WO2021179645A1

WO2021179645A1 - In-mold one-time foaming molding process and foam product

Info

Publication number: WO2021179645A1
Application number: PCT/CN2020/126770
Authority: WO
Inventors: 姜修磊; 李期筠; 余加保
Original assignee: 苏州申赛新材料有限公司
Priority date: 2020-03-09
Filing date: 2020-11-05
Publication date: 2021-09-16
Also published as: CN111300713A; CN111300713B

Abstract

An in-mold one-time foaming molding process, comprising the following steps: S1: pre-impregnating a resin bead in supercritical gas to obtain a bead to be foamed; S2: transferring the bead into a closed space, and introducing moist air, so that the bead is in a fluidized state; S3: heating the bead to be foamed and the moist air by using microwaves; and S4: conducting exhaust foaming molding to obtain a foam product. The foam product is obtained by one-step forming, no defects exist inside the product, and the performance is good. The bead is heated using microwaves, the heat efficiency is high, the heat transfer depth is large, and the heating time is short. A mold made from a non-polar material with dense small holes in the upper and lower surfaces is used, so that processing and obtaining are easy, and the cost is low. In addition, an air blowing device is provided below the mold to guarantee that the bead is in a fluidized state during microwave irradiation, so that the bead is uniformly heated and does not generate accumulation defects. A supercritical fluid is used as a physical foaming agent for impregnating and foaming, so that the production process is green and environmentally friendly, and the process is suitable for industrial production.

Description

In-mold one-time foaming molding process and foamed products

cross reference

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on March 9, 2020, the application number is 202010157235.7, and the invention title is "One-time in-mold foaming molding process and foamed products", the entire content of which is approved The reference is incorporated in this application.

Technical field

This application relates to the field of polymer material processing, and in particular to an in-mold one-time foaming molding process and foamed products.

Background technique

The polymer foam material refers to a polymer composite material with a porous structure formed by uniformly distributing the gas phase in the polymer solid phase. Due to its porous structure, the polymer foam material has excellent sound insulation and heat insulation performance, shock resistance and cushioning performance. Among them, the molding process of thermoplastic polymer foam material mainly includes three types: extrusion foam molding, injection foam molding and bead molding. The extrusion foam molding process can only produce products with a single cross-section, such as sheets, plates, pipes, etc.; injection foam molding can produce products with complex structures, but due to process limitations, the product density is high and the expansion ratio is low; bead molds Plastic molding can produce low-density, complex-shaped foam products, which is a hot research topic in recent years.

At present, the commonly used method of bead molding in the industry is a two-step process. First, the resin beads are foamed with a chemical foaming agent or a physical foaming agent to obtain foamed beads, and then the foamed beads are filled into the mold, and the foamed beads are heated and shaped by a medium such as water vapor. Mutual welding to obtain complex foamed products. This method has the following problems, and the performance loss of the prepared molded body is relatively large. When the beads are foamed at the first time, there will be internal defects. When the foamed beads are accumulated during the second molding, there must be voids. The accumulation of two defects will reduce the mechanical properties of the molded body and limit its application scenarios. At the same time, use steam heating The molding time is long and the industrialization efficiency is low.

Summary of the invention

For this reason, the technical problem to be solved by this application is to overcome the defects that the accumulation of defects in the existing two-step method will reduce the mechanical properties of the molded body and limit its application scenarios. At the same time, the use of water vapor to heat the molding takes a long time and the industrialization efficiency is low. Provided is an in-mold one-time foaming molding process and foamed products.

In order to solve the above technical problems, the technical solutions adopted in this application are as follows:

This application provides an in-mold one-time foam molding process, which includes the following steps:

S1: Pre-impregnating resin beads in supercritical gas to obtain beads to be expanded;

S2: Transfer the beads to be expanded into the mold, pass moist air into the mold, and use microwaves to heat the beads and moist air;

S3: Exhaust foam molding to obtain foamed products.

Preferably, in the step S2, the microwave power is 2000-3000 MHz, and the heating time is 30-180s.

The relative humidity of the humid air in the mold is 10-50%, and the pressure is 2-8 bar.

