Polypropylene sheet and preparation method thereof

Abstract

The present invention relates to the field of foaming materials technology, specifically providing a polypropylene sheet and its preparation method. The sheet is prepared from 50-70 parts of a propylene-octene copolymer, 30-50 parts of a propylene-styrene copolymer, 10-20 parts of an inorganic filler, 1-5 parts of a toughening agent, and 1-3 parts of an antioxidant. The foamed sheet produced using these raw materials exhibits significantly improved foaming performance, mechanical properties, surface quality, and heat resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of foaming materials, in particular to a polypropylene sheet and a preparation method thereof. Background Art

[0002] Polypropylene foam is widely used in various industries, particularly in the automotive, home appliance, construction, and packaging sectors. Conventional polypropylene foam boards often sacrifice mechanical properties, heat resistance, or surface appearance while reducing density, limiting their performance in demanding applications. Existing foam boards mostly utilize a single polypropylene resin or enhance certain properties by adding traditional modifiers and plasticizers. However, these often struggle to achieve optimal foaming, mechanical properties, thermal stability, and appearance.

[0003] Therefore, there is an urgent need for a new type of polypropylene foam material that can optimize the foaming effect, improve mechanical properties, rigidity and surface quality while maintaining lightweight, and is especially suitable for application scenarios with high requirements on appearance, strength and heat resistance. Summary of the Invention

[0004] In view of this, the present invention proposes a polypropylene sheet and a preparation method thereof, which combines low-crystallinity, high-fluidity polypropylene with high-rigidity, high-strength polypropylene. Through reasonable proportioning, a balance is achieved in the foaming effect, mechanical properties, surface appearance, heat resistance and other aspects of the foamed board.

[0005] The technical solution of the present invention is achieved as follows: the present invention provides a polypropylene sheet, the raw materials of which are prepared from 50-70 parts of propylene-octene copolymer, 30-50 parts of propylene-styrene copolymer, 10-20 parts of inorganic filler, 1-5 parts of toughening agent and 1-3 parts of antioxidant.

[0006] In some embodiments, the propylene-octene copolymer has a melt index of 50-100 g / 10 min at a temperature of 230° C. and a load of 2.16 kg.

[0007] In some embodiments, the propylene-octene copolymer has a crystallinity of no greater than 15%.

[0008] In some embodiments, the propylene-styrene copolymer has a melt index of 15-40 g / 10 min at a temperature of 230° C. and a load of 2.16 kg.

[0009] In some embodiments, the tensile strength of the propylene-styrene copolymer is ≥40 MPa.

[0010] In some embodiments, the heat distortion temperature of the propylene-styrene copolymer is ≥150°C.

[0011] In some embodiments, the inorganic filler is nano-calcium carbonate or nano-talc.

[0012] In some embodiments, the toughening agent is epoxidized olive oil.

[0013] In some embodiments, the antioxidant is BHT.

[0014] The second aspect of the present invention further provides a method for preparing the above-mentioned polypropylene sheet, comprising the following steps:

[0015] The raw materials are mixed according to weight ratio and added into a twin-screw extruder. After melting, extrusion, cooling and granulation, pellets are obtained. The pellets are mixed evenly with a foaming agent and then foamed and injection molded to obtain a polypropylene sheet.

[0016] The screw speed of the twin-screw extruder is 150-250rpm, the feed temperature is 150-170℃, the melting zone temperature is 180-220℃, the extrusion zone temperature is 200-230℃, the extrusion pressure is 10-30MPa, the cooling temperature is 15-25℃, and the granulation speed is 50-100rpm.

[0017] The screw temperature of foam injection molding is 180-220℃, the mold temperature is 40-70℃, the injection pressure is 50-90MPa, the injection speed is 30-60mm / s, the foaming temperature is 230-250℃, and the foaming pressure is 40-60MPa.

