Degradable cardanol phenolic resin foamed plastic as well as preparation method and application thereof

Abstract

The invention discloses degradable cardanol phenolic resin foamed plastic and a preparation method and application thereof.The preparation method comprises the following steps that phenol, a formaldehyde solution and cardanol are added into an alkali solution for condensation polymerization, and cardanol modified phenolic resin is obtained; adding a surfactant and a foaming agent into the cardanol modified phenolic resin, uniformly stirring, then adding a curing agent, and uniformly stirring again to obtain a mixture; and carrying out foaming treatment on the mixture to obtain the degradable cardanol phenolic resin foamed plastic. According to the invention, cardanol is adopted to replace non-renewable and difficult-to-degrade phenol as a main raw material to prepare a cardanol-based phenolic resin material, and then the cardanol-based phenolic resin material is foamed to prepare the degradable cardanol-based phenolic resin foam plastic which can be used as flower mud, and the degradable cardanol-based phenolic resin foam plastic has an excellent opening mechanism and water absorption performance; and after being used in the flower mud, the composite material can be naturally degraded in the environment, so that the composite material has a wide application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of degradable foam plastics, and in particular to a method for preparing degradable cardanol phenolic resin foam plastics. Background Art

[0002] Flower mud, also called flower spring or absorbent sponge, is a kind of flower arrangement product made of phenolic resin foam. Flower mud can be used to fix flowers and keep them moisturized. The top and four sides of flower mud can be used to insert flowers. It has a larger surface than flower inserts and is more flexible and convenient. The characteristic of flower mud is that it has a short lifespan. After being used 1-2 times, it will form many holes and is easy to break and cannot be used again. Therefore, flower mud is a disposable consumable. At present, there are two major categories of flower mud. One is specially used for fresh flower insertion after absorbing water. It has colors such as green, pink, blue, and brown. The other contains preservatives. After the flower branches are inserted, they are not only stable, but also can keep warm, moisturize, and keep fresh. However, no matter which type of flower mud, the base material is made of phenolic resin foam. In addition, in the field of soilless cultivation, phenolic resin foam materials also have a trend of replacing inorganic minerals such as vermiculite and perlite.

[0003] Existing flower mud is mainly made of phenol, polyformaldehyde, etc., with high open porosity, strong water absorption, and good water retention performance. It is suitable for use as flower mud. Inserting flowers into the fully water-absorbing phenolic foam can significantly extend the life of flowers, enhance the beauty and appreciation of flower arrangements or flower baskets, and is of special value for preserving flowers for long-distance transportation. However, the flower mud in the above technical solution is a non-degradable polymer material. Given that the service life of flower mud generally does not exceed half a month, it will be discarded after use, forming a large amount of difficult-to-degrade solid waste, which does not conform to the concept of green environmental protection.

[0004] In order to obtain a phenolic resin material with degradable properties, Ge Tiejun and others introduced easily degradable long-chain phenol (pentadecylphenol) and long-chain aldehyde (glutaraldehyde) in the synthesis process of the basic phenolic resin, replacing part of phenol and polyformaldehyde respectively, and prepared a composite modified resol phenolic resin, which was then used as a modifier to toughen the phenolic foam. The results show that with the addition of the composite modified phenolic resin, the density of the foam increases, while the water absorption rate decreases first and then increases. The addition of the modified resin greatly improves the toughness of the foam. When the addition amount of the modified resin is 40% to 50%, the foam has the best comprehensive performance.

[0005] In order to further improve the shortcomings of poor toughness of phenolic resin foam in the literature, Ge Tiejun et al. selected 3-pentadecylphenol as a modifier to prepare a foamable phenolic resin with excellent performance. The resin was successfully prepared by in-situ modification. The results show that 3-pentadecylphenol successfully changed the molecular structure of phenolic resin and reduced the gel time of the resin. The proton peak shift interval of the carbon in the benzene ring of phenol connected to the long chain of m-pentadecyl carbon was significantly enlarged, proving that the introduction of m-pentadecylphenol reduced the rigidity of the benzene ring, which is beneficial to improve the toughness of phenolic foam. When the amount of added 3-pentadecylphenol accounted for 15% of the total amount of phenol, the bending deflection of the modified phenolic foam increased to 300% compared with the unmodified phenolic foam.

