KR20220081721A - Expandable bead by microwave radiation, composite of bead foam therefrom and preparing method using the same - Google Patents

Abstract

Microwave foaming beads according to the present invention 100 parts by weight of the main material; and 20 to 60 parts by weight of a conductive filler; Microwave foaming beads comprising a, wherein the conductive filler is needle-shaped or fibrous, characterized in that it is dispersed in the main material.

Description

Microwave foaming beads, bead foam composites, and manufacturing method thereof

The present invention relates to microwave expandable beads, a bead foam composite, and a method for manufacturing the same. More specifically, the present invention relates to microwave foamable beads moldable by microwaves, bead foam composites, and a method for manufacturing the same.

Bead foam (BEAD FOAM) is used in various fields, and materials and manufacturing methods are also very diverse. In general, bead foam is formed by mixing a foaming agent, a flame retardant, etc. with a resin composition to form a bead, and then melt-bonding the beads through a steam chest molding (SCM) process.

Steam Chest Molding (hereinafter referred to as SCM) process is a process in which beads are filled in a mold and then high-temperature steam is injected to fuse and bond the surfaces of each bead. However, in this SCM process, there is a limit to the selection of plastics mainly applied to the steam temperature of 200 degrees or less. For example, in the case of general-purpose resins such as expanded polystyrene, composites can be molded into various shapes at a steam temperature of 180°C or less (required pressure 10 bar) in the SCM process, but engineering plastics have a steam temperature of 250°C ( Required pressure 40 Bar), super engineering plastics can be molded when the steam temperature is 330℃ (required pressure 130 Bar).

As such, in order to increase the steam pressure, there is a problem in that the investment in auxiliary equipment is inevitably increased, and there is a risk of handling and equipment.

To solve the problems of the SCM process, bead adhesion using microwaves (hereinafter referred to as MW) was developed. However, in the case of the MW process, there is a disadvantage that a polar group must be separately introduced for vibrational heat transfer, and in the case of a general plastic to which a polar group is not introduced, it takes a long time to reach the temperature required for melting. In addition, when forming thick products, there is a problem in that MW does not penetrate to the inside of the product, so that there is a problem of deviation between the external and internal melt adhesion.

Therefore, when high heat-resistant plastics such as engineering plastics are the main material, without using high-pressure steam or introducing a separate polar group, the manufacturing process is easy and the production cost is greatly reduced development is urgent.

As a background technology for this, there is Korean Patent Application Laid-Open No. 10-2016-0065595.

It is an object of the present invention to provide a microwave foamable bead, which is easy to manufacture and can significantly reduce production cost by not using high-pressure steam or introducing a separate polar group, even if high-heat-resistant plastic such as engineering plastic is used as the main material. .

Another object of the present invention is to provide a bead foam composite having excellent physical properties and a method for manufacturing the same.

The above and other objects of the present invention can all be achieved by the present invention described below.

1. One aspect of the present invention relates to microwave expandable beads.

The microwave foam bead is 100 parts by weight of the main material; and 20 to 60 parts by weight of a conductive filler; It is a microwave foaming bead comprising a, wherein the conductive filler is needle-shaped or fibrous, and is dispersed in the main material.

2. In the first embodiment, the main material may be any one or more of polyamide, polyphenylene sulfide, polyether ether ketone, polyether ketone ketone, polyaryl ether ketone, polyethylene terephthalate and polycarbonate.

3. In embodiment 1 or 2, the conductive filler may have a ratio of length to diameter of 1:100 to 1:290.

4. In any one of 1 to 3 above, the conductive filler may be needle-shaped carbon fibers or carbon nanotubes.

5. Another aspect of the present invention relates to a bead foam composite.

The bead foam composite is formed from the beads according to any one of the above 1 to 4 embodiments.

6. In the above 5 embodiments, in the bead foam composite, a bond between the beads may be formed by irradiating the beads with microwaves.

7. In the above 5 or 6 embodiments, the bead foam composite may have an average thickness of 20 to 50 mm.

8. Another aspect of the present invention relates to a method for manufacturing a bead foam composite.

The bead foam composite manufacturing method comprises the steps of (a) injecting the beads of any one of the above 1 to 4 embodiments into a mold; and (b) bonding between beads by irradiating microwaves to the outside of the mold.

