Nucleating agent master batch as well as preparation method and application thereof

Abstract

The invention relates to a nucleating agent master batch as well as a preparation method and application thereof. The preparation method comprises a mechanical activation process of the nucleating agent, an ultrathin film coating process and a pre-dispersion process of blending with the polymer, and the method can effectively avoid the physical agglomeration problem of the nucleating agent, so that the nucleating agent is efficiently dispersed in the resin. The invention also provides a method for preparing the special material for the low-haze LLDPE film from the nucleating agent master batch. The special material for the film comprises the following components in parts by mass: 90-95 parts of LLDPE resin; 0.05 to 0.15 part of an antioxidant; 0.01 to 0.05 part of an antistatic agent; 0.01 to 0.05 part of an acid acceptor; 0.1 to 0.5 part of a processing aid; the thin film prepared from the special material has the characteristic of low haze.

Description

Technical Field

[0001] This invention relates to the field of polyethylene, and more specifically to a nucleating agent masterbatch, its preparation method, and its application in the field of LLDPE film. Background Technology

[0002] LLDPE films possess high tensile strength, good tear and puncture resistance, and relatively low production costs. However, due to the linear structure of the LLDPE main chain, short branches, and highly regular molecular arrangement, a large number of crystals and supramolecular structures are formed during the blown film processing. These large crystal structures result in high haze in the film, limiting its widespread adoption and application. Currently, products from major domestic and international LLDPE film manufacturers, except for those using metallocene or other transition metal catalysts, all suffer from high haze.

[0003] As a crucial application form of LLDPE, film haze control is of paramount importance for film applications. Film haze can be categorized into surface haze and internal haze based on its cause, determined by the film's surface and internal structures, respectively. On one hand, surface roughness significantly impacts haze. During screw plasticizing and extrusion, LLDPE resin undergoes periodic melt fracture, resulting in a "sharkskin" effect and a rough surface. Currently, incorporating appropriate amounts of fluoropolymer processing aids into the resin can address this. Due to their high polarity, these aids are completely incompatible with the LLDPE melt but possess a high affinity for metal surfaces. Therefore, they migrate through the melt to the runner and die inner wall, forming a lubricating layer and effectively eliminating melt fracture. Conversely, adding appropriate amounts of polysiloxanes or silicone powders to the resin can effectively improve its processing fluidity, reduce roughness, and thus lower the haze of the film product. On the other hand, the size of the spherulites in the internal structure also has a significant impact on haze. Currently, by introducing nucleating agents with excellent nucleation effects, the crystallization nuclei of LLDPE can be replaced, allowing the crystallization process to directly enter the crystal growth stage based on the nucleating agent. This significantly increases the crystallization rate during molding, resulting in finer crystal sizes and reduced haze. Given the tendency of nucleating agents to agglomerate, a relatively large amount is usually required to ensure a sufficient number of heterogeneous nucleation sites for refining the grain size. However, if the nucleating agent can achieve highly efficient dispersion within the resin, a smaller dosage can achieve a good haze reduction effect. Summary of the Invention

[0004] To meet the demand for resins specifically designed for low-haze films, this invention provides a method for ultrafine dispersion of nucleating agents, including a mechanical activation process of the nucleating agent, an ultrathin film coating process, and a pre-dispersion process of blending with a high melt index polymer. The resulting nucleating agent masterbatch is used to prepare LLDPE films, which can effectively avoid the problem of physical agglomeration of nucleating agents. Compared with traditional LLDPE materials, this method can significantly reduce the haze of film products with the addition of a small amount of nucleating agent, expanding the application of materials in packaging films, agricultural films, and other fields.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing nucleating agent masterbatch, comprising the following steps:

[0007] 1) The nucleating agent is mechanically ground and activated in a ball mill to obtain nucleating agent powder;

[0008] 2) Preparation of a good solvent solution for polyvinyl alcohol;

[0009] 3) Under stirring conditions, nucleating agent powder is added to the dispersion of step 2) to obtain nucleating agent microemulsion;

[0010] 4) Place the nucleating agent microemulsion from step 3) at room temperature for 48-72 hours to allow the solvent in the microemulsion to evaporate completely, and obtain a nucleating agent powder with a polyvinyl alcohol ultrafilm coated on the surface.