[0006] Flower mud and seedling medium are commonly used plant cultivation materials, and cost is an aspect that must be considered. The main disadvantage of the above-mentioned method for preparing degradable foamed phenolic resin is that the prices of raw materials such as pentadecylphenol and glutaraldehyde are much higher than conventional phenol and formaldehyde, so they are not competitive in the flower auxiliary material market. Therefore, there is an urgent need to find low-cost, degradable raw materials.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The object of the present invention is to provide a degradable cardanol phenolic resin foam plastic and a preparation method and application thereof. The present invention adopts cardanol instead of non-renewable and difficult-to-degrade phenol as the main raw material to prepare a cardanol-based phenolic resin material, and then foams the cardanol phenolic resin foam plastic, which can be used as flower mud. The cardanol phenolic resin foam plastic has excellent opening structure and water absorption performance, and can be naturally degraded in the environment after being used in flower mud, so it has the prospect of wide application.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0010] The first aspect of the present invention provides a method for preparing a degradable cardanol phenolic resin foam plastic, the preparation method comprising the following steps:

[0011] (a) adding phenol, formaldehyde solution and cardanol into an alkaline solution to carry out polycondensation reaction to obtain a cardanol-modified phenolic resin;

[0012] (b) adding a surfactant and a foaming agent to the cardanol-modified phenolic resin and stirring evenly, then adding a curing agent and stirring evenly again to obtain a mixture;

[0013] (c) subjecting the mixture to foaming treatment to obtain the degradable cardanol phenolic resin foam plastic.

[0014] Preferably, in step (a), the molar ratio of phenol, formaldehyde and cardanol is 1:(2-2.5):(0.8-1.2).

[0015] Preferably, in step (a), the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; and the amount of the alkaline solution added is 0.3 to 0.4 times the mass of phenol.

[0016] Preferably, in step (a), the pH value of the polycondensation reaction is 9-10, the temperature is 80-85° C., and the time is 2.5-4 hours.

[0017] Preferably, in step (a), the concentration of the formaldehyde solution is 35% to 40%; and the concentration of the alkali solution is 8% to 12%.

[0018] Preferably, in the step (b), the mass ratio of the cardanol-modified phenolic resin, the surfactant, the foaming agent and the curing agent is 100:(6-10):(2.5-3.5):(5-9).

[0019] Preferably, the surfactant is sodium dodecylbenzenesulfonate; the foaming agent is n-pentane; and the curing agent is toluenesulfonic acid.

[0020] Preferably, in step (c), the foaming reaction temperature is 55-65° C. and the time is 12-20 min.

[0021] The second aspect of the present invention provides a degradable cardanol phenolic resin foam plastic prepared by the above preparation method.

[0022] The third aspect of the present invention provides an application of the degradable cardanol phenolic resin foam plastic prepared by the above preparation method in preparing a vegetable seedling substrate.

[0023] The fourth aspect of the present invention provides a vegetable seedling substrate, which is composed of a degradable cardanol phenolic resin foam plastic prepared by the preparation method and standard soil in a mass ratio of 1: (0.8-1.2);

[0024] The standard soil is composed of leaf mold, peat and river sand in a mass ratio of 1:(0.8-1.2):(0.8-1.2).

[0025] Compared with the prior art, the beneficial effects of the present invention include at least:

[0026] The present invention adopts cardanol as the main raw material instead of non-renewable and difficult-to-degrade phenol to prepare a cardanol-based phenolic resin material, and then foams the material to obtain a degradable cardanol phenolic resin foam plastic that can be used as flower mud. The foam plastic has excellent pore opening structure and water absorption performance, and can be naturally degraded in the environment after being used in flower mud, so it has the prospect of being widely used. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0028] Figure 1 is an infrared spectrum of the cardanol-based phenolic resin in Experimental Example 1 of the present invention;

[0029] Figure 2 This is a scanning electron microscope image of the cardanol phenolic resin foam plastic of Example 3 in Experimental Example 1 of the present invention;

