RU2539379C2 - Biodegradable superabsorbent polymer containing tetrazole and cellulose derivatives - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention refers to medicine, more specifically to a biodegradable absorbent polymer produced from a composition with nitrogen-containing heterocyclic monomer, polymerized acryl or methacryl, a non-organic excipients and an allyl compound of cellulose.

EFFECT: biodegradable absorbent polymer has excellent biodegradability and high absorbing capacity.

11 cl, 3 tbl, 2 dwg, 5 ex

Description

Field of Invention

The present invention relates to a biodegradable absorbent polymer obtained from a composition containing a nitrogen-containing heterocyclic compound and a monomer having polymerizable acrylic or methacrylic groups, an inorganic filler and allyl derivatives of cellulose, and a method for producing a biodegradable absorbent cross-linked polymer.

State of the art

Absorbent personal care products, such as baby diapers, panty liners for adults with urinary or fecal incontinence, and feminine care products typically contain an absorbent core that includes superabsorbent polymer particles dispersed within the fiber matrix. Superabsorbents are water-swellable and, as a rule, water-insoluble absorbent materials have a high absorption capacity for physiological body fluids.

General purpose superabsorbent polymers (SAPs) are mainly derived from acrylic acid, which in itself is derived from petroleum oil, non-renewable raw materials. Acrylic acid and SAP polymers are generally recognized as biodegradable.

The absorbent polymer includes partially neutralized polyacrylic acids, hydrolyzed starch / grafted acrylonitrile copolymer, neutralized starch / grafted acrylic acid copolymer, neutralized vinyl acetate / acrylic ester ester copolymer, and hydrolyzed biocomparable acrylamide copolymer.

Since there has recently been a rise in environmental issues, a biodegradable polymer has attracted much attention. Examples of a biodegradable absorbent polymer are a natural polymer, a mixture of a natural polymer and a synthetic polymer, and a mixture of a grafted polymer, a natural polymer and a synthetic polymer, and research is ongoing.

A commercially successful biodegradable polymer is sodium carboxymethyl cellulose, obtained by modifying natural cellulose. Cellulose as a starting material in itself is a relatively cheap material, and the polymer thus obtained has several advantages.

As examples of the preparation of super absorbent polymers with cellulose, one method involves reacting cellulose with a crosslinking agent having an ionic functional group to produce a product with high biodegradability, but requires high production costs. In another method, cellulose is first modified to obtain a carboxyl group using ClCH ₂ COOH or TEMPO, and then the modified cellulose is crosslinked using a crosslinking agent. The second method has some problems, such as low biodegradability, and includes limited use or prohibited material in the manufacturing process.

The generally accepted method for producing a biodegradable polymer using a natural polymer has some industrial limitations. That is, the conventional biodegradable cellulose-based polymer has low quality properties or is not competitive on the market due to the high production cost compared to a biodegradable absorbent polyacrylate-based polymer. In addition, grafting polyacrylate onto a natural polymer has several disadvantages, such as the difficulty in controlling the degree of polymer degradation, low ability to absorb water, low physical and mechanical properties, and the relatively high cost of additives.

Thus, there is a great need for a biodegradable absorbent polymer made from a natural polymer that has excellent biodegradability and high absorption capacity, but which can be obtained at low cost.

DETAILED DESCRIPTION OF THE INVENTION

The purpose of the invention

One embodiment of the present invention is to provide a biodegradable absorbent crosslinked polymer obtained from a composition comprising a nitrogen containing heterocyclic monomer and a polymerizable acrylic or methacrylic monomer, an inorganic filler and a cellulose derivative.

Another option is to provide a method for producing a biodegradable absorbent cross-linked polymer using a composition comprising a nitrogen-containing heterocyclic monomer and a polymerizable acrylic or methacrylic monomer, inorganic filler and cellulose derivatives.

Detailed description

To solve the problem of the present invention, one of the options of the present invention is to provide a biodegradable absorbent crosslinked polymer obtained from a composition comprising a nitrogen-containing heterocyclic monomer, a polymerizable monomer having an acrylic or methacrylic group, an inorganic filler and cellulose derivatives, and a method for producing a cross-linked polymer.

