阅读说明：本技术 一种泡沫塑料用复合阻燃型发泡剂及其制备方法 (Composite flame-retardant foaming agent for foamed plastic and preparation method thereof ) 是由 王新 黄广晋 于 2021-01-20 设计创作，主要内容包括：本发明公开了一种泡沫塑料用复合阻燃型发泡剂及其制备方法。复合阻燃性发泡剂由以下质量分数的原料组成,发泡剂微球90-95wt.%、复合阻燃剂5-10wt.%。发泡剂微球由偶氮二异丁腈、偶氮二甲酰胺、偶氮二异丁酸二甲酯、N,N-二亚硝基五亚甲基四胺中的任意一种作为发泡剂负载于聚已内酯微球中,再使用聚乙烯醇在聚已内酯微球表面形成一层保护膜制得。复合阻燃剂主要由如下重量份的原料组成,聚硅氧烷微球55-58份、亚磷酸三甲酯18-25份、聚磷酸铵18-25份。本发明制备的复合阻燃型发泡剂具有良好的阻燃性,发泡形成的泡沫塑料力学性能良好,泡沫塑料内部气孔孔径尺寸大小均匀,无塌陷。(The invention discloses a composite flame-retardant foaming agent for foamed plastic and a preparation method thereof. The composite flame-retardant foaming agent comprises the following raw materials in percentage by mass, wherein the foaming agent microspheres account for 90-95wt.%, and the composite flame retardant accounts for 5-10 wt.%. The foaming agent microsphere is prepared by loading any one of azodiisobutyronitrile, azodicarbonamide, dimethyl azodiisobutyrate and N, N-dinitrosopentamethylenetetramine serving as a foaming agent in a polycaprolactone microsphere and forming a layer of protective film on the surface of the polycaprolactone microsphere by using polyvinyl alcohol. The composite flame retardant mainly comprises the following raw materials, by weight, 55-58 parts of polysiloxane microspheres, 18-25 parts of trimethyl phosphite and 18-25 parts of ammonium polyphosphate. The composite flame-retardant foaming agent prepared by the invention has good flame retardance, the foamed plastic formed by foaming has good mechanical property, and the pore size of the internal pores of the foamed plastic is uniform without collapse.)

1. A composite flame-retardant foaming agent for foamed plastics is characterized in that; the composite flame-retardant foaming agent mainly comprises the following raw materials in percentage by mass, wherein the foaming agent microspheres account for 90-95wt.%, and the composite flame retardant accounts for 5-10 wt.%.

2. The compound flame-retardant foaming agent for foam plastics according to claim 1, which is characterized in that: the foaming agent microsphere is mainly prepared from the following raw materials, by weight, 65-70 parts of a foaming agent, 20-25 parts of polycaprolactone and 13-16 parts of polyvinyl alcohol.

3. The compound flame-retardant foaming agent for foam plastics according to claim 1, which is characterized in that: the composite flame retardant mainly comprises the following raw materials, by weight, 55-58 parts of polysiloxane microspheres, 18-25 parts of trimethyl phosphite and 18-25 parts of ammonium polyphosphate.

4. The compound flame-retardant foaming agent for foam plastics according to claim 1, which is characterized in that: the foaming agent is any one of azodiisobutyronitrile, azodicarbonamide, dimethyl azodiisobutyrate and N, N-dinitrosopentamethylenetetramine.

5. The compound flame-retardant foaming agent for foam plastics according to claim 1, which is characterized in that: the particle size of the foaming agent microspheres is 40-60 mu m.

6. A preparation method of a composite flame-retardant foaming agent for foamed plastics is characterized by comprising the following steps: comprises the following steps of (a) carrying out,

(1) preparing foaming agent microspheres;

(2) preparing a composite flame retardant;

(3) preparing the composite flame-retardant foaming agent.

