The swelling effect of the hydrogels obtained from each group in different liquid media was evaluated by a swelling test. Referring to the specification of 'Chinese pharmacopoeia' of 2015 edition, artificial gastric juice, artificial small intestine juice and artificial colon juice are prepared, and the specific preparation methods are respectively as follows:

artificial gastric juice: the diluted hydrochloric acid (16.4 mL) was added with about 800mL of water and 10g of pepsin, shaken, and then diluted with water to 1000mL to a final pH of 1.5.

Artificial small intestine liquid: taking 6.8g of monopotassium phosphate, adding 500mL of water for dissolving, and adjusting the pH value to 6.8 by using 0.1mol/L sodium hydroxide solution; taking another 10g of pancreatin, adding a proper amount of water to dissolve the pancreatin, mixing the two solutions, and adding water to dilute the solution to 1000 mL.

Artificial colon liquid: 5.59g of dipotassium phosphate and 0.41g of monopotassium phosphate are taken, water is added for dissolution, the volume is determined to be 1000mL, and 0.1mol/L sodium hydroxide solution is used for adjusting the pH value to 8.4.

Accurately weighing 0.500 +/-0.005 g of each group of dry hydrogel particles respectively, and recording as W_{Dry matter}Then putting each hydrogel particle into a flask filled with 500mL of artificial gastric juice, continuously stirring by using a magnetic stirrer under the heating of water bath at 37 ℃, obtaining a hydrogel sample swelled in the artificial gastric juice through suction filtration after the hydrogel is swelled for 90min, and accurately weighing and recording as W_{Stomach (stomach)}；

Respectively putting hydrogel samples swelled in artificial gastric juice into flasks filled with 500mL of artificial small intestine juice, continuously stirring by using a magnetic stirrer under the heating of water bath at 37 ℃, obtaining the hydrogel samples swelled in the artificial small intestine juice by suction filtration after the hydrogel is swelled for 90min, accurately weighing and recording as W_{Small intestine}；

Putting the hydrogel sample swelled in the artificial intestinal juice into a flask filled with 500mL of the artificial intestinal juice, continuously stirring by using a magnetic stirrer under the heating of water bath at 37 ℃, respectively obtaining the hydrogel sample swelled in the artificial intestinal juice after 1h, 6h, 12h, 24h and 48h through suction filtration, accurately weighing, and respectively recording as W_{Colon 1h}、W_{Colon 6h}、W_{Colon 12h}、W_{Colon 24h}、W_{Colon 48h}；

The swelling ratio of the hydrogel was calculated according to the following formula:

swelling ratio Q of hydrogel in artificial gastric juice_{Stomach (stomach)}＝W_{Stomach (stomach)}/W_{Dry matter}；

Swelling ratio Q of hydrogel in artificial small intestine liquid_{Small intestine}＝W_{Small intestine}/W_{Dry matter}；

Swelling ratio Q of hydrogel in artificial colon fluid_Colon＝W_Colon/W_{Dry matter}。

Q_{Colon 1h}、Q_{Colon 6h}、Q_{Colon 12h}、Q_{Colon 24h}、Q_{Colon 48h}Respectively with W_{Colon 1h}、W_{Colon 6h}、W_{Colon 12h}、W_{Colon is 24 hours,}W_{Colon 48h}Corresponding to the above (the same applies below).

The results are shown in Table 2 and FIG. 1.