In step S1, the resin beads are polar thermoplastic polymer resin beads, the particle size of the polar thermoplastic polymer resin beads is 0.5-5 mm, and the polar thermoplastic polymer resin beads are microwave absorbing Type material, which can be heated by microwave.

Preferably, the polar thermoplastic polymer resin beads are at least one of polyurethane elastomer, polyamide elastomer and polyester elastomer.

The supercritical gas is nitrogen and/or carbon dioxide;

Preferably, the supercritical gas is a mixed gas of nitrogen and carbon dioxide, and the volume ratio of nitrogen to carbon dioxide in the mixed gas is (3-49):1.

Further, the temperature of the pre-impregnation is 50-100° C., the pressure is 10-40 MPa, and the time is 10-480 min.

Further, the exhaust foaming molding in the S3 is to reduce the pressure to the standard atmospheric pressure at a pressure relief rate of 10-400 bar/s, and then pass cold air at 0-5°C for cooling.

Further, air flow holes are distributed on the surface of the mold, and the diameter of the air flow holes is smaller than the diameter of the resin beads. The mold is made of microwave-permeable non-polar polymer or ceramic, and the non-polar polymer is a polymer. Polymers whose side chains do not contain polar functional groups, such as polyethylene and/or polypropylene;

Moist air is continuously passed into the mold through the airflow holes to make the beads to be expanded in a fluidized state. The specific method is to set up a blowing device under the mold.

This application also provides foamed products prepared by the above-mentioned foaming process.

Compared with the prior art, this application has the following beneficial effects:

1. The application is one-step molding to obtain a foamed product. First, the resin beads are immersed in the supercritical fluid to dissolve the gas molecules in the resin beads; the beads to be foamed are transferred to the mold and passed into the mold The humid air makes the beads to be expanded in a fluidized state; after microwave heating, the temperature of the resin beads increases, and the solubility of the gas in the resin beads decreases; after exhausting the pressure, the beads are foamed and welded. This application avoids the accumulation of defects caused by multiple foaming in the two-step method from reducing the mechanical properties of the product. The product of this application has no internal defects and has good performance.

2. This application uses microwave to heat the beads to be foamed, which has high thermal efficiency and large heat transfer depth, and foamed products can be obtained in a short time. When polar thermoplastic polymer is irradiated by microwaves, the internal molecules generate dielectric loss through polarization, which converts microwaves into heat energy. At the same time, a certain pressure of humid air is introduced, and under microwave heating, the water molecules dispersed in the air are heated to ensure that the surface and interior of the beads in the foaming box are evenly heated, which helps to bond the beads during foaming.

3. This application uses a mold with dense small holes on the upper and lower surfaces, and the diameter of the small holes is smaller than the diameter of the resin beads. An air blowing device is set under the mold to ensure that the beads are in a fluidized state during microwave irradiation, uniform heating and no accumulation defects. At the same time, the mold of the present application is made of wave-permeable non-polar polymer or ceramic, which is easy to process and obtain and has low cost. In traditional bead molding, due to the high temperature and pressure, the mold is required to be high, and it is usually made of metal materials such as aluminum alloy, which has a high cost and is not easy to process. In this application, the beads are heated and molded by microwaves, the temperature and pressure of foaming are lower, and non-polar polymers and ceramic molds that are more easily available can be used, which greatly reduces the production and development costs.

4. This application uses supercritical fluid as the physical foaming agent to impregnate and foam, and the production process is environmentally friendly and suitable for industrial production.

Description of the drawings

In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the specific embodiments or the description of the prior art. Obviously, the appendix in the following description The drawings are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

Fig. 1 is a schematic structural diagram of a foaming device used in Examples 1-3 of the present application.

Reference signs:

1-foaming box; 2-microwave launching device; 3-mold; 4-blowing device; 5-inlet valve, 6-exhaust valve; 7-pressure monitoring device; 8-wet air compression device; 9-cold Air compression device.

Detailed ways

The following examples are provided for a better understanding of this application, and are not limited to the best embodiments, and do not limit the content and protection scope of this application. Any product that is the same or similar to the present application obtained by combining the features of other prior art shall fall within the protection scope of the present application.

In the description of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the pointed device or element must have a specific orientation or a specific orientation. The structure and operation cannot therefore be understood as a limitation of this application. In addition, the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance.

