CN109293972B

CN109293972B - High-strength phenolic aldehyde hollow microsphere and preparation method thereof

Info

Publication number: CN109293972B
Application number: CN201811180291.1A
Authority: CN
Inventors: 李�昊; 赵彤; 高建伟
Original assignee: Institute of Chemistry CAS
Current assignee: Institute of Chemistry CAS
Priority date: 2018-10-10
Filing date: 2018-10-10
Publication date: 2021-02-26
Anticipated expiration: 2038-10-10
Also published as: CN109293972A

Abstract

The invention relates to a high-strength phenolic aldehyde hollow microsphere and a preparation method thereof. The foaming agent and the surfactant are added into the thermosetting phenolic resin, and the foaming and curing of the phenolic resin are simultaneously realized in a closed circulation spray drying device protected by nitrogen by adopting a spray drying process. The invention also provides the phenolic aldehyde hollow microsphere obtained by the method, which has the advantages of small particle size, low sphere breaking rate and high compressive strength.

Description

High-strength phenolic aldehyde hollow microsphere and preparation method thereof

Technical Field

The invention relates to a hollow microsphere, in particular to a hollow microsphere prepared by spray drying.

Background

The phenolic resin hollow microsphere is a new chemical material with a special hollow structure, the inner core of which is air or other gases, and the outer layer of which is phenolic resin. The phenolic aldehyde hollow microsphere has the characteristics of small particle size, low density, low thermal conductivity, excellent thermal stability, low thermal conductivity coefficient, capability of absorbing electromagnetic waves and the like.

The phenolic aldehyde hollow microspheres are used as light functional fillers, and are easily damaged due to external force extrusion in the subsequent material forming process, so that the density reducing effect of the phenolic aldehyde hollow microspheres is greatly influenced. The existing phenolic aldehyde hollow microspheres generally have the defect of low compressive strength, the breakage rate of the phenolic aldehyde hollow microspheres exceeds 80% under 2MPa, and the source of the low compressive strength is that the phenolic aldehyde hollow microspheres are mostly prepared by adopting a spray drying process, and in a spray drying tower, high-temperature hot air causes serious thermal oxidation aging on phenolic resin, so that the compressive strength of hollow microsphere products is reduced.

Disclosure of Invention

The invention provides a preparation method of phenolic aldehyde hollow microspheres, which adopts closed spray drying equipment and takes high-temperature nitrogen as a drying medium, thereby avoiding the occurrence of dangerous conditions such as thermal-oxidative aging of phenolic resin, combustion and explosion of hollow microsphere powder and the like in the high-temperature drying process, and safely and efficiently preparing the high-strength phenolic aldehyde hollow microspheres.

As one aspect of the present invention, the present invention provides a method for preparing a high-strength phenolic aldehyde hollow microsphere, comprising uniformly mixing a thermosetting phenolic resin with a foaming agent and a surfactant to obtain a spray-dried material; the material is atomized by an atomizer to form fine liquid drops, and spray drying is carried out in a closed spray drying tower by taking nitrogen as drying air flow to obtain the phenolic aldehyde hollow microspheres. The weight ratio of each raw material component is as follows: 100 parts of phenolic resin, 0.5-5 parts of foaming agent and 1-5 parts of surfactant.

In order to obtain a hollow structure, 0.5-5 parts of foaming agent is added into the phenolic resin, and phenolic hollow microspheres with different densities can be obtained by using different amounts of the foaming agent. Preferably, the addition amount of the foaming agent is 0.5-3 parts. The decomposition of the foaming agent generates gas to expand atomized liquid drops to generate a hollow structure, hollow microspheres with different densities can be obtained by using different foaming agent amounts, a large amount of solid microspheres are easily generated when the amount is too low, and the decomposition gas is too much when the amount is too high, so that the ball wall is easily broken and the hollow structure is damaged. In order to realize the consistency of the solidification forming and foaming processes of the phenolic resin liquid drops, the selected foaming agent is a medium-high temperature foaming agent and comprises at least one of a foaming agent H, a foaming agent AC or a foaming agent ADC.