[0018] The foaming agent includes conventional physical foaming agents such as nitrogen, carbon dioxide, helium and chemical foaming agents such as one of azo compounds, chloride foaming agents and hydrolysis foaming agents, preferably azodicarbonamide.

[0019] When azodicarbonamide is used, the dosage is 0.5-3 wt% of the polypropylene.

[0020] The present invention has the following beneficial effects compared to the prior art:

[0021] The present invention optimizes the foaming effect by rationally selecting and proportioning low-crystallinity polypropylene and high-rigidity polypropylene. During the foaming process, low-crystallinity polypropylene helps to improve the distribution and uniformity of the foam, while high-rigidity polypropylene provides the required strength and rigidity. This combination ensures that the density of the foamed board is significantly reduced while maintaining good structural stability. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the present invention belong. If the definitions set forth in this section are contrary to or otherwise inconsistent with definitions set forth in the patents, patent applications, published patent applications, and other publications incorporated herein by reference, the definitions listed in this section take precedence over the definitions incorporated herein by reference.

[0024] Unless otherwise specified, the methods used in the following examples are conventional methods. The materials, reagents, and instruments used are conventional materials, reagents, and instruments in the art, unless otherwise specified, and can be obtained commercially by those skilled in the art.

[0025] When an amount, concentration or other value or parameter is expressed as a range, a preferred range or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within the range. In the present specification and claims, range definitions may be combined and / or interchanged, and if not otherwise stated, such ranges include all subranges contained therein.

[0026] By combining low-crystallinity propylene-octene copolymer with high-rigidity, high-strength propylene-styrene copolymer, this solution achieves an excellent balance between foaming efficiency and mechanical properties. The low-crystallinity polypropylene improves fluidity and bubble uniformity during the foaming process, while the high-rigidity, high-strength polypropylene ensures the material's high rigidity and high-temperature resistance.

[0027] Propylene-octene copolymer has a high melt index and low crystallinity, which allows for uniform bubble distribution during the foaming process and effectively reduces the density of the foamed board. This low density, combined with the high strength of propylene-styrene copolymer, significantly enhances the mechanical properties of the foamed board.

[0028] High-rigidity polypropylene ensures the rigidity and strength of the foam board by increasing its tensile strength and heat deflection temperature (HDT), especially when used in high-temperature and high-pressure environments, and can maintain good stability. The introduction of low-crystallinity polypropylene also reduces surface defects, giving the board a smooth, high-quality surface.

[0029] Epoxidized olive oil not only improves the impact toughness of the material, but also optimizes the low-temperature impact performance of the foam board, thereby improving the durability and long-term stability of the material.

[0030] The addition of antioxidant BHT can effectively prevent the thermal oxidation aging of polypropylene foam board and extend the service life of the board. Especially in high temperature or strong ultraviolet light environment, it can improve the stability of the foam board.

[0031] The propylene-octene copolymer used in the following examples has a melt index of 80 g / 10 min and a crystallinity of 10% under the conditions of a temperature of 230° C. and a load of 2.16 kg.

[0032] The propylene-styrene copolymer has a melt index of 30 g / 10 min, a tensile strength of 50 MPa, and a heat distortion temperature of 150° C. under the conditions of a temperature of 230° C. and a load of 2.16 kg.

[0033] Example 1

[0034] This embodiment provides a method for preparing a polypropylene sheet of two-component polypropylene.

[0035] Raw material ratio:

[0036] Propylene-octene copolymer: 60 parts

[0037] Propylene-styrene copolymer: 40 parts

[0038] Nano calcium carbonate: 10 parts

[0039] Epoxidized olive oil: 3 parts

[0040] BHT: 2 parts

[0041] Azodicarbonamide foaming agent: 1.5 parts

[0042] Preparation method:

[0043] The raw materials are mixed according to weight ratio and added into a twin-screw extruder. After melting, extrusion, cooling and granulation, pellets are obtained. The pellets are mixed evenly with a foaming agent and then foamed and injection molded to obtain a polypropylene sheet.

