Light micro-foaming packaging material

Abstract

The invention discloses a light micro-foaming packaging material. The light micro-foaming packaging material is an interlayer micro-foaming material of an A-B-A structure. Wherein A is a polyvinyl chloride film layer with the thickness of 0.02-0.2 mm; b is a micro-foaming layer with the thickness of 1-10 mm; the light micro-foaming packaging material is obtained through co-extrusion foaming of three layers, a composite foaming agent prepared from SBS rubber powder, low-alcoholysis-degree thermoplastic polyvinyl alcohol powder, a foaming agent and an inorganic nucleating agent is added into a foaming layer, bubbles are completely wrapped, cell collapse is prevented, and gas overflow in the presence of fiber filler is avoided; foaming agents with different gas generation temperatures are adopted during foaming, the gas generation amount of the low-temperature foaming agent is small, many and fine micro-bubbles are easily formed, and uniform micro-bubbles are constructed as initial foaming; the high-temperature foaming agent is large in gas generation amount and high in foaming temperature, and further performs re-foaming on the constructed microbubbles at high temperature; stepped foaming is carried out by designing the foaming agent composition, foam wall breakage and collapse caused by one-time large-air-flow foaming are avoided, and the stable high-quality micro-foaming packaging material is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of special foaming materials, and in particular relates to a light micro-foaming packaging material. Background Art

[0002] With the rapid development of logistics and e-commerce, the requirements for packaging materials are getting higher and higher. On the one hand, packaging materials are required to have good cushioning and protection functions, be lightweight, green, and low-cost; on the other hand, packaging materials must meet good strength support.

[0003] Polyvinyl chloride (PVC) has the characteristics of abundant sources, low price and wide application, and has great development potential in the fields of building materials and packaging materials. For example, polyvinyl chloride foam board has the characteristics of moisture resistance and easy cutting, and is widely used in construction, furniture, decorative materials, advertising panels, etc. In the packaging field, polyvinyl chloride replaces high-cost polyethylene and polyurethane, and has the characteristics of being more green and low-carbon.

[0004] Packaging materials made of foamed polyvinyl chloride are widely used. It can not only be used as a cushion for various cushioning packages, but also can be made into boxes and trays for take-out insulation boxes, packaging turnover boxes for precision devices such as LCD screens, etc., with the characteristics of lightness, durability and shockproof. However, the foaming process control of polyvinyl chloride foam materials is relatively difficult. Due to the poor plasticity and low melt strength of polyvinyl chloride, more plasticizers are used in thermoplastic processing, and it is difficult to form stable closed cells. The usual foaming is fine and concave and convex, resulting in reduced support strength of the foamed material and easy brittle impact fracture. Especially when more fillers are added to the foaming system to reduce costs, high filling will cause gas to escape, resulting in uneven pore structure and rough surface, which will affect the quality of the foamed material, and there are problems such as easy breakage, low support strength, and easy cracking on impact. Based on this background, the opening research purpose of the present invention is to promote the formation of closed-cell uniform microbubbles by introducing functional raw materials and process control, and to give the packaging material excellent cushioning support properties through microfoaming. Summary of the invention

[0005] At present, polyvinyl chloride high-filling foam materials have defects such as few closed cells and low supporting strength as packaging materials. The purpose of the present invention is to solve the above problems and provide a lightweight micro-foam packaging material. A composite foaming agent prepared by SBS rubber powder, low alcoholysis degree thermoplastic polyvinyl alcohol powder, foaming agent and inorganic nucleating agent is added to the foaming layer. The SBS rubber powder is easy to form a film, which will completely wrap the bubbles to prevent the collapse of the bubbles and avoid the escape of gas in the presence of fiber fillers, so as to achieve the purpose of micro-foaming. At the same time, a thin film layer is designed on the surface of the foaming material to further improve the quality of the foaming material.

[0006] In order to achieve the above purpose, the specific technical solution adopted is:

[0007] A light micro-foam packaging material, characterized in that: the light micro-foam packaging material is a sandwich micro-foam material with an ABA structure; wherein A is a polyvinyl chloride film layer with a thickness of 0.02-0.2 mm; B is a micro-foam layer with a thickness of 1-10 mm; the light micro-foam packaging material is prepared by the following method:

[0008] (1) Premixing of the A layer material: According to the formula design by weight, 100 parts of polyvinyl chloride, 3-5 parts of MBS resin, 30-40 parts by weight of plasticizer, 1-3 parts of heat stabilizer, and 0.2-0.5 parts of lubricating agent are added into a high-speed mixer and mixed evenly, so that the plasticizer can fully penetrate the polyvinyl chloride, and the mixture is used as the A layer material for standby use;

[0009] (2) Premixing of the base material of layer B: According to the formula design by weight, 100 parts of polyvinyl chloride, 15-20 parts of plasticizer, 35-45 parts of fibrous filler, 1-3 parts of foaming regulator, 1-3 parts of heat stabilizer, and 0.5-1 parts of lubricating agent are put into a high-speed mixer and mixed evenly, and the mixture is used as the base material of layer B for standby use;

