CN111016352A

CN111016352A - Integrally-formed thermal self-expansion foam body structure and preparation method thereof

Info

Publication number: CN111016352A
Application number: CN201910365140.1A
Authority: CN
Inventors: 蔡锦云; 李卫平; 谢容泉; 李步龙; 官江全
Original assignee: XIAMEN HOWER MATERIAL CO Ltd
Current assignee: XIAMEN HOWER MATERIAL CO Ltd
Priority date: 2019-04-30
Filing date: 2019-04-30
Publication date: 2020-04-17
Anticipated expiration: 2039-04-30
Also published as: CN111016352B

Abstract

The invention discloses an integrally formed thermal self-expanding foam body structure. The inner layer is rigid foam, and the outer layer is thermal self-expansion resin; the rigid foam is a polyurethane system. Spraying or paving a thermal self-expansion resin layer on the inner wall of the mold cavity, and after the inner wall of the mold cavity is fixed, pouring hard foam into the mold to foam and form and cure the hard foam; opening the mold and taking out. The thermal self-expansion resin layer and the rigid foam are integrally formed, so that fewer bubbles are formed on the interface, the binding force is stronger, and the strength of the product is uniformly improved. Meanwhile, the integrally formed foam structure has the effect of being suitable for forming special-shaped products. The composite material is used for preparing sandwich composite material structural parts, has excellent performances of high strength, light weight, good interlayer bonding, difficult delaminating and splitting, impact resistance and the like, and can be applied to the fields of aerospace, rail transit, automobile parts, sports and leisure and the like.

Description

Integrally-formed thermal self-expansion foam body structure and preparation method thereof

Technical Field

The invention relates to the field of fiber composite material forming, in particular to an integrally formed thermal self-expansion foam body structure and a preparation method thereof.

Background

The rigid foam material has the advantages of small density, strong energy absorption and buffering capacity, good sound absorption performance and the like, and is often used for the design of a sandwich structure, so that the sandwich structure material has excellent performances different from the traditional structure material, such as light weight, high rigidity, high strength and the like. Has wide application prospect in the aspects of aerospace, automobile manufacturing, sports and leisure and the like. The most typical sandwich structure composite material is generally composed of a panel (carbon fiber or glass fiber reinforced material), a core material (rigid foam) and a cementing layer, and the common preparation method is to coat a bonding layer on the rigid foam, then coat a carbon cloth/glass cloth prepreg and further form a product. However, there are the following problems:

1. in order to match the surface layer and the core material with each other, the bonding is firm, and the delamination is not generated, so that an adhesive layer is required to be used, and the process and the cost are increased.

2. Because some rigid foams have poor temperature resistance, i.e., high temperature shrinkage, resulting in poor appearance of the molded article and increased scrap rate.

3. Patent CN107901449A "a preparation method of a light high-strength high-energy adhesive-rigid foam composite structure" discloses a light high-strength high-energy adhesive-rigid foam composite structure, the structure is: the inner layer is hard foam, the middle is wrapped with high-energy glue, and the outer layer is fiber prepreg cloth. Although the problems in the two aspects can be solved, the problems that the high-energy adhesive is not enough in viscosity and poor in initial viscosity with the rigid foam, and particularly when a complex part is manufactured, the interlayer bonding operation of the high-energy adhesive and the rigid foam is difficult to ensure that the high-energy adhesive is completely bonded without bubbles, so that the operation is not easy to carry out exist.

4. The rigid foam needs CNC cutting, the equipment input cost is high, and the material waste is serious (and the rigid foam recycling difficulty is large).

Disclosure of Invention

The invention aims to provide an integrally formed thermal self-expanding foam structure.

In order to achieve the above object, the present invention provides an integrally formed thermal self-expanding foam structure, wherein the inner layer is a rigid foam, and the outer layer is a thermal self-expanding resin; the rigid foam is a polyurethane system.

Further, the polyurethane system is that two high-precision metering pumps respectively convey feed liquid of the component A and the component B with the weight ratio of 1:1 to a stirring head, the feed liquid is intensively stirred at a high speed, preferably more than 2500r/min, poured into a mould, foamed, molded and cured to form the required foam; the component A consists of polyol, a catalyst, a foaming agent, a foam stabilizer and a flame retardant; the component B is isocyanate.