7. The preparation method of the composite flame-retardant foaming agent for the foam plastic according to claim 6, wherein the foaming agent comprises the following components in percentage by weight: comprises the following steps of (a) carrying out,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 0-10 ℃ to obtain a suspension;

keeping the temperature at 0-10 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed, emulsifying, adding a polyvinyl alcohol solution, and emulsifying to obtain polycaprolactone/foaming agent microspheres;

adding polycaprolactone/foaming agent microspheres into distilled water at the temperature of 20-30 ℃, stirring, filtering, drying and screening to obtain foaming agent microspheres;

dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 2-3h, and distilling to remove ethanol to obtain the composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

8. The preparation method of the compound flame-retardant foaming agent for the foam plastic according to claim 7, wherein the foaming agent comprises the following components in percentage by weight: comprises the following steps of (a) carrying out,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 0-10 ℃ to obtain a suspension;

keeping the temperature at 0-10 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed of 8000-;

adding polycaprolactone/foaming agent microspheres into distilled water, stirring at the temperature of 20-30 ℃ and the stirring speed of 600-800r/min, filtering, drying, and screening to obtain foaming agent microspheres with the particle size of 40-60 mu m;

dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 2-3h, heating to 80-85 ℃, and distilling to remove ethanol to obtain a composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

Technical Field

The invention relates to the technical field of foaming materials, in particular to a composite flame-retardant foaming agent for foamed plastics and a preparation method thereof.

Background

The foaming agent is a substance which causes an action object to form a hole, and can be divided into three categories, namely a chemical foaming agent, a physical foaming agent and a surfactant according to different properties.

Chemical blowing agents are those compounds which decompose upon heating to release gases such as carbon dioxide and nitrogen and form pores in the polymer composition. The chemical foaming agent is divided into an inorganic foaming agent and an organic foaming agent, wherein the organic foaming agent mainly comprises three types of azo compounds, sulfonyl hydrazine compounds and nitroso compounds, and the inorganic foaming agent mainly comprises carbonate, water glass, silicon carbide and carbon black. Physical blowing agents are those in which the foam cells are formed by a change in the physical form of a substance, i.e., by expansion of a compressed gas, volatilization of a liquid, or dissolution of a solid; the foaming agent has higher surface activity, can effectively reduce the surface tension of liquid, and is arranged on the surface of the liquid film by two electron layers to surround air to form bubbles. Physical blowing agents commonly used are low boiling alkanes and fluorocarbons. The physical foaming agent is a compound physical foaming agent, has the advantages of high foaming times, good foam stability, low bleeding amount and the like, and is widely applied to the production of foaming magnesite products such as fire-proof plates, light partition plates and the like. The foaming principle of the surfactant foaming agent is the surface activity of the surfactant, and the surfactant serves as a foaming core. The surfactant foaming agent mainly comprises sodium dodecyl sulfate, fatty alcohol-polyoxyethylene ether sodium sulfate, rosin soap foaming agent, animal and vegetable protein foaming agent and the like. Surfactant foaming agents have been widely used in the fields of gypsum boards, foamed concrete and the like.

In the plastics industry, foams are often processed using chemical blowing agents as blowing agents, with azo-based organic blowing agents being most commonly used. The polypropylene foam plastic has a narrow temperature range suitable for foaming, so that the foaming process is difficult to stabilize, and the phenomena of foam wall rupture, bubble combination and pore opening are easily caused in the foaming process. In addition, the foaming performance existing in the market is single, and with the continuous development of the foam plastic industry, the requirement of each demand party on the foaming agent is not only single foaming performance, but also more requirements on the comprehensive performances such as oxidation resistance, heat resistance, flame retardance and the like.

Disclosure of Invention

The invention aims to provide a composite flame-retardant foaming agent for foam plastics and a preparation method thereof, and aims to solve the problems in the background art.

In order to solve the technical problems, the invention provides the following technical scheme: the composite flame-retardant foaming agent for the foamed plastic mainly comprises the following raw materials in percentage by mass, wherein the foaming agent microspheres account for 90-95 wt%, and the composite flame retardant accounts for 5-10 wt%.

Further, the foaming agent microsphere mainly comprises, by weight, 65-70 parts of a foaming agent, 20-25 parts of polycaprolactone and 13-16 parts of polyvinyl alcohol.

Furthermore, the composite flame retardant mainly comprises the following raw materials, by weight, 55-58 parts of polysiloxane microspheres, 18-25 parts of trimethyl phosphite and 18-25 parts of ammonium polyphosphate.

