CN111073131A - Composite flame-retardant conductive polypropylene foamed bead and molded body and preparation method thereof - Google Patents
Composite flame-retardant conductive polypropylene foamed bead and molded body and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/0095—Mixtures of at least two compounding ingredients belonging to different one-dot groups
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
- C08J2323/10—Homopolymers or copolymers of propene
- C08J2323/12—Polypropene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2463/00—Characterised by the use of epoxy resins; Derivatives of epoxy resins
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/02—Elements
- C08K3/04—Carbon
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/04—Oxygen-containing compounds
- C08K5/10—Esters; Ether-esters
- C08K5/101—Esters; Ether-esters of monocarboxylic acids
- C08K5/103—Esters; Ether-esters of monocarboxylic acids with polyalcohols
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K9/00—Use of pretreated ingredients
- C08K9/04—Ingredients treated with organic substances
- C08K9/06—Ingredients treated with organic substances with silicon-containing compounds
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- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
The invention belongs to the field of macromolecules, and particularly provides a composite flame-retardant conductive polypropylene foamed bead, a molded body thereof and a preparation method thereof. The composite flame-retardant conductive polypropylene foamed bead is prepared by coating a polypropylene foamed bead with flame-retardant conductive slurry and then drying; the flame-retardant conductive slurry contains conductive filler, adhesive, coupling agent and dispersing agent, wherein relative to 100 parts by weight of the polypropylene foaming beads, the conductive filler is 1-50 parts by weight, the adhesive is 5-50 parts by weight, the coupling agent is 0.1-5 parts by weight, and the dispersing agent is 0.1-5 parts by weight. According to the preparation method of the beads, the surface of each polypropylene foaming bead is completely covered with the flame-retardant conductive material, and during secondary foaming molding, the conductive material coated on the surface of the bead is extruded and fixed in the molded body, so that the molded body has uniform conductivity and excellent flame retardant property.
Description
Technical Field
The invention belongs to the field of polymers, and particularly relates to a composite flame-retardant conductive polypropylene foamed bead and a preparation method thereof, and a molded body using the composite flame-retardant conductive polypropylene foamed bead and a preparation method thereof.
Background
The polypropylene foaming material has excellent heat resistance, insulativity, heat preservation, cold resistance, oil resistance, chemical resistance and barrier property, and is easy to recycle. Therefore, compared with the common expanded polypropylene (EPS or XPS) or Expanded Polyurethane (EPU) in the existing market, the polypropylene expanded material has a very wide development and application prospect, and the polypropylene expanded material with excellent mechanical property is tried to replace the existing metal plate in the existing aerospace, military machinery, even coal wells, mines and other special production occasions with severe conditions, so that the material cost can be reduced, the construction strength can be reduced, the service life can be prolonged, the energy consumption of the working environment can be reduced, and the like.
However, the polypropylene foam material is an insulating material and is very easy to generate static electricity. Suspended dust in a plurality of harsh use environments and the surface of the polypropylene foam material mutually rub and collide, positive and negative charges are redistributed among the suspended dust and the surface of the polypropylene foam material, and the positive and negative charges are respectively accumulated on the surface of the polypropylene foam material and the dust. When the static charge accumulates to some extent, a spark is discharged, which may cause a fire or a chemical explosion. Meanwhile, the conventional polypropylene foam material has the disadvantage of flammability. In order to safely and reliably apply the polypropylene foaming material to production occasions such as coal wells and mines or become an ideal electrostatic protection (ESD) and electromagnetic shielding (EMI) material in special fields such as military aerospace and the like, the flame retardance and the electrical conductivity of the polypropylene foaming material need to be improved.
The preparation methods of the composite flame-retardant conductive polypropylene foam material are more, and the main methods adopted in the recent research are as follows: 1) the raw material modification method comprises the following steps: conductive filler, flame retardant and the like are doped into matrix polypropylene resin in advance, and then foaming is carried out according to foaming process conditions to prepare a corresponding conductive flame-retardant foamed polypropylene material, wherein the foaming ratio can be adjusted by controlling technical conditions such as the content of a foaming agent; 2) surface bonding method: putting the powdery conductive particles and the flame retardant on the surface of the foamed plastic, coating a certain bonding material, and pressing and grinding to enable the functional particles to enter pores of the foamed polypropylene to prepare the conductive flame-retardant foamed polypropylene material; 5) oxidative polymerization method: the intrinsic type conductive flame retardant monomer is dispersed into the foam matrix by a vapor deposition method (VDP) and then oxidatively polymerized.
However, the above preparation methods all have obvious disadvantages. The raw material modification method hinders the construction of a conductive network in the material due to the existence of foam pores in a foaming structure, seriously influences the antistatic property and the conductivity of the system, and simultaneously, excessive conductive filler is added to improve the conductivity, so that the rheological property and the melt strength of matrix resin are poor, the foaming ratio is greatly reduced, and even foaming cannot be carried out. The surface bonding method is not easy to cause the conductive flame-retardant substance to be uniformly distributed, the electrical property and the combustion performance are inconsistent, and the conductivity and the flame retardance of the material can be greatly reduced when the surface bonding layer is damaged. The oxidative polymerization method has complex process and difficult control and repetition of product performance indexes.