[0010] (3) Prefabrication of composite micro foaming agent: according to the formula design by weight, 60-70 parts of SBS rubber powder, 20-30 parts of inorganic nucleating agent, 5-10 parts of low alcoholysis degree thermoplastic polyvinyl alcohol powder, 2 parts of low-temperature foaming agent, and 3-5 parts of high-temperature foaming agent are added into a high-speed mixer and mixed evenly to prepare the composite micro foaming agent for standby use;

[0011] (4) A three-layer co-extrusion twin-screw extruder is used as the extrusion foaming equipment, and the A layer material is added to the upper extruder and the lower extruder for extrusion; the B layer base material is added to the middle layer extruder for extrusion, and a composite micro-foaming agent is added in the sixth section of the middle layer extruder through a loss-in-weight scale, and the amount of the composite micro-foaming agent added is 20% of the weight of the B layer base material; through hot melt extrusion of the three-layer co-extrusion twin-screw extruder, a composite layer of a three-layer structure is formed at the T-shaped die head, and extruded and foamed through the die, stretched, and roller-shaped to form a lightweight micro-foaming packaging material with an ABA structure.

[0012] Preferably, the polyvinyl chloride in step (1) is at least one of SG2, SG3, and SG4; it has good flexibility and film-forming properties and is distributed in the outer layer of the foaming material. On the one hand, it prevents the gas in the inner foaming layer from escaping during foaming to form unstable bubbles; on the other hand, the inner foaming layer uses more fibrous inorganic powder, and the good film-forming layer of the outer layer ensures that the appearance of the foaming material is smooth and without bumps.

[0013] Preferably, the MBS resin in step (1) is a terpolymer of methyl methacrylate-butadiene-styrene, and the content of methyl methacrylate is 60-70%. This ensures that MBS and polyvinyl chloride are well compatible and dispersed to form a homogeneous phase. MBS not only improves the flow and film-forming properties of polyvinyl chloride, but also is used for the outer layer of the foaming material to enhance the impact resistance of the foaming material, so that the foaming material has good impact resistance when used as a packaging material.

[0014] Preferably, the plasticizer in step (1) and step (2) is selected from at least one of dioctyl phthalate (DOP), diisooctyl phthalate (DIOP), and dibutyl phthalate (DBP) as a main plasticizer, and at least one of dioctyl sebacate (DOS) and epoxidized soybean oil as a secondary plasticizer, and the main plasticizer and the secondary plasticizer are used in a mass ratio of 100:5-10.

[0015] Preferably, the heat stabilizer in step (1) and step (2) is at least one of zinc stearate, calcium stearate and barium stearate.

[0016] Preferably, the lubricating aid in step (1) uses at least one of silicone powder and polyethylene wax as an external lubricant; using the external lubricant on the outer layer of the foaming material can easily obtain a foaming material with a smooth surface and at the same time can enhance the water repellency of the foaming material.

[0017] Preferably, the polyvinyl chloride in step (2) is selected from at least one of SG5, SG6, and SG7 as needed.

[0018] Preferably, the lubricating aid in step (2) uses at least one of stearic acid amide, N,N-ethylene bisstearamide, oleic acid amide, and tristearic acid glyceryl as an internal lubricant; using the internal lubricant in the inner layer of the foaming material can easily improve the extrusion processing fluidity of the material.

[0019] Preferably, the foaming regulator in step (2) is a commercial acrylate foaming regulator; the foaming regulator is used to improve the processing fluidity and melt strength of polyvinyl chloride and promote uniform and fine foaming.

[0020] Preferably, the fibrous filler in step (2) is selected from at least one of needle-shaped wollastonite, calcium sulfate whiskers, and sepiolite fibers with a fibrous structure; the fibrous filler is used to reduce costs on the one hand, and has good cushioning, flexibility, and support in the foaming material on the other hand. In the foaming material, the fibrous fillers are entangled and interwoven with each other, and are not easy to break when impacted, which effectively increases the packaging support strength of the foaming packaging material.

[0021] Preferably, the particle size of the SBS rubber powder in step (3) is ≤20 μm; the low alcoholysis thermoplastic polyvinyl alcohol powder is obtained by plasticizing polyvinyl alcohol with an alcoholysis degree of 80-85% with a plasticizer; the SBS rubber powder is a block copolymer of styrene and butadiene, and when combined with the low alcoholysis thermoplastic polyvinyl alcohol powder, it has good compatibility, adhesion, elasticity, and hot-melt film-forming properties in the polyvinyl chloride system. By preparing a composite foaming agent with a foaming agent and an inorganic nucleating agent, and adding it at the rear end of the extruder after the polyvinyl chloride and the fiber filler are completely dispersed, the SBS rubber powder is easy to form a film, which will completely wrap the bubbles, prevent the bubble collapse, and avoid the gas escape in the presence of the fiber filler, so as to achieve the purpose of micro-foaming.

[0022] Preferably, the inorganic nucleating agent in step (3) is light calcium carbonate with a particle size range of 3-5 μm.