9. In the eighth embodiment, the frequency of the microwave may be 2.45 GHz to 300 GHz.

10. The above 8 or 9 embodiments, wherein the microwave may be irradiated for 2 to 10 minutes.

The present invention provides a microwave foamable bead mainly made of engineering plastic or super engineering plastic, which is difficult to form bead foam.

Microwave foaming beads can bond engineering plastics without using high-temperature and high-pressure steam in the steam room molding process, including conductive fillers, and the amount of microwave foam can be adjusted to thermally bond only with microwave irradiation to form a bead foam composite. have.

The present invention provides a method for manufacturing a bead foam composite material capable of molding difficult-to-form engineering plastics through a process of irradiating microwaves as it is in a mold.

1 is a process flow diagram of a bead foam manufacturing method according to an embodiment of the present invention.
Figure 2 is a photograph of the bead foam composite according to Example 3 of the present invention.
3 is a photograph of the bead foam composite according to Example 2 of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. However, the following drawings are provided only to help the understanding of the present invention, and the present invention is not limited by the drawings. In addition, since the shape, size, ratio, angle, number, etc. disclosed in the drawings are exemplary, the present invention is not limited to the illustrated matters.

Like reference numerals refer to like elements throughout. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

When 'including', 'having', 'consisting', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, cases including the plural are included unless otherwise explicitly stated.

In the present specification, "a to b" representing a numerical range is defined as "≥a and ≤b".

residence

The main material is a reference resin for manufacturing the bead foam composite, and is a high heat-resistant plastic such as engineering plastic or super engineering plastic having a melting point of 200° C. or higher.

Steam chest molding (hereinafter, SCM) is normally operated at a steam temperature of 200 ° C or less, but in the case of the high heat-resistant plastic, high-pressure steam of 300 bar at 400 ° C is required, so bead form molding through SCM is limited.

Since the main material contains a conductive filler and has foaming properties upon microwave irradiation, the high heat-resistance plastic may also be suitably used.

In an embodiment, the main material is, polyamide (hereinafter 'PA'), polyphenylene sulfide (hereinafter 'PPS'), polyetheretherketone (hereinafter 'PEEK'), polyether ketone Any one of ketone (Polyetherketoneketone; hereinafter 'PEKK'), polyaryletherketone (hereinafter 'PAEK'), polyethylene terephthalate (hereinafter 'PET') and polycarbonate (hereinafter 'PC') More than that.

conductive filler

The conductive filler is dispersed in the continuous phase main material, and forms at least one contact point with the neighboring conductive filler. Accordingly, the conductive filler forms a conductive network between the beads to generate thermal bonding on the bead surface when exposed to microwaves.

In an embodiment, the conductive filler may preferably have an electrical conductivity of 5.2 to 20 S/cm.

The conductive filler is needle-shaped or fibrous. Due to this morphological specificity, heat can be uniformly transmitted to the inside through the conductive network connection, and even thick molded products can transmit microwaves to the inside of the product. When the conductive filler is in the form of granules, a conductive network is not formed, so that other inter-bead junctions are not generated by microwave irradiation.

In an embodiment, the ratio of the length to the diameter of the conductive filler may be 1: 100 to 1: 290.

Within the above range, the conductive filler may form a conductive network.

In an embodiment, the conductive filler may have a specific gravity of 1.2 to 1.6, for example, 1.5 to 1.6. In the above range, it is possible to effectively form a lightweight bead foam composite.

In an embodiment, the conductive filler is a carbon fiber or a carbon nano tube.

When the above type of conductive filler is used, it is possible to maintain the lightness of the bead foam composite, metal fibers are difficult to maintain lightness, and polymer fibers have low conductivity, so it is difficult to form a target conductive network.

In an embodiment, the conductive filler may be graphene or graphite as carbon nanoparticles having a high aspect ratio.

The conductive filler is included in an amount of 20 to 60 parts by weight based on 100 parts by weight of the main material. When the conductive filler is out of the above range, melting does not occur on the surface of the bead by microwave irradiation, so it is difficult to form a composite material by bonding the beads.

Specifically, the conductive filler is included in an amount of 20 to 40 parts by weight based on 100 parts by weight of the main material. The strength of the final composite material increases within the above range, has an electromagnetic wave shielding effect, and exhibits heat conduction and heat dissipation effects, so that it can be used as a heat shielding material in high-temperature electronic devices.

