CN110549707B

CN110549707B - A kind of foamed polypropylene composite sheet and preparation method thereof

Info

Publication number: CN110549707B
Application number: CN201910759338.8A
Authority: CN
Inventors: 王玲; 何顺涛; 何顺伦; 侯建鸣; 赵志刚
Original assignee: Hefei Senye Light Plastics Technology Co ltd
Current assignee: He Shuntao
Priority date: 2019-08-16
Filing date: 2019-08-16
Publication date: 2021-08-17
Anticipated expiration: 2039-08-16
Also published as: CN110549707A

Abstract

本发明公开了一种发泡聚丙烯复合片材及其制备方法，所述片材由外至内依次包括：增韧层，包括表面复合有热塑性弹性体或聚氯乙烯的交联发泡聚丙烯；增强层，包括聚酯/聚烯烃/有机蒙脱土复合物；芯层，包括发泡倍率为2～5倍的发泡复合材料；所述复合片材的厚度为4～6mm，弯曲模量为1100～1400MPa。本发明提供的发泡聚丙烯复合片材在发泡倍率提升的过程中，依然保有较高的弯曲强度，并且由于在复合片材中加入了高比表面、高表面活性的无机颗粒，使得产品对有害气体具有一定吸附能力，实现了降低VOC释放的目的，适合推广使用。The invention discloses a foamed polypropylene composite sheet and a preparation method thereof. The sheet sequentially includes from outside to inside: a toughening layer, comprising a cross-linked foamed polymer compound composited with thermoplastic elastomer or polyvinyl chloride on the surface. Propylene; reinforcement layer, including polyester/polyolefin/organic montmorillonite composite; core layer, including foamed composite material with an expansion ratio of 2 to 5 times; the thickness of the composite sheet is 4 to 6 mm, curved The modulus is 1100-1400MPa. The foamed polypropylene composite sheet provided by the present invention still maintains high bending strength in the process of increasing the foaming ratio, and since inorganic particles with high specific surface and high surface activity are added to the composite sheet, the product It has a certain adsorption capacity for harmful gases, and achieves the purpose of reducing VOC release, which is suitable for popularization and use.

Description

Foamed polypropylene composite sheet and preparation method thereof

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a foamed polypropylene composite sheet and a preparation method thereof.

Background

In recent years, with the development of polypropylene modified materials, the physical mechanical properties and the processability of the polypropylene modified materials are greatly improved, and the polypropylene modified materials are widely applied to automotive interiors. The comprehensive performance of the supercritical physical foaming polypropylene is higher than that of the commercialized PE/PS/PU foaming material at present, the supercritical physical foaming polypropylene is a preferable material for simultaneously realizing environmental friendliness and performance guarantee, can replace PS/PE and partial PU foaming materials, is used for manufacturing packaging and mechanical parts, has a great market development space, and becomes a development hotspot of novel functional plastics.

However, the expanded polypropylene material has the defect that the physical strength (particularly rigidity) is sharply reduced along with the increase of the expansion ratio, and the application of the expanded polypropylene material in mechanical parts such as automotive upholsteries is limited. The relation between the flexural modulus Ec and the bulk modulus Ea of the material is

Wherein

The volume fraction of the foam pores in the foaming material is shown, n is a modification coefficient of the foam pore form, n is more than 1 and less than 2, the intrinsic modulus 1500MPa of polypropylene is taken as a reference, when the foaming multiplying power is 3 times and n is 2, the modulus of the foaming polypropylene is reduced to 550MPa and is only slightly higher than 300MPa of PE foam, and the application range of the foaming polypropylene is greatly limited.

In addition, when the polypropylene modified material is synthesized and formed from raw materials, especially when the polypropylene modified material is used in a composite manner, volatile organic compounds (TVOC) such as hydrocarbons, benzenes, aldehydes and amines can be generated in the aging process, which is harmful to human health, so that the raw materials and the processing technology need to be controlled.

Chinese patent with application number 201510776113.5 discloses a special low-VOC (volatile organic compound) polypropylene composite material for soft touch automotive interior trim, which comprises the following components in percentage by mass: polypropylene resin: 44-72.5%; a toughening agent: 5-10%; soft touch modifier: 5-10%; talc powder: 15-30%; odor absorbent: 1-3%; weather resistant agent: 0.5-1%; antioxidant: 0.5-1%; dispersing agent: 0.5 to 1 percent. The low VOC polypropylene resin, the toughening agent, the soft touch modifier and the talcum powder are used as main components, the odor absorbent, the weather resistant agent, the antioxidant and the dispersing agent are added, the proportion of various materials is controlled, extrusion granulation is carried out, products with low VOC and soft touch feeling are obtained, and the compound can be widely applied to automobile interior parts such as instrument panels, upright posts, glove boxes, door panels and the like. However, in the invention, the foamed polypropylene is not used as a matrix material, and the components are only subjected to a process of mixing and granulating, so that the effects of light weight and high specific strength of the foamed polypropylene cannot be enhanced.