TABLE 2

Group of	Q_{Stomach (stomach)}	Q_{Small intestine}	Q_{Colon 1h}	Q_{Colon 6h}	Q_{Colon 12h}	Q_{Colon 24h}	Q_{Colon 48h}
								A₁	14.46	0	0	0	0	0	0
B₁	17.11	92.55	48.41	28.10	8.44	0	0
								C	15.34	82.67	54.72	34.34	25.57	12.38	0
D₁	12.86	40.44	51.83	47.65	34.45	24.56	0
								E₁	10.97	20.47	30.43	43.21	47.47	38.14	26.89

From table 2, when the crosslinking temperature is 90 ℃, the hydrogel is not crosslinked enough due to not reaching the self-crosslinking temperature of the sodium carboxymethyl cellulose, and the hydrogel is dissolved and dispersed in the artificial small intestine solution; when the crosslinking temperature is 100-140 ℃, the crosslinking degree of the hydrogel is proper, the hydrogel has a higher swelling ratio between the artificial gastric juice and the artificial small intestine juice, can be gradually dissolved in the alkaline artificial colon juice and continuously releases water within 48 hours and finally completely collapses, the crosslinking degree of the hydrogel increases along with the increase of the crosslinking temperature, the swelling ratio in acidic and neutral environments is slightly reduced, but the degradation time in the alkaline environment is prolonged, particularly when the crosslinking temperature is 140 ℃, due to the higher crosslinking degree, crosslinking chemical bonds are hydrolyzed at the initial stage in the artificial colon juice, and then further imbibe and expand, and the hydrogel starts to release water after 1 hour; when the crosslinking temperature is 150 ℃, the crosslinking temperature is high, so that the hydrogel is excessively crosslinked, the swelling ratio of the hydrogel in the artificial gastric juice and the artificial small intestine juice is reduced, the hydrogel cannot be completely dissolved in the artificial colon juice, the swelling ratio of the hydrogel in the artificial colon juice is gradually increased due to high crosslinking degree, and the hydrogel continues to absorb liquid in the first 12 hours without releasing water.

Test 2: effect of Cross-linking time on hydrogel Properties

The raw materials and crosslinking conditions used for each set of hydrogels are shown in Table 3, and the preparation method is the same as that of test 1.

TABLE 3

The swelling effect of each of the obtained hydrogels in different liquid media was evaluated by the same swelling test as in test 1, and the results are shown in table 4 and fig. 2.

TABLE 4

Group of	Q_{Stomach (stomach)}	Q_{Small intestine}	Q_{Colon 1h}	Q_{Colon 6h}	Q_{Colon 12h}	Q_{Colon 24h}	Q_{Colon 48h}
								A₂	21.75	95.14	0	0	0	0	0
B₂	16.74	86.33	45.14	17.76	4.44	0	0
								C	15.34	82.67	54.72	34.34	25.57	12.38	0
D₂	11.41	39.44	42.37	44.24	32.54	21.24	0
								E₂	10.55	37.64	48.64	49.17	37.37	28.57	4.14

As can be seen from Table 4, when the crosslinking time is 1min, the hydrogel is not crosslinked enough, and is rapidly dissolved and dispersed in the artificial colon fluid, so that the water can not be slowly released for a long time; when the crosslinking time is 5-30min, the crosslinking degree is proper, the artificial gastric juice and the artificial small intestine juice have higher swelling ratio, meanwhile, the artificial gastric juice and the artificial small intestine juice can be gradually dissolved in the alkaline artificial colon juice and continuously release water within 48 hours and finally completely break up, the crosslinking degree of the hydrogel is increased along with the extension of the crosslinking time, the swelling ratio in acid and neutral environments is slightly reduced, but the degradation time in the alkaline environment is prolonged, particularly when the crosslinking time is 30min, the obtained hydrogel has higher crosslinking degree, and in the initial stage of the artificial colon juice, crosslinking chemical bonds are hydrolyzed and further absorb and expand, and the water begins to be released after 6 hours; when the crosslinking time is 40min, the hydrogel is excessively crosslinked due to the fact that the crosslinking time exceeds the critical value, the swelling ratio of the hydrogel in artificial gastric juice and artificial small intestine juice is reduced, and the hydrogel cannot be completely dissolved in the artificial colon juice within 48 hours. In addition, the inventor has referred patent CN201780032349.5 at the initial stage of research, but found that when carboxymethylcellulose sodium (with a substitution degree of 0.7-1.2 and a viscosity of 1500-. The hydrogel obtained by the invention is light yellow, and is in a normal hydrogel state after swelling (see figure 3, the left figure is a dry state, and the right figure is a swelling state), the performance of the hydrogel is similar to that of the hydrogel obtained by the patent examples, and the production efficiency is improved.