[0044] Process conditions:

[0045] Twin-screw extruder temperature: feed temperature 160°C, melting zone: 200°C, extrusion zone: 220°C, cooling temperature: 20°C, pelletizing speed: 70 rpm.

[0046] Foam injection molding: screw temperature: 200℃, mold temperature: 60℃, injection pressure: 60MPa, injection speed: 50mm / s, foaming temperature: 240℃, foaming pressure: 50MPa.

[0047] Example 2

[0048] This embodiment provides a method for preparing a polypropylene sheet of two-component polypropylene.

[0049] Raw material ratio:

[0050] Propylene-octene copolymer: 50 parts

[0051] Propylene-styrene copolymer: 50 parts

[0052] Nano calcium carbonate: 15 parts

[0053] Epoxidized olive oil: 5 parts

[0054] BHT: 2 parts

[0055] Azodicarbonamide foaming agent: 2 parts

[0056] Preparation method:

[0057] The raw materials are mixed according to weight ratio and added into a twin-screw extruder. After melting, extrusion, cooling and granulation, pellets are obtained. The pellets are mixed evenly with a foaming agent and then foamed and injection molded to obtain a polypropylene sheet.

[0058] Process conditions:

[0059] Twin-screw extruder temperature: feed temperature 170°C, melting zone: 210°C, extrusion zone: 225°C, cooling temperature: 22°C, pelletizing speed: 80 rpm.

[0060] Foam injection molding: screw temperature: 210℃, mold temperature: 65℃, injection pressure: 70MPa, injection speed: 55mm / s, foaming temperature: 250℃, foaming pressure: 55MPa.

[0061] Example 3

[0062] This embodiment provides a method for preparing a polypropylene sheet of two-component polypropylene.

[0063] Raw material ratio:

[0064] Propylene-octene copolymer: 70 parts

[0065] Propylene-styrene copolymer: 30 parts

[0066] Nano calcium carbonate: 15 parts

[0067] Epoxidized olive oil: 3 parts

[0068] BHT: 2.5 parts

[0069] Azodicarbonamide foaming agent: 0.5 parts

[0070] Preparation method:

[0071] The raw materials are mixed according to weight ratio and added into a twin-screw extruder. After melting, extrusion, cooling and granulation, pellets are obtained. The pellets are mixed evenly with a foaming agent and then foamed and injection molded to obtain a polypropylene sheet.

[0072] Process conditions:

[0073] Twin-screw extruder temperature: feed temperature 165°C, melting zone: 195°C, extrusion zone: 215°C, cooling temperature: 18°C, pelletizing speed: 75 rpm.

[0074] Foam injection molding: screw temperature: 210℃, mold temperature: 55℃, injection pressure: 65MPa, injection speed: 45mm / s, foaming temperature: 245℃, foaming pressure: 52MPa.

[0075] Comparative Example 1

[0076] This comparative example provides a method for preparing a conventional polypropylene sheet.

[0077] Raw material ratio:

[0078] Single polypropylene: 100 parts

[0079] Nano calcium carbonate: 15 parts

[0080] Epoxidized olive oil: 5 parts

[0081] BHT: 2 parts

[0082] Azodicarbonamide foaming agent: 2 parts

[0083] Preparation method:

[0084] The raw materials are mixed according to weight ratio and added into a twin-screw extruder. After melting, extrusion, cooling and granulation, pellets are obtained. The pellets are mixed evenly with a foaming agent and then foamed and injection molded to obtain a polypropylene sheet.

[0085] Process conditions:

[0086] Twin-screw extruder temperature: feed temperature 160°C, melting zone: 190°C, extrusion zone: 210°C, cooling temperature: 18°C, pelletizing speed: 70 rpm.

[0087] Foam injection molding: screw temperature: 200℃, mold temperature: 50℃, injection pressure: 60MPa, injection speed: 40mm / s, foaming temperature: 240℃, foaming pressure: 50MPa.