[0030] Figure 3 This is a scanning electron microscope image of the phenolic resin foam plastic prepared in Comparative Example 1 of Experimental Example 1 of the present invention;

[0031] Figure 4 The results of the effect of the amount of the foaming agent used in Experimental Example 1 of the present invention on the water absorption rate of the cardanol phenolic resin foam plastic of Example 3;

[0032] Figure 5 The results of the effect of the amount of the blowing agent used in Experimental Example 1 of the present invention on the water absorption rate of the phenolic resin foam plastic in Comparative Example 1 are shown;

[0033] Figure 6 The results of the seedling raising experiment of the vegetable seedling raising matrix in Experimental Example 2 of the present invention are shown. DETAILED DESCRIPTION

[0034] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0035] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0036] The raw materials used in the following examples are as follows:

[0037] The surfactant is sodium dodecylbenzene sulfonate;

[0038] The blowing agent is n-pentane;

[0039] The curing agent is benzenesulfonic acid.

[0040] Example 1

[0041] This embodiment is a method for preparing a degradable cardanol phenolic resin foam plastic, and the preparation method comprises the following steps:

[0042] (a) adding phenol, formaldehyde solution and cardanol to an alkaline solution for polycondensation reaction to obtain a cardanol-modified phenolic resin, wherein the molar ratio of phenol, formaldehyde and cardanol is 1:2:0.8; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the concentration of the formaldehyde solution is 35%; the concentration of the alkaline solution is 8%, and the amount of the alkaline solution added is 0.4 times the mass of phenol; the pH value of the polycondensation reaction is 9, the temperature is 80°C, and the time is 4 hours;

[0043] (b) adding a surfactant and a foaming agent to the cardanol-modified phenolic resin in a mass ratio of 100:6:2.5:5, stirring evenly, adding a curing agent, stirring evenly again, and obtaining a mixture;

[0044] (c) placing the mixture in an oven and foaming it at 55° C. for 20 minutes to obtain the degradable cardanol phenolic resin foam plastic.

[0045] Example 2

[0046] This embodiment is a method for preparing a degradable cardanol phenolic resin foam plastic, and the preparation method comprises the following steps:

[0047] (a) adding phenol, formaldehyde solution and cardanol into an alkaline solution for polycondensation reaction to obtain a cardanol-modified phenolic resin, wherein the molar ratio of phenol, formaldehyde and cardanol is 1:2.5:1.2; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the concentration of the formaldehyde solution is 40%; the concentration of the alkaline solution is 12%, and the amount of the alkaline solution added is 0.3 times the mass of phenol; the pH value of the polycondensation reaction is 10, the temperature is 85° C., and the time is 2.5 h;

[0048] (b) adding a surfactant and a foaming agent to the cardanol-modified phenolic resin in a mass ratio of 100:10:3.5:9, stirring evenly, adding a curing agent, stirring evenly again, and obtaining a mixture;

[0049] (c) placing the mixture in an oven and foaming it at 65° C. for 12 minutes to obtain the degradable cardanol phenolic resin foam plastic.

[0050] Example 3

[0051] This embodiment is a method for preparing a degradable cardanol phenolic resin foam plastic, and the preparation method comprises the following steps:

[0052] (a) adding phenol, formaldehyde solution and cardanol to an alkaline solution for polycondensation reaction to obtain a cardanol-modified phenolic resin, wherein the molar ratio of phenol, formaldehyde and cardanol is 1:2.2:1; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the concentration of the formaldehyde solution is 37%; the concentration of the alkaline solution is 10%, and the amount of the alkaline solution added is 0.32 times the mass of phenol; the pH value of the polycondensation reaction is 9.5, the temperature is 82°C, and the time is 3h;

[0053] (b) adding a surfactant and a foaming agent to the cardanol-modified phenolic resin in a mass ratio of 100:8:3:7, stirring evenly, adding a curing agent, stirring evenly again, and obtaining a mixture;

[0054] (c) placing the mixture in an oven and foaming it at 60° C. for 15 minutes to obtain the degradable cardanol phenolic resin foam plastic.

