Flame-retardant low-density semi-rigid polyurethane foam as well as preparation method and packaging material thereof

Abstract

The invention relates to the technical field of packaging foam, in particular to flame-retardant low-density semi-rigid polyurethane foam, a preparation method thereof and a packaging material. The flame-retardant low-density semi-rigid polyurethane foam is prepared from the following raw materials in parts by weight: 100 parts of combined polyether polyol, 0.5 to 2.0 parts of an organic silicon surfactant, 0.5 to 2.0 parts of a catalyst, 15 to 30 parts of a flame retardant, 15 to 25 parts of a foaming agent and 110 to 150 parts of isocyanate. According to the flame-retardant low-density semi-rigid polyurethane foam, various polyether polyols and various organic silicon surfactants are introduced into the formula, and under the combined action of the polyether polyols and the organic silicon surfactants, the prepared flame-retardant low-density semi-rigid polyurethane foam is fine and smooth in foam hole, good in size stability, good in flame retardant distribution uniformity and low in foam product density.

Description

Technical Field

[0001] The invention relates to the technical field of packaging foam, in particular to a flame-retardant low-density semi-rigid polyurethane foam and a preparation method and packaging material thereof. Background Art

[0002] Semi-rigid polyurethane foam is a foam with performance between soft polyurethane foam and hard polyurethane foam. It is characterized by high compression load value and high density. Its cross-linking density is much higher than that of soft polyurethane foam and second only to that of hard polyurethane foam. Semi-rigid polyurethane foam (semi-rigid foam for short) is one of the main varieties of polyurethane. These characteristics of semi-rigid foam determine that it is not suitable for making seat cushion materials, and it is mainly used for shock absorption and energy absorption materials.

[0003] Low-density semi-rigid polyurethane foam is mostly used as packaging material for some equipment and instruments. It can be foamed and formed according to the shape of the equipment and instruments to play a role in fixing and shock absorption, protecting the equipment and instruments from damage caused by bumps and collisions during transportation.

[0004] However, the existing low-density semi-rigid polyurethane foam is prone to shrinkage and deformation at relatively low density, which cannot ensure the lightweight of packaging materials; in addition, the flame retardancy distribution of the foam is relatively poor, and more flame retardants need to be added. It is necessary to develop a flame-retardant low-density semi-rigid polyurethane foam with excellent low-density dimensional stability and good flame retardancy distribution.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a flame retardant low-density semi-rigid polyurethane foam and a preparation method and packaging material thereof. The flame retardant low-density semi-rigid polyurethane foam provided by the embodiment of the present invention has good open cell property, is not easy to shrink and has certain flame retardant performance.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a flame-retardant low-density semi-rigid polyurethane foam, wherein the raw materials thereof include, by weight, 100 parts of a combined polyether polyol, 0.5-2.0 parts of an organosilicon surfactant, 0.5-2.0 parts of a catalyst, 15-30 parts of a flame retardant, 15-25 parts of a blowing agent, and 110-150 parts of an isocyanate;

[0009] Wherein, the combined polyether polyol comprises 20-35 parts of polyether polyol A and 65-80 parts of polyether polyol B;

[0010] The polyether polyol A has a hydroxyl value of 400-460 mgKOH / g and a functionality of 4.0-4.5;

[0011] The polyether polyol B has a hydroxyl value of 32-35 mgKOH / g and a functionality of 2.8-3.2;

[0012] The organosilicon surfactant comprises a surfactant A and a surfactant B, and the mass ratio of the surfactant A to the surfactant B is (70:30)-(30:70);

[0013] The surfactant A is selected from the compounds shown in the following structural formula:

[0014] in,

[0015] The value of m is 10 to 80, the value of n is 1 to 10, the value of p is 1 to 10, and the value of m+n+p is 12 to 100;

[0016] R is C1-C3 alkyl, R1 or R2;

[0017] R1 is -CH2CH2CH2O(CH2CH2O) x (CH2CHCH3O) y R4;

[0018] R2 is -CH2CH2CH2O(CH2CH2O) x1 (CH2CHCH3O) y1 G Z ;

[0019] R3 is C1-C3 alkyl, R1 or R2;

[0020] R, R3 may be the same or different;

[0021] R4=-OH or alkyl with 1 to 4 carbon atoms;

[0022] x=10~30, y=0~10, x+y=10~40;

