A biodegradable superabsorbent polymer and its preparation method

Abstract

The present invention relates to a biodegradable superabsorbent polymer and its preparation method, belonging to the technical field of polymer materials. First, polyol I and terpene acid undergo a ring-opening polymerization reaction to generate an oligomer with carboxyl side chains. Then, the oligomer with carboxyl side chains and polyol II undergo a polycondensation cross-linking reaction to obtain a degradable cross-linked polymer. Finally, the degradable cross-linked polymer reacts with sodium salt to prepare the biodegradable superabsorbent polymer. Polyol I is ethylene glycol, propylene glycol, butylene glycol, hexanediol, octanediol, isosorbide, isomannide, isoidide, IIDML, IMDML, ISDML, 1,4-cyclohexanedimethanol or furan dimethanol. Polyol II is glycerol, triethanolamine, 1,2,4-butanetriol, pentaerythritol or erythritol. The chemical structural formula of the product is or, and the number-average molecular weight is 10000-80000 g / mol. The method of the present invention has a simple process; the product has both superabsorbent ability and excellent biodegradability.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials and relates to a biodegradable superabsorbent polymer and a preparation method thereof. Background Art

[0002] Superabsorbent resins (SAPs) are a kind of functional polymer materials, containing a large number of hydrophilic groups and having very high water absorption capacity, which are widely used in the fields related to hygiene and biology. Among them, baby diapers, feminine hygiene products and adult incontinence products account for more than 95% of the superabsorbent resin market.

[0003] The water absorption capacity is a standard parameter describing the water retention capacity of SAPs, which is defined as the weight of the absorbed liquid (g) divided by the dry weight of SAPs (g). At present, the common superabsorbent resins on the market are mainly polyacrylic acid and its sodium salt series products, which have extremely strong water absorption capacity. Although the polyacrylic acid and its sodium salt series products have brought great convenience to people's lives, with the increasing use quantity, the environmental problems caused by using this series of products have gradually attracted people's attention. Since most of these products are disposable and non-degradable in the natural environment, the white pollution in the natural world is increasing day by day, causing great damage to the ecological environment. Therefore, the research and development of biodegradable superabsorbent polymers are very urgent and necessary.

[0004] Biodegradable superabsorbent resins can be prepared from a variety of materials, which can be divided into natural and synthetic polymers according to the source of the materials. Natural polymers mainly include materials such as cellulose, starch and alginate. There are a large number of hydroxyl groups in the chemical structure of cellulose, and its hydrophilicity is relatively high, but the water absorption capacity is still insufficient for the application of SAPs. Starch is the most abundant polysaccharide in plants, with the advantages of low cost, easy modification and good processing performance. Starch is also a natural macromolecule containing abundant hydroxyl groups and has great potential for SAP development. However, the specific surface area of starch is low, and further chemical modification is required to enhance its water absorption capacity. Alginate is a naturally occurring anionic polymer, with a large output and low price, but the water absorption performance and mechanical properties of natural alginate resins are poor and do not meet the actual use requirements.

[0005] To solve the above problems, the prior art often further improves the water absorption performance by grafting acrylic molecules. For example, Patent CN 103122049 B modifies cellulose by adding (NH4)2S2O8 and an aqueous solution of sodium acrylate, and proposes a preparation method of a cellulose superabsorbent resin with a water absorption capacity of 975 g per gram of resin. Patent CN 103073684 B develops a superabsorbent resin based on a starch / sodium alginate / acrylic acid composite system by adding starch to the polymerization system of sodium alginate and acrylic acid, with a water absorption capacity of 960 g per gram of resin. However, although the above methods can achieve high water absorption of the resin, due to the introduction of non-degradable acrylic acid, it cannot be completely degraded, and there is even a risk of generating derivative microplastics.