The method disclosed in CN105504457B is to use polyolefin as matrix resin, add foaming auxiliary agent, antistatic agent and flame retardant to carry out banburying mixing, perform the mixture, and place the mixture into a foaming furnace to foam, so as to obtain the antistatic flame-retardant polyolefin foam material for vehicles. However, in order to ensure that the polyolefin can be foamed and molded, only a small amount of conductive components can be added to make the material only reach an antistatic level but not reach a conductive level, and in order to compensate for the decrease of foaming performance and mechanical property of matrix polyolefin resin caused by the addition of the flame retardant and the conductive components, the matrix resin needs to be crosslinked, so that the recycling of the product is influenced. There are also a number of patent applications which attempt to attach a functional layer to the surface of a foamed material, for example us7,7078,092.b2 discloses a radiation shielding mat comprising a polyurethane plastic foam having a network of open cells in communication with each other, with a metal layer thereon to provide electrical conductivity, and a method of making the same. CN101242733A is made of polyolefin foam as a substrate, and the surface thereof is metallized by evaporation, sputtering, electroless plating, etc. The metalized surface treatment avoids the problem that the metal layer is directly attached to the metal layer to cause easy damage and drop, and is easier to cut, but the process is complex and the production efficiency is low.
Particularly, when the flame-retardant conductive foamed polypropylene material is expected to be used as an ideal electrostatic protection (ESD) and electromagnetic shielding (EMI) material in special fields such as military aerospace, different shapes with complex appearances need to be prepared according to the design of different parts. Most of traditional methods for preparing flame-retardant conductive foamed polypropylene materials are subjected to extrusion foaming or die pressing foaming after raw material modification, so that only single-shaped plates, sheets, bars or wires can be obtained, and later-stage forming processing is performed, so that the cost is high, the precision is poor, and the design requirements are difficult to achieve.
Further, the polypropylene in-mold foamed molded article obtained by secondary foaming using the polypropylene expanded beads has advantages such as high shape flexibility and high dimensional accuracy, and is suitably used in various fields requiring high shape and dimensional accuracy of products. For example, CN105308107A discloses adding flame retardant (melamine cyanurate) and conductive carbon black into polypropylene matrix resin for modification, preparing flame-retardant conductive polypropylene expanded beads, and performing secondary molding. The modification mode has high requirements on process conditions and technical level, otherwise, the preparation of the flame-retardant conductive polypropylene expanded bead capable of being subjected to secondary molding is difficult. It can be seen from the examples of the patent document that the addition amount of the functionalized assistant is not too high, otherwise, the incompatible microparticles distributed in the bead can seriously destroy the growth density, the structural size and the integrity of the cell wall of the cell, which not only affects the expansion ratio and the mechanical property of the primary expanded bead and the final expanded molded product, but also significantly reduces the conductive property of the expanded molded product material, which is caused by the discontinuity of the conductive network due to the density, the size and the structural change of the cell in the material, thus greatly limiting the performance and the application range of the conductive flame-retardant expanded material.
Disclosure of Invention
The invention aims to overcome the defects of poor mechanical property foaming multiplying power, volatile efficiency, short service life, complex production process, high equipment cost and the like of the conventional composite flame-retardant conductive polypropylene foaming material, and provides composite flame-retardant conductive polypropylene foaming beads, flame-retardant conductive polypropylene foaming formed bodies prepared from the beads and a preparation method of the composite flame-retardant conductive polypropylene foaming formed bodies.
After intensive research, the inventor of the present invention finds that, flame retardant conductive slurry containing conductive filler, adhesive, coupling agent and dispersing agent is added into polypropylene expanded beads which are not modified at all, a layer of flame retardant conductive slurry is uniformly and completely covered on the surface of each polypropylene expanded bead, and after drying, each bead forms a complete and independent flame retardant conductive unit, so as to obtain the composite flame retardant conductive polypropylene expanded bead. And then adding the beads into a forming machine, and heating by steam for secondary forming to obtain the composite flame-retardant conductive polypropylene foaming forming body. Because the polypropylene foaming beads are subjected to secondary foaming during steam heating, the surfaces of the beads are melted and expanded, the flame-retardant conductive material covered on the surfaces of the beads can be well extruded and fixed in a foaming forming body, and a continuous cellular flame-retardant conductive network is formed, so that compared with the flame-retardant conductive polypropylene foaming material prepared by the traditional coating bonding method, the flame-retardant conductive network can still ensure that the material has excellent flame-retardant conductive performance even if a functional layer on the surface is damaged due to external force scraping or natural erosion. The composite flame-retardant conductive polypropylene foaming bead obtained by matching the polypropylene foaming bead with the conductive filler, the adhesive, the coupling agent and the dispersing agent is used for preparing a composite flame-retardant conductive polypropylene foaming forming body by adopting a general in-mold secondary forming process without greatly changing the production process, conditions and equipment, so that the economic requirement of the existing general in-mold secondary forming foaming body preparation is met, and meanwhile, because the flame-retardant conductive material does not enter the interior of the polypropylene foaming bead and each unit has a uniform and complete high-closed-cell-rate cell structure, the composite flame-retardant conductive polypropylene foaming bead or the composite flame-retardant conductive polypropylene foaming forming body has excellent flame retardant property, electric conductivity, surface appearance, forming property, processing property, mechanical property and foaming ratio, and is suitable for the requirements of electrostatic protection (ESD) and electromagnetic shielding (EMI), the application in the fields of aerospace, precision instruments, radio wave absorbers, automobile transportation and the like is met, and the method has great industrial application prospect. Based on this, the present invention has been completed.