[0023] Preferably, the low-temperature foaming agent in step (3) is at least one of 4,4-oxybisbenzenesulfonyl hydrazide (OBSH) and sodium bicarbonate; the high-temperature foaming agent is azodicarbonamide (AC). 4,4-oxybisbenzenesulfonyl hydrazide (OBSH) and sodium bicarbonate have small gas emission, are easy to form many and delicate microbubbles, and have low foaming temperature, and are used as initial foaming to construct uniform microbubbles; azodicarbonamide has large gas emission and high foaming temperature, and further re-foams the constructed microbubbles at high temperature; step-wise foaming is performed by designing the composition of the foaming agent, thereby avoiding the rupture and collapse of the bubble wall caused by a large amount of foaming at one time.

[0024] The three-layer co-extrusion twin-screw extruder in step (4) is automatically controlled to control the extrusion temperature by a temperature control meter and an electromagnetic water valve internal circulation, and the temperature error range is controlled within ±5°C; the temperature control standard is: 90°C for the first stage; 100°C for the second stage; 130°C for the third stage; 130°C for the fourth stage; 120°C for the fifth stage; 110°C for the sixth stage; 120°C for the seventh stage; 140°C for the eighth stage; 160°C for the ninth stage; 180°C for the tenth stage; and 200°C for the die. After the composite microfoaming agent is added by a weight loss scale in the sixth stage, as the temperature rises, the foaming agent gradually foams, thereby forming stable, uniform and delicate microfoams.

[0025] Three-layer co-extrusion can be melt extruded through independent extrusion units and compounded by a designed T-die at the die mouth of the die head. This design ensures that different materials are at different levels of the foaming material. In addition, by adjusting the speed and temperature of each extrusion unit, the thickness and flow rate of each layer of plastic can be accurately controlled, thereby ensuring the quality and performance of the film.

[0026] In step (4), the thickness of layer A and layer B are controlled by PLC according to the needs of extrusion foaming through the die. The thickness of each layer of extrusion foaming is controlled by PLC accurately controlling the feeding amount and the stretching and pulling speed; the gap between the shaping rollers is adjusted to accurately determine the thickness of the final product. The photoelectric automatic deviation correction device is used for correction and trimming.

[0027] As a wider application range, the lightweight micro-foam packaging material of the present invention has a wide thickness range. When the thickness is less than 2.5 mm, it can be collected in a winding manner; when the thickness is greater than 2.5 mm, it can be collected in a cutting and stacking manner.

[0028] The light micro-foam packaging material of the present invention can still be micro-foamed to form fine, uniform and delicate micro closed cells when highly filled through the selection and compounding of raw materials and process control. While achieving light-weight cushioning, the material has good support, anti-warping deformation and dimensional shrinkage, and greatly improves the quality of the micro-foam packaging material.

[0029] Compared with the prior art, the present invention has the following outstanding features:

[0030] (1) The polyvinyl chloride molecular chain is relatively short and the melt strength is low. During foaming, the melt is insufficient to wrap the bubbles. Especially when the filling is high, the foaming gas is very easy to escape and form large bubbles or break the wall and collapse. The present invention adds a composite foaming agent prepared by SBS rubber powder, low alcoholysis degree thermoplastic polyvinyl alcohol powder, foaming agent, and inorganic nucleating agent to the foaming layer to completely wrap the bubbles, prevent the cell collapse, and avoid gas escape in the presence of high filling of fiber filler, so as to achieve the purpose of obtaining stable and high-quality micro-foam packaging materials.

[0031] (2) The present invention forms a thin film layer on the surface of the foaming material through three-layer co-extrusion foaming to prevent the gas in the inner foaming layer from escaping and forming unstable bubbles during foaming; the inner foaming layer uses a large amount of fibrous inorganic powder, and the outer layer has a good film-forming layer to ensure that the appearance of the foaming material is smooth and without bumps.

[0032] (3) The present invention uses foaming agents with different gas generation temperatures during foaming. Sodium bicarbonate has a small gas generation amount and is easy to form many and fine microbubbles, and the foaming temperature is low. It is used as the initial foaming to construct uniform microbubbles; azodicarbonamide has a large gas generation amount and a high foaming temperature, and the constructed microbubbles are further re-foamed at a high temperature; and by designing the composition of the foaming agent for step-by-step foaming, it is avoided that the bubble wall ruptures and collapses caused by a large amount of foaming at one time.

[0033] (4) The lightweight micro-foam packaging material of the present invention is easy to prepare, the material thickness is adjustable, and it has good support, impact resistance, and cushioning properties; it has a wide range of applications and can be used as a cushion, support plate, box plate, etc. for packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to further clarify the technical implementation scheme of the present invention, the present invention is further described below in conjunction with the accompanying drawings:

[0035] Figure 1 It is a structural schematic diagram of a lightweight micro-foam packaging material of the present invention. DETAILED DESCRIPTION

[0036] The following examples are intended to further describe the implementation process of the technical content of the present invention, but are not intended to limit the scope of protection of the claims of the present invention. If no specific conditions are specified in the examples, the experiments were carried out according to conventional conditions or raw materials.