In order to ensure the form integrity of the liquid fog drops in the foaming and curing processes, 1-5 parts of surfactant is added into the material, and preferably 1.5-3 parts of surfactant is added. The selected surfactant includes anionic surfactant such as sodium dodecyl sulfate and sodium dodecyl sulfate; nonionic surfactant such as span 60 and Tween 80, and surfactant of organosiloxane type such as polyether modified organopolysiloxane and water-soluble silicone oil DC-193. The surfactant plays a role in stabilizing bubbles and is a key component for maintaining the integrity of a hollow structure, when the dosage is too small, foaming liquid drops are difficult to maintain the hollow spherical structure, and the problems of collapse, bubble combination and the like of the spherical structure of the hollow microspheres are easy to occur before drying and shaping. Above 5 parts, the foam stabilizing effect cannot be further enhanced.

The micro droplets generate physical and chemical changes such as decomposition and foaming of a foaming agent, solvent volatilization, resin curing and forming and the like in a short time under the action of high-temperature nitrogen gas flow, and finally the closed-cell hollow microspheres of the phenolic resin are formed. In the invention, in order to prevent the thermal-oxidative aging of the phenolic aldehyde hollow microsphere powder and avoid the burning and explosion of the powder in the drying tower, nitrogen is adopted as a drying airflow medium, so that the production safety and the compressive strength of the product are improved.

Further, the atomizer is a centrifugal atomizer, an air flow atomizer or a pressure atomizer.

When spray drying is carried out, the process parameters are selected as follows:

further, the air inlet temperature of the spray drying is 250-350 ℃, and preferably 280-320 ℃. The rapid drying and the full curing of the liquid thermosetting phenolic resin can be ensured within the air inlet temperature range. The proper temperature range can ensure that the liquid resin is quickly cured, dried and shaped after foaming, and is the key for obtaining the complete hollow structure product. The air inlet temperature is too low, the resin is not ready for curing and shaping, and the hollow microsphere product cannot be obtained due to the fact that the resin is wet and adhered to the wall in the spray drying process; the air inlet temperature is too high, the resin is cured too fast, and the foaming agent is not decomposed in time, so that a large amount of solid microspheres can be generated.

The invention also provides the high-strength phenolic aldehyde hollow microsphere obtained by the method, and the particle density of the high-strength phenolic aldehyde hollow microsphere is 0.2-0.4g/cm³The grain size is less than 300 microns, the ball breaking rate is less than 10 percent, the stacking coefficient is more than 50 percent, the breakage rate under the pressure of 2MPa is less than 60 percent, and the method has the advantages of small grain size, regular roundness, low ball breaking rate and high compressive strength.

In order to avoid thermo-oxidative aging of the phenolic resin in the spray drying process, closed spray drying equipment is adopted for preparing the phenolic hollow microspheres, high-temperature nitrogen airflow is used as a drying medium, and parameters of the spray drying equipment are controlled, so that thermo-oxidative aging of the phenolic resin can be effectively avoided, the compressive strength of the phenolic hollow microspheres is effectively improved, and the high-strength phenolic hollow microspheres are prepared; on the other hand, because nitrogen is adopted as the drying airflow, oxygen is isolated in the drying tower, potential safety hazards such as combustion, explosion and the like of the hollow microsphere powder are avoided, and the process method has the characteristics of safety and reliability.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 is an SEM photograph of high-strength hollow phenolic microspheres prepared in example 1 of the present invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