The chinese patent with application number 201810791650.0 discloses a PVC-PP foamed composite material, which comprises from bottom to top in sequence: a foam layer: the foam layer is a polypropylene foam layer; horny layer: the horny layer comprises the following components in parts by weight: PVC resin powder: 30-45 parts of a solvent; a stabilizer: 1-3 parts; plasticizer: 1-5 parts; foaming agent: 2-6 parts; flame retardant: 0.5-3 parts; the cuticle and the foam layer are connected by adopting an adhesive; surface layer: the surface layer is a water-based polycarbonate polyurethane treating agent. The PVC-PP foaming composite material and the preparation method thereof adopt a vacuum forming technology, and the PVC-PP foaming composite material prepared by the method has excellent pattern stereoscopic impression and pattern retentivity, and has the advantages of low odor, low VOC, heat aging resistance, flame retardance and the like, and is long in service life and capable of meeting the application of automotive interior materials. Although the patent uses the foamed polypropylene and the polyvinyl chloride as the composite material, the adjustment of the self-component of the foamed polypropylene is not involved, and how to reduce the VOC cannot be known, and the description of the embodiment only refers to the hydrogen sulfide gas pollution parameter of the composite material, and the VOC can not be reduced due to the use of the plasticizer and the adhesive.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a foamed polypropylene composite sheet and a preparation method thereof, wherein a supercritical fluid foaming technology is utilized, and inorganic powder (with a certain particle size, length-diameter ratio and more active centers) with stronger adsorption effect on TVOC is added into the components of the foamed polypropylene, so that the adsorption of VOC is ensured, and the mechanical property of the foamed polypropylene of a core layer is improved to a certain extent. In addition, the composite sheet also has a reinforcing layer and a toughening layer, so that the comprehensive mechanical property of the sheet is further improved.

In order to solve the technical problems, the invention adopts the technical scheme that:

the invention provides a foamed polypropylene composite sheet, which sequentially comprises the following components from outside to inside: the toughening layer comprises crosslinked foaming polypropylene of which the surface is compounded with a thermoplastic elastomer or polyvinyl chloride; a reinforcing layer comprising a polyester/polyolefin/organo montmorillonite composite; the core layer comprises a foaming composite material with the foaming ratio of 2-5 times; the thickness of the composite sheet is 4-6 mm, and the flexural modulus is 1100-1400 MPa.

In the scheme, in order to reduce the influence of the foaming process on the intrinsic modulus of the polypropylene, the reinforcing layer containing the polyester and the organic modified montmorillonite is compounded with the foamed polypropylene core layer, so that the overall mechanical property of the sheet is improved. The foaming composite material of the core layer adopts the environment-friendly short-flow supercritical fluid extrusion foaming technology, compared with the traditional method in which Freon and alkane foaming agents are used for foaming, the harm of the foaming agents to the environment in the foaming process is reduced, and simultaneously, as CO is used for foaming₂Or N₂The gas stripping effect of the gas on TVOC small molecular substances and the rapid exchange effect of the gas and the air in the foaming process eliminate VOC in the finished product of the foaming composite material.

The further scheme of the invention is as follows: the foaming composite material of the core layer is prepared by supercritical foaming of the following raw materials:

in the scheme, the high melt strength polypropylene has wider processing temperature range compared with the traditional polypropylene, and the melt has excellent anti-sagging performance at higher temperature and longer heating time,is beneficial to the foaming processes of extrusion foaming, hollow forming, thermal forming and the like; and high melt strength polypropylene has a higher crystallization temperature and shorter crystallization time, thus allowing the thermoformed article to be demolded at higher temperatures. The supercritical foaming molding adopted by the invention is to inject supercritical carbon dioxide or nitrogen into a special plasticizing device, so that single-phase mixed sol is formed after the gas and the molten raw material are fully and uniformly mixed/diffused, and then the sol is guided into a mold cavity or an extrusion opening mold to generate large pressure drop of the sol, so that the gas is separated out to form a large amount of bubble cores; in the subsequent cooling and forming process, bubble nuclei in the sol continuously grow and are formed, and finally, the micropore foaming plastic product is obtained. The high melt strength polypropylene has higher melt strength and extensional viscosity, the extensional viscosity of the high melt strength polypropylene is increased along with the increase of shear stress and time, the strain hardening behavior promotes the growth stability of foam pores, the damage of microporous walls is limited, the foaming ratio of the polypropylene material is improved under the action of a supercritical foaming process, the collapse and shrinkage phenomena are reduced and avoided, and the cooled foaming material forms a uniform foam cell structure. The uniform cellular structure also ensures that the composite sheet material provided by the invention has the advantage of light weight under the condition of keeping a certain mechanical property, and the density of the composite sheet material is only 0.28-0.31 g/cm³。

The further scheme of the invention is as follows: the particle size of the inorganic powder is 10-50 microns, preferably 25-40 microns, and the length-diameter ratio of the inorganic powder is 5-20: 1, preferably 7-15: 1; the inorganic powder is selected from wollastonite, sericite or attapulgite, and is preferably attapulgite.

In the scheme, the inorganic powder with high major diameter ratio has a needle-shaped crystal structure similar to short fiber, and when the inorganic powder is used as a resin filler, the mechanical property and the dimensional stability of a product can be improved. And because the specific surface area of the wollastonite, the sericite and the attapulgite is larger and has certain polarity, the TVOC generated in the processing and forming process of the composite material can be adsorbed. Wherein the surface of the attapulgite crystal has 3 active adsorption centers, namely oxygen atoms in silicon-oxygen tetrahedrons, water molecules coordinated with magnesium ions at the edges and Si-OH ion groups on the outer surfaces of the tetrahedrons. And residual charges exist in the structure due to the crystal growth defects of the attapulgite, and the defect sites become crystal surface energy gathering points, have high adsorption activity and generally become active centers, so that the attapulgite becomes a polar adsorbent with high surface active center density, and the attapulgite is also the preferred inorganic powder.