The nitrogen-containing heterocyclic monomer acts to improve the water-absorbing activity of the crosslinked polymer and, for example, includes a tetrazole compound. Preferred examples of tetrazole monomer are compounds represented by chemical formula 1:

[Chemical formula 1]

Where

R ¹ independently represents a C ₁ -C ₁₀ hydrocarbon having polymerizable or crosslinkable unsaturated groups (e.g., vinyl or allyl), and R ² represents hydrogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkenyl or C ₁ -C ₆ halogenated alkyl group, where the halogen is F, Cl, Br or I.

A preferred amount of tetrazole monomer may be in the range of 4 to 16% by weight of the polymerizable composition, as a solid content. A decrease in the amount of tetrazole monomer leads to a decrease in the rate of biological decomposition and the rate of absorption of the crosslinked polymer in physiological fluid. If the amount of tetrazole monomer exceeds 20%, this reduces the polymerization rate, the degree of conversion of monomers to polymers and the yield of the product.

The monomer having a polymerizable acrylic group or methacrylic group may be any having an unsaturated carbon double bond that is capable of polymerizing due to radical polymerization. Preferably, the polymerizable monomer may be any monomer that can polymerize by free radical polymerization.

Examples of the monomer include polymerizable (meth) acrylic groups such as acrylate and its derivatives, methacrylate and its derivatives, acrylic acid and its derivatives, and methacrylic acid and its derivatives.

The amount of polymerizable monomer can be from 30 to 50% of the mass. in the polymerizable composition, as a solid content.

Cellulose derivatives can be obtained by acetylation or etherification on the hydroxyl group of a repeating unit of cellulose, and cellulose nitrate (SC), cellulose acetate (AC), methyl cellulose (MC), dimethyl cellulose, triacetyl cellulose, ethyl cellulose (EC) and the like. Further, the resulting cellulose derivatives can be further modified with an allyl compound. Preferred examples of cellulose derivatives are represented by chemical formula 2.

[Chemical formula 2]

where R ³ independently represents hydrogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkenyl, C ₂ -C ₆ alkyl carboxyl group such as carboxymethyl group, C ₂ -C ₆ alkanoyl such as acetyl, or C ₁ -C ₆ halogenated alkyl group, where the halogen is F, Cl, Br or I, n is an integer from 5 to 100.

The number of derivatives of cellulose can be from 2 to 10.0% of the mass. in the polymerizable composition as solid content, since a higher content of the allyl compound of cellulose derivatives in the composition leads to an uncontrolled decomposition rate.

The inorganic filler may be a clay mineral such as bentonite, montmorillonite, zeolite, kaolin or the like. The clay mineral has a layered structure and excellent water-absorbing properties, and, therefore, can be used in the present invention so that the cross-linked polymer molded product easily disintegrates. In particular, the clay mineral is preferably bentonite.

The inorganic filler may be used in the form of a dry powder or suspension. For example, a suspension of bentonite can be prepared by adding bentonite to water and mixing.

Inorganic filler may be contained in an amount of from 0.01-10% of the mass. from the composition. A small amount of inorganic filler leads to the applicability of the theory of small additives (nano-systems). The increase in part of the inorganic filler leads to a decrease in the absorption capacity of polymers.

Preferably, in one embodiment of the present invention, the polymerization can be carried out by radical or thermal polymerization using an initiating system (for example, a redox initiating system).

In the polymerization process of the present invention, the amine-containing compound acts as a reducing agent of the redox pair of the initiating system, and the oxidizing agents can be used together with the amine-containing compound to form the initiating system.

Preferred oxidizing agents include potassium persulfate, ammonium persulfate, sodium persulfate and alkali metal persulfate.

Examples of amino-containing compounds used in the present invention typically include allylamines, di- and triamines, alkoxyamines, and ammonium and iminium salts. Specific examples include diallylamine, and 2- (dimethylamino) ethyl methacrylate; ethylene diamines such as tetraethylenediamine, tetramethylenediamine; propylene diamine, such as N, N, N ', N' - (3-pentamethylene) diamine; triamines and tetraamines, such as N, N, N ', N', N "-pentamethyl-diethylenediamine and hexamethylenetetramine; as well as ammonium and iminium salts, such as tetrabutylammonium chloride and dimethylmethyleneammonium chloride.