Further, the polyol in the component A is polyether or polyester polyol with the hydroxyl value of 400-500 KOH/g;

optionally, the catalyst is an amine catalyst or an organometallic catalyst; the amine catalyst is NN-dimethylcyclohexylamine, triethylene diamine or triethanolamine, and the using amount of the amine catalyst is 2-5 wt% of the polyhydric alcohol; the organic metal catalyst is dibutyltin dilaurate or stannous octoate, and the using amount of the organic metal catalyst is 0.1-0.5 wt% of the polyol; the catalyst is used for controlling the foaming reaction speed and the curing speed.

Optionally, the foaming agent is prepared by using low-boiling-point volatile liquid F11 and water together, wherein the amount of F11 is 30-40% of that of the polyol, and the amount of water is 2 wt% of that of the polyol;

optionally, the foam stabilizer is Si-C type or Si-O-C type, and the using amount of the foam stabilizer is 2-4 wt% of the polyol; the foam stabilizer with the use amount of 2-4 wt% of the polyol has the functions of promoting the mixing of isocyanate and the polyol, reducing the surface tension of a system and playing a vital role in the formation and stability of cells and the regulation of the pore size.

Optionally, the flame retardant is an additive flame retardant; preferably, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate or dimethyl methylphosphonate, in an amount of from 0 to 30% by weight of the polyol. The flame retardant is a functional auxiliary agent capable of endowing the polyurethane foam with flame retardancy, can be an additive flame retardant, and is added by a mechanical mixing method to enable the polyurethane foam to have flame retardancy.

Optionally, the isocyanate is polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate or toluene diisocyanate. The isocyanate is used to react with a polyol to form a polyurethane.

Further, the density of the thermal self-expanding resin is 20-700kg/m³Preferably, it is 30 to 100kg/m³。

Further, the thermal self-expansion resin is prepared by sequentially adding 30-70 parts by weight of thermosetting resin, 0-20 parts by weight of toughening agent, 1-20 parts by weight of foaming agent, 0-20 parts by weight of diluent and 0-30 parts by weight of flame retardant into a stirring barrel and uniformly stirring.

Further, the thermosetting resin is epoxy resin or phenolic resin; providing a carrier and adhesive function;

optionally, the toughening agent is a rubber toughening agent or a thermoplastic resin; preferably, the rubber toughening agent is liquid polysulfide rubber or liquid nitrile rubber; the thermoplastic resin is polyether sulfone, polysulfone, polyimide or polyphenyl ether; the toughening agent is used for improving the flexibility of the thermal self-expansion resin, preventing the cracking and delamination of the rigid foam and the surface layer and enhancing the bonding property and the impact resistance.

Optionally, the foaming agent is a chemical foaming agent or a physical foaming agent, preferably, the chemical foaming agent is azodiisobutyronitrile or azodicarbonamide, and the physical foaming agent is expandable microspheres; the foaming agent has the function of expanding under heat.

Optionally, the diluent is a reactive diluent or an organic solvent; preferably, the reactive diluent is 1, 4-butanediol diglycidyl ether or C12-14 fatty glycidyl ether, and the organic solvent is esters or ketones; the diluent is used to adjust the viscosity.

Optionally, the flame retardant is an additive flame retardant or an inorganic flame retardant or a reactive flame retardant; preferably, the additive flame retardant is bromine, phosphorus nitrogen or nitrogen, and the inorganic flame retardant is antimony trioxide, magnesium hydroxide, aluminum hydroxide or silicon; the reactive flame retardant is 2, 3-dibromopropanol, dibromophenol or tetrabromophthalic anhydride. The flame retardant is a functional auxiliary agent capable of providing flame retardancy to the thermal self-expandable resin, can be an additive flame retardant, is added by a mechanical mixing method to enable the thermal self-expandable resin to have flame retardancy, such as organic flame retardants of bromine series, phosphorus nitrogen series, nitrogen series and the like, or inorganic flame retardants of antimony trioxide, magnesium hydroxide, aluminum hydroxide, silicon series and the like; or a reactive flame retardant, which is a monomer participating in polymerization, such as 2, 3-dibromopropanol, dibromophenol, tetrabromophthalic anhydride, etc.