Further, the foaming agent is any one of azodiisobutyronitrile, azodicarbonamide, dimethyl azodiisobutyrate and N, N-dinitrosopentamethylenetetramine.

Furthermore, the particle size of the foaming agent microsphere is 40-60 μm.

A preparation method of a composite flame-retardant foaming agent for foam plastic comprises the following steps,

(1) preparing foaming agent microspheres;

(2) preparing a composite flame retardant;

(3) preparing the composite flame-retardant foaming agent.

Further, the preparation method of the composite flame-retardant foaming agent for the foamed plastic is characterized by comprising the following steps of: the step (1) is as follows,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 0-10 ℃ to obtain a suspension;

keeping the temperature at 0-10 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed, emulsifying, adding a polyvinyl alcohol solution, and emulsifying to obtain polycaprolactone/foaming agent microspheres;

adding polycaprolactone/foaming agent microspheres into distilled water at the temperature of 20-30 ℃, stirring, filtering, drying and screening to obtain foaming agent microspheres;

(2) dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 2-3h, and distilling to remove ethanol to obtain the composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

Further, the preparation method of the composite flame-retardant foaming agent for the foamed plastic is characterized by comprising the following steps of: comprises the following steps of (a) carrying out,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 0-10 ℃ to obtain a suspension;

keeping the temperature at 0-10 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed of 8000-;

adding polycaprolactone/foaming agent microspheres into distilled water, stirring at the temperature of 20-30 ℃ and the stirring speed of 600-800r/min, filtering, drying, and screening to obtain foaming agent microspheres with the particle size of 40-60 mu m;

(2) dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 2-3h, heating to 80-85 ℃, and distilling to remove ethanol to obtain a composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2), adding the mixture into an ethanol solvent, and uniformly dispersing to obtain the composite flame-retardant foaming agent.

Compared with the prior art, the invention has the following beneficial effects: the invention provides a composite flame-retardant foaming agent for foam plastic production and a preparation method thereof. The foaming agent in the polycaprolactone microspheres can be slowly released, the action uniformity of foaming in the plastic resin is better, the pore size of the generated pores is stable and uniform, and the phenomena of foam collapse and foam combination in the foaming process caused by instant aggregation and foaming of the foaming agent are greatly avoided. The polycaprolactone has good compatibility with plastic polyester, is easy to degrade to generate carbon dioxide and water, and can also play a role of a plasticizer in plastic products.

The organic phosphorus flame retardant is added into high polymer materials such as plastics and the like, so that the flame retardance of the high polymer materials can be improved, and meanwhile, the mechanical property of the high polymer materials can be reduced; in order to solve the problem, the fire retardant is loaded in the polyoxosilane microspheres, and the-Si-O-bonds in the polyoxosilane can increase the fire resistance of ammonium polyphosphate and trimethyl phosphite; and then soaking the polysiloxane microspheres in a polyvinyl alcohol solution to form a layer of polyvinyl alcohol film on the surfaces of the polysiloxane microspheres, and packaging the flame retardant in the polysiloxane microspheres. The polysiloxane microspheres can enhance the mechanical strength of the polymer, increase the specific surface area of the flame retardant and avoid the phenomena of uneven dispersion and agglomeration of the flame retardant in a polymer system.

The flame retardant is a 1:1 mixture of ammonium polyphosphate and trimethyl phosphite, the synergistic flame retardant effect of the two organophosphorus flame retardants is better, and a large amount of carboxyl, hydroxyl and amino groups exist on the surfaces of the ammonium polyphosphate and trimethyl phosphite molecules, so that the interfacial binding force with polysiloxane can be increased, and the stability of the composite flame retardant is improved.

In the process of mixing the foaming agent microspheres and the composite flame retardant, hydrogen bonds can be formed between a large amount of hydroxyl groups on the surfaces of the foaming agent microspheres and silicon oxygen groups on the surfaces of polysiloxane microspheres, and bridging effect is formed between the foaming agent microspheres and the composite flame retardant due to the existence of the hydrogen bonds, so that the composite foaming agent is endowed with good flame retardance.