[0011] 5) The nucleating agent powder coated with polyvinyl alcohol ultrafilm in step 4) is heated and melt-blended with POE and polyethylene wax to obtain nucleating agent masterbatch.

[0012] In this invention, the nucleating agent in step 1) is a carboxylate nucleating agent, preferably a benzoate nucleating agent, and more preferably a hexahydrophthalic acid metal salt nucleating agent; the ball milling speed is 300-450 r / min, and the ball milling time is 1-3 h;

[0013] In this invention, the degree of polymerization of the polyvinyl alcohol in step 2) is 300-1700, preferably 300-500; the degree of alcoholysis of the polyvinyl alcohol is 78-99%, preferably 78-88%; the good solvent is one or more of water, DMF, and DMSO; preferably, the solution preparation process is accompanied by heating and stirring, with the temperature set at 90-100℃ and the stirring speed set at 200-300 r / min; preferably, the concentration of the solution is 2-8 wt%.

[0014] In this invention, the nucleating agent content in the nucleating agent microemulsion in step 3) is 20-40 wt%, preferably 20-30 wt%; the stirring speed is 200-1000 r / min, preferably 400-600 r / min;

[0015] In this invention, the POE mentioned in step 5) is selected from POE with a melt flow rate of 1-2 g / 10 min under conditions of 2.16 kg and 190 °C; preferably, the density of the POE is 0.890-0.910 g / cm³. 3 The weight-average molecular weight of the polyethylene wax is 500-5000 g / mol; the mass ratio of POE to polyethylene wax is 2-9:1; the heating and melting temperature is 170-200℃; and the concentration of the nucleating agent masterbatch is 1-5 wt%, preferably 1-2 wt%.

[0016] Secondly, the present invention provides a low-haze LLDPE film-specific material, comprising the following components:

[0017] LLDPE resin: 90-95 parts;

[0018] Antioxidant: 0.05-0.15 parts;

[0019] Antistatic agent: 0.01-0.05 parts;

[0020] Acid absorbent: 0.01-0.05 parts;

[0021] Processing aids: 0.1-0.5 parts;

[0022] Nucleating agent masterbatch: 1-8 parts.

[0023] The low-haze LLDPE film-specific material of the present invention preferably has a density of 0.915-0.925 g / cm³. 3 The melt flow rate under the conditions of 2.16 kg and 190 °C is preferably 0.5-5.0 g / 10 min.

[0024] The low-haze LLDPE film material of the present invention preferably contains one or more of the antioxidants selected from 1076, 1010, 168, and 3114.

[0025] The low-haze LLDPE film material of the present invention preferably contains one or more of fatty acid esters, amine ethoxide, and fatty amine polyoxyethylene ether.

[0026] The low-haze LLDPE film material of the present invention preferably contains one or more of zinc stearate and calcium stearate as the acid absorber.

[0027] The low-haze LLDPE film material of the present invention preferably contains one or more of the following processing aids: vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer, polysiloxane, and silicone.

[0028] The low-haze LLDPE film-specific material of the present invention, wherein the nucleating agent masterbatch is the nucleating agent masterbatch prepared by the preparation method described in the first aspect of the present invention.

[0029] Thirdly, the present invention provides a method for preparing a low-haze LLDPE film-specific material, comprising the following steps:

[0030] S1. Add LLDPE resin, antioxidant, antistatic agent, acid absorbent, processing aid, nucleating agent masterbatch to the mixer according to the formula and stir evenly to obtain a preliminary mixture;

[0031] S2. The uniformly mixed material is extruded and granulated in a twin-screw extruder. After cooling, pelletizing, and drying, a low-haze LLDPE film material is obtained, which can then be blown into an LLDPE film.

[0032] Preferably, the heating and melting temperature of the twin-screw extruder is 180-230℃, the extrusion temperature is 190-220℃, and the screw speed is 200-350 r / min.

[0033] Fourthly, the LLDPE film prepared by this invention can be applied to various packaging films and agricultural films.