Preferred examples of the initiating system can be a persulfate compound and an amine compound, and more preferably a mixture of ammonium persulfate and tetramethylenediamine (TMDA). The persulfate compound and the amine compound in the initiating system can be mixed in a weight ratio of 1: 2 or 1: 1 of the persulfate compound to the amine compound.

The amount of each component in the initiating system is from 0.5 to 5% by weight, or preferably 1-2% by weight, with respect to the total amount of solid content of the polymerizable composition. For example, the initiating system may be a mixed solution of ammonium persulfate and tetramethylenediamine, mixed in a mass ratio of 1: 2 or 1: 1.

The use of the initiating system allows to lower the polymerization temperature, and, therefore, the choice of the initiating system is of great practical importance. When the amount of TMDA is out of range, the resulting product will have reduced strength, such as hardness, stiffness in a swollen state.

As a solid content, the amount of polymerizable monomer in the polymerizable composition may be from 30 to 50% of the mass. from the total mass of the polymerizable composition, which is associated with a high degree of conversion of monomers in the reaction.

In another embodiment of the present invention, a method for producing a biodegradable absorbent crosslinked polymer includes the step of radical polymerization in an aqueous medium at a temperature of 20-70 ° C for 2-4 hours under the conditions of a redox system of ammonium tetramethylenediamine persulfate, including a molar mixture ratio from 1: 0.5 to 1: 2.

Technical effect

The cross-linked polymer of the present invention has physicochemical properties proportional to or higher than the properties of the known superabsorbent polymer based on polyacrylate, and acquires biodegradability through the use of allyl-CMC and tetrazole comonomer. The cross-linked polymer and the method of its preparation do not cause difficulties in maintaining good physical and chemical properties and competitiveness due to the high production cost. In addition, the knowledge of certain experience and technologies accumulated in the production field regarding a superabsorbent polymer based on polyacrylate can be easily applied in the present invention.

Further, the present invention is described in more detail in the examples. However, the following examples are only for understanding the present invention, and the present invention is not limited to the following examples.

Brief Description of the Figures

Figure 1 shows the dependence of gelation in the synthesis of a biodegradable composition depending on the concentration of 2-methyl-5-vinyltetrazole.

Figure 2 shows the results of a study of biodegradability tests in comparative example 2.

Example 1

In the first step, an allyl-CMC was synthesized as a cross-linking agent used as a cross-linking agent. Weighted carboxymethyl cellulose was placed in a flask with a reflux condenser, stirrer and dropping funnel. Isopropyl alcohol (M = 1: 30) was added to the flask and then heated to 50 ° C. After 1 hour, 1 mol of NaOH was added to the flask and stirred at 50 ° C for one hour. After that, allyl bromide was added to the flask and heated at 50 ° C for 1 hour. The reaction mixture, including allyl carboxymethyl cellulose (AKMC), was distilled to remove isopropyl alcohol, and the resulting product was dried during the day at 40 ° C to obtain 10 g of AKMC powder.

In a second step, to partially neutralize acrylic acid, 2.1 g of acrylic acid (0.029 mol) was added to 0.8 g (0.005 mol) of 14 N NaOH. The result was 1.25 g of partially neutralized acrylic acid (α = 0.8).

Partially neutralized acrylic acid (α = 0.8), bentonite (4% wt.) In the form of a dry powder and AKMC were added to the flask. Then, 0.02 g of TMDA and 2-methyl-5-vinyl-tetrazole were added to the flask and thoroughly mixed with an ultrasonic stirrer for 10-15 minutes. The solid content and mass percent of partially neutralized acrylic acid, bentonite, AKMC and 2-methyl-5-vinyl-tetrazole (MBT) in the reaction mixture for radical polymerization were summarized in table 1.

At the polymerization stage, 0.02 g of ammonium persulfate (1% wt.) Was added to the flask and placed in a thermostat at 40 ± 2 ° C for complete polymerization. The resulting product was dried at 40 ° C in an oven.