[0055] Example 4

[0056] This embodiment is a vegetable seedling substrate, which is composed of a degradable cardanol phenolic resin foam plastic prepared by the preparation method of Example 1 and standard soil in a mass ratio of 1:0.8;

[0057] The standard soil is composed of leaf mold, peat and river sand in a mass ratio of 1:0.8:1.2.

[0058] Example 5

[0059] This embodiment is a vegetable seedling substrate, which is composed of a degradable cardanol phenolic resin foam plastic prepared by the preparation method of Example 2 and standard soil in a mass ratio of 1:1.2;

[0060] The standard soil is composed of leaf mold, peat and river sand in a mass ratio of 1:1.2:0.8.

[0061] Example 6

[0062] This embodiment is a vegetable seedling substrate, which is composed of a degradable cardanol phenolic resin foam plastic prepared by the preparation method of Example 3 and standard soil in a mass ratio of 1:1;

[0063] The standard soil is composed of leaf mold, peat and river sand in a mass ratio of 1:1:1.

[0064] Comparative Example 1

[0065] This comparative example is a method for preparing a phenolic resin foam plastic, and the preparation method comprises the following steps:

[0066] (a) adding phenol and formaldehyde solution to an alkaline solution for polycondensation to obtain a phenolic resin, wherein the molar ratio of phenol to formaldehyde is 2:2.2; the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the concentration of the formaldehyde solution is 37%; the concentration of the alkaline solution is 10%, and the amount of the alkaline solution added is 0.16 times the mass of the phenol; the pH value of the polycondensation reaction is 9.5, the temperature is 82° C., and the time is 3 hours;

[0067] (b) adding a surfactant and a foaming agent to the cardanol-modified phenolic resin in a mass ratio of 100:8:3:7 to the phenolic resin, the surfactant, the foaming agent and the curing agent, stirring evenly, and then adding the curing agent and stirring evenly again to obtain a mixture;

[0068] (c) placing the mixture in an oven at 60° C. for foaming for 15 minutes to obtain the cardanol phenolic resin foam plastic.

[0069] Experimental Example 1

[0070] 1. Obtain the cardanol-modified phenolic resin prepared in Example 3 and perform red light spectrum detection. The detection result is as follows: Figure 1 As shown;

[0071] Depend on Figure 1 It can be seen that:

[0072] 3350cm -1 is the stretching vibration peak of hydroxyl group, 3110-3010cm -1 It is the CH stretching vibration peak of the benzene ring, 2926-2854cm -1 It is the CH stretching vibration of the cardanol side chain and the CH stretching vibration of the methylene generated during the reaction, 1382-1350cm -1 It is the deformation vibration of the CH structure of CH2 and CH3, 1600-1438cm -1 Benzene ring skeleton C=C vibration, 1266cm -1 It is the CO stretching vibration of phenol, 1227-1023cm -1 Symmetric vibration of CH in benzene ring, 997-823 cm -1 Olefin CH vibration absorption, 722 and 884 cm -1 Represents the ortho and para substitutions in the benzene ring. The raw material formaldehyde is at 1700cm -1 The aldehyde peak of the product disappeared, proving that the aldehyde group was reacted during the reaction of formaldehyde and cardanol. -1 The peak width of the methylene peak at the location is larger than that of the cardanol, which is due to the condensation of phenolic formaldehyde to form a methylene group. This is the stretching vibration absorption peak of -CH. The above results indicate that the cardanol-modified phenolic resin has been prepared.

[0073] 2. Obtain the degradable cardanol phenolic resin foam plastic prepared in Example 3 and the cardanol phenolic resin foam plastic prepared in Comparative Example 1;

[0074] The viscosity of the cardanol-modified phenolic resin of Example 3 and the phenolic resin of Comparative Example 1 was tested;

[0075] The free formaldehyde, compressive strength and apparent density in the degradable cardanol phenolic resin foam plastic prepared in Example 3 and the cardanol phenolic resin foam plastic prepared in Comparative Example 1 were tested, and the testing method was as follows:

[0076] Determination of apparent density:

[0077] The apparent density of phenolic resin foam will affect the water absorption of floral mud and cultivation medium. Therefore, the method described in GB / T6343-86 is used to test the apparent density of phenolic resin foam.