[0006] Based on the above technical status, in recent years, researchers have begun to focus on developing a new generation of more environmentally friendly SAPs. For example, using bio-based raw materials to develop low-carbon or biodegradable products. Itaconic acid (IA) is a bio-based monomer, and the double bond in its chemical structure can undergo free radical polymerization, having a structure very similar to that of acrylic acid. Researchers have developed some new SAPs around itaconic acid. Although itaconic acid has a structure very similar to that of acrylic acid, the olefin bond faces greater steric hindrance, and the polymer prepared from itaconic acid has a lower molecular weight. To overcome this problem, Patent CN113089181 B proposes to react sodium p-styrenesulfonate, diol, initiator, and itaconic acid to prepare a copolyester with high strength and good water absorption. However, whether it is homopolymerization or copolymerization, with itaconic acid as the polymer backbone with a C-C bond structure, this structure is extremely stable under natural conditions, so the final products prepared do not have biodegradable properties.

[0007] In order to obtain better biodegradability, some new technical solutions have emerged. Some researchers use degradable substrates as the base and achieve water absorption by spraying water-absorbing materials. For example, in Patent CN 111920587 B, a poly(lactic acid) fiber mesh is used as the matrix, which is thermally reinforced and then sprayed with poly(vinyl alcohol) superabsorbent resin powder to prepare a degradable water-absorbing composite material for use in disposable hygiene products. The poly(lactic acid) fiber mesh used in this method can be biodegradable. However, the added poly(vinyl alcohol) superabsorbent resin powder is still non-degradable SAPs, so the problem of the degradability of the water-absorbing resin has not been fundamentally solved. Patent CN 112625306 B prepares a fully degradable superabsorbent resin by simply mixing natural degradable polymer materials (such as carboxymethyl chitosan, chitosan quaternary ammonium salt, carboxymethylated starch, sodium alginate, carboxymethyl cellulose, hydroxypropylated cellulose, gelatin, etc.) with calcium chloride through a solution blending process. Although the fully degradable superabsorbent resin in this patent has excellent degradation performance and water absorption capacity, it is prepared by a solution processing method, using a large amount of organic solvents during the preparation process, causing environmental pollution, harming the health of operators, and trace solvent residues may be toxic.

[0008] Therefore, it is of great significance to study a biodegradable superabsorbent polymer and its preparation method to solve the problem of superabsorbent polymers in the prior art that cannot simultaneously possess superabsorbent ability, excellent biodegradability, and processing performance. Summary of the Invention

[0009] The object of the present invention is to solve the problems existing in the prior art and provide a biodegradable superabsorbent polymer and its preparation method.

[0010] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0011] A preparation method of a biodegradable superabsorbent polymer. First, polyol I and terpene acid undergo a ring-opening polymerization reaction to generate an oligomer with carboxyl side chains. Then, the oligomer with carboxyl side chains and polyol II undergo a polycondensation crosslinking reaction to obtain a degradable crosslinked polymer. The degradable crosslinked polymer has poor water absorption performance. Finally, the degradable crosslinked polymer reacts with a sodium salt (other high-valence salts such as calcium salts and aluminum salts, Ca²⁺ and Al³⁺ will crosslink with multiple carboxylic acid groups, resulting in the densification of the network structure and significantly reducing the water absorption capacity) to obtain a biodegradable superabsorbent polymer. After the degradable crosslinked polymer reacts with the sodium salt to form sodium carboxylate, an osmotic pressure difference is formed during water absorption, thereby further absorbing water and having excellent water absorption performance;

[0012] Polyol I is ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, octylene glycol, isosorbide, isomannitol, isoidide, IIDML (isoidose-2,5-dimethanol, ), IMDML (Isomannide - 2,5 - dimethanol, ), ISDML (Isoidide - 2,5 - dimethanol, ), 1,4 - cyclohexanedimethanol or furan - dimethanol. Polyol I includes but is not limited to these aliphatic diols and cyclic diols. For example, the cyclic diol can also be Galx - OH (2,3:4,5 - di - O - Methylene - galactitol, ), Manx - OH (2,3:4,5 - di - O - Methylene - D - mannitol, ), BCD (4,4’ - Bicyclohexanone Glycerol Diketal, ), CHD (1,4 - Cyclohexanedione Glycerol Diketal, ), CaG (Camphorquinone Diketal Glycerol, ), CM diol (2,4:3,5 - di - O - camphor - D - mannitol, ), etc. Polyol II is a triol such as glycerol, triethanolamine, 1,2,4 - butanetriol or a tetrol such as pentaerythritol, erythritol, etc. Similarly, polyol II includes but is not limited to these two types of polyols.