Further, the preparation method comprises the following steps:

spraying or paving a thermal self-expansion resin layer on the inner wall of the mold cavity, wherein the thickness of the thermal self-expansion resin layer is preferably 0.05-0.5 mm; after the inner part of the die cavity is fixed, pouring hard foam into the die, and foaming, forming and curing the hard foam; opening the mold and taking out.

Further, the spraying is manual spraying or full-automatic spraying for uniformly spraying the thermal self-expansion resin on the inner wall of the die cavity, and the spraying mode is traditional air spraying or thermal spraying; preferably, a cross spraying method is adopted for spraying for 1-3 times;

optionally, the pouring mode is that the rigid foam A, B with calculated weight is uniformly stirred and poured into a mould through a pouring machine; the perfusion rate is 1-2 Kg/min.

The invention also provides a preparation method of the integrally formed thermal self-expansion foam body structure, wherein a thermal self-expansion resin layer is sprayed or paved on the inner wall of the mold cavity, and preferably, the thickness of the thermal self-expansion resin layer is 0.05-0.5 mm; after the inner part of the die cavity is fixed, pouring hard foam into the die, and foaming, forming and curing the hard foam; opening the mold and taking out.

The free expansion multiplying power of the thermal self-expansion resin layer is 1-20 times, and the expansion pressure is 0.1-20 MPa. The initial thickness of the thermal self-expanding resin layer is 0.05-1 mm. The density of the thermal self-expansion resin layer is 20-700kg/m³. The thermal self-expansion resin has proper fluidity and viscosity range of 15-40s (4 cup coating test) at normal temperature or 50-100 ℃, and meets the process requirements of spraying or coating.

Has the advantages that:

1. the structure comprises rigid foam and a thermal self-expansion resin layer coated outside;

2. the thermal self-expansion resin layer can expand by heating, so that the problems of product scrapping caused by shrinkage of the rigid foam at high temperature and poor product appearance in the compression molding process are effectively solved;

3. the thermal self-expansion resin layer simultaneously plays a role in bonding the foam and the surface layer, has strong initial viscosity, effectively eliminates bubbles between interface layers and is convenient to operate.

4. The process of CNC cutting of the hard foam is reduced, the cost is saved, and the size is more stable; and the working procedure of wrapping high-energy glue outside the hard foam core material is also reduced.

5. The thermal self-expansion resin layer and the rigid foam are integrally formed, so that fewer bubbles are formed on the interface, the binding force is stronger, and the strength of the product is uniformly improved. Meanwhile, the integrally formed foam structure has the effect of being suitable for forming different-shaped products.

6. The thermal self-expansion resin layer can be added with a flame retardant component, and the prepared product has a better flame retardant effect.

The thermal self-expansion foam is used for preparing a sandwich composite material structural member, has excellent performances of high strength, light weight, good interlayer bonding, difficult delamination and splitting, impact resistance and the like, and can be applied to the fields of aerospace, rail transit, automobile parts, sports and leisure and the like.

Drawings

FIG. 1 is a schematic cross-sectional view of an integrally formed thermal self-expanding foam structure according to the present invention.

FIG. 2 is a schematic cross-sectional view of an article incorporating the integrally formed thermal self-expanding foam structure of the present invention.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

The following examples are for the preparation of thermally self-expanding resins: the flame retardant is prepared by sequentially adding 30-70 parts by weight of thermosetting resin, 0-20 parts by weight of toughening agent, 1-20 parts by weight of foaming agent, 0-20 parts by weight of diluent and 0-30 parts by weight of flame retardant into a stirring barrel and uniformly stirring. The formulation ratio of the thermal self-expandable resin is shown in Table 1, but is not limited to Table 1.

TABLE 1 formulation of thermal self-expanding resins

	Example 1	Example 2	Example 3	Example 4	Example 5
						Thermosetting resin	30	70	60	50	40
Toughening agent	20	10	0	5	15
						Foaming agent	1	20	5	10	15
Diluent	18	0	10	20	5
						Flame retardant	0	10	20	15	30

Wherein the toughening agent is a rubber toughening agent or a thermoplastic resin; preferably, the rubber toughening agent is liquid polysulfide rubber or liquid nitrile rubber; the thermoplastic resin is polyether sulfone, polysulfone, polyimide or polyphenyl ether;

the foaming agent is a chemical foaming agent or a physical foaming agent, preferably, the chemical foaming agent is azodiisobutyronitrile or azodicarbonamide, and the physical foaming agent is expandable microspheres;

the diluent is an active diluent or an organic solvent; preferably, the reactive diluent is 1, 4-butanediol diglycidyl ether or C12-14 fatty glycidyl ether, and the organic solvent is esters or ketones;

the flame retardant is an additive flame retardant, an inorganic flame retardant or a reactive flame retardant; preferably, the additive flame retardant is bromine, phosphorus nitrogen or nitrogen, and the inorganic flame retardant is antimony trioxide, magnesium hydroxide, aluminum hydroxide or silicon; the reactive flame retardant is 2, 3-dibromopropanol, dibromophenol or tetrabromophthalic anhydride.