According to a first aspect of the invention, the invention provides a composite flame-retardant conductive polypropylene foamed bead, which is prepared by coating a polypropylene foamed bead with flame-retardant conductive slurry and then drying; the flame-retardant conductive paste contains conductive filler, adhesive, coupling agent and dispersing agent, and relative to 100 parts by weight of the polypropylene foamed beads, the conductive filler is 1-50 parts by weight, the adhesive is 5-50 parts by weight, the coupling agent is 0.1-5 parts by weight, and the dispersing agent is 0.1-5 parts by weight.
According to a second aspect of the present invention, the present invention provides a preparation method of the composite flame-retardant conductive polypropylene expanded beads, which comprises:
1) uniformly mixing the conductive filler and the coupling agent to obtain a mixture, sequentially adding the mixture and the dispersing agent into the adhesive, and uniformly dispersing to obtain the flame-retardant conductive slurry;
2) and coating the flame-retardant conductive slurry on the polypropylene foamed beads, and then drying to obtain the composite flame-retardant conductive polypropylene foamed beads.
According to a third aspect of the invention, the invention provides a composite polypropylene foamed molded body, which is prepared by carrying out secondary foaming molding on the composite flame-retardant conductive polypropylene foamed beads.
According to a fourth aspect of the present invention, there is provided a method for producing the composite polypropylene foamed molding, comprising: filling the composite flame-retardant conductive polypropylene foamed beads into a mold, and heating the beads through steam to enable the beads to be mutually fused in a hot way, so as to prepare a composite polypropylene foamed forming body; wherein the pressure of the steam is 0.05-0.5MPa, and the time for introducing the steam is 10 s-2 min.
The invention has the following beneficial effects:
(1) during steam heating, the flame-retardant conductive polypropylene foaming beads are subjected to secondary foaming, the surfaces of the beads are melted and expanded, the flame-retardant conductive material covering the surfaces of the beads can be well extruded and fixed in a foaming forming body, and a continuous cellular flame-retardant conductive network is formed, so that compared with the flame-retardant conductive polypropylene foaming material prepared by the traditional coating and bonding method, the flame-retardant conductive network can ensure that the material has excellent flame-retardant conductive performance even if the flame-retardant conductive layer on the surface is damaged due to external force scraping or natural erosion.
(2) Because the flame-retardant conductive material does not enter the interior of the polypropylene foamed bead, and the interior of each conductive unit is a uniform and complete high-closed-cell-rate cellular structure, the composite flame-retardant conductive polypropylene foamed bead or the composite flame-retardant conductive polypropylene foamed molded body has excellent surface appearance, molding performance, processing performance, mechanical property and foaming ratio.
(3) The method for preparing the composite flame-retardant conductive polypropylene foamed bead and the composite flame-retardant conductive polypropylene foamed molded body is simple, easy to operate and suitable for large-scale production and application, and can directly use the existing equipment and devices of the polypropylene foamed molded body of a manufacturer without additional investment for modification.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
Exemplary embodiments of the present invention will be described in more detail by referring to the accompanying drawings.
FIG. 1 is a photograph of the outer skin of the composite polypropylene foamed molding produced in example 2.
FIG. 2 is a photograph showing a cut surface of a composite polypropylene foamed molding produced in example 2.
FIG. 3 is a SEM image of a cross section of beads in the composite polypropylene foam molding prepared in example 2.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
According to a first aspect of the invention, the invention provides a composite flame-retardant conductive polypropylene foamed bead, which is prepared by coating a polypropylene foamed bead with flame-retardant conductive slurry and then drying; the flame-retardant conductive paste comprises conductive filler, a binder, a coupling agent and a dispersing agent, wherein relative to 100 parts by weight of the polypropylene foamed beads, the conductive filler accounts for 1-50 parts by weight, the binder accounts for 5-50 parts by weight, the coupling agent accounts for 0.1-5 parts by weight, and the dispersing agent accounts for 0.1-5 parts by weight.
Preferably, the conductive filler is 5 to 40 parts by weight, the binder is 10 to 40 parts by weight, the coupling agent is 0.1 to 2 parts by weight, and the dispersant is 0.1 to 2 parts by weight, relative to 100 parts by weight of the polypropylene expanded beads.
Preferably, the amount of the binder is not less than the amount of the conductive filler.
In the present invention, the polypropylene expanded beads refer to any unmodified polypropylene expanded beads, and can be prepared by foaming commercially available expandable polypropylene particles by using a pre-foaming machine, and the specific preparation method is well known to those skilled in the art and is not described herein; the beads may be commercially available polypropylene expanded beads as long as the foamed molded article can be produced by the in-mold secondary molding process. Typically the polypropylene expanded beads have an apparent density of from 10 to 700 g/L. Hereinafter, the polypropylene expanded beads are also referred to as base polypropylene expanded beads. The polypropylene foaming beads are coated with the flame-retardant conductive slurry, which means that the surface of each bead is coated with the flame-retardant conductive slurry, and after drying, the formed flame-retardant conductive material also covers the surface of the bead.