Test 3

The raw materials and crosslinking conditions used for each set of hydrogels are shown in Table 5, and the preparation methods are the same as those in test 1.

TABLE 5

The swelling effect of each of the obtained hydrogels in different liquid media was evaluated by the same swelling test as in test 1, and the results are shown in Table 6.

TABLE 6

Group of	Q_{Stomach (stomach)}	Q_{Small intestine}	Q_{Colon 1h}	Q_{Colon 6h}	Q_{Colon 12h}	Q_{Colon 24h}	Q_{Colon 48h}
								F	14.67	61.24	36.57	22.34	2.42	0	0
G	12.32	33.74	54.33	39.85	32.67	26.64	0
								H	13.84	51.31	45.72	31.45	24.38	2.12	0
I	16.12	71.43	51.34	42.75	27.61	17.21	0

The sodium carboxymethylcellulose used in test 1 and test 2 was made by Shanghai Michelin Biochemical technology Ltd, model number C804618; the sodium carboxymethylcellulose used in group F is produced by Shanghai Mielin Biochemical technology limited, and has the model number of C804620; the sodium carboxymethylcellulose used in group G is made by Shanghai Michelin Biochemical technology limited, and has the model number of C804626; the sodium carboxymethylcellulose used in group H is made by Shanghai Michelin Biochemical technology limited, and has the model number of C804622; the sodium carboxymethylcellulose manufacturer adopted by group I is Shanghai Allantin Biotechnology Co., Ltd., type C104978.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. The hydrogel with the function of relaxing the bowels is characterized by being formed by crosslinking the following raw materials in parts by weight: 100 parts of sodium carboxymethylcellulose and 0.5-3 parts of polycarboxylic acid; wherein the substitution degree of the sodium carboxymethyl cellulose is 0.7-1.2, and the viscosity of an aqueous solution with the mass concentration of 1 percent prepared by the sodium carboxymethyl cellulose at 25 ℃ is 1500-5000mPa & s; the crosslinking temperature is 100-140 ℃, and the crosslinking time is 5-30 min.

2. The hydrogel of claim 1, wherein the crosslinking temperature is 120 ℃ and the crosslinking time is 15 min.

3. The hydrogel according to claim 1, wherein the degree of substitution of the sodium carboxymethylcellulose is 0.9, and the viscosity of a 1% by mass aqueous solution prepared from the sodium carboxymethylcellulose at 25 ℃ is 2500-.

4. The hydrogel of claim 2, wherein the polycarboxylic acid is at least one of malic acid, citric acid, tartaric acid, succinic acid, fumaric acid.

5. The hydrogel of claim 3, wherein the polycarboxylic acid is malic acid.

6. The hydrogel according to claim 5, wherein the weight ratio of the sodium carboxymethyl cellulose to the malic acid is sodium carboxymethyl cellulose: malic acid is 100: 1.

7. a process for the preparation of a hydrogel according to any of claims 1 to 6, comprising the steps of:

(1) dissolving polycarboxylic acid in water to obtain a solution;

8. The method according to claim 7, further comprising, between the step (2) and the step (3), a step A of: drying the micelle at a temperature below 50 ℃ until the water content is reduced to 50-90 wt%.

9. A hydrogel capsule having a laxative function, comprising a gastro-soluble or enteric capsule shell and contents within the capsule shell, the contents comprising the hydrogel of any one of claims 1 to 6, the hydrogel being in the form of dry particles.

10. The hydrogel capsule according to claim 9, wherein the hydrogel has a particle size of not more than 2 mm.