[0013] The present invention utilizes the ring - opening polymerization reaction and the alcohol - acid polycondensation reaction of polyols and terpene acids. The molecular weight of the polymer is increased through ring - opening polymerization, and cross - linking sites are provided through the alcohol - acid polycondensation reaction, thereby constructing a new polymer system in which the polymer main chain is degradable and has excellent water - absorption performance. Compared with traditional non - degradable polyacrylic acid superabsorbent materials, due to the presence of ester groups in the polymer main chain, the prepared biodegradable superabsorbent polymer can be degraded under conditions such as hydrolysis, soil, compost, and microorganisms. Due to the presence of sodium carboxylate groups in the polymer side chains, the prepared biodegradable superabsorbent polymer has excellent water - absorption performance, and the biodegradable superabsorbent polymer has a cross - linked structure, which can ensure that it still maintains a solid shape after absorbing water.

[0014] As a preferred technical solution:

[0015] For the preparation method of a biodegradable superabsorbent polymer as described above, the chemical structural formula of the terpene acid is , where R1 and R2 are each independently selected from one of methyl, ethyl, and aldehyde groups.

[0016] A preparation method of a biodegradable superabsorbent polymer as described above, the ring-opening polymerization reaction is carried out under the action of catalyst A, and catalyst A is one or more of stannous octoate, tin tetrachloride, aluminum isopropoxide and stannous chloride;

[0017] The temperature of the ring-opening polymerization reaction is 100~150 °C and the time is 1~5 h.

[0018] A preparation method of a biodegradable superabsorbent polymer as described above, the molar ratio of polyol I to terpene acid is 1:2~18, and the addition amount of catalyst A is 0.07~0.12 mol% of polyol I.

[0019] A preparation method of a biodegradable superabsorbent polymer as described above, the molecular weight of the carboxyl-containing side-chain oligomer is 300~3000 g / mol.

[0020] A preparation method of a biodegradable superabsorbent polymer as described above, the polycondensation crosslinking reaction is carried out under the action of catalyst B, and catalyst B is one or more of tetrabutyl titanate, antimony trioxide, antimony acetate and ethylene glycol antimonate;

[0021] The temperature of the polycondensation crosslinking reaction is 160~200 °C. First, the reaction is carried out at atmospheric pressure for 1~3 h, and then the reaction is continued under vacuum conditions for 1~2 h.

[0022] A preparation method of a biodegradable superabsorbent polymer as described above, the molar ratio of polyol II to the carboxyl-containing side-chain oligomer is 1:50~100, and the addition amount of catalyst B is 0.05~0.1 mol% of polyol II.

[0023] A preparation method of a biodegradable superabsorbent polymer as described above, the sodium salt is NaCl, Na2CO3 or NaHCO3;

[0024] The molar ratio of the sodium salt to the biodegradable crosslinked polymer is 1~1.5;

[0025] The temperature of the reaction between the biodegradable crosslinked polymer and the sodium salt is 50~100 °C and the time is 1~2 h. [[ID=2,9]]

[0026] The present invention also provides a biodegradable superabsorbent polymer prepared by the preparation method described in any one of the above, and the chemical structural formula is as shown in formula (I) or formula (II);

[0027] ;

[0028] (I)

[0029] ;

[0030] (II)

[0031] In the formula, R is , , , , , , , , , , , , , , , , , or , R1 and R2 are each independently selected from one of methyl, ethyl and aldehyde group, and R3 is , or , and R4 is or , and n is the degree of polymerization;

[0032] The number-average molecular weight of the biodegradable superabsorbent polymer is 10,000 - 80,000 g / mol.