The composite flame-retardant foaming agent prepared by the invention has good flame retardance, the foamed plastic formed by foaming has good mechanical property, and the pore size of the internal pores of the foamed plastic is uniform without collapse.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The composite flame-retardant foaming agent for the foamed plastic comprises the following raw materials in percentage by mass, wherein the foaming agent microspheres account for 90wt.%, and the composite flame retardant accounts for 10 wt.%.

The foaming agent microsphere consists of the following raw materials, by weight, 65 parts of a foaming agent, 20 parts of polycaprolactone and 13 parts of polyvinyl alcohol.

The composite flame retardant mainly comprises the following raw materials, by weight, 55 parts of polysiloxane microspheres, 18 parts of trimethyl phosphite and 18 parts of ammonium polyphosphate.

The foaming agent is azodiisobutyronitrile, and the particle size of the foaming agent microspheres is 40 microns.

A preparation method of a composite flame-retardant foaming agent for foam plastic comprises the following steps,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 0 ℃ to obtain a suspension;

keeping the temperature at 0 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed of 8000r/min, emulsifying for 5min, adding a polyvinyl alcohol solution, and emulsifying at a rotating speed of 800r/min for 20min to obtain polycaprolactone/foaming agent microspheres;

adding polycaprolactone/foaming agent microspheres into distilled water, stirring at 20 ℃ and 600r/min, filtering, drying, and screening to obtain foaming agent microspheres with the particle size of 800 microns;

(2) dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 2 hours, heating to 80 ℃, and distilling to remove ethanol to obtain the composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

Example 2

The composite flame-retardant foaming agent for the foamed plastic comprises the following raw materials in percentage by mass, 93wt.% of foaming agent microspheres and 7wt.% of composite flame retardant.

The foaming agent microsphere consists of the following raw materials, by weight, 68 parts of a foaming agent, 21 parts of polycaprolactone and 15 parts of polyvinyl alcohol.

The composite flame retardant mainly comprises the following raw materials in parts by weight, 57 parts of polysiloxane microspheres, 20 parts of trimethyl phosphite and 21 parts of ammonium polyphosphate.

The foaming agent is dimethyl azodiisobutyrate, and the particle size of the foaming agent microspheres is 50 microns.

A preparation method of a composite flame-retardant foaming agent for foam plastic comprises the following steps,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 5 ℃ to obtain a suspension;

keeping the temperature at 5 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed of 9000r/min, emulsifying for 5-7min, adding a polyvinyl alcohol solution, and emulsifying at a rotating speed of 900r/min for 22min to obtain polycaprolactone/foaming agent microspheres;

adding polycaprolactone/foaming agent microspheres into distilled water, stirring at 20-30 ℃ and the stirring speed of 750r/min, filtering, drying, and screening to obtain foaming agent microspheres with the particle size of 900 microns;

(2) dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 2.5h, heating to 82 ℃, and distilling to remove ethanol to obtain the composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

Example 3

The composite flame-retardant foaming agent for the foamed plastic comprises the following raw materials in percentage by mass, 95wt.% of foaming agent microspheres and 5wt.% of composite flame retardant.

The foaming agent microsphere consists of the following raw materials, by weight, 70 parts of a foaming agent, 25 parts of polycaprolactone and 16 parts of polyvinyl alcohol.

The composite flame retardant mainly comprises the following raw materials, by weight, 58 parts of polysiloxane microspheres, 25 parts of trimethyl phosphite and 25 parts of ammonium polyphosphate.

The foaming agent is azodicarbonamide, and the particle size of the foaming agent microspheres is 60 microns.

A preparation method of a composite flame-retardant foaming agent for foam plastic comprises the following steps,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 10 ℃ to obtain a suspension;

keeping the temperature at 10 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed of 10000r/min, emulsifying for 7min, adding a polyvinyl alcohol solution, and emulsifying at a rotating speed of 1000r/min for 25min to obtain polycaprolactone/foaming agent microspheres;

adding polycaprolactone/foaming agent microspheres into distilled water, stirring at 30 ℃ and the stirring speed of 800r/min, filtering, drying, and screening to obtain foaming agent microspheres with the particle size of 1000 microns;

(2) dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 3 hours, heating to 85 ℃, and distilling to remove ethanol to obtain the composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

Example 4

The composite flame-retardant foaming agent for the foamed plastic comprises the following raw materials in percentage by mass, 95wt.% of foaming agent microspheres and 5wt.% of composite flame retardant.