Examples 2-4

In accordance mainly with the method of Example 1, a crosslinked polymer was produced, except that the added amounts of 2-methyl-5-vinyl-tetrazole in the reaction mixture were changed as shown in Table 1.

Table 1
The use of quantities of components in the polymerizable composition Classification Acrylic Acid (g) AKMC (g) MW (g) Bentonite (g) Example 1 2.1 0.05 (2% wt.) 0.1 (4% wt.) 0.1 (4% wt.) Example 2 2.1 0.05 (2% wt.) 0.2 (8% wt.) 0.1 (4% wt.) Example 3 2.1 0.05 (2% wt.) 0.3 (12% of the mass.) 0.1 (4% wt.) Example 4 2.1 0.05 (2% wt.) 0.4 (16% wt.) 0.1 (4% wt.)

Comparative Example 1: Test for gelation time and absorption activity

Gel time

Depending on the concentration of MW, the time of the onset of gelation to obtain the polymer was studied and the result was shown in Fig. 1.

One of the main characteristics of the formation of the polymer network is the start time of gelation (gelation time), which is not understood as the start time of polymerization. Nevertheless, gelation in almost all cases begins immediately after the introduction of the initiator. The viscosity of the reaction mixture increases while polymerization occurs. With an increase in the concentration of the MVT monomer, the gelation time decreases. Thus, there is a need to study the effect of specific parameters on the gelation time, as well as the main parameters, such as the concentration of the cross-linking agent, initiator and inorganic filler, and the reaction temperature. Gelation in the synthesis of a biodegradable polymer is shown as a function of the concentration of 2-methyl-5-vinyltetrazole in FIG. 1.

As the concentration of 2-methyl-5-vinyltetrazole in the polymerizable composition increases, the gelation time decreases, as shown in FIG. It seems possible that the MBT monomers are able to accelerate the polymerization if the amount of MBT in the mixture increases.

(2) Absorbent properties

The absorbent properties of the crosslinked polymer containing 2-methyl-5-vinyltetrazole comonomer and inorganic filler were investigated in distilled water and physiological saline. The test results of the absorbent properties (degree of swelling) for water and saline are shown in table 2.

table 2
Absorption properties (degree of swelling) Classification MW (g) Absorption properties for water (g / g) Absorption properties for saline solution (g / g) Example 1 0.1 (4% wt.) 180 40 Example 2 0.2 (8% wt.) 165 70 Example 3 0.3 (12% of the mass.) 270 60 Example 4 0.4 (16% wt.) 110 thirty

The research method for absorption properties has been described in detail.

1 g of the sample was placed in a glass vessel containing 250 ml of distilled water or saline, and left to swell for 1-3 days in saline and 2 days in distilled water. The test temperature was 18 ° C. The equilibrium degree of swelling (Q) was calculated by the following formula:

Q = (MSP / MDP)

where Q is the equilibrium degree of swelling (g / g), MSP is the weight of the swollen polymer (g), and MDP is the weight of the dry polymer (g).

As shown in table 2, the maximum absorption capacity of the hydrogel was 270 g / g in example 3 tests in distilled water and 70 g / g in example 2 tests in physiological saline.

Example 5

Biodegradability measurement

In accordance mainly with the method of example 1, a biodegradable crosslinked polymer was obtained as samples 1-4, except that the amount of solid content and the percentage of partially neutralized acrylic acid (AK), bentonite, AKMC and 2-methyl- 5-vinyl-tetrazole (MBT) in the reaction mixture was used in the amount shown in table 3.

Table 3
Used amounts of components in the polymerizable composition Sample Number AK (g) AKMC (g) MW (g) Bentonite (g) Sample 1 2 0.2 0 0 Sample 2 2 0.2 0 0.1 Sample 3 2 0.2 0.4 0 Sample 4 2 0.2 0.4 0.1

Comparative Example 2: Biodegradability Test

The biodegradability of synthetic polymers was investigated in accordance with the method described in the article by Hao Feng, Jian Li and Lijuan Wang. Preparation of biodegradable flax shive cellulose-based superabsorbent polymer under microwave irradiation. Bioresources 5 (3), pp. 1484-1495). The biodegradability test of the polymer samples obtained in Example 5 was carried out at 40 ° C. for 2 weeks, and compared with cotton as a control.