[0023] x1=10~30, y1=0~10, x1+y1=10~40;

[0024] G Z is polybenzyl ether;

[0025] The surfactant B is selected from the compounds represented by the following structural formula:

[0026]

[0027] Wherein, the value of m is 40 to 100, the value of n is 1 to 10, the value of p is 1 to 10, and the value of m+n+p is 42 to 120;

[0028] R1 is CH2CH2CH2O(CH2CH2O)x (CH2CHCH3O) y R3;

[0029] R2 is CH2CH2CH2O(CH2CH2O) x1 (CH2CHCH3O) y1 CH2CH(OH)CH2OR4;

[0030] R3=H;

[0031] R4=

[0032] R5=

[0033] R6=Si(CH3)[OSi(CH3)3]2;

[0034] x=10~30, y=0~10, x+y=10~40;

[0035] x1=15~40, y1=0~5, x1+y1=15~45.

[0036] In a second aspect, the present invention provides a method for preparing the flame-retardant low-density semi-rigid polyurethane foam described in the aforementioned embodiment, comprising weighing a combined polyether polyol, an organosilicon surfactant, a catalyst, a foaming agent and a flame retardant in parts by weight and mixing;

[0037] The mixed combination material is then mixed with isocyanate to react and foam to form a shape.

[0038] In a third aspect, the present invention provides a packaging material, which includes the flame retardant low-density semi-rigid polyurethane foam described in the aforementioned embodiment.

[0039] The present invention has the following beneficial effects: the embodiments of the present invention introduce a variety of polyether polyols and a variety of silicone surfactants into the formula for forming a flame-retardant low-density semi-rigid polyurethane foam. Under their joint action, the prepared flame-retardant low-density semi-rigid polyurethane foam has fine pores, good dimensional stability, good uniformity of flame retardant distribution, and a low density of the foam product. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0041] Figure 1Schematic diagram of flame retardancy sampling of foam provided for performance testing of the present invention. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0043] In the first aspect, the embodiment of the present invention provides a flame retardant low-density semi-rigid polyurethane foam, wherein the raw materials include, by weight: 100 parts of a combined polyether polyol, 0.5-2.0 parts of an organosilicon surfactant, 0.5-2.0 parts of a catalyst, 15-30 parts of a flame retardant, 15-25 parts of a foaming agent, and 110-150 parts of an isocyanate. The embodiment of the present invention introduces a variety of polyether polyols and a variety of organosilicon surfactants into the formula system, and under their combined action, the flame retardant low-density semi-rigid polyurethane foam prepared has fine pores, good dimensional stability, good uniformity of flame retardant distribution, and a low density of the foam product.

[0044] Specifically, the combined polyether polyol is two polyether polyols, and on the premise that the total amount of the polyether polyols used is 100 parts, the combined polyether polyol includes 20-35 parts of polyether polyol A and 65-80 parts of polyether polyol B.

[0045] Specifically, the polyether polyol A is any value between 20 and 35 parts, such as 20 parts, 25 parts, 30 parts, and 35 parts, for example, preferably 25 to 30 parts. The hydroxyl value of the polyether polyol A is 400 to 460 mgKOH / g, such as 400 mgKOH / g, 410 mgKOH / g, 420 mgKOH / g, 430 mgKOH / g, 440 mgKOH / g, 450 mgKOH / g, and 460 mgKOH / g. The functionality is 4.0 to 4.5, such as 4.0, 4.1, 4.2, 4.3, 4.4, and 4.5.

[0046] The polyether polyol B is any value between 65 and 80 parts, such as 65 parts, 70 parts, 75 parts and 80 parts, for example, preferably 70 to 75 parts. The hydroxyl value of the polyether polyol B is 32 to 35 mgKOH / g, such as 32 mgKOH / g, 33 mgKOH / g, 34 mgKOH / g and 35 mgKOH / g. The functionality is 2.8 to 3.2; for example, any value between 2.8 to 3.2, such as 2.8, 2.9, 3.0, 3.1 and 3.2.

[0047] Furthermore, polyether polyol A and polyether polyol B are both polyhydroxy organic polymers obtained by reacting ethylene oxide and / or propylene oxide with an initiator. Specifically, polyether polyol A and polyether polyol B can be obtained by reacting ethylene oxide with an initiator, or by reacting propylene oxide with an initiator, or by reacting ethylene oxide and propylene oxide with an initiator.