[0034] The beneficial effects of this invention are as follows:

[0035] The nucleating agent masterbatch used in this invention is coated with a polyvinyl alcohol ultrafilm on the surface of the nucleating agent powder after ultrafine dispersion treatment via emulsion method. This effectively avoids the physical agglomeration problem of micro-nucleating agents. Finally, it is melt-blended with POE and polyethylene wax to prepare masterbatch, which can further improve the pre-dispersion of nucleating agent in masterbatch. This ensures that the nucleating agent masterbatch can fully exert the heterogeneous nucleation effect during the processing of the prepared film-specific material, forming a large number of crystal nuclei, thereby reducing the size of spherulites and reducing the haze of film products. In addition, the processing aid used in this invention can migrate and adsorb onto the surface of the blown film die during the processing of polyethylene resin, forming a lubricating layer. At the same time, it improves the processing fluidity of the resin, reduces the surface roughness of the film, and further reduces the haze of the film products. Attached Figure Description

[0036] Figure 1 A polarized light microscope image of the blown film of the low-haze LLDPE film-specific material in Example 1;

[0037] Figure 2 A polarized microscope image of the blown film in Comparative Example 2;

[0038] Figure 3 This is a polarized microscope image of the blown film in Comparative Example 4. Detailed Implementation

[0039] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0040] All ranges disclosed herein include endpoints and are independently combinable. The endpoints of the ranges and any values ​​disclosed herein are not limited to the exact ranges or values, which should be understood to include values ​​close to those ranges or values.

[0041] In the various embodiments and comparative examples of this invention, the main raw materials are sourced as follows; other raw materials and reagents, unless otherwise specified, were obtained through ordinary commercial channels:

[0042] LLDPE: DFDA 7047, density 0.919 g / cm³ 3 The melt flow rate at 2.16 kg and 190℃ was 1.0 g / 10 min, purchased from Wanhua Chemical; DFDA 7042, density 0.918 g / cm³. 3 The melt flow rate at 2.16 kg and 190 °C was 2.0 g / 10 min, purchased from Wanhua Chemical.

[0043] Antioxidants: SONOX 1076, SONOX 168, purchased from Mitutoyo Chemical.

[0044] Antistatic agent: 1800, purchased from Sanfeng Chemical;

[0045] Acid absorbent: Zinc stearate, calcium stearate, purchased from Sanfeng Chemical;

[0046] Processing aids: PPA 9000E, purchased from Luju Chemical; Kynar Flex PPA 2821, purchased from Arkema;

[0047] Nucleating agent; NP503, purchased from Jihaichuan; HPN20E, purchased from Milliken;

[0048] Polyvinyl alcohol: 088-05, with a degree of polymerization of 500 and a degree of alcoholysis of 88%, purchased from Sichuan Weixin Chemical Co., Ltd.; 088-07, with a degree of polymerization of 700 and a degree of alcoholysis of 88%, purchased from Sichuan Weixin Chemical Co., Ltd.

[0049] POE: 8540, 8480, purchased from Dow Chemical;

[0050] Polyethylene wax: WH WAX, weight average molecular weight 500 g / mol, purchased from Wanhua Chemical.

[0051] The main performance characteristics of the embodiments and comparative examples of this invention were tested using the following methods:

[0052] Density: Ray-Ran DGA density gradient column;

[0053] Melt flow index: Goettfert MI40 melt flow indexer, temperature 190℃, 2.16kg;

[0054] Weight-average molecular weight: Polymer Char GPC-IR chromatography;

[0055] Haze level: BYK Haze-gardi haze meter.

[0056] The accompanying drawings used in this invention were taken using a Zeiss Axio Scope A1 microscope.

[0057] Example 1

[0058] The low-haze LLDPE film-grade material contains the following components:

[0059] LLDPE: DFDA 7047 90 servings;

[0060] Antioxidant: 0.1 parts of SONOX 1076;

[0061] Antistatic agent: 1800 0.05 parts;

[0062] Acid absorbent: 0.05 parts zinc stearate;

[0063] Processing aid: 0.5 parts of PPA 9000E;

[0064] Nucleating agent masterbatch: 8 parts.

[0065] The steps for preparing the nucleating agent masterbatch are as follows:

[0066] 1) The nucleating agent NP503 was mechanically ground in a ball mill at a speed of 450 r / min for 2 h to obtain nucleating agent powder;

[0067] 2) Polyvinyl alcohol 088-05 was dissolved in DMSO at a temperature of 90℃ and a rotation speed of 200r / min to form a 5wt% polyvinyl alcohol dispersion.