The foaming agent microsphere consists of the following raw materials, by weight, 70 parts of a foaming agent, 25 parts of polycaprolactone and 16 parts of polyvinyl alcohol.

The composite flame retardant mainly comprises the following raw materials, by weight, 58 parts of polysiloxane microspheres, 25 parts of trimethyl phosphite and 25 parts of ammonium polyphosphate.

The foaming agent is N, N-dinitrosopentamethylenetetramine, and the particle size of the foaming agent microsphere is 60 mu m.

A preparation method of a composite flame-retardant foaming agent for foam plastic comprises the following steps,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 10 ℃ to obtain a suspension;

keeping the temperature at 10 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed of 10000r/min, emulsifying for 7min, adding a polyvinyl alcohol solution, and emulsifying at a rotating speed of 1000r/min for 25min to obtain polycaprolactone/foaming agent microspheres;

adding polycaprolactone/foaming agent microspheres into distilled water, stirring at 30 ℃ and the stirring speed of 800r/min, filtering, drying, and screening to obtain foaming agent microspheres with the particle size of 1000 microns;

(2) dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 3 hours, heating to 85 ℃, and distilling to remove ethanol to obtain the composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

Comparative example 1

The composite flame-retardant foaming agent for the foamed plastic comprises the following raw materials in percentage by mass, 95wt.% of foaming agent microspheres and 5wt.% of composite flame retardant.

The foaming agent microsphere consists of the following raw materials, by weight, 70 parts of a foaming agent, 25 parts of polycaprolactone and 16 parts of polyvinyl alcohol.

The composite flame retardant mainly comprises the following raw materials in parts by weight, 58 parts of polysiloxane microspheres and 25 parts of ammonium polyphosphate.

The foaming agent is azodicarbonamide, and the particle size of the foaming agent microspheres is 60 microns.

A preparation method of a composite flame-retardant foaming agent for foam plastic comprises the following steps,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 10 ℃ to obtain a suspension;

keeping the temperature at 10 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed of 10000r/min, emulsifying for 7min, adding a polyvinyl alcohol solution, and emulsifying at a rotating speed of 1000r/min for 25min to obtain polycaprolactone/foaming agent microspheres;

adding polycaprolactone/foaming agent microspheres into distilled water, stirring at 30 ℃ and the stirring speed of 800r/min, filtering, drying, and screening to obtain foaming agent microspheres with the particle size of 1000 microns;

(2) dispersing ammonium polyphosphate in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 3 hours, heating to 85 ℃, and distilling to remove ethanol to obtain a composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

Compared with example 3, the flame retardant is made of polysiloxane microspheres and ammonium polyphosphate, and the rest is the same as example 3.

Comparative example 2

The composite flame-retardant foaming agent for the foam plastic comprises the following raw materials in percentage by mass, wherein 95wt.% of the foaming agent and 5wt.% of the composite flame retardant; the foaming agent is azodicarbonamide.

The composite flame retardant mainly comprises the following raw materials, by weight, 58 parts of polysiloxane microspheres, 25 parts of trimethyl phosphite and 25 parts of ammonium polyphosphate.

A preparation method of a composite flame-retardant foaming agent for foam plastic comprises the following steps,

(1) dispersing ammonium polyphosphate and trimethyl phosphite in an ethanol solution, stirring, adding polysiloxane microspheres, adsorbing for 3 hours, heating to 85 ℃, and distilling to remove ethanol to obtain the composite flame retardant;

(2) and (2) mixing a foaming agent with the composite flame retardant prepared in the step (1) to obtain the composite flame-retardant foaming agent.

In comparison with example 3, the blowing agent was azodicarbonamide without any treatment, and the rest was the same as in example 3.

Comparative example 3

The composite flame-retardant foaming agent for the foamed plastic comprises the following raw materials in percentage by mass, 95wt.% of foaming agent microspheres and 5wt.% of composite flame retardant.

The foaming agent microsphere consists of the following raw materials, by weight, 70 parts of a foaming agent, 25 parts of polycaprolactone and 16 parts of polyvinyl alcohol.