[0078] Determination of free formaldehyde:

[0079] Formaldehyde is a known carcinogen and an important raw material for preparing phenolic resin foam materials. The lower the residual free formaldehyde in floral mud and cultivation medium, the better, and the lower the toxicity. Therefore, the method described in GB / T29121-1998 is used to test the free formaldehyde content in phenolic resin foam plastics.

[0080] Determination of compressive strength:

[0081] Ordinary phenolic resin foam is brittle and easily powdered and slags during production, transportation, storage and use, resulting in defective products. Therefore, the method described in GB / T8813-1988 is used to test the compressive strength of phenolic resin foam plastics.

[0082] The test results are shown in Table 1:

[0083] Table 1

[0084]

[0085]

[0086] From Table 1, we can see that:

[0087] The properties of the two phenolic resins and their foam materials are very similar. The free formaldehyde, compressive strength and apparent density of the degradable cardanol phenolic resin foam plastic prepared in the embodiment of the present invention are better than those of the comparative example product, indicating that the degradable cardanol phenolic resin foam plastic of the present invention has better performance and can be used to make flower mud.

[0088] 3. Analysis of the degradation properties of the degradable cardanol phenolic resin foam plastic prepared in Example 3 and the cardanol phenolic resin foam plastic prepared in Comparative Example 1:

[0089] Here’s how:

[0090] In order to characterize the degradation effect of the degradable cardanol phenolic resin plastic of the present invention, the oxygen content in the phenolic resin plastic was determined by using a Flash EA 1112 organic element analyzer;

[0091] The degradable cardanol phenolic resin foam plastic prepared in Example 3 and the cardanol phenolic resin foam plastic prepared in Comparative Example 1 were placed in soil respectively, and the oxygen content in the materials at different placement times was detected. The test results are shown in Table 2;

[0092] Table 2

[0093]

[0094] From Table 2, we can see that:

[0095] After the degradable cardanol phenolic resin plastic of the present invention was placed in the soil for 6 months, the oxygen element decreased by 2.5% cumulatively, while the product of comparative example 1 only changed by 0.3%; it can be seen that the degradable cardanol phenolic resin plastic of the present application has more excellent degradation performance.

[0096] 4. The phenolic resin foam plastics of Example 3 and Comparative Example 1 were scanned by electron microscope. The results are as follows: Figure 2 , Figure 3 As shown;

[0097] in, Figure 2 The degradable cardanol phenolic resin foam plastic of Example 3, Figure 3 The phenolic resin foam plastic of Comparative Example 1;

[0098] Depend on Figures 2-3 It can be seen that:

[0099] The pores of the foam obtained by pentane foaming of the phenolic resin foam plastic of Comparative Example 1 are similar in size to the pores of the foam obtained by the homemade cardanol phenolic resin foam plastic of the present invention. The difference is that the foam obtained by the product of Comparative Example 1 is brittle, and large pieces of debris can be observed, while the cross-section of the phenolic resin foam plastic of the embodiment of the present invention is very small. This may be because the unsaturated double bond carbon 15 straight chain contained in the meta position of cardanol can give the resin good toughness.

[0100] 5. Study the effect of different foaming agent dosages on the water absorption properties of phenolic resin foam:

[0101] The open-cell structure of phenolic resin foam plastics can store nutrients, water and oxygen, while providing growth space for plant roots. The water absorption rate of phenolic resin foam plastics is an important indicator to characterize the performance of phenolic resin foam matrix.