[0033] As a preferred technical solution:

[0034] For a biodegradable superabsorbent polymer as described above, the biodegradable polymer backbone has a degradable group, ester group, and can undergo degradation under conditions such as hydrolysis, soil, composting and microorganisms;

[0035] The hydrolysis conditions are alkaline solution, acidic solution, fresh water environment or marine environment. The alkaline solution is preferably an alkaline solution with a pH of 10 - 14, the acidic solution is preferably an acidic solution with a pH of 1 - 4, the fresh water environment is preferably rivers, lakes and simulated aqueous culture media, and the marine environment is preferably seawater;

[0036] Soil degradation means that under soil landfill conditions, the polymer can ultimately be decomposed into simple compounds such as carbon dioxide or methane and water;

[0037] Compost degradation means that under household composting conditions or industrial composting conditions, the polymer can ultimately be decomposed into simple compounds such as carbon dioxide or methane and water;

[0038] Microbial degradation means that under the action of microorganisms, the polymer can ultimately be decomposed into simple compounds such as carbon dioxide or methane and water;

[0039] The biodegradable superabsorbent polymer can degrade within 1 - 10 months under composting or the presence of microorganisms;

[0040] The water absorption rate of the biodegradable superabsorbent polymer for distilled water at room temperature is 100 - 200 g / g, and for brine is 30 - 60 g / g.

[0041] Beneficial effects:

[0042] (1) In the preparation method of a biodegradable superabsorbent polymer of the present invention, using a bio-based polyol I and a terpene acid as raw materials, through a ring-opening polymerization and polycondensation cross-linking process, a new polymer system is constructed with a biodegradable polymer main chain and excellent water absorption performance; this system degrades in nature and will not produce persistent microplastics when released into the environment, reducing the risk of microplastic pollution; at the same time, due to the presence of sodium carboxylate groups in the polymer side chain, it has excellent water absorption performance, and this product system can be used in current superabsorbent application fields, such as disposable hygiene products, soil water retainers, absorbent pads, etc.

[0043] (2) In the preparation method of a biodegradable superabsorbent polymer of the present invention, water-absorbing groups are introduced by in-situ modification to prepare a biodegradable superabsorbent polymer, and the preparation process is simple and environmentally friendly.

[0044] (3) A biodegradable superabsorbent polymer of the present invention, the prepared polymer has both superabsorbent ability and excellent biodegradability, and can degrade in natural environments and under defined artificial simulated degradation conditions, effectively protecting the ecological environment. Description of the drawings

[0045] Figure 1 It is a reaction flow chart of the preparation method of the biodegradable superabsorbent polymer. Specific embodiments

[0046] The following further elaborates the present invention in combination with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0047] The test methods for the performance indicators in the embodiments and comparative examples of the present invention are as follows:

[0048] Number-average molecular weight: The number-average molecular weight of oligomers with carboxyl side chains and biodegradable superabsorbent polymers is tested according to the GB / T 36214.1 - 2018 standard.

[0049] Water absorption rate for distilled water and brine: The water absorption rate of the biodegradable superabsorbent polymer for distilled water and brine is tested according to the GB / T 39748 - 2021 standard.

[0050] Degradation experiment: The composting experiment was carried out according to the standard of GB / T 19277.1-2011. The household composting was based on soil with a temperature of 25 °C; the industrial composting was based on farm and garden waste with a temperature of 58 °C. The microbial degradation experiment was carried out according to the standard of GB / T 41010-2021 to test the biodegradation rate of the biodegradable superabsorbent polymer.

[0051] Example 1

[0052] A preparation method of a biodegradable superabsorbent polymer is as follows:

[0053] (1)Preparation of raw materials:

[0054] Catalyst A: stannous octoate;

[0055] Polyol I: propylene glycol;

[0056] Terpenic acid: ;

[0057] Catalyst B: tetrabutyl titanate;

[0058] Polyol II: triethanolamine;

[0059] Sodium salt: NaCl;

[0060] (2)As Figure 1 shown, under the action of catalyst A, polyol I and terpenic acid were subjected to ring-opening polymerization reaction at a temperature of 100 °C for 5 h to generate a carboxyl group-containing side chain oligomer with a molecular weight of 300 g / mol;

[0061] Among them, the molar ratio of polyol I to terpenic acid was 1:2, and the addition amount of catalyst A was 0.07 mol% of polyol I;

[0062] (3)Under the action of catalyst B, the carboxyl group-containing side chain oligomer and polyol II were first subjected to polycondensation cross-linking reaction at a temperature of 160 °C under normal pressure for 3 h, and then continued to react for 1 h under vacuum conditions to obtain a biodegradable cross-linked polymer;

[0063] Among them, the molar ratio of polyol II to the carboxyl group-containing side chain oligomer was 1:50, and the addition amount of catalyst B was 0.1 mol% of polyol II;

[0064] (4)The biodegradable cross-linked polymer and the sodium salt were reacted at a temperature of 50 °C for 2 h to prepare a biodegradable superabsorbent polymer;

[0065] Among them, the molar ratio of the sodium salt to the biodegradable cross-linked polymer was 1.