[0037] Raw material preparation:

[0038] Low alcoholysis degree thermoplastic polyvinyl alcohol powder: obtained by using polyvinyl alcohol with an alcoholysis degree of 80-85% and glycerol plasticizer.

[0039] Foaming regulator QL-903 was provided by Linqu Qili Catalyst Co., Ltd.

[0040] Foaming agent regulators HL-100 and HL-200 were provided by Shandong Riko Chemical Co., Ltd.

[0041] Example 1

[0042] A light micro-foam packaging material is a sandwich micro-foam material with an ABA structure; wherein A is a polyvinyl chloride film layer with a thickness of 0.05 mm; and B is a micro-foam layer with a thickness of 2 mm. The light micro-foam packaging material is prepared by the following method:

[0043] (1) Premixing of the A layer material: According to the formula design by weight, 100 parts of SG4 polyvinyl chloride, 5 parts of MBS resin with a methyl methacrylate content of 60%, 30 parts of plasticizer dioctyl phthalate, 2 parts of plasticizer epoxy soybean oil, 1 part of heat stabilizer zinc stearate, 1 part of barium stearate, and 0.3 parts of lubricating auxiliary polyethylene wax are added into a high-speed mixer and mixed evenly to allow the plasticizer to fully penetrate the polyvinyl chloride, and the mixture is used as the A layer material for standby use;

[0044] (2) Premixing of the base material of layer B: According to the formula design by weight, 100 parts of SG7 polyvinyl chloride, 14 parts of plasticizer dioctyl phthalate, 1 part of plasticizer epoxy soybean oil, 35 parts of fibrous filler calcium sulfate whisker, 2 parts of HL-100 foaming regulator, 1 part of heat-resistant stabilizer calcium stearate, 1 part of barium stearate, and 1 part of lubricating aid N,N-ethylene bisstearamide are put into a high-speed mixer and mixed evenly, and used as the base material of layer B for later use;

[0045] (3) Preparation of composite micro foaming agent: according to the formula design by weight, 65 parts of SBS rubber powder with a particle size of ≤20 μm, 30 parts of light calcium carbonate with a particle size range of 3-5 μm, 10 parts of thermoplastic polyvinyl alcohol powder with low alcoholysis degree, 2 parts of 4,4-oxybisbenzenesulfonyl hydrazide (OBSH), and 4 parts of azodicarbonamide (AC) are added into a high-speed mixer and mixed evenly to prepare the composite micro foaming agent for standby use;

[0046] (4) A three-layer co-extrusion twin-screw extruder is used as the extrusion foaming equipment, and the A layer material is added to the upper extruder and the lower extruder for extrusion; the B layer base material is added to the middle layer extruder for extrusion, and a composite micro-foaming agent is added to the sixth section of the middle layer extruder through a weight loss scale, and the amount of the composite micro-foaming agent added is 20% of the weight of the B layer base material; the three-layer co-extrusion twin-screw extruder is automatically controlled by a temperature controller and an electromagnetic water valve internal circulation to control the extrusion temperature, and the temperature error range is controlled within ±5°C; the temperature control standard is: 90°C for the first section; 100°C for the second section; 130°C for the third section; 130°C for the fourth section; 120°C for the fifth section; 110°C for the sixth section; 120°C for the seventh section; 140°C for the eighth section; 160°C for the ninth section; 180°C for the tenth section; and 200°C for the die. The three-layer co-extrusion can be melt-extruded through an independent extrusion unit, and compounded by designing a T-die at the die mouth of the die head. This design ensures that different materials are at different levels of the foaming material. As the temperature rises, the foaming agent gradually foams to form stable, uniform, and delicate micro-bubbles. PLC is linked to control, and the thickness of each layer of extruded foaming is controlled by accurately controlling the feeding amount and stretching traction speed through PLC; the gap between the shaping rollers is adjusted to accurately determine the thickness of the final product. The photoelectric automatic deviation correction device is used for correction, trimming, and winding to obtain a lightweight micro-foam packaging material.

[0047] Example 2

[0048] A light micro-foam packaging material is a sandwich micro-foam material with an ABA structure; wherein A is a polyvinyl chloride film layer with a thickness of 0.1 mm; and B is a micro-foam layer with a thickness of 8 mm. The light micro-foam packaging material is prepared by the following method:

[0049] (1) Premixing of the A layer material: According to the formula design by weight, 100 parts of SG4 polyvinyl chloride, 5 parts of MBS resin with a methyl methacrylate content of 60%, 30 parts of plasticizer dioctyl phthalate, 2 parts of plasticizer epoxy soybean oil, 1 part of heat-resistant stabilizer calcium stearate, 1 part of barium stearate, and 0.3 parts of lubricating auxiliary polyethylene wax are added into a high-speed mixer and mixed evenly, so that the plasticizer can fully penetrate the polyvinyl chloride, and the mixture is used as the A layer material for standby use;