In the present invention, the conductive filler may be a carbon material generally used in a composite type polymer foam material having flame retardant conductivity, for example, at least one selected from carbon black, graphite, carbon nanotubes, and carbon fibers. The carbon black may be at least one selected from acetylene black, superconducting carbon black and specific conductive carbon black. The graphite may be selected from at least one of natural graphite, expandable graphite, expanded graphite, and graphene. The carbon nanotubes may be selected from single-walled carbon nanotubes and/or multi-walled carbon nanotubes which are not surface-modified or surface-modified, and the methods for surface modification are well known to those skilled in the art and will not be described herein.
In the present invention, the binder may be at least one selected from the group consisting of epoxy resin, phenol resin, urea resin, silicone resin, and polyvinyl alcohol resin.
In the present invention, the coupling agent may be a titanate coupling agent and/or a silane coupling agent.
Preferably, the titanate coupling agent is selected from at least one of isopropyl tris (dioctylpyrophosphate) titanate, isopropyl triisostearate, titanium bis (dioctylpyrophosphate) oxoacetate and tetraisopropyl bis (dioctylphosphite) titanate.
Preferably, the silane coupling agent is selected from at least one of gamma-aminopropyltriethoxysilane (KH550), gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane (KH560), gamma- (methacryloyloxy) propyltrimethoxysilane (KH570), gamma-aminoethylaminopropyltrimethoxysilane (KH792), and N- β - (aminoethyl) -gamma-aminopropylmethyldimethoxysilane (DL 602).
In the present invention, the dispersant may be selected from at least one of sodium lauryl sulfate, methyl amyl alcohol, polyacrylamide, fatty acid polyglycol ester, glyceryl monostearate and glyceryl tristearate.
In addition, the composite flame-retardant conductive polypropylene foamed bead can also contain other additives commonly used in polypropylene foaming materials, and the other additives can not generate adverse effects on the flame retardant property, the electric conductivity, the surface appearance, the foaming multiplying power, the mechanical property, the processing property and the like of the composite flame-retardant conductive polypropylene foamed bead. Such other adjuvants include, but are not limited to: at least one of antioxidant, slipping agent, and anti-sticking agent. In addition, the amount of the other additives can be selected conventionally in the field, and those skilled in the art can know the amount and will not be described herein.
According to a second aspect of the present invention, the present invention provides a preparation method of the composite flame-retardant conductive polypropylene expanded beads, comprising:
1) uniformly mixing the conductive filler and the coupling agent to obtain a mixture, sequentially adding the mixture and the dispersing agent into the adhesive, and uniformly dispersing to obtain the flame-retardant conductive slurry;
2) and coating the flame-retardant conductive slurry on the polypropylene foamed beads, and then drying to obtain the composite flame-retardant conductive polypropylene foamed beads.
In step 2), the coating can be achieved by conventional means, for example, the polypropylene foamed beads are contacted with the flame-retardant conductive paste, and then are uniformly stirred and dispersed, so as to ensure that the surface of each bead is coated with the flame-retardant conductive paste. The drying can be carried out at a temperature of 60-70 deg.C, and the drying time can be controlled at 0.5-3 hr.
When the composite flame-retardant conductive polypropylene foamed bead further contains other additives, the conductive filler, the adhesive and other components can be uniformly mixed together to form the flame-retardant conductive slurry.
The surface of the composite flame-retardant conductive polypropylene foaming bead is covered with a layer of flame-retardant conductive material formed by the flame-retardant conductive slurry, and the composite flame-retardant conductive polypropylene foaming bead has a complete and uniform internal cell structure and good secondary forming capability.
According to a third aspect of the invention, the invention provides a composite polypropylene foamed molded body, which is prepared by carrying out secondary foaming molding on the composite flame-retardant conductive polypropylene foamed beads.
According to the invention, the composite polypropylene foaming forming body has excellent surface appearance, foaming multiplying power, mechanical property, processing property and flame-retardant conductivity. The performance of the composite flame-retardant conductive polypropylene foaming forming body can meet the following requirements: the apparent density is adjustable between 30 and 500g/L, and the surface resistivity is 10 to 109Omega, preferably 102-107Omega. Furthermore, the end points in the range of the surface resistivity mentioned represent the order of magnitude of the surface resistivity, for example 1X 107Ω-9.9×107Omega can all be expressed as 107Ω。
The composite flame-retardant conductive polypropylene foaming beads can be processed into the composite polypropylene foaming forming body (for example, a plate) by adopting a general intra-film secondary forming process, and the method does not need to greatly change the production process method, conditions and equipment, and is suitable for the economic requirement of the existing general preparation of the in-mold secondary forming foaming body.
To this end, according to a fourth aspect of the present invention, there is provided a method for producing the composite polypropylene foam-molded body, comprising: filling the composite flame-retardant conductive polypropylene foamed beads into a mold, and heating the beads through steam to enable the beads to be mutually fused in a hot melting way, so as to obtain a composite polypropylene foamed forming body; wherein the pressure of the steam is 0.05-0.5MPa, and the time for introducing the steam is 10 s-2 min.
The following examples are given by way of illustration only, and the scope of the present invention is not limited to these examples.
In the following examples and comparative examples, the apparent densities of polypropylene expanded beads were 30g/L, 60g/L and 90g/L, respectively, and they were obtained by expanding commercially available expandable polypropylene particles using a pre-expander, respectively.