[0068] 3) Under stirring at 500 r / min, the nucleating agent powder is slowly added to the polyvinyl alcohol dispersion in step 2) to obtain a 20 wt% nucleating agent microemulsion.

[0069] 4) Place the nucleating agent microemulsion from step 3) at room temperature for 48 hours to allow the DMSO in the microemulsion to evaporate completely, and obtain a nucleating agent powder with a polyvinyl alcohol ultrafilm coated on the surface.

[0070] 5) POE 8540 and polyethylene wax WH WAX are mixed at a mass ratio of 8:2 to obtain a mixture. The nucleating agent powder with a polyvinyl alcohol ultrafilm coated on the surface in step 4) is heated and melt-blended with the above mixture in an internal mixer at 190°C to obtain a nucleating agent masterbatch with a concentration of 2wt%.

[0071] The steps for preparing the low-haze LLDPE film-specific material are as follows:

[0072] According to the formula, LLDPE resin, antioxidant, antistatic agent, acid scavenger, processing aid, and nucleating agent masterbatch are mixed in a high-speed mixer for 5 minutes. The uniformly mixed material is then granulated in a twin-screw extruder. The extruder temperature is set as follows: Zone I 190℃, Zone II 200℃, Zone III 210℃, Zone IV 220℃, Zone V 210℃, Zone VI 210℃, Die head 210℃, and screw speed 250 r / min. After extrusion, the material is cooled, pelletized, and dried, then blown into a 30μm thick film with a haze of 6.3% using a blown film extruder.

[0073] Example 2

[0074] The low-haze LLDPE film-grade material contains the following components:

[0075] LLDPE: DFDA 7047 94.5 portions;

[0076] Antioxidants: 0.1 parts of SONOX 1076, 0.05 parts of SONOX 168;

[0077] Antistatic agent: 1800 0.02 parts;

[0078] Acid absorbent: 0.03 parts calcium stearate;

[0079] Processing aid: 0.3 parts of PPA 9000E;

[0080] Nucleating agent masterbatch: 5 parts.

[0081] The steps for preparing the nucleating agent masterbatch are as follows:

[0082] 1) The nucleating agent HPN20E was mechanically ground in a ball mill at a speed of 450 r / min for 3 h to obtain nucleating agent powder;

[0083] 2) Polyvinyl alcohol 088-07 was dissolved in water at 100℃ and 300r / min to form a polyvinyl alcohol dispersion with a concentration of 8wt%.

[0084] 3) Under stirring at 600 r / min, the nucleating agent powder was slowly added to the polyvinyl alcohol dispersion in step 2) to obtain a 30 wt% nucleating agent microemulsion.

[0085] 4) Place the nucleating agent microemulsion from step 3) at room temperature for 72 hours to allow the water in the microemulsion to evaporate completely, and obtain a nucleating agent powder with a polyvinyl alcohol ultrafilm coated on the surface.

[0086] 5) POE 8480 and polyethylene wax WH WAX are mixed at a mass ratio of 9:1 to obtain a mixture. The nucleating agent powder with a polyvinyl alcohol ultrafilm coated on the surface in step 4) is heated and melt-blended with the above mixture in an internal mixer at 190°C to obtain a nucleating agent masterbatch with a concentration of 1wt%.

[0087] The steps for preparing the low-haze LLDPE film-specific material are as follows:

[0088] According to the formula, LLDPE resin, antioxidant, antistatic agent, acid scavenger, processing aid, and nucleating agent masterbatch are mixed in a high-speed mixer for 5 minutes. The uniformly mixed material is then granulated in a twin-screw extruder. The extruder temperature is set as follows: Zone I 190℃, Zone II 200℃, Zone III 210℃, Zone IV 220℃, Zone V 210℃, Zone VI 210℃, Die head 210℃, and screw speed 250 r / min. After extrusion, the material is cooled, pelletized, and dried, then blown into a 30μm thick film with a haze of 6.8% using a blown film extruder.