[0050] (2) Premixing of the base material of layer B: According to the formula design by weight, 100 parts of SG5 polyvinyl chloride, 16 parts of plasticizer dioctyl phthalate, 1 part of plasticizer epoxy soybean oil, 45 parts of fibrous filler calcium sulfate whisker, 3 parts of QL-903 foaming regulator, 1 part of heat stabilizer calcium stearate, 1 part of barium stearate, and 1 part of lubricating aid oleic acid amide are put into a high-speed mixer and mixed evenly, and used as the base material of layer B for standby use;

[0051] (3) Preparation of composite micro foaming agent: according to the formula design by weight, 65 parts of SBS rubber powder with a particle size of ≤20 μm, 30 parts of light calcium carbonate with a particle size range of 3-5 μm, 10 parts of thermoplastic polyvinyl alcohol powder with low alcoholysis degree, 2 parts of 4,4-oxybisbenzenesulfonyl hydrazide (OBSH), and 5 parts of azodicarbonamide (AC) are added into a high-speed mixer and mixed evenly to prepare the composite micro foaming agent for standby use;

[0052] (4) A three-layer co-extrusion twin-screw extruder is used as the extrusion foaming equipment, and the A layer material is added to the upper extruder and the lower extruder for extrusion; the B layer base material is added to the middle layer extruder for extrusion, and a composite micro-foaming agent is added to the sixth section of the middle layer extruder through a weight loss scale, and the amount of the composite micro-foaming agent added is 20% of the weight of the B layer base material; the three-layer co-extrusion twin-screw extruder is automatically controlled by a temperature controller and an electromagnetic water valve internal circulation to control the extrusion temperature, and the temperature error range is controlled within ±5°C; the temperature control standard is: 90°C for the first section; 100°C for the second section; 130°C for the third section; 130°C for the fourth section; 120°C for the fifth section; 110°C for the sixth section; 120°C for the seventh section; 140°C for the eighth section; 160°C for the ninth section; 180°C for the tenth section; and 200°C for the die. The three-layer co-extrusion can be melt-extruded through an independent extrusion unit, and compounded by designing a T-die at the die mouth of the die head. This design ensures that different materials are at different levels of the foaming material. As the temperature rises, the foaming agent gradually foams to form stable, uniform, and delicate micro-bubbles. PLC is linked to control, and the thickness of each layer of extruded foaming is controlled by accurately controlling the feeding amount and stretching traction speed through PLC; the gap between the shaping rollers is adjusted to accurately determine the thickness of the final product. The photoelectric automatic deviation correction device is used for correction, trimming, cutting on demand, and stacking to obtain lightweight micro-foam packaging materials.

[0053] Example 3

[0054] A light micro-foam packaging material is a sandwich micro-foam material with an ABA structure; wherein A is a polyvinyl chloride film layer with a thickness of 0.1 mm; and B is a micro-foam layer with a thickness of 6 mm. The light micro-foam packaging material is prepared by the following method:

[0055] (1) Premixing of the A layer material: According to the formula design by weight, 100 parts of SG4 polyvinyl chloride, 5 parts of MBS resin with a methyl methacrylate content of 60%, 30 parts of plasticizer dioctyl phthalate, 2 parts of plasticizer epoxy soybean oil, 1 part of heat-resistant stabilizer calcium stearate, 1 part of barium stearate, and 0.3 parts of lubricating auxiliary polyethylene wax are added into a high-speed mixer and mixed evenly, so that the plasticizer can fully penetrate the polyvinyl chloride, and the mixture is used as the A layer material for standby use;

[0056] (2) Premixing of the base material of layer B: According to the formula design by weight, 100 parts of SG6 polyvinyl chloride, 15 parts of plasticizer dibutyl phthalate, 1 part of plasticizer dioctyl sebacate, 40 parts of fibrous filler sepiolite fiber, 2 parts of HL-200 foaming regulator, 1 part of heat-resistant stabilizer calcium stearate, 1 part of barium stearate, and 1 part of lubricating auxiliary oleic acid amide are put into a high-speed mixer and mixed evenly, and used as the base material of layer B for standby use;

[0057] (3) Preparation of composite micro foaming agent: according to the formula design by weight, 65 parts of SBS rubber powder with a particle size of ≤20 μm, 25 parts of light calcium carbonate with a particle size range of 3-5 μm, 10 parts of thermoplastic polyvinyl alcohol powder with low alcoholysis degree, 2 parts of sodium bicarbonate, and 4 parts of azodicarbonamide (AC) are added into a high-speed mixer and mixed evenly to prepare the composite micro foaming agent for standby use;