[0048] The above reactions are all prior art and will not be described in detail in the embodiments of the present invention.

[0049] The initiator is one or more low molecular weight compounds containing active hydrogen, and the active hydrogen can be hydroxyl or amino or both. Ethylene oxide, propylene oxide and the initiator are all commercially available raw materials. Alternatively, commercially available polyether polyol A and polyether polyol B can be directly purchased, as long as they meet the hydroxyl value and functionality.

[0050] Furthermore, the silicone surfactant includes a surfactant A and a surfactant B, and the mass ratio of the surfactant A to the surfactant B is (70:30)-(30:70); for example, any value between (70:30)-(30:70) such as 70:30, 60:40, 50:50, 40:60 and 70:30, for example, preferably 60:40-40:60.

[0051] Furthermore, the surfactant A is selected from the compounds represented by the following structural formula:

[0052] in,

[0053] The value of m is 10 to 80, the value of n is 1 to 10, the value of p is 1 to 10, and the value of m+n+p is 12 to 100;

[0054] R is C1-C3 alkyl, R1 or R2;

[0055] R1 is -CH2CH2CH2O(CH2CH2O) x (CH2CHCH3O) y R4;

[0056] R2 is -CH2CH2CH2O(CH2CH2O) x1 (CH2CHCH3O) y1 G Z ;

[0057] R3 is C1-C3 alkyl, R1 or R2;

[0058] R, R3 may be the same or different;

[0059] R4=-OH or alkyl with 1 to 4 carbon atoms;

[0060] x=10~30, y=0~10, x+y=10~40;

[0061] x1=10~30, y1=0~10, x1+y1=10~40;

[0062] G Z is polybenzyl ether;

[0063] The surfactant B is selected from the compounds represented by the following structural formula:

[0064]

[0065] Wherein, the value of m is 40 to 100, the value of n is 1 to 10, the value of p is 1 to 10, and the value of m+n+p is 42 to 120;

[0066] R1 is CH2CH2CH2O(CH2CH2O) x (CH2CHCH3O) y R3;

[0067] R2 is CH2CH2CH2O(CH2CH2O) x1 (CH2CHCH3O) y1 CH2CH(OH)CH2OR4;

[0068] R3=H;

[0069] R4=

[0070] R5=

[0071] R6=Si(CH3)[OSi(CH3)3]2;

[0072] x=10~30, y=0~10, x+y=10~40;

[0073] x1=15~40, y1=0~5, x1+y1=15~45.

[0074] For example, R is methyl or R1, R2;

[0075] Or R3 is methyl or R1, R2;

[0076] or G Z Any one of the groups shown in the following structural formulas:

[0077]

[0078] The above-mentioned surfactant A and surfactant B are synthesized according to patents CN202011589443.0 and CN202211294180.X respectively.

[0079] Further, the amount of the catalyst is any value between 0.5 and 2.0 parts, such as 0.5, 1.0, 1.5 and 2.0 parts, for example, preferably 0.8 to 1.5 parts. The catalyst is selected from amine substances; for example, including but not limited to any one or more of N, N-dimethylcyclohexylamine, pentamethyldiethylenetriamine and 33% triethylenediamine alcohol solution.

[0080] The amount of the foaming agent is any value between 15 and 25 parts, such as 15 parts, 18 parts, 20 parts, 23 parts, and 25 parts, for example, preferably 18 to 22 parts. The foaming agent is water.

[0081] The amount of the flame retardant is any value between 15 and 30 parts, such as 15, 20, 25 and 30 parts, preferably 20 to 30 parts. The flame retardant is selected from phosphate flame retardants, such as but not limited to tris(chloroisopropyl) phosphate or trichloroethyl phosphate.

[0082] The amount of isocyanate used is any value between 110-150 parts, such as 110 parts, 120 parts, 130 parts, 140 parts and 150 parts, for example, preferably 120-140 parts. Isocyanate includes but is not limited to polymethylene polyphenyl polyisocyanate.

[0083] For example, the raw materials of the flame-retardant low-density semi-rigid polyurethane foam include, by weight, 100 parts of a combined polyether polyol, 1.0-1.5 parts of an organosilicon surfactant, 0.8-1.5 parts of a catalyst, 20-30 parts of a flame retardant, 18-22 parts of a foaming agent and 120-140 parts of an isocyanate; wherein the combined polyether polyol includes 25-30 parts of a polyether polyol A and 70-75 parts of a polyether polyol B; the mass ratio of the surfactant A to the surfactant B is 60:40-40:60; and the amount of each component is optimized to further improve the dimensional stability of the prepared foam and the dispersibility of the flame retardant.