In the description of this application, it should be noted that the terms "installation", "connection", and "connection" should be understood in a broad sense, unless otherwise clearly specified and limited. For example, it can be a fixed connection or a detachable connection. Connected or integrally connected; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication between two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood under specific circumstances.

If the specific experimental steps or conditions are not indicated in the examples, it can be carried out according to the operations or conditions of the conventional experimental steps described in the literature in the field. The reagents or instruments used without the manufacturer's indication are all conventional reagent products that can be purchased commercially.

The mold 3 used in the following Examples 1-3 is made of a wave-permeable polyethylene material, and the diameter of the airflow holes distributed on the surface of the mold is 0.3 mm.

Example 1

This embodiment provides an in-mold one-time foam molding process, which includes the following steps:

(1) The thermoplastic polyurethane elastomer (TPU) beads with a melting point of 165°C, a hardness of 85A and a particle size of 0.5-5 mm are immersed in an autoclave for 10 minutes. The immersion temperature is 100°C, the immersion pressure is 40MPa, and the supercritical gas used is nitrogen: carbon dioxide volume ratio = 3:1;

(2) Spread the immersed TPU beads into the mold 3 and close the mold, place it in the foaming box 1, turn on the humid air compression device 8, and fill the foaming box with 50% relative humidity through the air inlet valve 5. For humid air, use the pressure monitoring device 7 to make the pressure in the foaming box 1 reach 2 bar, and at the same time turn on the blowing device 4 to make the beads in a fluidized state;

(3) Turn on the microwave transmitter 2 and heat the beads by microwave, set the microwave frequency to 2000MHz and the heating time to be 180s;

(4) Open the exhaust valve 6 to vent the standard atmospheric pressure at a rate of 10 bar/s, and then open the cold air compression device 9 to pass cold air at 0°C into the foaming box 1 for cooling to obtain a foamed product.

The finally obtained foamed product has no defects on the surface observed by naked eyes, the particles are welded tightly, the density is 0.18g/cm ³ , the right-angle tear strength (test standard: ISO 8067:2008) is 140N/cm, and the falling ball rebounds (test standard: ASTM D3574) is 62%.

Example 2

(1) The thermoplastic polyamide elastomer (TPAE) beads with a melting point of 170°C, a hardness of 94A and a particle size of 0.5-5 mm are immersed in an autoclave for 480 minutes. The immersion temperature is 50°C, the immersion pressure is 10MPa, and the supercritical gas used is nitrogen: carbon dioxide volume ratio = 49:1;

(2) Spread the immersed TPAE beads over the mold 3 and close the mold, place it in the foaming box 1, turn on the humid air compression device 8, and fill the foaming box with 10% relative humidity through the air inlet valve 5. For humid air, use the pressure monitoring device 7 to make the pressure in the foaming box 1 reach 8 bar, and at the same time turn on the blowing device 4 to make the beads in a fluidized state;

(3) Turn on the microwave transmitter 2 to microwave the beads, set the microwave frequency to 3000MHz, and the heating time to be 30s;

(4) Open the exhaust valve 6, vent the standard atmospheric pressure at a rate of 400 bar/s, and then open the cold air compression device 9 to pass cold air at 5°C into the foaming box 1 for cooling to obtain a foamed product.

The resulting foamed product has no defects on the surface observed by naked eyes, the particles are fused tightly, the density is 0.07g/cm3, the right-angle tear strength (test standard: ISO 8067:2008) is 60N/cm, and the ball rebounds (test standard: ASTM) D3574) is 72%.

Example 3

(1) The thermoplastic polyester elastomer (TPEE) beads with a melting point of 160°C, a hardness of 98A and a particle size of 0.5-5 mm are immersed in an autoclave for 200 minutes. The impregnation temperature is 70℃, the impregnation pressure is 20MPa, and the supercritical gas used is nitrogen: carbon dioxide volume ratio = 4:1;

(2) Spread the immersed TPEE beads over the mold 3 and close the mold, place it in the foaming box 1, turn on the humid air compression device 8, and fill the foaming box with 30% relative humidity through the air inlet valve 5. For humid air, use the pressure monitoring device 7 to make the pressure in the foaming box 1 reach 4 bar, and at the same time turn on the blowing device 4 to make the beads in a fluidized state;

(3) Turn on the microwave transmitter, microwave the beads, set the microwave frequency to 2500MHz, and the heating time to 60s;

(4) Open the exhaust valve 6 to vent the standard atmospheric pressure at a rate of 60 bar/s, and then open the cold air compression device 9 to pass 2°C cold air into the foaming box 1 for cooling to obtain a foamed product.