[0058] (4) A three-layer co-extrusion twin-screw extruder is used as the extrusion foaming equipment, and the A layer material is added to the upper extruder and the lower extruder for extrusion; the B layer base material is added to the middle layer extruder for extrusion, and a composite micro-foaming agent is added to the sixth section of the middle layer extruder through a weight loss scale, and the amount of the composite micro-foaming agent added is 20% of the weight of the B layer base material; the three-layer co-extrusion twin-screw extruder is automatically controlled by a temperature controller and an electromagnetic water valve internal circulation to control the extrusion temperature, and the temperature error range is controlled within ±5°C; the temperature control standard is: 90°C for the first section; 100°C for the second section; 130°C for the third section; 130°C for the fourth section; 120°C for the fifth section; 110°C for the sixth section; 120°C for the seventh section; 140°C for the eighth section; 160°C for the ninth section; 180°C for the tenth section; and 200°C for the die. The three-layer co-extrusion can be melt-extruded through an independent extrusion unit, and compounded by designing a T-die at the die mouth of the die head. This design ensures that different materials are at different levels of the foaming material. As the temperature rises, the foaming agent gradually foams to form stable, uniform, and delicate micro-bubbles. PLC is linked to control, and the thickness of each layer of extruded foaming is controlled by accurately controlling the feeding amount and stretching traction speed through PLC; the gap between the shaping rollers is adjusted to accurately determine the thickness of the final product. The photoelectric automatic deviation correction device is used for correction, trimming, cutting on demand, and stacking to obtain lightweight micro-foam packaging materials.

[0059] Comparative Example 1

[0060] According to the scheme of Example 2, the extrusion of the upper and lower layers of material A is directly shut down during the process, and the A layer film is not laminated above and below the foaming layer. During foaming, there is a certain amount of gas leakage from the foaming layer, resulting in an uneven surface or openings, which affects the appearance quality and impact strength of the foaming material.

[0061] Comparative Example 2

[0062] A light micro-foam packaging material is a sandwich micro-foam material with an ABA structure; wherein A is a polyvinyl chloride film layer with a thickness of 0.1 mm; and B is a micro-foam layer with a thickness of 8 mm. The light micro-foam packaging material is prepared by the following method:

[0063] (1) Premixing of the A layer material: According to the formula design by weight, 100 parts of SG4 polyvinyl chloride, 5 parts of MBS resin with a methyl methacrylate content of 60%, 30 parts of plasticizer dioctyl phthalate, 2 parts of plasticizer epoxy soybean oil, 1 part of heat-resistant stabilizer calcium stearate, 1 part of barium stearate, and 0.3 parts of lubricating auxiliary polyethylene wax are added into a high-speed mixer and mixed evenly, so that the plasticizer can fully penetrate the polyvinyl chloride, and the mixture is used as the A layer material for standby use;

[0064] (2) Premixing of the base material of layer B: According to the formula design by weight, 100 parts of SG5 polyvinyl chloride, 16 parts of plasticizer dioctyl phthalate, 1 part of plasticizer epoxy soybean oil, 45 parts of fibrous filler calcium sulfate whisker, 3 parts of QL-903 foaming regulator, 1 part of heat stabilizer calcium stearate, 1 part of barium stearate, and 1 part of lubricating aid oleic acid amide are put into a high-speed mixer and mixed evenly, and used as the base material of layer B for standby use;

[0065] (3) Preparation of composite micro foaming agent: according to the formula design by weight, 65 parts of SBS rubber powder with a particle size of ≤20 μm, 30 parts of light calcium carbonate with a particle size range of 3-5 μm, 10 parts of thermoplastic polyvinyl alcohol powder with low alcoholysis degree, and 7 parts of azodicarbonamide are added into a high-speed mixer and mixed evenly to prepare the composite micro foaming agent for standby use;

[0066] (4) A three-layer co-extrusion twin-screw extruder is used as the extrusion foaming equipment, and the A layer material is added to the upper extruder and the lower extruder for extrusion; the B layer base material is added to the middle layer extruder for extrusion, and a composite micro-foaming agent is added to the sixth section of the middle layer extruder through a weight loss scale, and the amount of the composite micro-foaming agent added is 20% of the weight of the B layer base material; the three-layer co-extrusion twin-screw extruder is automatically controlled by a temperature controller and an electromagnetic water valve internal circulation to control the extrusion temperature, and the temperature error range is controlled within ±5°C; the temperature control standard is: 90°C for the first section; 100°C for the second section; 130°C for the third section; 130°C for the fourth section; 120°C for the fifth section; 110°C for the sixth section; 120°C for the seventh section; 140°C for the eighth section; 160°C for the ninth section; 180°C for the tenth section; and 200°C for the die. The three-layer co-extrusion can be melt extruded through an independent extrusion unit, and compounded by designing a T-die at the die mouth of the die head, and PLC is linked to control. The PLC accurately controls the feeding amount and the stretching and pulling speed to control the thickness of each layer of the extruded foaming; adjust the gap between the shaping rollers to accurately determine the thickness of the final product. Use the photoelectric automatic deviation correction device to correct, trim, cut on demand, and stack to obtain lightweight micro-foam packaging materials.