[0102] The variation trends of the water absorption rate of the phenolic resin foam plastic of Comparative Example 1 and the degradable cardanol phenolic resin foam plastic of Example 3 and the amount of pentane added as a blowing agent are as follows: Figures 4-5 As shown, Figure 4 The effect of the amount of foaming agent added on the water absorption performance of the degradable cardanol phenolic resin foam plastic of Example 3 is shown in FIG. Figure 5 The effect of the amount of foaming agent added on the water absorption performance of the phenolic resin foam plastic of Comparative Example 1;

[0103] Depend on Figure 4 , Figure 5 It can be seen that:

[0104] Whether it is the phenolic resin foam plastic of Comparative Example 1 or the degradable cardanol phenolic resin foam plastic of Example 3, the water absorption rate of the obtained foam increases with the increase of the amount of foaming agent added. When too much pentane is added, the water absorption rate of the foam matrix will decrease. This may be because too much pentane will generate more macropores, resulting in a decrease in bound water and an increase in free water, leading to a decrease in water absorption rate. The experimental results also show that the degradable cardanol phenolic resin foam plastic prepared in Example 3 of the present invention has a higher water absorption rate than the phenolic resin foam plastic of Comparative Example 1.

[0105] Experimental Example 2

[0106] This experimental example is a planting experiment:

[0107] The vegetable seedling medium and standard soil in Example 6 were used to carry out rape and Chinese cabbage seedling experiments. The experimental method was different only in the planting medium, and other conditions were the same;

[0108] The experimental results are as follows Figure 6 As shown, Figure 6 Area A: baby spinach - standard soil; Area B: baby spinach - vegetable seedling medium; Area C: pakchoi - vegetable seedling medium; Area D: pakchoi - standard soil.

[0109] Depend on Figure 6 It can be seen that:

[0110] Five days after seedling cultivation, the small spinach in area A that used only standard soil had not emerged, while a small number of small spinach in area B that used vegetable seedling medium had emerged. This was because the porous structure of the cashew phenolic resin foam had a good thermal insulation effect, which increased the temperature of the root system of the vegetable seedlings and was beneficial to the emergence of the small spinach.

[0111] Similar conclusions were drawn from the seedling raising experiments of Chinese cabbage in zone C using vegetable seedling raising substrate and Chinese cabbage in zone D using only standard soil, namely, the seedling raising substrate with added granular phenolic resin foam substrate germinated more quickly.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a degradable cardanol phenolic resin foam, characterized in that: The preparation method comprises the following steps: (a) adding phenol, formaldehyde solution and cardanol into an alkaline solution to carry out polycondensation reaction to obtain a cardanol-modified phenolic resin; (b) adding a surfactant and a foaming agent to the cardanol-modified phenolic resin and stirring evenly, then adding a curing agent and stirring evenly again to obtain a mixture; (c) subjecting the mixture to foaming treatment to obtain the degradable cardanol phenolic resin foam plastic.

2. The preparation method according to claim 1, characterized in that: In the step (a), the molar ratio of phenol, formaldehyde and cardanol is 1:(2-2.5):(0.8-1.2).

3. The preparation method according to claim 1, characterized in that: In the step (a), the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.

4. The preparation method according to claim 1, characterized in that: In the step (a), the pH value of the polycondensation reaction is 9-10, the temperature is 80-85° C., and the time is 2.5-4 hours.

5. The preparation method according to claim 1, characterized in that: In the step (a), the concentration of the formaldehyde solution is 35% to 40%; the concentration of the alkali solution is 8% to 12%.

6. The preparation method according to claim 1, characterized in that: In the step (b), the mass ratio of the cardanol-modified phenolic resin, the surfactant, the foaming agent and the curing agent is 100:(6-10):(2.5-3.5):(5-9).

7. The preparation method according to claim 1, characterized in that: In the step (c), the foaming reaction temperature is 55 to 65° C. and the time is 12 to 20 minutes.

8. The degradable cardanol phenolic resin foam plastic prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the degradable cardanol phenolic resin foam plastic prepared by the preparation method according to any one of claims 1 to 7 in preparing a vegetable seedling medium.

10. A vegetable seedling substrate, characterized in that: The vegetable seedling substrate is composed of a degradable cardanol phenolic resin foam plastic prepared by the preparation method according to any one of claims 1 to 7 and standard soil in a mass ratio of 1: (0.8 to 1.2); The standard soil is composed of leaf mold, peat and river sand in a mass ratio of 1:(0.8-1.2):(0.8-1.2).

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