The further scheme of the invention is as follows: the hyper-dispersant is selected from high molecular weight modified hyperbranched polyester without volatile components, preferably the Lobotai YY-502 or the Lobotai YY-702, and more preferably the Lobotai YY-502 and the Lobotai YY-702 are compounded in a mass ratio of 1: 2-3.

In the scheme, the high molecular weight hyper-dispersant is modified hyper-branched polyester without volatile components, such as hyper-branched polyester with hydroxyl terminated by isophorone diisocyanate modified lauric acid, part of the end cyano groups are made to be grafted into molecules by silane such as KH550, and end groups capable of anchoring on the surface of inorganic powder are formed; during foaming, according to heterogeneous nucleation theory, cell nuclei are preferentially formed on the surface of the inorganic powder, and the dispersing agent becomes a cell homogenizing agent in situ, so that the dispersing agent has higher efficiency relative to a small molecular weight cell homogenizing agent (such as stearic acid monoglyceride MS), and the cells of a foamed product are smaller and more uniform. The Lobotai YY-502 or YY-702 is a product model produced by Guangzhou Yuntai synthetic materials, Inc.

The further scheme of the invention is as follows: the enhancement layer is made of the following raw materials:

the intrinsic viscosity of the polyethylene terephthalate is 0.6 to 0.8dl/g, preferably 0.65 to 0.7 dl/g.

In the scheme, the polyethylene glycol terephthalate is selected from PET slices produced by Yanshan petrochemical engineering or characterized chemical fiber, the organic montmorillonite is selected from DK7 polymer grade organic soil of a Zhejiang Fenghong new material, and the montmorillonite has unique layered one-dimensional nano-structure characteristic, has designable reactivity among layers and has an ultra-large specific surface area (750 m)²The nanometer structure and the morphological characteristics are different from other two-dimensional and three-dimensional inorganic nanometer particles, and when the nanometer structure and the morphological characteristics are compounded with a polymer, the polymer material can be endowed with excellent mechanical property and thermal property, and the mechanical property of the foaming composite material is further improved.

The further scheme of the invention is as follows: the type of the polypropylene is selected from T30S or EPS30R, the type of the polypropylene in the foaming composite material of the core layer is EPS30R, and the type of the polypropylene in the raw material of the reinforcing layer is preferably T30S.

In the scheme, the EPS30R polypropylene is impact-resistant polypropylene, and the polypropylene and the high-melt-strength polypropylene are compounded in the core layer, so that the foamed core layer still keeps good flexural modulus and impact resistance; the T30S polypropylene is wire-drawing-grade homopolymerized polypropylene resin, has the characteristics of high tensile strength and low elongation, can replace glass fiber with poor compatibility with resin, and further improves the mechanical strength of the reinforcing layer after being compounded with other raw materials of the reinforcing layer.

The further scheme of the invention is as follows: the compatilizer is selected from one of PP-g-MA, PP-g-GMA, POE-g-MA or POE-g-GMA, and is preferably PP-g-MA or POE-g-MA; the particle size of the organic montmorillonite is 15-25 mu m.

The further scheme of the invention is as follows: the foaming polypropylene is cross-linked foaming polypropylene, and the foaming ratio is 10-30 times, preferably 15-20 times.

The invention also provides a preparation method of the foamed polypropylene composite sheet, which comprises the following steps:

(1) extruding and granulating raw materials of the foaming composite material, and then preparing a core layer sheet by a supercritical fluid extrusion foaming process;

(2) extruding and granulating the raw materials of the enhancement layer, plasticizing and extruding, and compounding the raw materials on two sides of the core layer sheet obtained in the step (1) to obtain an enhancement sheet;

(3) and (3) coating an adhesive film on the surface of the reinforced sheet obtained in the step (2), and then compounding the toughening layer on the surface of the reinforced sheet through hot pressing of the adhesive film to obtain the foamed polypropylene composite sheet.

In the preparation method, the two surfaces of the core layer sheet are preferably compounded with the reinforced layers respectively, one reinforced layer is selected to be compounded with the toughening layer, and the viscose film is selected from a thermoplastic elastomer POE film.

According to the preparation method, in the step (1), the raw material extrusion granulation of the foaming composite material comprises the following steps: stirring the weighed inorganic powder and the hyperdispersant at a high speed for 5-10 min, adding the weighed polypropylene with high melt strength and the polypropylene into the mixture, stirring the mixture at a low speed for 3-5 min, and extruding and granulating the mixture at 160-240 ℃; in the step (2), the raw material extrusion granulation of the reinforcing layer comprises: the weighed compatilizer, organic montmorillonite and polypropylene raw materials are dried for 2-3 hours in vacuum at 100 ℃, then extruded by a double screw to prepare precursor master batch, then the weighed polyethylene glycol terephthalate is dried for 4-6 hours in vacuum at 70-80 ℃, mixed with the precursor master batch and the like in a high-speed mixer for 5-10 min, and the obtained mixture is extruded and granulated at 180-260 ℃.

In the scheme, the extrusion granulation of the core layer raw material in the step (1) and the extrusion granulation of the enhancement layer raw material in the step (2) both limit the adding sequence and the stirring time of the raw materials, so as to further increase the uniformity of the raw materials, and enable the core layer and the enhancement layer produced subsequently to have better properties.