The test equipment and the test method comprise the following steps:
1. microscopic morphology: the expanded beads of the molded article were quenched with liquid nitrogen, sprayed with gold on the cross section, and the cell structure inside the expanded beads was examined by a scanning electron microscope (SEM, model XL-30, available from FEI, USA).
2. Apparent density: the product is obtained by adopting a density tester (CPA225D, Density attachment YDK01, Satorius Germany) according to the GB/T6343-2009 standard test and utilizing a drainage method.
3. Surface resistivity: and (4) measuring each sample at any three positions (respectively marked as surface resistivity A, surface resistivity B and surface resistivity C) according to the method specified in GB/T1410-2006, and inspecting whether the conductivity of the sample is uniform or not.
4. Flame retardant property: the flame-retardant steel is measured according to the method specified in the horizontal burning test method (GB2408-80) and the vertical burning test method (GB2409-84), and the results are graded and judged according to the UL94 flame-retardant grade specification.
Example 1
This example is used to illustrate the composite flame-retardant conductive polypropylene expanded beads of the present invention, the molded articles thereof, and the respective methods of preparation.
The composite flame-retardant conductive polypropylene expanded bead provided by the embodiment contains a base polypropylene expanded bead with the apparent density of 60g/L, a conductive filler, an adhesive, a coupling agent and a dispersing agent. The conductive filler is acetylene black, the adhesive is epoxy resin, the coupling agent is a silane coupling agent KH550, the dispersing agent is monoglyceride monostearate, the basic polypropylene foamed beads are 0.6kg, the acetylene black is 0.04kg, the epoxy resin is 0.05kg, the silane coupling agent KH550 is 1g, and the monoglyceride monostearate is 1 g.
(1) Preparing flame-retardant conductive slurry:
firstly, mixing and stirring the conductive filler and the coupling agent for 5 minutes, then sequentially adding the obtained mixture and the dispersing agent into the adhesive, and mixing and stirring for 5 minutes to obtain the flame-retardant conductive slurry.
(2) Preparing composite flame-retardant conductive polypropylene foaming beads:
and (2) slowly adding the basic polypropylene foamed beads into the flame-retardant conductive slurry obtained in the step (1) under stirring, uniformly stirring to enable the slurry to be uniformly coated on the surfaces of the basic polypropylene foamed beads, and drying for 2 hours at 65 ℃ by using fluidized bed drying equipment to obtain the composite flame-retardant conductive polypropylene foamed beads.
(3) Preparing a composite flame-retardant conductive polypropylene foaming forming body:
filling the composite flame-retardant conductive polypropylene foaming beads prepared in the step (2) into a preheated plate forming machine, introducing steam at the temperature of 105-115 ℃ into the mold for heating, keeping the pressure at 0.08-0.15MPa, and introducing the steam for 30 s. And cooling and demolding after ventilation is finished, and finally bonding the composite flame-retardant conductive polypropylene foaming beads to obtain the composite flame-retardant conductive polypropylene foaming plate with the apparent density of 40 g/L. The appearance of the plate is smooth and regular, the section of the plate is observed by adopting SEM, and the cell structure is complete and uniform. The sheet was subjected to basic performance tests, and the results are shown in table 1.
Example 2
This example is used to illustrate the composite flame-retardant conductive polypropylene expanded beads of the present invention, the molded articles thereof, and the respective methods of preparation.
The composite flame-retardant conductive polypropylene expanded bead provided by the embodiment contains a base polypropylene expanded bead with the apparent density of 30g/L, a conductive filler, an adhesive, a coupling agent and a dispersing agent. Wherein the conductive filler is bead-shaped superconducting carbon black, the adhesive is phenolic resin, the coupling agent is isopropyl triisostearate, the dispersant is fatty acid polyethylene glycol ester, 0.4kg of basic polypropylene foamed beads, 0.15kg of bead-shaped superconducting carbon black, 0.15kg of phenolic resin, 5g of isopropyl triisostearate titanate and 4g of fatty acid polyethylene glycol ester.
(1) Preparing flame-retardant conductive slurry:
firstly, mixing and stirring the conductive filler and the coupling agent for 5 minutes, then sequentially adding the obtained mixture and the dispersing agent into the adhesive, and mixing and stirring for 5 minutes to obtain the flame-retardant conductive slurry.
(2) Preparing composite flame-retardant conductive polypropylene foaming beads:
and (2) slowly adding the basic polypropylene foamed beads into the flame-retardant conductive slurry obtained in the step (1) under stirring, uniformly stirring to enable the slurry to be uniformly coated on the surfaces of the basic polypropylene foamed beads, and drying for 2 hours at 65 ℃ by using fluidized bed drying equipment to obtain the composite flame-retardant conductive polypropylene foamed beads.