[0066] The chemical structural formula of the finally prepared biodegradable superabsorbent polymer is , the number-average molecular weight is 10,000 g / mol; the biodegradable superabsorbent polymer can be degraded within 1 month under the condition of household composting; the biodegradable superabsorbent polymer has an absorption rate of 100 g / g for distilled water and 30 g / g for brine at room temperature.

[0067] Example 2

[0068] A preparation method of a biodegradable superabsorbent polymer is as follows:

[0069] (1) Preparation of raw materials:

[0070] Catalyst A: tin tetrachloride;

[0071] Polyol I: butanediol;

[0072] Terpenoic acid: ;

[0073] Catalyst B: antimony trioxide;

[0074] Polyol II: erythritol;

[0075] Sodium salt: Na2CO3;

[0076] (2) As Figure 1 shown, under the action of catalyst A, polyol I and terpenoic acid carry out ring-opening polymerization reaction at a temperature of 110 °C for 4 h to generate a carboxyl-side-chain oligomer with a molecular weight of 1000 g / mol;

[0077] Among them, the molar ratio of polyol I to terpenoic acid is 1:6, and the addition amount of catalyst A is 0.08 mol% of polyol I;

[0078] (3) Under the action of catalyst B, the carboxyl-side-chain oligomer and polyol II are first subjected to polycondensation crosslinking reaction at a temperature of 180 °C under normal pressure for 2 h, and then continue to react for 1.5 h under vacuum conditions to obtain a degradable crosslinked polymer;

[0079] Among them, the molar ratio of polyol II to the carboxyl-side-chain oligomer is 1:60, and the addition amount of catalyst B is 0.06 mol% of polyol II;

[0080] (4) The degradable crosslinked polymer reacts with the sodium salt at a temperature of 60 °C for 1.75 h to obtain a biodegradable superabsorbent polymer;

[0081] Among them, the molar ratio of the sodium salt to the degradable crosslinked polymer is 1.1.

[0082] The chemical structural formula of the finally prepared biodegradable superabsorbent polymer is , with a number-average molecular weight of 30,000 g / mol; the biodegradable superabsorbent polymer can be degraded within 3 months under the condition of household composting; the biodegradable superabsorbent polymer has an absorption rate of 121 g / g for distilled water and 38 g / g for brine at room temperature.

[0083] Example 3

[0084] A preparation method of a biodegradable superabsorbent polymer is as follows:

[0085] (1) Preparation of raw materials:

[0086] Catalyst A: Aluminum isopropoxide;

[0087] Polyol I: 1,4-Cyclohexanedimethanol;

[0088] Terpenic acid: ;

[0089] Catalyst B: Antimony acetate;

[0090] Polyol II: 1,2,4-Butanetriol;

[0091] Sodium salt: NaHCO3;

[0092] (2) Under the action of catalyst A, polyol I and terpenic acid are subjected to a ring-opening polymerization reaction at a temperature of 120 °C for 3 h to generate a carboxyl-containing side-chain oligomer with a molecular weight of 1700 g / mol;

[0093] Among them, the molar ratio of polyol I to terpenic acid is 1:10, and the addition amount of catalyst A is 0.1 mol% of polyol I;

[0094] (3) Under the action of catalyst B, the carboxyl-containing side-chain oligomer and polyol II are first subjected to a polycondensation crosslinking reaction at a temperature of 200 °C under normal pressure for 1 h, and then continue to react for 2 h under vacuum conditions to obtain a degradable crosslinked polymer;

[0095] Among them, the molar ratio of polyol II to the carboxyl-containing side-chain oligomer is 1:80, and the addition amount of catalyst B is 0.05 mol% of polyol II;

[0096] (4) The degradable crosslinked polymer and the sodium salt are reacted at a temperature of 80 °C for 1.5 h to obtain a biodegradable superabsorbent polymer;

[0097] Among them, the molar ratio of the sodium salt to the degradable crosslinked polymer is 1.3.