Example 1

According to the following phenolic resin: foaming agent: surfactant 100: 1: 2 (weight ratio), and fully and uniformly stirring the components to obtain the resin material for spray drying. Wherein the foaming agent is foaming agent H, and the surfactant is BD3088 (an organosilicon surfactant). And then, inputting the materials into a centrifugal atomizer at a constant speed, and carrying out spray drying in a closed spray drying tower by taking nitrogen as drying air flow to obtain the phenolic aldehyde hollow microspheres. The inlet air temperature of the closed spray drying equipment is controlled to be 280 ℃. The product obtained by the process and the formula has the particle density of 0.32g/cm³(ii) a The ball breaking rate is 4.1%; the stacking coefficient is 50%; the breakage rate under the pressure of 2MPa is 52 percent. As shown in an SEM picture of an attached drawing 1, the prepared phenolic aldehyde hollow microsphere has the advantages of particle size of less than 300 microns, regular roundness and less ball breakage.

Example 2

According to the following phenolic resin: foaming agent: surfactant 100: 3: 3 (weight ratio), and fully and uniformly stirring the components to obtain the resin material for spray drying. Wherein the foaming agent is foaming agent AC, and the surfactant is sodium dodecyl sulfate. Then the material is input into a centrifugal atomizer at a constant speed, nitrogen is used as drying air flow,and (4) carrying out spray drying in a closed spray drying tower to obtain the phenolic aldehyde hollow microspheres. The air inlet temperature of the closed spray drying equipment is controlled to be 300 ℃. The product obtained by the process and the formula has the particle density of 0.27g/cm³(ii) a The ball breaking rate is 5.5 percent; the stacking factor is 51%; the breakage rate under the pressure of 2MPa is 57 percent.

Example 3

According to the following phenolic resin: foaming agent: surfactant 100: 0.5: 1.5 (weight ratio), and fully and uniformly stirring the components to obtain the resin material for spray drying. Wherein the foaming agent is foaming agent H, and the surfactant is Tween 80. And then, inputting the materials into a centrifugal atomizer at a constant speed, and carrying out spray drying in a closed spray drying tower by taking nitrogen as drying air flow to obtain the phenolic aldehyde hollow microspheres. The inlet air temperature of the closed spray drying equipment is controlled to be 320 ℃. The product obtained by the process and the formula has the particle density of 0.38g/cm³(ii) a The ball breaking rate is 4.5 percent; the stacking factor is 54%; the breakage rate is 50% under the pressure of 2 MPa.

Comparative example

According to the following phenolic resin: foaming agent: surfactant 100: 2: 2 (weight ratio), and fully and uniformly stirring the components to obtain the resin material for spray drying. Wherein the foaming agent is foaming agent H, and the surfactant is BD3088 (an organosilicon surfactant). And then inputting the materials into a centrifugal atomizer at a constant speed, and carrying out spray drying in an open spray drying tower by taking air as drying air flow to obtain the phenolic aldehyde hollow microspheres. The inlet air temperature of the spray drying equipment is controlled to be 260 ℃. The product obtained by the process and the formula has the particle density of 0.36g/cm³(ii) a The ball breaking rate is 6.8%; the stacking coefficient is 50%; the breakage rate is 88 percent under the pressure of 2 MPa.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. A preparation method of high-strength phenolic aldehyde hollow microspheres is characterized by comprising the steps of uniformly mixing thermosetting phenolic resin with a foaming agent and a surfactant to obtain a spray-dried material; atomizing the material by an atomizer to form fine liquid drops, and performing spray drying in a closed spray drying tower by taking nitrogen as drying air flow, wherein the inlet air temperature of the spray drying is 250-350 ℃, and finally forming the phenolic aldehyde hollow microspheres; the weight ratio of the raw material components is as follows: 100 parts of phenolic resin; 0.5-5 parts of a foaming agent; 1-5 parts of a surfactant;

the foaming agent is at least one of foaming agent H and foaming agent AC;

the atomizer is a centrifugal atomizer;

the surfactant is BD3088, sodium dodecyl sulfate or Tween 80.

2. The method of claim 1, wherein: the air inlet temperature of the spray drying is 280-320 ℃.