The following examples are for the preparation of rigid foams: the rigid foam is a polyurethane system.

The polyurethane system is characterized in that feed liquids of two components A and B in a weight ratio of 1:1 are respectively conveyed to a stirring head by two high-precision metering pumps, are intensively stirred at a high speed, preferably more than 2500r/min, are poured into a mold, are foamed and molded, and are cured to form the required foam. The component A consists of polyol, a catalyst, a foaming agent, a foam stabilizer and a flame retardant; the component B is isocyanate. The formulation ratio of the A component is shown in Table 2, but is not limited to Table 2.

TABLE 2A component formulation Table (parts by weight)

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6
							Polyhydric alcohols	100	100	100	100	100	100
Catalyst and process for preparing same	2	5	3	0.1	0.5	0.3
							Foaming agent	32	34	36	38	40	42
Foam stabilizer	2	3	4	3	2.5	3.5
							Flame retardant	0	30	10	20	15	25

Wherein the polyol is polyether or polyester polyol with the hydroxyl value of 400-500 KOH/g;

the catalyst is an amine catalyst or an organic metal catalyst; the amine catalyst is NN-dimethylcyclohexylamine, triethylene diamine or triethanolamine, and the using amount of the amine catalyst is 2-5 wt% of the polyhydric alcohol; the organic metal catalyst is dibutyltin dilaurate or stannous octoate, and the using amount of the organic metal catalyst is 0.1-0.5 wt% of the polyol;

the foaming agent adopts low-boiling-point volatile liquid F11 and water together, the using amount of F11 is 30-40 wt% of the polyol, and the using amount of the water is 2 wt% of the polyol;

optionally, the foam stabilizer is of Si-C type or Si-O-C type;

optionally, the flame retardant is an additive flame retardant; preferably, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate or dimethyl methylphosphonate.

Optionally, the isocyanate is polymethylene polyphenyl polyisocyanate, diphenylmethane diisocyanate or toluene diisocyanate.

The following examples are illustrated in conjunction with the schematic diagram of figure 1. Wherein 1 is a thermal self-expanding resin, 2 is a rigid foam, and 3 is a mold; and 4 is a fiber prepreg cloth.

Example 1 preparation of an integrally formed thermal self-expanding foam Structure

Spraying or paving a thermal self-expansion resin layer on the inner wall of the mold cavity, and after the inner wall of the mold cavity is fixed, pouring hard foam into the mold to foam and form and cure the hard foam; opening the mold and taking out.

The spraying method can be manual spraying or full-automatic spraying, in which thermal self-expansion resin is uniformly sprayed on the inner wall of the die cavity by manual or automatic spraying equipment. The spray pattern may be a conventional air spray or a thermal spray. In order to ensure the spraying uniformity, a cross spraying method is adopted, and the spraying is carried out once, wherein the thickness is 0.1 mm.

Or the thermal self-expansion resin is coated in advance, the coating thickness is 0.1mm, then the cutting is carried out according to the shape specification of the mould, and the layer is manually laid on the surface of the mould.

The pouring is to pour the rigid foam A, B component into a mould through a pouring machine after the rigid foam A, B component is evenly stirred by the calculated weight, and the pouring speed is controlled to be 1-2 Kg/min.

The thermal self-expansion resin has proper fluidity and viscosity range of 15-40s (4 cup coating test) at normal temperature or 50-100 ℃, and meets the process requirements of spraying or coating.

The prepared integrally-formed thermal self-expansion foam body structure comprises the following steps:

the initial stickiness was touched with a finger pressing the surface of the hot self-expanding resin layer for 15s, and the resin layer stuck to the hand but not transferred to the finger;

the prepared foam is put into an oven at 150 ℃ to be heated for 30 minutes, and the foaming ratio (volume ratio before and after heating) is 1: 1.18.

the prepared foam is put into an equal-volume closed die and heated under 150 ℃ to generate the expansion pressure of 0.11 Mpa.