[0084] The embodiment of the present invention also provides a method for preparing a flame retardant low-density semi-rigid polyurethane foam, comprising: preparing the flame retardant low-density semi-rigid polyurethane foam using the raw materials of the above flame retardant low-density semi-rigid polyurethane foam, and the existing preparation process can be used, which is not limited here.

[0085] In some embodiments, the preparation method includes the following steps: weighing a combination of polyether polyol, silicone surfactant, catalyst, foaming agent and flame retardant in parts by weight and mixing; mixing at a stirring speed of 4000 to 5000 r / min and a mixing time of 3 to 5 min.

[0086] The mixed composite material is then mixed with isocyanate for reaction and foaming. In actual operation, when the mixed composite material is mixed with isocyanate, the stirring speed can be controlled to be 4000-5000 r / min and the mixing time can be 8-10 s.

[0087] In a third aspect, the present invention provides a packaging material, which includes the flame retardant low-density semi-rigid polyurethane foam described in the aforementioned embodiment.

[0088] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0089] Examples 1-6 and Comparative Examples 1-12

[0090] Examples 1-6 respectively provide a flame retardant low-density semi-rigid polyurethane foam and Comparative Examples 1-12 respectively provide a semi-rigid polyurethane foam. The operations of the preparation methods of the above embodiments and comparative examples are basically the same, and the only difference is that the raw material combinations and ratios are different. The raw material combinations and ratios of Examples 1-6 and Comparative Examples 1-12 are shown in Tables 1 to 3.

[0091] The specific steps are as follows:

[0092] (1) Weigh the combined polyether polyol, the combined silicone surfactant, the catalyst, the foaming agent and the flame retardant according to the weight proportions and mix them; in the actual operation process, when the combined polyether polyol, the combined silicone surfactant, the catalyst, the foaming agent and the flame retardant are mixed, the stirring speed can be controlled to be 4000-5000 r / min, and the mixing time can be controlled to be 3-5 min.

[0093] (2) Mixing the mixed composite material with isocyanate to react and foam. In actual operation, when the mixed composite material is mixed with isocyanate, the stirring speed can be controlled to be 4000-5000 r / min and the mixing time can be 8-10 s.

[0094] The sources of raw materials used in Examples 1-6 and Comparative Examples 1-12 are as follows:

[0095] Polyether polyol A: hydroxyl value 430 mgKOH / g, functionality 4.2, purchased from Ningwu, Jurong; polyether polyol B: hydroxyl value 34 mgKOH / g, functionality 3.0, purchased from Zhongshan Chemical.

[0096] Surfactant A and surfactant B are synthesized according to patents CN202011589443.0 and CN202211294180.X, respectively. Specifically, the specific structures of the surfactants are as follows:

[0097] Surfactant A-1:

[0098] (CH3)3Si-O-[Si(CH3)2O] 38 -[Si(CH3)R1O] 2.2 -[Si(CH3)R2O] 1.8 -Si(CH3)3;

[0099] wherein:

[0100] R1 = -CH2CH2CH2O(CH2CH2O) 10 (CH2CHCH3O)4H;

[0101] R2 = -CH2CH2CH2O(CH2CH2O) 15 (CH2CHCH3O)3G1, and G1 is:

[0102] Surfactant A-2:

[0103] (CH3)3Si-O-[Si(CH3)2O] 41 -[Si(CH3)R1O]3-[Si(CH3)R2]O2-Si(CH3)3;

[0104] wherein:

[0105] R1 = -CH2CH2CH2O(CH2CH2O) 13 (CH2CHCH3O)5H;

[0106] R2 = -CH2CH2CH2O(CH2CH2O) 13 (CH2CHCH3O)5G2, and G2 is

[0107] Surfactant B-1:

[0108] (CH3)3Si-O-[Si(CH3)2O] 43 -[Si(CH3)R1O] 3.1 -O-[Si(CH3)R2O] 3.9 -Si(CH3)3;

[0109] wherein:

[0110] R1 = -CH2CH2CH2O(CH2CH2O) 10 (CH2CHCH3O)3H;

[0111] R2 = -CH2CH2CH2O(CH2CH2O) 15 (CH2CHCH3O)4CH2CH(OH)CH2OR4;

[0112] R4=

[0113] R5=

[0114] R6=Si(CH3)[OSi(CH3)3]2.