[0067] Compared with Example 2, this test scheme uses a foaming agent AC with a large gas generation amount and a high foaming temperature. Due to rapid foaming, it is easy to cause the foam wall to rupture and form open holes, making it difficult to obtain a micro-foaming effect, which is manifested in the low impact strength of the material in the final material. This defect is more obvious when the filling is high. For example, in Comparative Example 3, the amount of calcium sulfate whiskers added is reduced to 20 parts, and the gas escape is reduced, and the amount of open holes is reduced.

[0068] Comparative Example 3

[0069] According to the scheme of Comparative Example 2, the amount of calcium sulfate whisker added was reduced from 45 parts to 20 parts.

[0070] Comparative Example 4

[0071] A light micro-foam packaging material is a sandwich micro-foam material with an ABA structure; wherein A is a polyvinyl chloride film layer with a thickness of 0.1 mm; and B is a micro-foam layer with a thickness of 8 mm. The light micro-foam packaging material is prepared by the following method:

[0072] (1) Premixing of the A layer material: According to the formula design by weight, 100 parts of SG4 polyvinyl chloride, 5 parts of MBS resin with a methyl methacrylate content of 60%, 30 parts of plasticizer dioctyl phthalate, 2 parts of plasticizer epoxy soybean oil, 1 part of heat-resistant stabilizer calcium stearate, 1 part of barium stearate, and 0.3 parts of lubricating auxiliary polyethylene wax are added into a high-speed mixer and mixed evenly, so that the plasticizer can fully penetrate the polyvinyl chloride, and the mixture is used as the A layer material for standby use;

[0073] (2) Premixing of the base material of layer B: According to the formula design by weight, 100 parts of SG5 polyvinyl chloride, 16 parts of plasticizer dioctyl phthalate, 1 part of plasticizer epoxy soybean oil, 45 parts of fibrous filler calcium sulfate whisker, 3 parts of QL-903 foaming regulator, 1 part of heat stabilizer calcium stearate, 1 part of barium stearate, and 1 part of lubricating aid oleic acid amide are put into a high-speed mixer and mixed evenly, and used as the base material of layer B for standby use;

[0074] (3) Preparation of composite micro foaming agent: According to the formula design by weight, 30 parts of light calcium carbonate with a particle size range of 3-5 μm, 2 parts of 4,4-oxybisbenzenesulfonyl hydrazide (OBSH), and 5 parts of azodicarbonamide (AC) are added into a high-speed mixer and mixed evenly to prepare the composite micro foaming agent for standby use;

[0075] (4) A three-layer co-extrusion twin-screw extruder is used as the extrusion foaming equipment, and the A layer material is added to the upper extruder and the lower extruder for extrusion; the B layer base material is added to the middle layer extruder for extrusion, and a composite micro-foaming agent is added to the sixth section of the middle layer extruder by a loss-in-weight scale, and the amount of the composite micro-foaming agent added is 6.6% of the weight of the B layer base material; the three-layer co-extrusion twin-screw extruder is automatically controlled by a temperature controller and an electromagnetic water valve internal circulation to control the extrusion temperature, and the temperature error range is controlled within ±5°C; the temperature control standard is: 90°C for the first section; 100°C for the second section; 130°C for the third section; 130°C for the fourth section; 120°C for the fifth section; 110°C for the sixth section; 120°C for the seventh section; 140°C for the eighth section; 160°C for the ninth section; 180°C for the tenth section; and 200°C for the die. The three-layer co-extrusion can be melt-extruded through an independent extrusion unit, and compounded by designing a T-die at the die mouth of the die head. This design ensures that different materials are at different levels of the foaming material. As the temperature rises, the foaming agent gradually foams to form stable, uniform, and delicate micro-bubbles. PLC is linked to control, and the thickness of each layer of extruded foaming is controlled by accurately controlling the feeding amount and stretching traction speed through PLC; the gap between the shaping rollers is adjusted to accurately determine the thickness of the final product. The photoelectric automatic deviation correction device is used for correction, trimming, cutting on demand, and stacking to obtain lightweight micro-foam packaging materials.

[0076] This solution does not use SBS rubber powder and low-alcoholysis thermoplastic polyvinyl alcohol powder. The gas encapsulation property becomes poor during foaming, the bubbles are easy to collapse, and the gas escape is obvious in the presence of fiber fillers, making it difficult to obtain stable and high-quality micro-foam packaging materials.

[0077] Performance effect evaluation:

[0078] The density, impact strength and compression strength of the samples of Examples 1-3 and Comparative Examples 1-4 were tested. The compression properties of each sample were tested with reference to GB / T8813-2020 "Determination of Compression Properties of Rigid Foam Plastics". As shown in Table 1. The simply supported beam impact strength, compression strength and density were comprehensively compared for evaluation.