Samples of the polymer were placed in a nylon container and placed in a box with soil to a depth of 10 cm. The box was placed in a thermostat with a temperature of 40 ° C and maintaining humidity. Sample weight control was carried out every 2 days. The mass check of the samples was stopped when the polymer was merged with the container. Samples could not be separated from the container in which they were placed for biodegradation experiments in the soil.

The test result was shown in FIG. 2, where the weight reduction of the polymer sample was indicated as a function of the time of the test. On the first day of the biodegradability test, the reason for the increase in the initial mass of the sample is the absorption of moisture from the air.

Claims (11)

1. Biodegradable absorbent cross-linked polymer obtained from a composition comprising a polymerizable monomer having an acrylic or methacrylic group, a tetrazole monomer represented by chemical formula 1, an inorganic filler and an allyl compound of a cellulose derivative represented by chemical formula 2:
[Chemical formula 1]

where R ¹ represents vinyl,
R ² represents hydrogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkenyl or a C ₁ -C ₆ halogenated alkyl group, where the halogen is F, Cl, Br or I,
[Chemical formula 2]

where R ³ independently represents hydrogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkenyl, C ₂ -C ₆ alkylcarboxyl group, C ₂ -C ₆ alkanoyl, or C ₁ -C ₆ halogenated alkyl group, where halogen represents F, Cl, Br or I, n is an integer from 5 to 100. 2. The biodegradable absorbent cross-linked polymer according to claim 1, characterized in that R ² independently represents hydrogen or methyl. 3. The biodegradable absorbent crosslinked polymer according to claim 1, characterized in that the tetrazole monomer is 5-vinyltetrazole or 2-methyl-5-vinyltetrazole. 4. The biodegradable absorbent cross-linked polymer according to claim 1, characterized in that R ³ independently represents hydrogen, a C ₂ -C ₆ alkylcarboxyl group or a C ₂ -C ₆ alkanoyl. 5. The biodegradable absorbent crosslinked polymer according to claim 4, wherein the allyl compound of the cellulose derivative is an allyl compound of carboxymethyl cellulose, methyl cellulose, dimethyl cellulose, or triacetyl cellulose. 6. The biodegradable absorbent cross-linked polymer according to claim 1, characterized in that the inorganic filler is selected from the group consisting of bentonite, montmorillonite, zeolite or kaolin. 7. The biodegradable absorbent cross-linked polymer according to claim 1, characterized in that the monomer containing polymerizable (meth) acrylic groups is acrylic acid or methacrylic acid. 8. The biodegradable absorbent cross-linked polymer according to claim 1, characterized in that the composition contains from 30 to 50 wt.% Polymerizable monomer, from 3 to 16 wt.% Tetrazole monomer, and from 2 to 10.0 wt.% Allyl compounds, 0.01-10 wt.% inorganic filler from 100% of the composition by weight, as solid content. 9. A method for producing a biodegradable cross-linked polymer, comprising the step of polymerizing a composition comprising a polymerizable monomer having an acrylic or methacrylic group, a tetrazole monomer represented by chemical formula 1, an inorganic filler and an allyl compound of a cellulose derivative represented by chemical formula 2:
[Chemical formula 1]

where R ¹ independently represents vinyl,
R ² represents hydrogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkenyl or a C ₁ -C ₆ halogenated alkyl group, where the halogen is F, Cl, Br or I,
[Chemical formula 2]

where R ³ independently represents hydrogen, C ₁ -C ₆ alkyl, C ₁ -C ₆ alkenyl, C ₂ -C ₆ alkylcarboxyl group, C ₂ -C ₆ alkanoyl, or C ₁ -C ₆ halogenated alkyl group, where halogen represents F, Cl, Br or I, n is an integer from 5 to 100. 10. The method according to claim 9, characterized in that the inorganic filler is added in the form of a suspension or powder. 11. The method according to claim 9, characterized in that the polymerization is a radical polymerization.

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