[0115] Surfactant B-2:

[0116] (CH3)3Si-O-[Si(CH3)2O] 55 -[Si(CH3)R1O] 1.9 -O-[Si(CH3)R2O] 4.1 -Si(CH3)3; wherein:

[0117] R1=-CH2CH2CH2O(CH2CH2O) 15 (CH2CHCH3O)5H;

[0118] R2=-CH2CH2CH2O(CH2CH2O) 15 (CH2CHCH3O)1CH2CH(OH)CH2OR4;

[0119] R4=

[0120] R5=

[0121] R6=Si(CH3)[OSi(CH3)3]2.

[0122] The catalyst is N,N-dimethylcyclohexylamine MAYCAT 808, purchased from Jiangsu Meside; pentamethyldiethylenetriamine MAYCAT 805, purchased from Jiangsu Meside; 33% triethylenediamine alcohol solution MAYCAT 633, purchased from Jiangsu Meside.

[0123] The foaming agent used was distilled water, purchased from Nanjing Wanqing.

[0124] The flame retardant used was tris(chloroisopropyl) phosphate TCPP, purchased from Jiangsu Yake.

[0125] The isocyanate used was polymethylene polyphenyl polyisocyanate PM-200, purchased from Yantai Wanhua.

[0126] Performance Testing

[0127] The flame retardant low-density semi-rigid polyurethane foams of Examples 1-6 and the semi-rigid polyurethane foams of Comparative Examples 1-12 were tested for performance, and the specific test contents were as follows: foam density, number of cells, dimensional stability (20-25° C., 45-55% RH, 7d), foam open cell ratio, and flame retardant performance of different positions of the foam (self-extinguishing time after leaving the fire). The test standards are shown in Table 4.

[0128] Table 4 Test Standards

[0129]

[0130]

[0131] The detection method is as follows:

[0132] Foam density: Tested according to GB / T 6343-2009 Determination of apparent density of foam plastics and rubber.

[0133] Dimensional stability: Tested in accordance with GB / T 8811-2008 Test method for dimensional stability of rigid foam plastics.

[0134] Open cell rate: tested according to GB / T 10799-2008 Determination of open and closed cell volume percentage of rigid foam plastics.

[0135] Number of cells: Use an electron microscope to observe the number of cells over a length of 1 cm; the more cells there are, the finer the cells are; conversely, the coarser the cells are.

[0136] Flame retardancy: Samples were taken at different locations of the foam (five fixed points, the sampling locations are as follows Figure 1 As shown in the figure, the unit is mm), ignite the foam with a fire source, remove the fire source after 2s, and observe the self-extinguishing time of the foam (start timing after the fire source is removed). The shorter the time, the better the flame retardancy; conversely, the worse the flame retardancy.

[0137] Please refer to Tables 1 to 3 for specific test results.

[0138] Table 1 Formula and performance test results of flame retardant low-density semi-rigid polyurethane foam of Examples 1-6

[0139]

[0140]

[0141] Table 2 Comparative Examples 1-6 Formulations and Performance Test Results of Semi-rigid Polyurethane Foam

[0142]

[0143]

[0144] Table 3 Comparative Examples 7-12 Semi-rigid polyurethane foam formulations and performance test results

[0145]

[0146]

[0147] According to Table 2 and Table 3, the foam stabilizing performance of some proportions of comparative examples 1-6 is insufficient, resulting in foam collapse, which cannot meet the requirements; the dimensional stability of some proportions of foam decreases, the foam openness is insufficient, and the flame retardant performance of different positions of the foam is unevenly distributed; the comprehensive performance is significantly worse than that of Examples 1-6, proving that the combination ratio of the two silicone surfactants provided in the embodiments of the present invention has a synergistic effect.

[0148] Comparative Examples 7-12 showed severe foam shrinkage or foam collapse; the foam opening rate and dimensional stability of the relatively normal foaming were worse than those of the examples; this proved that the ratio of the two polyether polyols provided in the examples of the present invention had a synergistic effect.

[0149] In summary, the flame retardant low-density semi-rigid polyurethane foam provided by the embodiment of the present invention has fine pores, a high open porosity, good dimensional stability, and a good flame retardant dispersion effect, and can basically meet the requirements of flame retardant low-density semi-rigid polyurethane foam.