[0079] Table 1:

[0080]

[0081] Through comprehensive comparative analysis of test data and performance, the technical solution of the present invention adds a composite foaming agent prepared by SBS rubber powder, low alcoholysis thermoplastic polyvinyl alcohol powder, foaming agent, and inorganic nucleating agent to the foaming layer, which will completely wrap the bubbles, prevent the collapse of the bubbles, and avoid the gas escape in the presence of fiber fillers, so as to achieve the purpose of obtaining stable and high-quality micro-foam packaging materials. At a lower foaming density, it has both good impact strength and compression strength; a thin film layer is formed on the surface of the foaming material to prevent the gas from escaping from the inner foaming layer during foaming to form unstable bubbles; the inner foaming layer uses more fibrous inorganic powder, and the outer layer has a good film-forming layer to ensure that the appearance of the foaming material is smooth and has no bumps. The foaming material is suitable for various pads and boxes.

[0082] It should be understood that although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of protection of the technical solution of the present invention. Moreover, the description of each feature or aspect in each embodiment should be applicable to other similar features or aspects in other embodiments. It should be understood by those of ordinary skill in the art that the packaging materials involved in the technical ideas of the present invention are not limited to being used as packaging materials in a narrow sense, but are within the scope of protection of the present invention without departing from the technology of the present invention.

Claims

1. A lightweight micro-foam packaging material, characterized in that: The lightweight micro-foam packaging material is a sandwich micro-foam material with an ABA structure; wherein A is a polyvinyl chloride film layer with a thickness of 0.02-0.2 mm; and B is a micro-foam layer with a thickness of 1-10 mm. The lightweight micro-foam packaging material is prepared by the following method: (1) Premixing of the A layer material: According to the formula design by weight, 100 parts of polyvinyl chloride, 3-5 parts of MBS resin, 30-40 parts by weight of plasticizer, 1-3 parts of heat stabilizer, and 0.2-0.5 parts of lubricating agent are added into a high-speed mixer and mixed evenly, so that the plasticizer can fully penetrate the polyvinyl chloride, and the mixture is used as the A layer material for standby use; (2) Premixing of the base material of layer B: According to the formula design by weight, 100 parts of polyvinyl chloride, 15-20 parts of plasticizer, 35-45 parts of fibrous filler, 1-3 parts of foaming regulator, 1-3 parts of heat stabilizer, and 0.5-1 parts of lubricating agent are put into a high-speed mixer and mixed evenly, and the mixture is used as the base material of layer B for standby use; (3) Prefabrication of composite micro foaming agent: according to the formula design by weight, 60-70 parts of SBS rubber powder, 20-30 parts of inorganic nucleating agent, 5-10 parts of low alcoholysis degree thermoplastic polyvinyl alcohol powder, 2 parts of low-temperature foaming agent, and 3-5 parts of high-temperature foaming agent are added into a high-speed mixer and mixed evenly to prepare the composite micro foaming agent for standby use; (4) A three-layer co-extrusion twin-screw extruder is used as the extrusion foaming equipment, and the A layer material is added to the upper extruder and the lower extruder for extrusion; the B layer base material is added to the middle layer extruder for extrusion, and a composite micro-foaming agent is added in the sixth section of the middle layer extruder through a loss-in-weight scale, and the amount of the composite micro-foaming agent added is 20% of the weight of the B layer base material; through hot melt extrusion of the three-layer co-extrusion twin-screw extruder, a composite layer of a three-layer structure is formed at the T-shaped die head, and extruded and foamed through the die, stretched, and roller-shaped to form a lightweight micro-foaming packaging material with an ABA structure.

2. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: The polyvinyl chloride in step (1) is selected from at least one of SG2, SG3, and SG4; the polyvinyl chloride in step (2) is selected from at least one of SG5, SG6, and SG7.

3. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: The MBS resin in step (1) is a terpolymer of methyl methacrylate-butadiene-styrene, and the content of methyl methacrylate in the terpolymer is 60-70%.

4. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: In step (1) and step (2), the plasticizer is selected from at least one of dioctyl phthalate, diisooctyl phthalate, and dibutyl phthalate as a main plasticizer, and at least one of dioctyl sebacate and epoxy soybean oil as a secondary plasticizer. The main plasticizer and the secondary plasticizer are used in a mass ratio of 100:5-10.

5. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: The heat stabilizer in step (1) and step (2) is at least one of zinc stearate, calcium stearate and barium stearate.

6. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: The lubricating agent in step (1) uses at least one of silicone powder and polyethylene wax as an external lubricant; the lubricating agent in step (2) uses at least one of stearic acid amide, N,N-ethylene bisstearamide, oleic acid amide, and tristearic acid glyceryl as an internal lubricant.

7. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: The foaming regulator in step (2) is an acrylic foaming regulator.

8. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: The particle size of the SBS rubber powder in step (3) is ≤20 μm; the low alcoholysis degree thermoplastic polyvinyl alcohol powder is obtained by plasticizing polyvinyl alcohol with an alcoholysis degree of 80-85% with a plasticizer.

9. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: The inorganic nucleating agent in step (3) is light calcium carbonate with a particle size range of 3-5 μm.

10. A lightweight micro-foam packaging material as claimed in claim 1, characterized in that: In step (3), the low-temperature foaming agent is selected from at least one of 4,4-oxobisbenzenesulfonylhydrazine and sodium bicarbonate; and the high-temperature foaming agent is selected from azodicarbonamide.

Images