Example 2 preparation of an integrally formed thermal self-expanding foam Structure

The spraying method can be manual spraying or full-automatic spraying, in which thermal self-expansion resin is uniformly sprayed on the inner wall of the die cavity by manual or automatic spraying equipment. The spray pattern may be a conventional air spray or a thermal spray. In order to ensure the spraying uniformity, a cross spraying method is adopted, and the spraying is carried out for three times, wherein the thickness is 0.3 mm.

Or the thermal self-expansion resin is coated in advance, the coating thickness is 0.3mm, then the cutting is carried out according to the shape specification of the mould, and the layer is manually laid on the surface of the mould.

initial tack by finger touch, pressing the surface of the thermal self-expansion resin layer for 10s by a finger, and sticking the resin layer to the hand without transferring to the finger;

the prepared foam is put into an oven at 150 ℃ to be heated for 30 minutes, and the foaming ratio (volume ratio before and after heating) is 1: 1.46.

the prepared foam is put into an equal-volume closed die and heated under 150 ℃ to generate the expansion pressure of 0.58 Mpa.

Example 3 preparation of an integrally formed thermal self-expanding foam Structure

The spraying method can be manual spraying or full-automatic spraying, in which thermal self-expansion resin is uniformly sprayed on the inner wall of the die cavity by manual or automatic spraying equipment. The spray pattern may be a conventional air spray or a thermal spray. In order to ensure the spraying uniformity, a cross spraying method is adopted, five times of spraying are carried out, and the thickness is 0.5 mm.

Or the thermal self-expansion resin is coated in advance, the coating thickness is 0.5mm, then the cutting is carried out according to the shape specification of the mould, and the layer is manually laid on the surface of the mould.

initial stickiness by finger touch, pressing the surface of the thermal self-expansion resin layer for 8s by a finger, and sticking the resin layer to the hand without transferring to the finger;

the prepared foam is put into an oven at 150 ℃ to be heated for 30 minutes, and the foaming ratio (volume ratio before and after heating) is 1: 2.1.

the prepared foam is put into an isometric closed mould and heated under 150 ℃ to generate the expansion pressure of 0.8 Mpa.

Example 4: application of integrally formed thermal self-expansion foam body structure

1) And cutting the carbon cloth or glass cloth prepreg.

2) The one-piece, thermally self-expanding foam structure obtained in any of examples 1-3 above was wrapped with carbon cloth/glass cloth prepreg, depending on the structural design.

3) And (5) placing the mixture into a mold for molding.

4) The molding temperature is 100 ℃ and 200 ℃.

5) The molding time is 10-120 min.

6) Cooling, demoulding and taking out the product. The cross-sectional view of the structure is schematically shown in fig. 2.

The obtained product has the following excellent effects:

1) the density of the thermal self-expansion resin layer after thermal expansion is 50-1000kg/m³Reduced to 10kg/m³The density of the product is lower than that of pure rigid foam, so that the density of the product can be further reduced;

2) the thermal self-expansion resin has an expansion force, so that the defects of uneven appearance of a product caused by using pure rigid foam or poor appearance of the product caused by high-temperature shrinkage and the like are overcome, and the appearance of the product matched with the die cavity form is free from defects of glue deficiency, pinholes and the like through the expansion force;

3) the interlayer combination of the fiber prepreg cloth is tighter, and the mechanical strength of the product (compared with pure rigid foam) is improved by more than 10 percent;

4) the comprehensive cost is reduced by more than 30 percent (compared with pure rigid foam);

5) the operation flow is shortened, the working procedures are saved, and the product yield is improved;

6) by adding the flame retardant component, the flame retardant grade of the thermal self-expansion resin layer can reach UL94-V0, and the application field of the thermal self-expansion resin layer is widened;

7) the bonding strength of the rigid foam and the fiber prepreg is improved, and the product can meet the test conditions of high-low temperature alternating experiments.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.

Claims

1. An integrally formed thermal self-expanding foam structure is characterized in that an inner layer is made of hard foam, and an outer layer is made of thermal self-expanding resin; the rigid foam is a polyurethane system.