[0088] Comparative Example 2

[0089] This comparative example provides a method for preparing a conventional modified polypropylene sheet.

[0090] Raw material ratio:

[0091] Propylene-ethylene copolymer: 60 parts

[0092] Polyethylene: 40 parts

[0093] Nano calcium carbonate: 15 parts

[0094] Epoxidized olive oil: 5 parts

[0095] BHT: 2 parts

[0096] Azodicarbonamide foaming agent: 2 parts

[0097] Preparation method:

[0098] The raw materials are mixed according to weight ratio and added into a twin-screw extruder. After melting, extrusion, cooling and granulation, pellets are obtained. The pellets are mixed evenly with a foaming agent and then foamed and injection molded to obtain a polypropylene sheet.

[0099] Process conditions:

[0100] Twin-screw extruder temperature: feed temperature 160°C, melting zone: 200°C, extrusion zone: 220°C, cooling temperature: 20°C, pelletizing speed: 75 rpm.

[0101] Foam injection molding: screw temperature: 210℃, mold temperature: 60℃, injection pressure: 65MPa, injection speed: 45mm / s, foaming temperature: 250℃, foaming pressure: 55MPa.

[0102] The tensile strength, flexural strength, heat deformation temperature, and surface quality of the polypropylene sheets prepared in the above different embodiments and comparative examples were measured and evaluated, and the results were shown in the following table:

[0103]

[0104] By comparing the above embodiments and comparative examples, it can be seen that the solution of the present application significantly improves the foaming ratio by precisely controlling the ratio of low crystallinity and high rigidity polypropylene, and can significantly reduce the density of the material compared to traditional single polypropylene or traditional modified polypropylene.

[0105] Comparing the tensile strength, flexural strength, heat deformation temperature and other data of the embodiments and comparative examples, the scheme of the present application has a very obvious improvement. For example, the tensile strength in the embodiments is above 40 MPa, and the flexural strength exceeds 60 MPa, while these traditional indicators are lower.

[0106] In terms of surface smoothness and defect control, this application ensures that the surface quality of the foamed board far exceeds that of traditional solutions through reasonable proportions and precise foaming processes. The surface of the embodiment is smooth with almost no obvious defects, while the traditional solution has a rough surface and bubble defects.

[0107] The present invention utilizes high-rigidity polypropylene to increase the heat distortion temperature of the material. For example, the heat distortion temperature in the embodiment reaches over 150°C, while the heat distortion temperature in conventional solutions is lower (around 140°C). This makes the polypropylene foam board of the present invention more stable in high-temperature environments.

[0108] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A polypropylene sheet, characterized in that: The invention is prepared from 50-70 parts of a propylene-octene copolymer, 30-50 parts of a propylene-styrene copolymer, 10-20 parts of an inorganic filler, 1-5 parts of a toughening agent and 1-3 parts of an antioxidant. The propylene-octene copolymer has a melt index of 50-100 g / 10 min at a temperature of 230° C. and a load of 2.16 kg, a crystallinity of no more than 15%, a melt index of 15-40 g / 10 min at a temperature of 230° C. and a load of 2.16 kg, a tensile strength of 40 MPa or greater, and a heat distortion temperature of 150° C. or greater.

2. The polypropylene sheet according to claim 1, wherein The inorganic filler is nano calcium carbonate or nano talc.

3. The polypropylene sheet according to claim 1, wherein The toughening agent is epoxidized olive oil.

4. The polypropylene sheet according to claim 1, wherein The antioxidant is BHT.

5. A method for preparing a polypropylene sheet according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: mixing raw materials in proportion by weight and adding them into a twin-screw extruder; melting, extruding, cooling and granulating to obtain pellets; uniformly mixing the pellets with a foaming agent; and performing foaming injection molding to obtain a polypropylene sheet.

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