementioned easy-opening, highly slippery, transparent linear low-density polyethylene film, comprising the following steps:

[0027] S1, mix linear low-density polyethylene, compound opening agent, slip agent and antioxidant evenly;

[0028] S2, the uniformly mixed mixture is granulated in a twin-screw extruder to obtain a special material for polyethylene film;

[0029] S3, blow the polyethylene film material into a film.

[0030] The preparation method of the easy-opening, high-smooth, transparent linear low-density polyethylene film of the present invention includes the following steps: Step S1: mixing at 10-50°C for 2-5 minutes; Step S2: granulation temperature at 170-230°C; Step S3: blowing temperature at 170-200°C.

[0031] Beneficial effects of this invention:

[0032] This invention uses two opening agents in combination, which significantly reduces the amount of silica used compared to the prior art using silica alone. At the same amount added, it has better opening properties and transparency compared to the prior art. This invention is also easier to implement for continuous industrial production than general blending modification methods. Detailed Implementation

[0033] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0034] The raw materials used in the experiment and their sources are as follows:

[0035] LLDPE: Model DFDA7042: Powder from Lanzhou Petrochemical Company's ethylene plant, density: 0.918 g / cm³ 3 .

[0036] Cyclic olefin polymer: Zeon 1060R (Japan), 230℃, 2.16KG melt mass flow rate 14g / 10min.

[0037] Silica: Shanghai Liangjiang Titanium Dioxide Chemical Products Co., Ltd., particle size 1300 mesh.

[0038] Erucamide: Shandong Alinda Chemical Co., Ltd.

[0039] Oleamide: Shandong Jiahong Chemical Co., Ltd.

[0040] Antioxidant: Compound antioxidant B561, Yingkou Fengguang Chemical Co., Ltd.

[0041] Silane coupling agent KH-550: Nanjing Shuguang Chemical Group Co., Ltd.

[0042] Talc powder: Qingdao Lukuang Talc Powder Co., Ltd.

[0043] Analysis method:

[0044] Film blowing: Film blowing was performed using a COLLIN E45P film blowing machine.

[0045] Haze: The haze was measured using a Yokosuka HGM-2DP haze meter from Japan.

[0046] Friction coefficient: Tested using the E-2 friction coefficient tester from the Italian company CEAST.

[0047] Impact quality of the dart: Tested using the CEAST-2062 free-fall dart impact tester from the Italian company CEAST. Specific implementation examples:

[0049] Example 1

[0050] Preparation of silane-modified silica and cyclic olefin polymer compound opening agent: Silica and cyclic olefin polymer are compounded at a mass ratio of 4:1. 1000 parts of dry silica and 250 parts of cyclic olefin polymer are weighed and placed in a high-speed mixer. Then, 20 parts of silane coupling agent KH-550 are added and stirred at 80℃ for 20 min to obtain the silane-modified silica and cyclic olefin polymer compound opening agent.

[0051] 100 parts of LLDPE resin DFDA7042, 0.05 parts of silane-modified silica and cyclic olefin polymer compound opening agent, 0.05 parts of erucamide and 0.15 parts of antioxidant B561 were added to a high-speed mixer and mixed at 25°C for 2 min. The mixed material was then granulated in a twin-screw extruder at a temperature of 170-230°C to obtain polyethylene film material. Finally, the polyethylene film material was blown into a film at a temperature of 170-200°C with a film thickness of 30 μm. The film properties are shown in Table 1.

[0052] Example 2

[0053] Other conditions were the same as in Example 1, except that the amount of antioxidant added was 0.05 parts, the amount of silane-modified silica and cyclic olefin polymer compound opening agent added was 0.03 parts, and the amount of slip agent added was 0.1 parts. The film properties are shown in Table 1.

[0054] Example 3

[0055] Other conditions were the same as in Example 1, except that the amount of antioxidant added was 0.05 parts, the amount of silane-modified silica and cyclic olefin polymer compound opening agent added was 0.04 parts, and the amount of slip agent added was 0.15 parts. The film properties are shown in Table 1.

[0056] Example 4

[0057] Other conditions were the same as in Example 1, except that the amount of antioxidant added was 0.2 parts, the amount of silane-modified silica and cyclic olefin polymer compound opening agent added was 0.025 parts, and the amount of slip agent added was 0.2 parts. The film properties are shown in Table 1.

[0058] Example 5

[0059] Other conditions were the same as in Example 3, except that silica and cyclic olefin polymer were mixed in a 1:1 ratio during the preparation of the compound opening agent. The amounts of each raw material used in the preparation of the compound opening agent were: 600 parts silica, 600 parts cyclic olefin polymer, and 18 parts silane coupling agent KH-550. The film properties are shown in Table 1.

[0060] Example 6

[0061] Other conditions were the same as in Example 3, except that silica and cyclic olefin polymer were compounded in a 6:1 ratio during the preparation of the compound opening agent. The amounts of each raw material used in the preparation of the compound opening agent were: 600 parts silica, 100 parts cyclic olefin polymer, and 6 parts silane coupling agent KH-550. The film properties are shown in Table 1.

[0062] Comparative Example 1

[0063] Other conditions were the same as in Example 1, except that 0.02 parts of silane-modified silica and cyclic olefin polymer were used as the opening agent. The film properties are shown in Table 1.