Microwave Effervescent Beads

Microwave foaming beads may be prepared by extruding a mixed composition by adding additives as needed to the main material and conductive filler.

The microwave foamable beads are heated by microwave irradiation to enable foam molding.

Bead Foam Composite

The bead foam composite is a product in which bonding between beads is formed by irradiating microwaves to the microwave foamable beads.

In the bead form composite, the conductive filler not only imparts conductivity to the inside of the bead form, but also forms a conductive network between beads to uniformly transmit microwaves to the inside of the product, so that the melt adhesion deviation by product thickness / location can be reduced. .

Therefore, even if the thickness of the molded product is thick, product uniformity can be maintained. In an embodiment, the bead foam composite may have an average thickness of 20 to 50 mm.

The bead foam composite material reduces the amount of expensive engineering plastic used, reduces manufacturing cost by using a low-cost conductive filler, and improves physical properties by adding a conductive filler exhibiting high strength.

The bead foam composite exhibits an electromagnetic wave shielding effect while increasing strength, and may exhibit heat conduction and heat dissipation performance.

The bead foam composite has high strength and exhibits heat conduction and heat dissipation performance, so it can be used as a heat shield in a high temperature environment.

Bead Foam Composite Manufacturing

1 is a process flow chart of a bead foam manufacturing method according to one embodiment of the present invention. First, the microwave foaming beads are injected into the mold (S100).

At this time, additives may be added to the mold together.

The additive includes a lubricant, a heat-resisting agent, and a polar monomer, and is not limited thereto unless it is contrary to the purpose of the present invention.

The lubricant facilitates the separation of the surface of the final composite from the mold, and the heat resistant agent increases the stability of the polymer resin in the bead form molding process by microwave irradiation.

When the polar monomer is added, it is preferable because the bonding performance can be increased by increasing crosslinking.

In an embodiment, the lubricant is stearic acid, wax, oil or sodium-based (Na-based) lubricant, and the processing heat-resistant agent is barium-cadmium-based, and phenol-based, phosphorus-based, sulfur-based, or amine-based heat-resistant agent.

The additive may be added in an amount of 3 to 5 parts by weight based on 100 parts by weight of the main material.

As long as the mold can transmit microwaves, the material is not limited.

The mold is predetermined according to the shape of the composite material.

The mold is irradiated with microwaves to bond the beads to each other (S200).

The frequency of the microwave may be 2.45 GHz to 300 GHz.

In the above range, a bond between beads is formed through a conductive network connection between beads, and it is possible to transmit microwaves by penetrating into the inside of a thick composite material, thereby reducing melt adhesion deviation according to product thickness or location. If it is less than the above range, it is difficult to transmit sufficient microwaves into the mold, and if it exceeds the above range, unnecessary energy other than bonding between beads is consumed, resulting in a decrease in composite manufacturing efficiency.

The microwave may be irradiated for 2 to 10 minutes. When it is less than the above range, bonding between beads does not occur, and when it exceeds 10 minutes, unnecessary energy is consumed in addition to bonding, and there is a fear that the physical properties of the target composite material are changed.

Hereinafter, preferred examples are presented to help the understanding of the present invention, but the following examples are only illustrative of the present invention and the scope of the present invention is not limited to the following examples.

Examples 1 to 5. Bead foam composites

PA (DOMO), PEKK (Arkema), and PPS (Sigma-Aldrich) were selected as the main materials, and wax lubricants and sulfur-based (Pentaerythrityl tetrakis (3-laurylthiopropionate)) processing heat resistant agents were selected as additives.

Microwave foamable beads containing 100 parts by weight of the main material, 5 parts by weight of the additive and the conductive filler were prepared using a twin-screw extruder with the types and contents shown in Table 1 below.

A bead foam composite was prepared by filling the mold with the foamed beads prepared above, and applying a current to the electrode of the microwave irradiation device to generate an electric field to emit a frequency of 2.45 GHz.

The bead foam composite material was separated from the mold to confirm the presence or absence of bonding.

Experimental Example 1. Confirm the creation of bead-to-bead junctions

Example 1 Example 2 Reference Example 1 Example 3 Reference Example 2 residence PA PA PPS PPS PEKK Conductive filler addition amount (parts by weight) 0 20 0 20 0 Filler type CF CF CF CF CF with or without bonding partial joint join X join X Time required to join (t) 13 minutes 6 minutes X 12 minutes X CF : Carbon Fiber, CB : Carbon Black, GF : Glass Fiber

Table 1 shows the presence or absence of bonding between beads and the time required for bonding according to the standard resin, the amount and type of the conductive filler added.