According to the preparation method, the preparation method specifically comprises the following steps:

(1) stirring weighed inorganic powder and hyperdispersant with the length-diameter ratio of 5-20: 1 and the particle size of 10-50 mu m at a high speed for 5-10 min, adding weighed high-melt-strength polypropylene and general polypropylene into the mixture, stirring the mixture at a low speed for 3-5 min to obtain a mixture, and extruding and granulating the mixture at 160-240 ℃ to obtain the special foaming material, wherein the weight ratio of each component in the special foaming material is as follows:

(2) adding the foaming special material obtained in the step (1) into a supercritical fluid extrusion foaming screw extruder, and accurately injecting CO into a metering section₂Controlling the injection amount of the liquid to be 0.3-3% of the special foaming material, so that the foaming ratio of the core layer is 2-5, adjusting the temperature of the extruder to 140-240 ℃, and simultaneously adjusting the pressure to be 7.8-20 MPa to enable CO to be in the range of₂The foaming sheet is in a supercritical state, is molded in a foaming mold and is foamed at a mold opening after temperature and pressure balance, and enters a laminating machine head for rigidity enhancement after cooling, rolling and traction;

(3) the method comprises the following steps of (1) drying weighed compatilizers, organic montmorillonite with the particle size of 15-25 mu m and polypropylene at 100 ℃ for 2-3 hours in vacuum, extruding the mixture through a double screw to prepare precursor master batch, drying weighed polyethylene glycol terephthalate with the intrinsic viscosity of 0.6-0.8 dl/g at 70-80 ℃ for 4-6 hours in vacuum, mixing the weighed polyethylene glycol terephthalate with the precursor master batch and the like in a high-speed stirrer for 5-10 minutes to obtain a mixture, and extruding and granulating the mixture at 180-260 ℃ to obtain the special material for the enhancement layer, wherein the weight ratio of each component in the special material for the enhancement layer is as follows:

(4) guiding the core layer prepared in the step (2) into a double roller of a double-layer laminating machine head through a guide roller, plasticizing and extruding the special material for the enhancement layer prepared in the step (3) into the double roller, adjusting the rotating speed of the double roller and the gap between the double rollers, controlling the composite thickness of the enhancement layer on the surface of the core layer to be 0.09-0.11 mm, cooling the sheets of the composite core layer and the enhancement layer, and guiding the sheets into a toughening layer composite machine head;

(5) and (3) coating a layer of POE film with the thickness of 0.03-0.05 mm on the surface of the composite sheet prepared in the step (4), meanwhile, guiding the toughening layer to the surface of the sheet coated with the POE composite layer through a guide roller, performing double-roller calendering treatment, and thermally compounding the toughening layer on the surface of the sheet coated with POE to prepare the foamed polypropylene composite sheet with the thickness of 4-6 mm.

After adopting the technical scheme, compared with the prior art, the invention has the following beneficial effects:

1. the core layer adopts high melt strength polypropylene and impact-resistant polypropylene, and is matched with a supercritical foaming process, so that the foaming ratio of the polypropylene material is improved, the collapse and shrinkage phenomena are reduced and avoided, the cooled foaming material forms a uniform cell structure, and the TVOC of the foaming material is reduced to the detection limit;

2. the core layer foaming composite material adopts inorganic powder with a certain length-diameter ratio and adsorption capacity, so that the mechanical property of the core layer foaming polypropylene is improved to a certain extent while the adsorption of VOC is ensured;

3. according to the preparation method of the foaming composite material, the raw materials of the core layer and the reinforcing layer are extruded and granulated in advance, and the raw materials are more uniform by adjusting the adding sequence and the stirring mode of the components, so that the core layer and the reinforcing layer which are produced subsequently have more excellent properties.

The following describes in further detail embodiments of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below, and the following embodiments are used for illustrating the present invention and are not used for limiting the scope of the present invention.

Example 1

In this example, the following method and components were used to prepare a foamed polypropylene composite sheet:

(1) the weighed attapulgite with the length-diameter ratio of 5:1 and the particle size of 30 mu m and the Lobotai YY-502 are stirred at a high speed for 10min, then the weighed polypropylene with high melt strength and the EPS30R polypropylene are added and stirred at a low speed for 5min, the mixture is obtained and extruded and granulated at 240 ℃ to obtain the special foaming material, and the special foaming material comprises the following components in parts by weight:

(2) adding the special foaming material obtained in the step (1) into a supercritical foaming screw extruder, and accurately injecting CO into a metering section₂Controlling the injection amount of the liquid to be 3 percent of the special foaming material and the foaming ratio to be 5, adjusting the temperature of the extruder to 140 ℃, and simultaneously adjusting the pressure to be 8.0MPa to ensure that CO is introduced₂The foaming sheet is in a supercritical state, is molded in a foaming mold and is foamed at a mold opening after temperature and pressure balance, and enters a laminating machine head for rigidity enhancement after cooling, rolling and traction;

(3) vacuum drying PP-g-MA, organic montmorillonite with the particle size of 25 mu m and T30S polypropylene at 100 ℃ for 2-3 hours, extruding by a double screw to prepare precursor master batch, vacuum drying polyethylene glycol terephthalate with the weighed intrinsic viscosity of 0.8dl/g at 80 ℃ for 4-6 hours, mixing with the precursor master batch and the like in a high-speed stirrer for 10 minutes to obtain a mixture, extruding and granulating at 260 ℃ to obtain the special material for the enhancement layer, wherein the weight ratio of each component in the special material for the enhancement layer is as follows:

(4) guiding the core layer prepared in the step (2) into a double roller of a double-layer laminating machine head through a guide roller, plasticizing and extruding the special material for the enhancement layer prepared in the step (3) into the double roller, adjusting the rotating speed of the double roller and the gap between the double rollers, controlling the composite thickness of the enhancement layer on the surface of the core layer to be 0.11mm, cooling the sheets of the composite core layer and the enhancement layer, and guiding the sheets into a toughening layer composite machine head;

(5) and (3) coating a layer of POE film with the thickness of 0.03mm on the surface of the composite sheet prepared in the step (4), meanwhile, guiding the toughening layer to the surface of the sheet coated with the POE composite layer through a guide roller, performing double-roller calendering treatment, and thermally compounding the toughening layer on the surface of the sheet coated with POE to prepare the foamed polypropylene composite sheet with the thickness of 4 mm.

Example 2

(1) the weighed attapulgite with the length-diameter ratio of 7:1 and the particle size of 10 mu m and the Lobotai YY-702 are stirred at a high speed for 5min, then the weighed polypropylene with high melt strength and the EPS30R polypropylene are added and stirred at a low speed for 3min, the mixture is obtained and extruded and granulated at 220 ℃ to obtain the special foaming material, and the special foaming material comprises the following components in parts by weight:

(2) adding the special foaming material obtained in the step (1) into a supercritical foaming screw extruder, and accurately injecting CO into a metering section₂Controlling the injection amount of liquid to be 3% of the special foaming material and the foaming ratio to be 5 times, adjusting the temperature of the extruder to 240 ℃, and simultaneously adjusting the pressure to be 20MPa to ensure that CO is introduced₂The foaming sheet is in a supercritical state, is molded in a foaming mold and is foamed at a mold opening after temperature and pressure balance, and enters a laminating machine head for rigidity enhancement after cooling, rolling and traction;

(3) vacuum drying POE-g-MA, organic montmorillonite with the particle size of 15 mu m and T30S polypropylene at 100 ℃ for 2-3 hours, extruding by a double screw to prepare precursor master batch, vacuum drying polyethylene glycol terephthalate with the weighed intrinsic viscosity of 0.6dl/g at 70 ℃ for 4-6 hours, mixing with the precursor master batch and the like in a high-speed stirrer for 5 minutes to obtain a mixture, extruding and granulating at 210 ℃ to obtain the special material for the enhancement layer, wherein the weight ratio of each component in the special material for the enhancement layer is as follows:

(4) guiding the core layer prepared in the step (2) into a double roller of a double-layer laminating machine head through a guide roller, plasticizing and extruding the special material for the enhancement layer prepared in the step (3) into the double roller, adjusting the rotating speed of the double roller and the gap between the double rollers, controlling the composite thickness of the enhancement layer on the surface of the core layer to be 0.09mm, and guiding the sheets of the composite core layer and the enhancement layer into a toughening layer composite machine head after cooling;

(5) and (3) coating a layer of POE film with the thickness of 0.05mm on the surface of the composite sheet prepared in the step (4), meanwhile, guiding the toughening layer to the surface of the sheet coated with the POE composite layer through a guide roller, performing double-roller calendering treatment, and thermally compounding the toughening layer on the surface of the sheet coated with POE to prepare the foamed polypropylene composite sheet with the thickness of 4 mm.

Example 3

(1) the weighed wollastonite with the length-diameter ratio of 18:1 and the particle size of 50 mu m and the hyperdispersant of the Robotai YY-502 and YY-702 (the ratio is 1:3) are stirred at a high speed for 10min, then the weighed high melt strength polypropylene and EPS30R polypropylene are added and stirred at a low speed for 5min, the mixture is obtained and extruded and granulated at 230 ℃ to obtain the special foaming material, and the special foaming material comprises the following components in parts by weight:

(2) adding the special foaming material obtained in the step (1) into a supercritical foaming screw extruder, and accurately injecting CO into a metering section₂Controlling the injection amount of liquid to be 0.3 percent of the special foaming material and the foaming ratio to be 2, adjusting the temperature of the extruder to 170 ℃, and simultaneously adjusting the pressure to be 12.5MPa to ensure that CO is introduced₂The foaming sheet is in a supercritical state, is molded in a foaming mold and is foamed at a mold opening after temperature and pressure balance, and enters a laminating machine head for rigidity enhancement after cooling, rolling and traction;

(3) weighing POE-g-GMA, organic montmorillonite with the particle size of 20 mu m and T30S polypropylene, drying for 2-3 hours in vacuum at 100 ℃, then extruding by a double screw to prepare precursor master batch, drying weighed polyethylene glycol terephthalate with the intrinsic viscosity of 0.65dl/g in vacuum at 75 ℃ for 4-6 hours, mixing with the precursor master batch and the like in a high-speed stirrer for 7.5 minutes to obtain a mixture, extruding and granulating at 210 ℃ to obtain the special material for the enhancement layer, wherein the weight ratio of each component in the special material for the enhancement layer is as follows:

(4) guiding the core layer prepared in the step (2) into a double roller of a double-layer laminating machine head through a guide roller, plasticizing and extruding the special material for the enhancement layer prepared in the step (3) into the double roller, adjusting the rotating speed of the double roller and the gap between the double rollers, controlling the composite thickness of the enhancement layer on the surface of the core layer to be 0.1mm, cooling the sheets of the composite core layer and the enhancement layer, and guiding the sheets into a toughening layer composite machine head;

(5) and (3) coating a layer of POE film with the thickness of 0.04mm on the surface of the composite sheet prepared in the step (4), meanwhile, guiding the toughening layer to the surface of the sheet coated with the POE composite layer through a guide roller, performing double-roller calendering treatment, and thermally compounding the toughening layer on the surface of the sheet coated with POE to prepare the foamed polypropylene composite sheet with the thickness of 5 mm.