[0089] Example 3

[0090] The low-haze LLDPE film-grade material contains the following components:

[0091] LLDPE: DFDA 7042 91.4 portions;

[0092] Antioxidant: 0.1 parts SONOX 1076, 0.05 parts SONOX;

[0093] Antistatic agent: 1800 0.03 parts;

[0094] Acid absorbent: 0.01 parts zinc stearate, 0.01 parts calcium stearate;

[0095] Processing aid: Kynar Flex PPA 2821 0.4 parts;

[0096] Nucleating agent masterbatch: 8 parts.

[0097] The steps for preparing the nucleating agent masterbatch are as follows:

[0098] 1) The nucleating agent NP503 was mechanically ground in a ball mill at a speed of 300 r / min for 3 h to obtain nucleating agent powder;

[0099] 2) Polyvinyl alcohol 088-05 was dissolved in DMF at a temperature of 90℃ and a rotation speed of 250r / min to form a 5wt% polyvinyl alcohol dispersion.

[0100] 3) Under stirring at 500 r / min, the nucleating agent powder is slowly added to the polyvinyl alcohol dispersion in step 2) to obtain a nucleating agent microemulsion with a concentration of 30 wt%.

[0101] 4) Place the nucleating agent microemulsion from step 3) at room temperature for 48 hours to allow the DFM in the microemulsion to evaporate completely, and obtain a nucleating agent powder with a polyvinyl alcohol ultrafilm coated on the surface.

[0102] 5) POE 8540 and polyethylene wax WH WAX are blended at a mass ratio of 7:3 to obtain a mixture. The nucleating agent powder coated with polyvinyl alcohol ultrafilm from step 4) is then melt-blended with the above mixture in a mixer at 190°C to obtain a nucleating agent masterbatch with a concentration of 5 wt%. The steps for preparing the low-haze LLDPE film-specific material are as follows:

[0103] LLDPE resin, antioxidant, antistatic agent, acid scavenger, processing aid, and nucleating agent masterbatch were mixed in a high-speed mixer for 5 minutes according to the specified ratio. The uniformly mixed material was then granulated in a twin-screw extruder. The extruder temperatures were set as follows: Zone I 190℃, Zone II 200℃, Zone III 210℃, Zone IV 220℃, Zone V 210℃, Zone VI 210℃, Die head 210℃, and screw speed 250 r / min. After extrusion, the material was cooled, pelletized, and dried before being blown into a 30 μm thick film with a haze of 6.5%.

[0104] Comparative Example 1

[0105] The only difference from Example 1 is that the nucleating agent NP503 is not subjected to mechanical grinding in a ball mill, and everything else is the same as in Example 1; it is blow-molded into a 30μm thick film with a haze of 7.5%.

[0106] Comparative Example 2

[0107] The difference from Example 1 is that after mechanically grinding the nucleating agent NP503 in a ball mill, it is not treated with polyvinyl alcohol dispersion to form a nucleating agent powder with a polyvinyl alcohol ultrafilm on the surface. Instead, the ball-milled nucleating agent powder is directly mixed with POE and polyethylene wax to form a masterbatch, that is, steps 2), 3), and 4) are omitted. Everything else is the same as in Example 1. It is blow-molded into a 30μm thick film with a haze of 8.0%.

[0108] Comparative Example 3

[0109] The difference from Example 1 is that the nucleating agent powder coated with a polyvinyl alcohol ultrafilm is not mixed with POE and polyethylene wax to form a masterbatch, but is directly added to the special material (i.e., step 5 is omitted). Then, the nucleating agent powder coated with a polyvinyl alcohol ultrafilm is directly mixed with LLDPE resin, antioxidant, antistatic agent, acid scavenger, and processing aid to form granules. All other conditions are the same as in Example 1. The film is blow-molded to a thickness of 30 μm with a haze of 7.4%.

[0110] Comparative Example 4

[0111] The difference from Example 1 is that no nucleating agent masterbatch is added to the low-haze LLDPE film special material; otherwise, it is the same as Example 1. It is blown into a 30μm thick film with a haze of 9.2%.