The composite flame retardant mainly comprises the following raw materials, by weight, 25 parts of trimethyl phosphite and 25 parts of ammonium polyphosphate.

The foaming agent is azodicarbonamide, and the particle size of the foaming agent microspheres is 60 microns.

A preparation method of a composite flame-retardant foaming agent for foam plastic comprises the following steps,

(1) dissolving polycaprolactone in dichloromethane to obtain a mixed solution A; dispersing a foaming agent in deionized water at the temperature of 10 ℃ to obtain a suspension;

keeping the temperature at 10 ℃, adding the suspension prepared in the step (1) into the mixed solution A, stirring at a high speed of 10000r/min, emulsifying for 7min, adding a polyvinyl alcohol solution, and emulsifying at a rotating speed of 1000r/min for 25min to obtain polycaprolactone/foaming agent microspheres;

adding polycaprolactone/foaming agent microspheres into distilled water, stirring at 30 ℃ and the stirring speed of 800r/min, filtering, drying, and screening to obtain foaming agent microspheres with the particle size of 1000 microns;

(2) mixing ammonium polyphosphate and trimethyl phosphite according to the mass ratio of 1:1 to obtain a composite flame retardant;

(3) and (3) mixing the foaming agent microspheres prepared in the step (1) with the composite flame retardant prepared in the step (2) to obtain the composite flame-retardant foaming agent.

Compared with the embodiment 3, the composite flame retardant is prepared by mixing ammonium polyphosphate and trimethyl phosphite, is not loaded in the polysiloxane microspheres, and the rest is the same as the embodiment 3.

Examples of the experiments

The composite flame-retardant foaming agent prepared in the examples 1-4 and the comparative examples 1-3 is used for foaming performance experiments, and the foaming experiment steps are as follows: 100 parts of polypropylene, 8 parts of composite flame-retardant foaming agent, 10760.75 parts of antioxidant, 0.5 part of calcium carbonate and 0.2 part of white oil are taken, mixed, put into a double-screw machine for melting, extruding and foaming to form the polypropylene foam plastic board.

In the process, the composite flame-retardant foaming agent is prepared in examples 1-4 and comparative examples 1-3, parameters of each group of double-screw extruders are the same, and the temperature, the rotating speed and the pressure of the double-screw extruders are adjusted according to a conventional method.

The polypropylene foam boards prepared in examples 1 to 4 and comparative examples 1 to 3 were cut into standard sizes of 1 × 15cm, respectively, and subjected to performance tests. The flame retardant property test detects the oxygen index of the polypropylene foam board according to the regulation of GB/T2406.2-2009 part 2 of determination of combustion behavior by oxygen index method, and the detection result is shown in the following table 1;

	extreme oxygen value	Closed cell rate,%	Expansion ratio	Tensile strength, MPa
					Example 1	33	96.5	14	24.5
Example 2	32	96.3	14	24.8
					Example 3	34	97.4	14	24.8
Example 4	32	97.0	14	24.6
					Comparative example 1	28	96.1	14	23.5
Comparative example 2	31	92.5	10	22.5
					Comparative example 3	30	94.7	12	22.7

TABLE 1

As can be seen from the data in Table 1, the polar oxygen values of the polypropylene foam boards prepared in examples 1 to 4 are 32 or more, the closed cell ratio of the polypropylene foam boards is more than 96%, and the foaming ratio and the tensile strength are high, so that the composite flame-retardant foaming agent prepared in the scheme guarantees good foaming performance and also guarantees the flame retardance and the mechanical strength of the polypropylene foam plastic. In comparative example 1, the flame retardant performance was slightly reduced because trimethyl phosphite was removed; in the comparative example 2, the foaming agent is only azodicarbonamide and is not loaded in the polycaprolactone microspheres, and the foaming agent cannot be slowly released, so that the instantaneous aggregation of the foaming agent causes the opening phenomenon, and the closed cell rate and the strength of the polypropylene foam plastic plate are obviously reduced. In comparative example 3, the composite flame retardant was not supported in the polysiloxane microspheres, resulting in a decrease in the strength of the polypropylene foam sheet thereof.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.