Example 4

(1) the weighed wollastonite with the length-diameter ratio of 15:1 and the particle size of 25 mu m and the hyperdispersant of the Robotai YY-502 and YY-702 (the ratio is 1:2) are stirred at a high speed for 10min, then the weighed polypropylene with high melt strength and the EPS30R polypropylene are added and stirred at a low speed for 5min, the mixture is obtained and extruded and granulated at 160 ℃ to obtain the special foaming material, and the special foaming material comprises the following components in parts by weight:

(2) adding the special foaming material obtained in the step (1) into a supercritical foaming screw extruder, and accurately injecting CO into a metering section₂Controlling the injection amount of the liquid to be 2.1 percent of the special foaming material and the foaming ratio to be 4, adjusting the temperature of the extruder to 145 ℃, and simultaneously adjusting the pressure to be 8.2MPa to ensure that CO is introduced₂The foaming sheet is in a supercritical state, is molded in a foaming mold and is foamed at a mold opening after temperature and pressure balance, and enters a laminating machine head for rigidity enhancement after cooling, rolling and traction;

(3) vacuum drying PP-g-GMA, organic montmorillonite with the particle size of 20 mu m and T30S polypropylene at 100 ℃ for 2-3 hours, extruding by a double screw to prepare precursor master batch, vacuum drying polyethylene glycol terephthalate with the weighed intrinsic viscosity of 0.7dl/g at 75 ℃ for 4-6 hours, mixing with the precursor master batch and the like in a high-speed stirrer for 7.5 minutes to obtain a mixture, extruding and granulating at 180 ℃ to obtain the special material for the enhancement layer, wherein the weight ratio of each component in the special material for the enhancement layer is as follows:

(5) and (3) coating a layer of POE film with the thickness of 0.04mm on the surface of the composite sheet prepared in the step (4), meanwhile, guiding the toughening layer to the surface of the sheet coated with the POE composite layer through a guide roller, performing double-roller calendering treatment, and thermally compounding the toughening layer on the surface of the sheet coated with POE to prepare the foamed polypropylene composite sheet with the thickness of 6 mm.

Example 5

(1) the weighed sericite with the length-diameter ratio of 20:1 and the particle size of 40 mu m, and the hyperdispersant of the Robotia Y-502 and YY-702 (the ratio of 1:2.5) are stirred at a high speed for 10min, and then the weighed polypropylene with high melt strength and the EPS30R polypropylene are added and stirred at a low speed for 5min to obtain a mixture, and the mixture is extruded and granulated at 200 ℃ to obtain the special foaming material, wherein the special foaming material comprises the following components in parts by weight:

(2) adding the special foaming material obtained in the step (1) into a supercritical foaming screw extruder, and accurately injecting N into a metering section₂Controlling the injection amount of the liquid to be 3 percent of the special foaming material and the foaming ratio to be 5, adjusting the temperature of the extruder to 210 ℃, and simultaneously adjusting the pressure to be 15MPa to ensure that N is added₂The foaming sheet is in a supercritical state, is molded in a foaming mold and is foamed at a mold opening after temperature and pressure balance, and enters a laminating machine head for rigidity enhancement after cooling, rolling and traction;

(3) vacuum drying PP-g-MA, organic montmorillonite with the particle size of 20 mu m and T30S polypropylene at 100 ℃ for 2-3 hours, extruding by a double screw to prepare precursor master batch, vacuum drying polyethylene glycol terephthalate with the weighed intrinsic viscosity of 0.65dl/g at 75 ℃ for 4-6 hours, mixing with the precursor master batch and the like in a high-speed stirrer for 7.5 minutes to obtain a mixture, extruding and granulating at 190 ℃ to obtain the special material for the enhancement layer, wherein the weight ratio of each component in the special material for the enhancement layer is as follows:

Example 6

Example 7

(2) adding the special foaming material obtained in the step (1) into a supercritical foaming screw extruder, and accurately injecting CO into a metering section₂Controlling the injection amount of the liquid to be 3 percent of the special foaming material and the foaming ratio to be 5, adjusting the temperature of the extruder to 140 ℃, and simultaneously adjusting the pressure to be 8.0MPa to ensure that CO is introduced₂Is in super clinical conditionThe boundary state is formed in a foaming mould and foamed at a mould opening after the temperature and the pressure are balanced, and the foamed sheet enters a laminating machine head for reinforcement and strengthening after cooling, rolling and traction;

Example 8

(1) the weighed attapulgite with the length-diameter ratio of 15:1 and the particle size of 35 mu m, and the hyperdispersant of the Robotai YY-502 and YY-702 (the ratio is 1:2.5) are stirred at a high speed for 10min, and then the weighed polypropylene with high melt strength and the EPS30R polypropylene are added and stirred at a low speed for 5min, so that a mixture is obtained, and the mixture is extruded and granulated at the temperature of 200 ℃ to obtain the special foaming material, wherein the special foaming material comprises the following components in parts by weight:

(2) adding the special foaming material obtained in the step (1) into a supercritical foaming screw extruder, and accurately injecting CO into a metering section₂Controlling the injection amount of liquid to be 3% of the special foaming material and the foaming ratio to be 5, adjusting the temperature of the extruder to 150 ℃, and simultaneously adjusting the pressure to be 9.0MPa to ensure that CO is introduced₂The foaming sheet is in a supercritical state, is molded in a foaming mold and is foamed at a mold opening after temperature and pressure balance, and enters a laminating machine head for rigidity enhancement after cooling, rolling and traction;

(3) vacuum drying POE-g-MA, organic montmorillonite with the particle size of 20 mu m and T30S polypropylene at 100 ℃ for 2-3 hours, extruding by a double screw to prepare precursor master batch, vacuum drying polyethylene glycol terephthalate with the weighed intrinsic viscosity of 0.65dl/g at 75 ℃ for 4-6 hours, mixing with the precursor master batch and the like in a high-speed stirrer for 7.5 minutes to obtain a mixture, extruding and granulating at 190 ℃ to obtain the special material for the enhancement layer, wherein the weight ratio of each component in the special material for the enhancement layer is as follows:

Example 9

In this example, on the basis of example 8, the composition of the core layer raw material in step (1) is adjusted as follows:

the other embodiments of this example are the same as example 8.

Example 10

the other embodiments of this example are the same as example 8.

Example 11

the other embodiments of this example are the same as example 8.

Example 12

the other embodiments of this example are the same as example 8.

Example 13

In this example, the aspect ratio of the attapulgite in the step (1) was adjusted to 5:1 in addition to example 8, and other embodiments of this example were the same as example 8.

Example 14

In this example, the aspect ratio of the attapulgite in the step (1) was adjusted to 7:1 in addition to example 8, and other embodiments of this example were the same as example 8.

Example 15

In this example, the aspect ratio of the attapulgite in the step (1) was adjusted to 11:1 in addition to example 8, and other embodiments of this example were the same as example 8.

Example 16

In this example, the aspect ratio of the attapulgite in the step (1) was adjusted to 20:1 in addition to example 8, and other embodiments of this example were the same as example 8.

Comparative example 1

This comparative example is based on example 8 and is otherwise the same as example 8 except that the hyperdispersant in step (1) was removed.

Comparative example 2

In this comparative example, the inorganic powder in step (1) was removed from example 8, and the other embodiments of this example were the same as example 8.

Comparative example 3

In the comparative example, on the basis of example 8, the raw materials of the core layer in the step (1) are directly mixed and stirred at a high speed for 10min, and then extruded and granulated at 200 ℃ to obtain the special foaming material, and other embodiments of the present example are the same as those of example 8.

Comparative example 4

In this comparative example, on the basis of example 8, the raw material of the reinforcing layer in step (3) is dried, directly mixed and stirred at a high speed for 7.5min, and then extruded and granulated at 190 ℃ to obtain the special material for the reinforcing layer, and other embodiments of this example are the same as example 8.

Test example 1

The performance of the foamed polypropylene composite sheets of examples 1 to 16 and comparative examples 1 to 4 of the present application was measured, wherein the flexural modulus was measured by a method described in GB/T9341-2008 plastic flexural performance measurement, the TVOC was measured by a method described in GB/T27630-2011 passenger car interior air quality evaluation guideline, and the notched impact strength was measured by a method described in GB/T1043.1-2008 plastic simple beam impact performance measurement, and the results are shown in the following table:

as can be seen from the above table, in examples 1 to 16 of the present application, since the supercritical extrusion foaming process is adopted and the inorganic powder with adsorption capacity is introduced into the foamed composite material, the finally prepared foamed polypropylene composite sheet has extremely low VOC. The TVOC test value in comparative example 1 is higher because the core layer raw material in comparative example 1 does not use a specific hyper-dispersant, so that the inorganic powder is agglomerated during the mixing process, and the adsorption effect on VOC is reduced. In comparative example 2, although the components in the raw material can be uniformly mixed by using the hyper-dispersant, the adsorption effect on VOC is greatly weakened due to the removal of the inorganic powder, so that the TVOC test value is high. In addition, the flexural modulus of comparative examples 1 and 2 is reduced compared with that of example 8, and the reason for this is that the inorganic powder is partially agglomerated due to the lack of the hyperdispersant in comparative example 1, and the mechanical strength is partially affected, while the flexural modulus of comparative example 2 is obviously reduced because the inorganic powder has the effect of enhancing the mechanical properties of the foam material, and the mechanical properties are obviously reduced due to the removal of the inorganic powder. In addition, the density of the sheet prepared in comparative example 1 was high because the inorganic powder was not uniformly distributed because the hyperdispersant was not added, and therefore, the density of some samples was large during sampling calculation, and correspondingly, the density of the other portions of the samples was small, indicating the importance of the hyperdispersant in the dispersion of the inorganic powder.

Further, comparative examples 3 and 4 are based on direct mixing in the preparation of the raw materials for the core layer and the reinforcing layer, and are not prepared according to the addition sequence and mixing method of the components described in the present invention, so that the mechanical properties of the core layer and the reinforcing layer are reduced, and the adsorption effect of VOC and the notch impact strength are affected.