[0150] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A flame retardant low-density semi-rigid polyurethane foam, characterized in that: In parts by weight, the raw materials include 100 parts of combined polyether polyol, 0.5-2.0 parts of organosilicon surfactant, 0.5-2.0 parts of catalyst, 15-30 parts of flame retardant, 15-25 parts of foaming agent and 110-150 parts of isocyanate; Wherein, the combined polyether polyol comprises 20-35 parts of polyether polyol A and 65-80 parts of polyether polyol B; The polyether polyol A has a hydroxyl value of 400-460 mgKOH / g and a functionality of 4.0-4.5; The polyether polyol B has a hydroxyl value of 32-35 mgKOH / g and a functionality of 2.8-3.2; The organosilicon surfactant comprises a surfactant A and a surfactant B, and the mass ratio of the surfactant A to the surfactant B is (70:30)-(30:70); The surfactant A is selected from the compounds represented by the following structural formula: in, The value of m is 10 to 80, the value of n is 1 to 10, the value of p is 1 to 10, and the value of m+n+p is 12 to 100; R is C1-C3 alkyl, R1 or R2; R1 is -CH2CH2CH2O(CH2CH2O) x (CH2CHCH3O) y R4; R2-CH2CH2CH2O(CH2CH2O) x1 (CH2CHCH3O) y1 G Z ; R3 is C1-C3 alkyl, R1 or R2; R, R3 may be the same or different; R4=-OH or alkyl with 1 to 4 carbon atoms; x=10~30, y=0~10, x+y=10~40; x1=10~30, y1=0~10, x1+y1=10~40; G Z is polybenzyl ether; The surfactant B is selected from the compounds represented by the following structural formula: Wherein, the value of m is 40 to 100, the value of n is 1 to 10, the value of p is 1 to 10, and the value of m+n+p is 42 to 120; R1 is CH2CH2CH2O(CH2CH2O) x (CH2CHCH3O) y R3; R2 is CH2CH2CH2O(CH2CH2O) x1 (CH2CHCH3O) y1 CH2CH(OH)CH2OR4; R3=H; R6=Si(CH3)[OSi(CH3)3]2; x=10~30, y=0~10, x+y=10~40; x1=15~40, y1=0~5, x1+y1=15~45.

2. The flame-retardant low-density semi-rigid polyurethane foam according to claim 1, characterized in that: R is methyl or R1, R2; Or R3 is methyl or R1, R2; or G Z Any one of the groups shown in the following structural formulas:

3. The flame-retardant low-density semi-rigid polyurethane foam according to claim 1, characterized in that: The polyether polyol A and the polyether polyol B are both polyhydroxy organic polymers obtained by reacting ethylene oxide and / or propylene oxide with an initiator; Wherein, the initiator is one or more compounds containing active hydrogen.

4. The flame-retardant low-density semi-rigid polyurethane foam according to claim 3, characterized in that: The functionality of the initiator is 2.5 to 5.0; Preferably, the initiator is selected from at least one of aliphatic amines and aromatic amines.

5. The flame-retardant low-density semi-rigid polyurethane foam according to claim 1, characterized in that: The catalyst is selected from amine substances; Preferably, the catalyst is selected from any one or more of N,N-dimethylcyclohexylamine, pentamethyldiethylenetriamine and 33% alcohol solution of triethylenediamine.

6. The flame-retardant low-density semi-rigid polyurethane foam according to claim 1, characterized in that: The foaming agent is water.

7. The flame-retardant low-density semi-rigid polyurethane foam according to claim 1, characterized in that: The flame retardant is selected from phosphate flame retardants; preferably tris(chloroisopropyl) phosphate or trichloroethyl phosphate.

8. The flame-retardant low-density semi-rigid polyurethane foam according to claim 1, characterized in that: The isocyanate is polymethylene polyphenyl polyisocyanate.

9. A method for preparing the flame-retardant low-density semi-rigid polyurethane foam according to claim 1, characterized in that: Weigh the combined polyether polyol, silicone surfactant, catalyst, foaming agent and flame retardant according to weight and mix; The mixed combination material is then mixed with isocyanate to react and foam to form a shape.

10. A packaging material, characterized in that: The invention comprises the flame-retardant low-density semi-rigid polyurethane foam as claimed in claim 1.

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