[0064] Comparative Example 2

[0065] Other conditions were the same as in Example 3, except that 0.05 parts of cyclic olefin polymer were used instead of the composite opening agent. The film properties are shown in Table 1.

[0066] Comparative Example 3

[0067] Other conditions were the same as in Example 3, except that 0.05 parts of silicon dioxide were used instead of the composite opening agent. The film properties are shown in Table 1.

[0068] Comparative Example 4

[0069] Other conditions were the same as in Example 3, except that the opening agent was not modified during the preparation of the polyethylene film special material. A mixture of silica and cyclic olefin polymer in a mass ratio of 4:1 was used as the compound opening agent. The film properties are shown in Table 1.

[0070] Comparative Example 5

[0071] Other conditions were the same as in Example 3, except that silica and cyclic olefin polymer were compounded in a 7:1 ratio during the preparation of the compound opening agent. The film properties are shown in Table 1.

[0072] Comparative Example 6

[0073] Other conditions were the same as in Example 3, except that talc was used as the opening agent, and the film properties are shown in Table 1.

[0074] Comparative Example 7

[0075] Other conditions were the same as in Example 3, except that oleic acid amide was selected as the slip agent. The film properties are shown in Table 1.

[0076] Table 1

[0077] performance Haze, % static friction coefficient coefficient of kinetic friction Impact mass of the dart, g Example 1 15.0 0.3758 0.3564 95.3 Example 2 13.2 0.2788 0.2716 98.7 Example 3 12.0 0.1533 0.1350 101.2 Example 4 11.6 0.1530 0.1340 97.5 Example 5 13.5 0.2910 0.2900 99.3 Example 6 13.8 0.2700 0.2690 90.2 Comparative Example 1 17.2 0.5368 0.5154 93.2 Comparative Example 2 14.5 0.3713 0.3710 95 Comparative Example 3 18.2 0.5200 0.5100 85 Comparative Example 4 18.0 0.4095 0.4045 88 Comparative Example 5 18.5 0.3020 0.3010 87 Comparative Example 6 17.5 0.4120 0.4110 83 Comparative Example 7 17.8 0.4700 0.4520 91

[0078] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A compound opening agent for low-density polyethylene film, characterized in that, It is obtained by compounding silane-modified silica with cyclic olefin polymer, wherein the mass ratio of silica to cyclic olefin polymer is 1:1 to 6:

1.

2. The compound opening agent for low-density polyethylene film according to claim 1, characterized in that, The preparation method of the compound opening agent is as follows: mix silica, cyclic olefin polymer and silane coupling agent, stir at 80-100°C to obtain the compound opening agent.

3. The compound opening agent for low-density polyethylene film according to claim 2, characterized in that, The mass ratio of silicon dioxide to silane coupling agent is 100:1 to 3.

4. The compound opening agent for low-density polyethylene film according to any one of claims 1 to 3, characterized in that, The silica has a particle size of 900–2000 mesh.

5. The compound opening agent for low-density polyethylene film according to any one of claims 1 to 3, characterized in that, The cyclic olefin polymer is a polymer of monocyclic or polycyclic olefins.

6. The compound opening agent for low-density polyethylene film according to claim 5, characterized in that, The monocyclic or polycyclic olefins are monosubstituted or polysubstituted cyclic olefins.

7. The compound opening agent for low-density polyethylene film according to claim 5, characterized in that, The cyclic olefin polymer is a copolymer of monocyclic or polycyclic olefins and acyclic olefins; the acyclic olefin is one or more of ethylene, propylene and butene; the cyclic olefin is norbornene.

8. An easy-opening, highly smooth, transparent linear low-density polyethylene film, characterized in that, It is prepared from the following raw materials: 100 parts by weight of linear low-density polyethylene, 0.025 to 0.055 parts by weight of the compound opening agent according to any one of claims 1 to 7, 0.05 to 0.20 parts by weight of slip agent and 0.05 to 0.20 parts by weight of antioxidant, wherein the slip agent is erucamide, and the melt mass flow rate of the cyclic olefin polymer at 230°C and 2.16 kg is 11 g / 10 min to 30 g / 10 min.

9. The easy-opening, high-smooth, transparent linear low-density polyethylene film according to claim 8, characterized in that, The linear low-density polyethylene has a density of 0.915–0.921 g / cm³. 3 .

10. The easy-opening, high-smooth, transparent linear low-density polyethylene film according to claim 8, characterized in that, The antioxidant is a hindered phenolic antioxidant, or a mixture of a hindered phenolic antioxidant and a phosphite antioxidant.

11. The method for preparing the easy-opening, highly smooth, transparent linear low-density polyethylene film according to any one of claims 8 to 10, characterized in that, Includes the following steps: S1, mix linear low-density polyethylene, compound opening agent, slip agent and antioxidant evenly; S2, the uniformly mixed mixture is granulated in a twin-screw extruder to obtain a special material for polyethylene film; S3, blow the polyethylene film material into a film.

12. The method for preparing an easy-opening, highly smooth, transparent linear low-density polyethylene film according to claim 11, characterized in that, The mixing in step S1 is carried out at 10-50°C for 2-5 minutes; the granulation temperature in step S2 is 170-230°C; and the blowing temperature in step S3 is 170-200°C.