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A foamed polypropylene composite sheet is characterized in that, the sheet comprises sequentially from outside to inside:

Toughening layer, including foamed polypropylene compounded with thermoplastic elastomer or polyvinyl chloride on the surface;

Reinforcement layers, including polyester, polyolefin and organic montmorillonite composites;

The core layer includes a foamed composite material with a foaming ratio of 2 to 5 times;

The thickness of the composite sheet is 4-6 mm, and the flexural modulus is 1100-1400 MPa;

The foamed composite material of the core layer is made by extruding and foaming the following raw materials through supercritical fluid:

High melt strength polypropylene 40～60wt%

General purpose polypropylene 30～50wt%

Inorganic powder 0.5～15wt%

Hyperdispersant 1.5～3wt%;

The particle size of the inorganic powder is 10-50 μm, and the aspect ratio of the inorganic powder is 5-20:1; the inorganic powder is selected from wollastonite, sericite or attapulgite.

2 . The foamed polypropylene composite sheet according to claim 1 , wherein the particle size of the inorganic powder is 25-40 μm, and the aspect ratio of the inorganic powder is 7-15:1; 3 . The inorganic powder is selected from attapulgite.

3 . The foamed polypropylene composite sheet according to claim 1 , wherein the hyperdispersant is selected from high molecular weight modified hyperbranched polyesters that do not contain volatile components. 4 .

4 . The foamed polypropylene composite sheet according to claim 3 , wherein the hyperdispersant is selected from Luptech YY-502 or Luptech YY-702. 5 .

5 . The foamed polypropylene composite sheet according to claim 3 , wherein the hyperdispersant is selected from Luptech YY-502 and Luptech YY-702 in a mass ratio of 1:2 to 3. 6 . compound.

6. The foamed polypropylene composite sheet according to claim 1, wherein the reinforcing layer is made of the following raw materials:

Polyethylene terephthalate 60～75wt%

General purpose polypropylene 18～30wt%

Compatibilizer 3～5wt%

Organic montmorillonite 1～3.5wt%

Oxidized polymer wax 0.3～1.5wt%;

The intrinsic viscosity of the polyethylene terephthalate is 0.6-0.8 dl/g.

7 . The foamed polypropylene composite sheet according to claim 6 , wherein the intrinsic viscosity of the polyethylene terephthalate is 0.65˜0.7 dl/g. 8 .

8. The foamed polypropylene composite sheet according to claim 1 or 6, characterized in that, the model of the general-purpose polypropylene is selected from T30S or EPS30R.

9 . The foamed polypropylene composite sheet according to claim 8 , wherein the general-purpose polypropylene in the foamed composite material of the core layer is EPS30R. 10 .

10 . The foamed polypropylene composite sheet according to claim 8 , wherein the general-purpose polypropylene in the raw material of the reinforcing layer is T30S. 11 .

11. The foamed polypropylene composite sheet according to claim 6, wherein the compatibilizer is selected from PP-g-MA, PP-g-GMA, POE-g-MA or POE-g- A kind of GMA; the particle size of the organic montmorillonite is 15-25 μm.

12. The foamed polypropylene composite sheet according to claim 11, wherein the compatibilizer is selected from PP-g-MA or POE-g-MA.

13 . The foamed polypropylene composite sheet according to claim 1 , wherein the foamed polypropylene is cross-linked foamed polypropylene, and the foaming ratio is 10 to 30 times. 14 .

14 . The foamed polypropylene composite sheet according to claim 13 , wherein the foaming ratio of the foamed polypropylene is 15 to 20 times. 15 .

15. A method for preparing a foamed polypropylene composite sheet according to any one of claims 1 to 14, characterized in that, comprising: (1) extruding and granulating the raw material of the foamed composite material to obtain foaming special material, and then extruding the special foaming material through a supercritical fluid foaming process to obtain a core layer sheet;

(2) extruding and granulating the raw material of the reinforcing layer to obtain a special material for the reinforcing layer, and then compounding on both sides of the core layer sheet obtained in step (1) after plasticizing and extruding to obtain a reinforcing sheet;

(3) Coating an adhesive film on the surface of the reinforcing sheet obtained in step (2), and then compounding the toughening layer on the surface of the reinforcing sheet by hot pressing the adhesive film to obtain a foamed polypropylene composite sheet.

16 . The method for preparing a foamed polypropylene composite sheet according to claim 15 , wherein in step (1), extruding and granulating the raw material of the foamed composite material comprises: extruding the weighed inorganic The powder and hyperdispersant are stirred at high speed for 5 to 10 minutes, and then weighed high-melt strength polypropylene and general-purpose polypropylene are added to it and stirred at low speed for 3 to 5 minutes to obtain the mixture. Extrusion and granulation at 160 to 240 ° C , to obtain a special foaming material; in step (2), the extrusion and granulation of the raw materials of the reinforcing layer includes: vacuum drying the weighed compatibilizer, organic montmorillonite and general polypropylene at 100 ° C for 2 ～3 hours, then the precursor masterbatch is obtained by twin-screw extrusion, and then the weighed polyethylene terephthalate is vacuum-dried at 70～80 ℃ for 4～6 hours, and the precursor is mixed with the precursor. The master batch is mixed in a high-speed mixer for 5 to 10 minutes, and the mixture is extruded and granulated at 180 to 260 ° C to obtain a special material for the reinforcement layer.