[0098] The finally prepared chemical structural formula of the biodegradable superabsorbent polymer is , with a number-average molecular weight of 50,000 g / mol; the biodegradable superabsorbent polymer can be degraded within 5 months under the condition of industrial composting; the biodegradable superabsorbent polymer has an absorption rate of 150 g / g for distilled water and 45 g / g for brine at room temperature.

[0099] Example 4

[0100] A preparation method of a biodegradable superabsorbent polymer is as follows:

[0101] (1) Preparation of raw materials:

[0102] Catalyst A: stannous chloride;

[0103] Polyol I: ethylene glycol;

[0104] Terpenic acid: ;

[0105] Catalyst B: antimony glycolate;

[0106] Polyol II: pentaerythritol;

[0107] Sodium salt: Na2CO3;

[0108] (2) Under the action of catalyst A, polyol I and terpenic acid carry out ring-opening polymerization reaction at a temperature of 130 °C for 2 h to generate a carboxyl-containing side-chain oligomer with a molecular weight of 2300 g / mol;

[0109] Among them, the molar ratio of polyol I to terpenic acid is 1:14, and the addition amount of catalyst A is 0.11 mol% of polyol I;

[0110] (3) Under the action of catalyst B, the carboxyl-containing side-chain oligomer and polyol II are first subjected to polycondensation cross-linking reaction at a temperature of 170 °C under normal pressure for 2.5 h, and then continue to react for 1 h under vacuum conditions to obtain a degradable cross-linked polymer;

[0111] Among them, the molar ratio of polyol II to the carboxyl-containing side-chain oligomer is 1:90, and the addition amount of catalyst B is 0.07 mol% of polyol II;

[0112] (4) The degradable cross-linked polymer reacts with the sodium salt at a temperature of 90 °C for 1.25 h to obtain a biodegradable superabsorbent polymer;

[0113] Among them, the molar ratio of the sodium salt to the degradable cross-linked polymer is 1.4.

[0114] The chemical structural formula of the finally prepared biodegradable superabsorbent polymer is , number average molecular weight is 65000g / mol; the biodegradable super absorbent polymer can be degraded within 8 months under the conditions of industrial composting; the absorption rate of the biodegradable super absorbent polymer for distilled water at room temperature is 185g / g, and the absorption rate for salt water is 51g / g.

[0115] Example 5

[0116] A method for preparing a biodegradable super absorbent polymer, comprising the following steps:

[0117] (1) Preparation of raw materials:

[0118] Catalyst A: aluminum isopropoxide and stannous chloride in a 1:1 mass ratio;

[0119] Polyol I: Isosorbide;

[0120] Terpene acids: ;

[0121] Catalyst B: antimony acetate and antimony glycolate in a mass ratio of 1:1;

[0122] Polyol II: glycerol;

[0123] Sodium salt: NaHCO3;

[0124] (2) In the presence of catalyst A, polyol I and terpene acid undergo a ring-opening polymerization reaction at 150°C for 1 h to generate a carboxyl side chain oligomer with a molecular weight of 3000 g / mol;

[0125] The molar ratio of polyol I to terpene acid is 1:18, and the amount of catalyst A added is 0.12 mol% of polyol I;

[0126] (3) Under the action of catalyst B, the carboxyl side chain oligomer and polyol II are subjected to polycondensation and cross-linking reaction at 190°C under normal pressure for 1.5 hours, and then continue to react under vacuum conditions for 2 hours to obtain a degradable cross-linked polymer;

[0127] The molar ratio of polyol II to carboxyl side chain oligomer is 1:100, and the amount of catalyst B added is 0.09 mol% of polyol II;

[0128] (4) The degradable cross-linked polymer is reacted with sodium salt at 100°C for 1 hour to obtain a biodegradable super absorbent polymer;

[0129] The molar ratio of the sodium salt to the degradable cross-linked polymer is 1.5.