Figure 2 is a photograph of the bead foam composite according to Example 3 of the present invention.

The left is a picture of the junction (PPS/CF), and the right is a cross-sectional picture of the junction.

Referring to Table 1 and FIG. 2, when a conductive filler is not added, it is difficult to form a bond between beads by microwave irradiation, and even for partial joining, the time required for joining is increased. It was confirmed that the efficiency to form is very low.

3 is a photograph of the bead foam composite according to Example 2 of the present invention.

When a conductive filler was added, it was confirmed that complete bonding between beads occurred, and the time required for bonding was significantly shortened.

In particular, it was confirmed that even in the case of high heat-resistant engineering plastics such as PA and PPS, when a conductive filler is added, a bead foam composite can be effectively formed by bonding between beads.

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 residence pp pp pp PA PA PA PPS PPS PPS PEKK Filler addition amount (parts by weight) 0 20 20 0 20 40 0 20 20 40 Filler type - GF/CB CF - GF/CB CF - GF CF GF/CB with or without bonding × × partial joint partial joint partial joint join × × join × Time required to join (t) × × 8 minutes 13 minutes 10 minutes 3 minutes × × 12 minutes × CF : Carbon Fiber, CB : Carbon Black, GF : Glass Fiber

After microwave irradiation, the presence or absence of bonding was visually checked and the time required for bonding was measured.

In Comparative Examples 1 to 3, in the case of polypropylene (PP), which is not an engineering plastic, when even a part of the conductive filler is added, a bond is partially formed, but a complete bond is not formed.

In Comparative Examples 4 to 6, in the case of PA, it was confirmed that no conductive filler was added or thermal bonding was not formed when the conductive filler was not acicular, and when any of the acicular or fibrous conductive filler was included (Comparative Example 5 ) It was confirmed that a junction between beads was formed.

In addition, it was confirmed that the bonding formation time decreased when the addition amount was increased.

In Comparative Examples 7 to 9, it was confirmed that, in Comparative Examples 7 to 9, when the conductive filler was not needle-shaped or fibrous, bonding due to microwave irradiation was not formed, and even when the amount of filler was increased in Comparative Example 10, needle-shaped conductive filler If not, it was confirmed that the junction was not formed.

Therefore, the present invention prepares a wave-foaming bead by adding a conductive filler to engineering plastic, which is difficult to be molded by the conventional SCM process, and is a very efficient process in which a bond between beads is formed through microwave irradiation in a mold. Beads with high heat resistance and high strength Foam composites can be prepared.

Up to now, the present invention has been looked at focusing on examples. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention can be implemented in modified forms without departing from the essential characteristics of the present invention. Therefore, the disclosed embodiments are to be considered in an illustrative rather than a restrictive sense. The scope of the present invention is indicated in the claims rather than the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

Claims (10)

100 parts by weight of main material; and 20 to 60 parts by weight of a conductive filler;
It is a microwave foaming bead comprising,
The conductive filler is needle-shaped or fibrous, and is dispersed in the main material.
The microwave foamable bead of claim 1, wherein the main material comprises at least one of polyamide, polyphenylene sulfide, polyether ether ketone, polyether ketone ketone, polyaryl ether ketone, polyethylene terephthalate, and polycarbonate. .
The microwave foamable bead of claim 1, wherein the conductive filler has a length to diameter ratio of 1: 100 to 1: 290.
The microwave expandable bead according to claim 1, wherein the conductive filler is carbon fiber or carbon nanotube.
A bead foam composite formed from the beads of any one of claims 1 to 4.
The bead foam composite of claim 5, wherein the bead foam composite is formed by irradiating microwaves to the beads to form a bond between the beads.
[Claim 6] The composite bead foam according to claim 5, wherein the bead foam composite has an average thickness of 20 to 50 mm.
(a) injecting the beads of any one of claims 1 to 4 into a mold; and
(b) bonding between beads by irradiating microwaves to the mold;
A method for manufacturing a bead foam composite comprising a.
The method of claim 8, wherein the frequency of the microwave is 2.45 GHz to 300 GHz.
The method of claim 8, wherein the microwave is irradiated for 2 to 10 minutes.

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