(3) Preparing a composite flame-retardant conductive polypropylene foaming forming body:
filling the composite flame-retardant conductive polypropylene foaming beads prepared in the step (2) into a preheated plate forming machine, introducing steam at the temperature of 105-115 ℃ into the mold for heating, keeping the pressure at 0.08-0.15MPa, and introducing the steam for 45 s. And cooling and demolding after ventilation is finished, and finally bonding the composite flame-retardant conductive polypropylene foaming beads to obtain the composite flame-retardant conductive polypropylene foaming plate with the apparent density of 35 g/L. The photograph of the outer skin of the plate is shown in FIG. 1. As can be seen from FIG. 1, the plate has a smooth and regular appearance. The cut surface of the plate was observed by SEM, and the result is shown in fig. 2, and it can be seen from fig. 2 that the plate has a conductive network formed by a conductive material inside, and the conductive network is in a similar honeycomb shape. The SEM image of the section of the bead in the plate is shown in FIG. 3. it can be seen from FIG. 3 that the conductive filler is coated outside the bead on the right side, and the structure of the inner pore is complete and the pore wall is smooth as seen from the section of the bead on the left side.
Example 3
This example is used to illustrate the composite flame-retardant conductive polypropylene expanded beads of the present invention, the molded articles thereof, and the respective methods of preparation.
The composite flame-retardant conductive polypropylene expanded bead provided by the embodiment contains a base polypropylene expanded bead with the apparent density of 90g/L, a conductive filler, an adhesive, a coupling agent and a dispersing agent. The conductive filler is graphene, the adhesive is phenolic resin, the coupling agent is tetraisopropyl bis (dioctyl phosphite) titanate, the dispersing agent is methyl amyl alcohol, the base polypropylene foam beads are 1kg, the graphene is 0.15kg, the phenolic resin is 0.25kg, the tetraisopropyl bis (dioctyl phosphite) titanate is 2g, and the methyl amyl alcohol is 2 g.
(1) Preparing flame-retardant conductive material:
firstly, mixing and stirring the conductive filler and the coupling agent for 5 minutes, then sequentially adding the obtained mixture and the dispersing agent into the adhesive, and mixing and stirring for 5 minutes to obtain the pasty flame-retardant conductive slurry.
(2) Preparing composite flame-retardant conductive polypropylene foaming beads:
and (2) slowly adding the basic polypropylene foamed beads into the flame-retardant conductive slurry obtained in the step (1) under stirring, uniformly stirring to enable the slurry to be uniformly coated on the surfaces of the basic polypropylene foamed beads, and drying for 2 hours at 65 ℃ by using fluidized bed drying equipment to obtain the composite flame-retardant conductive polypropylene foamed beads.
(3) Preparing a composite flame-retardant conductive polypropylene foaming forming body:
filling the composite flame-retardant conductive polypropylene foaming beads prepared in the step (2) into a preheated plate forming machine, introducing steam at the temperature of 105-115 ℃ into the mold for heating, keeping the pressure at 0.08-0.15MPa, and introducing the steam for 45 s. And cooling and demolding after ventilation is finished, and finally bonding the composite flame-retardant conductive polypropylene foaming beads to obtain the composite flame-retardant conductive polypropylene foaming plate with the apparent density of 55 g/L. The appearance of the plate is smooth and regular, the section of the plate is observed by adopting SEM, and the cell structure is complete and uniform. The sheet was subjected to basic performance tests, and the results are shown in table 1.
Example 4
This example is used to illustrate the composite flame-retardant conductive polypropylene expanded beads of the present invention, the molded articles thereof, and the respective methods of preparation.
The composite flame-retardant conductive polypropylene expanded bead provided by the embodiment contains a base polypropylene expanded bead with the apparent density of 30g/L, a conductive filler, an adhesive, a coupling agent and a dispersing agent. The conductive filler is multi-walled carbon nanotubes (MWNTs), the adhesive is organic silicon resin, the coupling agent is silane coupling agent KH792, the dispersing agent is glyceryl tristearate, the basic polypropylene foamed beads are 0.3kg, the multi-walled carbon nanotubes are 0.01kg, the polyvinyl alcohol resin is 0.1kg, the silane coupling agent KH792 is 1g, and the glyceryl tristearate is 1 g.
(1) Preparing flame-retardant conductive slurry:
firstly, mixing and stirring the flame-retardant conductive filler and the coupling agent for 5 minutes, then sequentially adding the obtained mixture and the dispersing agent into the adhesive, and mixing and stirring for 5 minutes to obtain the flame-retardant conductive slurry.
(2) Preparing composite flame-retardant conductive polypropylene foaming beads:
and (2) slowly adding the basic polypropylene foamed beads into the flame-retardant conductive slurry obtained in the step (1) under stirring, uniformly stirring to enable the slurry to be uniformly coated on the surfaces of the basic polypropylene foamed beads, and drying for 2 hours at 65 ℃ by using fluidized bed drying equipment to obtain the composite flame-retardant conductive polypropylene foamed beads.
(3) Preparing a composite flame-retardant conductive polypropylene foaming forming body:
filling the composite flame-retardant conductive polypropylene foaming beads prepared in the step (2) into a preheated plate forming machine, introducing steam at the temperature of 105-115 ℃ into the mold for heating, keeping the pressure at 0.08-0.15MPa, and introducing the steam for 20 s. And cooling and demolding after ventilation is finished, and finally bonding the composite flame-retardant conductive polypropylene foaming beads to obtain the composite flame-retardant conductive polypropylene foaming plate with the apparent density of 25 g/L. The appearance of the plate is smooth and regular, the section of the plate is observed by adopting SEM, and the cell structure is complete and uniform. The sheet was subjected to basic performance tests, and the results are shown in table 1.