[0130] The chemical structure of the biodegradable super absorbent polymer finally obtained is , the number-average molecular weight is 80,000 g / mol; the biodegradable superabsorbent polymer can be degraded within 10 months under the condition of industrial composting; the biodegradable superabsorbent polymer has an absorption rate of 200 g / g for distilled water and 60 g / g for brine at room temperature.

Claims

1. A method for preparing a biodegradable super absorbent polymer, characterized in that: First, polyol I undergoes a ring-opening polymerization reaction with terpene acid to generate a carboxyl side chain oligomer, then the carboxyl side chain oligomer undergoes a condensation cross-linking reaction with polyol II to obtain a degradable cross-linked polymer, and finally the degradable cross-linked polymer reacts with sodium salt to obtain a biodegradable super absorbent polymer. Polyol I is ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, octanediol, isosorbide, isomannide, isoidide, isoidose-2,5-dimethanol, isomannose-2,5-dimethanol, isosorbide-2,5-dimethanol, 1,4-cyclohexanedimethanol or furandimethanol; polyol II is glycerol, triethanolamine, 1,2,4-butanetriol, pentaerythritol or erythritol; The chemical structure of terpene acid is In the formula, R1 and R2 are each independently selected from one of methyl, ethyl and aldehyde groups.

2. The method for preparing a biodegradable super absorbent polymer according to claim 1, wherein: The ring-opening polymerization reaction is carried out under the action of catalyst A, which is one or more of stannous octoate, tin tetrachloride, aluminum isopropoxide and stannous chloride; The temperature of the ring-opening polymerization reaction is 100-150° C., and the time is 1-5 hours.

3. The method for preparing a biodegradable super absorbent polymer according to claim 2, wherein: The molar ratio of polyol I to terpene acid is 1:2-18, and the added amount of catalyst A is 0.07-0.12 mol% of polyol I.

4. The method for preparing a biodegradable super absorbent polymer according to claim 3, wherein: The molecular weight of the carboxyl side chain oligomer is 300 to 3000 g / mol.

5. The method for preparing a biodegradable super absorbent polymer according to claim 1, wherein: The polycondensation cross-linking reaction is carried out under the action of catalyst B, which is one or more of tetrabutyl titanate, antimony trioxide, antimony acetate and ethylene glycol antimony; The temperature of the polycondensation cross-linking reaction is 160-200° C., and the reaction is first carried out at normal pressure for 1-3 hours, and then continued to react under vacuum conditions for 1-2 hours.

6. The method for preparing a biodegradable super absorbent polymer according to claim 5, wherein: The molar ratio of polyol II to the carboxyl side chain oligomer is 1:50-100, and the added amount of catalyst B is 0.05-0.1 mol% of polyol II.

7. The method for preparing a biodegradable super absorbent polymer according to claim 1, wherein: Sodium salt is NaCl, Na2CO3 or NaHCO3; The molar ratio of the sodium salt to the degradable cross-linked polymer is 1 to 1.5; The temperature for reacting the degradable cross-linked polymer with the sodium salt is 50-100° C., and the time is 1-2 hours.

8. A biodegradable super absorbent polymer obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The chemical structural formula is shown in formula (I) or formula (II); In the formula, R is -CH2·OH2-, -CH2·CH2·CH2-, -CH2·CH2·CH2·CH2-, -CH2·CH2·CH2·CH2·CH2-, -CH2·CH2·CH2·CH2·CH2·OH2-, -CH2·CH2·CH2·CH2·CH2·CH2·CH2·CH2-, R1 and R2 are each independently selected from one of methyl, ethyl and aldehyde groups, and R3 is R4 is n is the degree of polymerization; The number average molecular weight of the biodegradable super absorbent polymer is 10,000 to 80,000 g / mol.

9. The biodegradable super absorbent polymer according to claim 8, characterized in that: Biodegradable superabsorbent polymers can be degraded within 1 to 10 months in the presence of compost or microorganisms; The biodegradable super absorbent polymer has an absorption rate of 100 to 200 g / g for distilled water and an absorption rate of 30 to 60 g / g for saline at room temperature.

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