2. The integrally formed thermal self-expanding foam structure according to claim 1, wherein said polyurethane system is formed by feeding two kinds of component a and B in a weight ratio of 1:1 to a stirring head, pouring the mixture into a mold by high speed intensive stirring, preferably 2500r/min or more, foaming and curing to form a desired foam; the component A consists of polyol, a catalyst, a foaming agent, a foam stabilizer and a flame retardant; the component B is isocyanate.

3. The integrally formed thermally self-expanding foam structure of claim 1, wherein the polyol of said a-component is a polyether or polyester polyol having a hydroxyl number of 400-500 KOH/g;

optionally, the catalyst is an amine catalyst or an organometallic catalyst; the amine catalyst is NN-dimethylcyclohexylamine, triethylene diamine or triethanolamine, and the using amount of the amine catalyst is 2-5 wt% of the polyhydric alcohol; the organic metal catalyst is dibutyltin dilaurate or stannous octoate, and the using amount of the organic metal catalyst is 0.1-0.5 wt% of the polyol;

optionally, the foam stabilizer is Si-C type or Si-O-C type, and the using amount of the foam stabilizer is 2-4 wt% of the polyol;

optionally, the flame retardant is an additive flame retardant; preferably, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate or dimethyl methylphosphonate, in an amount of from 0 to 30% by weight of the polyol.

4. The integrally formed thermal self-expanding foam structure of claim 3, wherein said thermal self-expanding resin has a density of 20-700kg/m³。

5. The integrally formed thermally self-expanding foam structure of claim 1, wherein said thermally self-expanding resin has a density of 30-100kg/m³。

6. The integrally formed thermal self-expanding foam structure according to claim 1, wherein the thermal self-expanding resin is prepared by sequentially adding 30-70 parts by weight of thermosetting resin, 0-20 parts by weight of toughening agent, 1-20 parts by weight of foaming agent, 0-20 parts by weight of diluent and 0-30 parts by weight of flame retardant into a stirring barrel and uniformly stirring.

7. The integrally formed thermal self-expanding foam structure of claim 1, wherein said thermosetting resin is an epoxy resin or a phenolic resin;

optionally, the toughening agent is a rubber toughening agent or a thermoplastic resin; preferably, the rubber toughening agent is liquid polysulfide rubber or liquid nitrile rubber; the thermoplastic resin is polyether sulfone, polysulfone, polyimide or polyphenyl ether;

optionally, the foaming agent is a chemical foaming agent or a physical foaming agent, preferably, the chemical foaming agent is azodiisobutyronitrile or azodicarbonamide, and the physical foaming agent is expandable microspheres;

optionally, the diluent is a reactive diluent or an organic solvent; preferably, the reactive diluent is 1, 4-butanediol diglycidyl ether or C12-14 fatty glycidyl ether, and the organic solvent is esters or ketones;

optionally, the flame retardant is an additive flame retardant or an inorganic flame retardant or a reactive flame retardant; preferably, the additive flame retardant is bromine, phosphorus nitrogen or nitrogen, and the inorganic flame retardant is antimony trioxide, magnesium hydroxide, aluminum hydroxide or silicon; the reactive flame retardant is 2, 3-dibromopropanol, dibromophenol or tetrabromophthalic anhydride.

8. The integrally formed thermal self-expanding foam structure of claim 1, prepared by the process of:

spraying or paving a thermal self-expansion resin layer on the inner wall of the mold cavity; preferably, the thickness of the thermal self-expansion resin layer is 0.05-0.5 mm; after the inner part of the die cavity is fixed, pouring hard foam into the die, and foaming, forming and curing the hard foam; opening the mold and taking out.

9. The integrally formed thermal self-expanding foam structure of claim 1, wherein said spraying is a manual or fully automatic spraying of the thermal self-expanding resin uniformly onto the inner walls of the mold cavity by conventional air or thermal spraying; preferably, a cross spraying method is adopted for spraying for 1-3 times;

10. A method for producing an integrally molded self-expanding foam structure according to any one of claims 1 to 9, wherein a layer of a thermally self-expanding resin is sprayed or laid on the inner wall of the cavity; preferably, the thickness of the thermal self-expansion resin layer is 0.05-0.5 mm; after the inner part of the die cavity is fixed, pouring hard foam into the die, and foaming, forming and curing the hard foam; opening the mold and taking out.