Example 5
A polypropylene foamed material was prepared in the same manner as in example 2, except that 0.4kg of the base expanded polypropylene beads having an apparent density of 30g/L was replaced with 1.2kg of the base expanded polypropylene beads having an apparent density of 90g/L, to finally obtain a composite flame-retardant conductive polypropylene foamed sheet having an apparent density of 80 g/L. The appearance of the plate is smooth and regular, the section of the plate is observed by adopting SEM, and the cell structure is complete and uniform. The sheet was subjected to basic performance tests, and the results are shown in table 1.
Comparative example 1
The basic expanded polypropylene beads with the apparent density of 30g/L are directly subjected to secondary molding in a mold by adopting the process conditions of the step (3) in the example 1 to prepare a foamed molded body plate, and a blank polypropylene foamed plate with the apparent density of 17g/L is obtained. The sheet was subjected to basic performance tests, and the results are shown in table 1.
Comparative example 2
Flame-retardant conductive paste was prepared by the method of step (1) of example 1, except that the base expanded polypropylene beads having an apparent density of 60g/L were subjected to in-mold secondary molding directly under the process conditions of step (3) of example 1 to prepare a foamed molded body sheet, the flame-retardant conductive material prepared by the method of step (1) of example 2 was uniformly coated on the surface of the foamed molded body sheet, and the sheet was dried in an oven at 65 ℃ for 2 hours to obtain a modified polypropylene foamed sheet having an apparent density of 30 g/L. The sheet was subjected to basic performance tests, and the results are shown in table 1.
Comparative example 3
Flame-retardant conductive paste was prepared by the method of step (1) of example 2, except that the base expanded polypropylene beads having an apparent density of 30g/L were subjected to in-mold secondary molding directly under the process conditions of step (3) of example 2 to prepare a foamed molded body sheet, the flame-retardant conductive paste prepared by the method of step (1) of example 2 was coated on the surface of the foamed molded body sheet, and the sheet was dried in an oven at 65 ℃ for 2 hours to obtain a modified polypropylene foamed sheet having an apparent density of 22 g/L. The sheet was subjected to basic performance tests, and the results are shown in table 1.
Comparative example 4
Flame-retardant conductive paste was prepared by the method of step (1) of example 3, except that the base expanded polypropylene beads having an apparent density of 90g/L were subjected to in-mold secondary molding directly under the process conditions of step (3) of example 3 to prepare a foamed molded body sheet, the flame-retardant conductive paste prepared by the method of step (1) of example 3 was applied to the surface of the foamed molded body sheet, and the sheet was dried in an oven at 65 ℃ for 2 hours to obtain a modified polypropylene foamed sheet having an apparent density of 40 g/L. The sheet was subjected to basic performance tests, and the results are shown in table 1.
Comparative example 5
Flame-retardant conductive paste was prepared by the method of step (1) of example 4, except that the base expanded polypropylene beads having an apparent density of 30g/L were subjected to in-mold secondary molding directly under the process conditions of step (3) of example 1 to prepare a foamed molded body sheet, the flame-retardant conductive paste prepared by the method of step (1) of example 4 was coated on the surface of the foamed molded body sheet, and the sheet was dried in an oven at 65 ℃ for 2 hours to obtain a modified polypropylene foamed sheet having an apparent density of 20 g/L. The sheet was subjected to basic performance tests, and the results are shown in table 1.
TABLE 1
From examples 1 to 4, it can be seen that the composite flame-retardant conductive polypropylene expanded bead obtained after the flame-retardant conductive material provided by the invention is coated on the surface of a common general-purpose basic polypropylene expanded bead on the market still has excellent secondary forming capability, and a general steam heating, molding and secondary foaming process can be adopted to form the composite flame-retardant conductive polypropylene expanded forming body. In addition, because the continuous honeycomb flame-retardant conductive network distributed along the surfaces of the bead units is formed inside the bead units, even if the flame-retardant conductive layer on the surface is damaged due to external force scraping or natural erosion, the internal functional network can still ensure that the material has excellent flame-retardant conductive performance.
From the comparison between example 2 and example 5, it can be seen that the surface conductivity and flame retardant property of the foam material modified with the same flame retardant conductive material do not decrease greatly as the apparent density decreases. This is because the flame-retardant conductive material does not enter the interior of the polypropylene expanded beads, and the interior of each bead unit is a uniform and complete high-closed-cell-rate cell structure. The conductive network of the foaming formed body is continuously distributed along the outer surface of the bead unit, and the change and difference of the cell structure in the bead can not cause any influence on the conductive network in the foaming formed body.
The surface resistivity was measured at any three points of examples 1 to 5, i.e., surface resistivity a, surface resistivity B, and surface resistivity C. Table 1 shows that the samples prepared by examples 1 to 5 have small differences in surface resistivity at any three places, indicating that the samples have uniform distribution of the conductive component and uniform flame-retardant and conductive capabilities of the foamed molded articles.
As can be seen from comparative example 1, the foamed molded body without any modification is prepared by the same process with the common general-purpose basic polypropylene foamed beads on the market, the insulating property is good, the surface resistivity is far larger than the required range of the flame-retardant conductive material, and the foamed molded body is not suitable for being used in various fields with requirements on flame-retardant conductivity.