The resulting foamed product has no defects on the surface observed by naked eyes, the particles are fused tightly, the density is 0.15g/cm3, the right-angle tear strength (test standard: ISO 8067:2008) is 95N/cm, and the ball rebounds (test standard: ASTM) D3574) is 70%.

Comparative example 1

Compared with Example 1, this comparative example is a traditional two-step method for preparing foamed products, including the following steps:

(1) Thermoplastic polyurethane elastomer (TPU) beads with a melting point of 165°C and a hardness of 85A are immersed in an autoclave and pressure-relieved and foamed. The immersion time is 30min, the immersion temperature is 110℃, the immersion pressure is 40MPa, the practical supercritical fluid is nitrogen: carbon dioxide volume ratio=3:1, and the pressure relief rate is 400MPa/s.

(2) Spread the foamed TPU beads into a steam hot-pressing mold, close the mold and pass in steam, the steam pressure is 1.8bar, keep for 3min, turn off the steam, and input cold water for cooling.

The resulting foamed product has defects on the surface observed by naked eyes. The density is 0.2g/cm3, the right-angle tear strength (test standard: ISO 8067:2008) is 34N/cm, and the ball rebound (test standard: ASTMD3574) is 60%. .

Compared with Example 1, the foamed product obtained in Comparative Example 1 has defects, and at the same time, the tear strength is significantly lower than that of Example 1, and the quality difference is obvious.

Obviously, the above-mentioned embodiments are merely examples for clear description, and are not intended to limit the implementation manners. For those of ordinary skill in the art, other changes or modifications in different forms can be made on the basis of the above description. It is unnecessary and impossible to list all the implementation methods here. The obvious changes or changes derived from this are still within the scope of protection created by this application.

Claims

An in-mold one-time foaming molding process is characterized in that it comprises the following steps:

S1: Pre-impregnating resin beads in supercritical gas to obtain beads to be expanded;

S2: Transfer the beads to be expanded into the mold, pass moist air into the mold, and use microwaves to heat the beads and moist air;

S3: Exhaust foam molding to obtain foamed products.
The foam molding process according to claim 1, characterized in that, in the step S3, the microwave power is 2000-3000 MHz, and the heating time is 30-180s.
According to the foam molding process of claim 1 or 2, in the step S2, the relative humidity of the humid air in the mold is 10-50%, and the pressure is 2-8 bar.
The foam molding process according to any one of claims 1 to 3, wherein in step S1, the resin beads are polar thermoplastic polymer resin beads, and the polar thermoplastic polymer resin beads The particle size is 0.5-5mm.
The foam molding process according to claim 4, wherein the polar thermoplastic polymer resin beads are at least one of polyurethane elastomer, polyamide elastomer and polyester elastomer.
The foam molding process according to any one of claims 1 to 5, wherein the supercritical gas is nitrogen and/or carbon dioxide;

Preferably, the supercritical gas is a mixed gas of nitrogen and carbon dioxide, and the volume ratio of nitrogen and carbon dioxide in the mixed gas is (3-49):1.
The foam molding according to any one of claims 1-6, wherein the temperature of the pre-impregnation is 50-100° C., the pressure is 10-40 MPa, and the time is 10-480 min.
The foaming molding process according to any one of claims 1-7, wherein the exhaust foaming molding in S4 is reduced to standard atmospheric pressure at a pressure relief rate of 10-400 bar/s, and then passed Cool with cold air at 0-5°C.
The foaming molding process according to any one of claims 1-8, wherein air holes are distributed on the surface of the mold, and the diameter of the air holes is smaller than the diameter of the resin beads;

Moist air is continuously passed into the mold through the airflow holes to make the beads to be expanded in a fluidized state.
A foamed product, characterized in that it is prepared by the foaming process of any one of claims 1-9.