Claims

1. A method for preparing a nucleating agent masterbatch, comprising the following steps: 1) The nucleating agent is mechanically ground and activated to obtain nucleating agent powder; 2) Prepare a uniform dispersion of polyvinyl alcohol and a good solvent; 3) Add the nucleating agent powder to the dispersion of step 2) to obtain a nucleating agent microemulsion; 4) Let the nucleating agent microemulsion from step 3) stand until the solvent in the microemulsion evaporates completely to obtain nucleating agent powder with a polyvinyl alcohol ultrafilm coated on the surface. 5) The nucleating agent powder coated with polyvinyl alcohol ultrafilm in step 4) is melt-blended with POE and polyethylene wax to obtain nucleating agent masterbatch.

2. The preparation method according to claim 1, characterized in that: Step 1) The nucleating agent is a carboxylate nucleating agent, preferably a benzoate nucleating agent, and more preferably a hexahydrophthalic acid metal salt nucleating agent; the mechanical grinding activation is preferably carried out by ball milling, with a ball milling speed of 300-450 r / min and a ball milling time of 1-3 h.

3. The preparation method according to claim 1, characterized in that: Step 2) The degree of polymerization of the polyvinyl alcohol is 300-1700, preferably 300-500; preferably, the degree of alcoholysis of the polyvinyl alcohol is 78-99%, more preferably 78-88%; the good solvent is preferably one or more of water, DMF, and DMSO; the concentration of the dispersion is preferably 2-8 wt%; the preparation process is preferably accompanied by heating and stirring, with a heating temperature of 90-100℃ and a stirring speed of 200-300 r / min.

4. The preparation method according to claim 1, characterized in that: Step 3) The nucleating agent content in the microemulsion is 20-40 wt%, preferably 20-30 wt%; Step 3) preferably involves adding the nucleating agent powder while stirring, with a stirring speed of 200-1000 r / min, preferably 400-600 r / min.

5. The preparation method according to claim 1, characterized in that: Step 5) The POE melt flow rate is 1-2 g / 10 min, under test conditions of 2.16 kg and 190℃; the preferred density is 0.890-0.910 g / cm³. 3 The preferred polyethylene wax has a weight-average molecular weight of 500-5000 g / mol.

6. The preparation method according to claim 1 or 5, characterized in that: Step 5) The mass ratio of POE to polyethylene wax is 2-9:1; preferably, the concentration of the nucleating agent masterbatch is 1-5wt%, more preferably 1-2wt%; the heating and melting temperature is preferably 170-200℃.

7. A low-haze LLDPE film-specific material, characterized in that, It includes the following components: LLDPE resin: 90-95 parts; Antioxidant: 0.05-0.15 parts; Antistatic agent: 0.01-0.05 parts; Acid absorbent: 0.01-0.05 parts; Processing aids: 0.1-0.5 parts; Nucleating agent masterbatch: 1-8 parts.

8. The low-haze LLDPE film-specific material according to claim 7, characterized in that: The density of the LLDPE resin is 0.915-0.925 g / cm³. 3 Preferably, the melt flow rate of the LLDPE resin is 0.5-5.0 g / 10 min, under test conditions of 2.16 kg and 190 °C; the antioxidant is preferably one or more of 1076, 1010, 168, and 3114; the antistatic agent is preferably one or more of fatty acid esters, amine ethoxide, and fatty amine polyoxyethylene ether; the acid scavenger is preferably one or more of zinc stearate and calcium stearate; and the processing aid is preferably one or more of vinylidene fluoride / tetrafluoroethylene / hexafluoropropylene copolymer, polysiloxane, and silicone.

9. A method for preparing a low-haze LLDPE film-specific material, characterized in that, Includes the following steps: S1: Mix the LLDPE resin, antioxidant, antistatic agent, acid absorber, processing aid, and nucleating agent masterbatch prepared by any one of the preparation methods described in claims 7 or 8 evenly to obtain a preliminary mixture; S2: The preliminary mixture obtained in step S1 is transferred to a twin-screw extruder for extrusion granulation. After cooling, pelletizing, and drying, a low-haze LLDPE film-specific material is obtained. Preferably, the heating and melting temperature of the twin-screw extruder is 180-230℃, the extrusion temperature is 190-220℃, and the screw speed is 200-350 r / min.

10. The application of the LLDPE film special material prepared by the preparation method according to claim 9 in the fields of packaging film and agricultural film.

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