Comparative examples 2 to 5 are respectively that a foamed molded body is prepared by the same process with common general basic polypropylene foamed beads on the market, and then the same flame-retardant conductive material is covered on the surface of the product, so that the modified polypropylene foamed molded body is produced by the process route. As can be seen from comparison of the products obtained in comparative examples 2 to 5 with those obtained in examples 1 to 4, the products obtained in comparative examples 2 to 5 are not only inferior in flame-retardant conductivity but also have a possibility that the surface thereof is damaged or eroded and the flame-retardant conductivity of the foamed molded article is greatly lowered. The surface resistivity was measured at any three places of comparative examples 2 to 5, and was surface resistivity a, surface resistivity B, and surface resistivity C, respectively. Table 1 shows that the samples obtained in comparative examples 2 to 5 have large differences in surface resistivity at any three points, which indicates that the conductive component coated on the surface of the sample is not uniform and the conductive capability of the foamed molded article is not uniform, and thus the samples are difficult to apply to the high-precision industrial production field.
From the results, the preparation method provided by the invention can be used for producing the composite flame-retardant conductive polypropylene foamed bead with excellent secondary forming performance, and the composite flame-retardant conductive polypropylene foamed forming body which has excellent flame retardance and electric conductivity and can meet different requirements in various high-precision industries can be prepared by adopting a universal steam heating in-mold secondary forming process and equipment. The common technical means of modifying matrix resin by using the flame-retardant conductive filler, then foaming, conducting coating modification after foaming the matrix resin and the like at present have respective obvious defects and cannot achieve the effect of the invention.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention. In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.
Claims (10)
1. The composite flame-retardant conductive polypropylene foamed bead is characterized in that the composite flame-retardant conductive polypropylene foamed bead is prepared by coating polypropylene foamed beads with flame-retardant conductive slurry and then drying; the flame-retardant conductive paste contains conductive filler, adhesive, coupling agent and dispersing agent, and relative to 100 parts by weight of the polypropylene foamed beads, the conductive filler is 1-50 parts by weight, the adhesive is 5-50 parts by weight, the coupling agent is 0.1-5 parts by weight, and the dispersing agent is 0.1-5 parts by weight.
2. The composite type flame-retardant conductive polypropylene expanded bead as claimed in claim 1, wherein the apparent density of the polypropylene expanded bead is 10-700 g/L; the conductive filler is selected from at least one of carbon black, graphite, carbon nanotubes, and carbon fibers.
3. The composite type flame retardant conductive polypropylene expanded bead according to claim 1, wherein the binder is at least one selected from the group consisting of epoxy resin, phenol resin, urea resin, silicone resin and polyvinyl alcohol resin.
4. The composite type flame-retardant conductive polypropylene foamed bead according to claim 1, wherein the coupling agent is a titanate coupling agent and/or a silane coupling agent, the titanate coupling agent is preferably at least one selected from isopropyl tris (dioctyl pyrophosphato) titanate, isopropyl triisostearate, bis (dioctyl pyrophosphato) oxotitanate and tetraisopropyl bis (dioctyl phosphite) titanate, and the silane coupling agent is preferably at least one selected from gamma-aminopropyltriethoxysilane, gamma- (2, 3-epoxypropoxy) propyltrimethoxysilane, gamma- (methacryloyloxy) propyltrimethoxysilane, gamma-aminoethylaminopropyltrimethoxysilane and N- β - (aminoethyl) -gamma-aminopropylmethyldimethoxysilane.
5. The composite type flame retardant conductive polypropylene foamed bead according to claim 1, wherein the dispersant is at least one selected from sodium dodecyl sulfate, methyl amyl alcohol, polyacrylamide, fatty acid polyethylene glycol ester, glyceryl monostearate and glyceryl tristearate.
6. The preparation method of the composite type flame-retardant conductive polypropylene expanded bead as claimed in any one of claims 1 to 5, which is characterized by comprising the following steps:
1) uniformly mixing the conductive filler and the coupling agent to obtain a mixture, sequentially adding the mixture and the dispersing agent into the adhesive, and uniformly dispersing to obtain the flame-retardant conductive slurry;
2) and coating the flame-retardant conductive slurry on the polypropylene foamed beads, and then drying to obtain the composite flame-retardant conductive polypropylene foamed beads.
7. A composite polypropylene foamed molded body, which is characterized in that the composite polypropylene foamed molded body is prepared by carrying out secondary foaming molding on the composite flame-retardant conductive polypropylene foamed beads according to any one of claims 1 to 5.
8. The composite polypropylene foam-molded body according to claim 7, wherein the composite polypropylene foam-molded body has a surface resistivity of 10 to 109Omega, preferably 102-107Ω。
9. The composite polypropylene foam-molded body according to claim 7 or 8, wherein the composite polypropylene foam-molded body has an apparent density of 30 to 500 g/L.
10. The method for producing a composite polypropylene foamed molding according to any one of claims 7 to 9, which comprises: filling the composite flame-retardant conductive polypropylene foamed beads into a mold, and heating the beads through steam to enable the beads to be mutually fused in a hot way, so as to prepare a composite polypropylene foamed forming body; the pressure of the steam is 0.05-0.5MPa, and the time for introducing the steam is 10 s-2 min.
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| CN113999455A (en) * | 2021-11-23 | 2022-02-01 | 成都佳驰电子科技股份有限公司 | Preparation method of conductive EPP foam with isolation structure |
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