A sponge product and its preparation method

Abstract

The present invention relates to a sponge product and a preparation method thereof. The method includes: 1) pre-treating plant fibers to obtain pre-treated fibers; 2) reacting the pre-treated fiber dispersion with acrylic monomers until floccules are formed, then adjusting the pH value and adding water for volume expansion to obtain a gel sponge body; 3) performing thermal drying and shaping to obtain a shaped prefabricated sponge body; 4) softening the shaped prefabricated sponge body in water, filtering and drying to obtain the sponge product. The present invention can realize the preparation of a natural fiber-like sponge with very few raw material auxiliaries, endow it with the characteristics of high affinity and high softness of natural sponges, and at the same time enhance its durability and cleaning power.

Description

Technical Field

[0001] The present invention relates to the technical field of sponge products, and particularly to a sponge product and a preparation method thereof. Background Art

[0002] Sponge is a very common and commonly used product for cleaning. It is mostly used for cleaning kitchen utensils or the human body. These two uses have significantly different requirements for sponges. For example, cleaning kitchen utensils usually requires higher durability of the sponge, with higher hardness and sponge density to improve the cleaning effect. For cleaning the human body, higher requirements are placed on affinity and softness.

[0003] Therefore, at present, most sponge products for cleaning are divided into synthetic sponges and natural sponges. Synthetic sponges have characteristics such as low cost, high cost performance, usually stronger durability, and relatively higher hardness, and are used for cleaning kitchen utensils. Natural sponges have higher affinity for the human body, are softer, and are less likely to cause damage to the human epidermis or cause allergies, and are commonly used for cleaning the human body. However, with the development of natural sponges and the increasing demand for the safety of cleaning sponges, more and more natural sponges are now used for cleaning kitchen utensils.

[0004] However, most of the existing natural sponges for cleaning kitchen utensils are wood pulp sponges or bamboo fiber sponges. In the processing process, to solve the defects that wood pulp sponges are prone to mildew, bamboo fiber sponges have poor wear resistance and short service life, and the problem that it is difficult for wood pulp fibers and bamboo fibers to effectively construct a sponge body with a rich pore structure by themselves, a large amount of auxiliaries and regulators are mostly used to assist in foaming to construct the sponge body through auxiliaries, regulators, etc., and a large amount of adhesives are used. The actual safety and softness are relatively limited, and the water retention property is also relatively poor, prone to water loss and drying, and the adsorption and dispersion ability of water and detergent is insufficient, and the actual cleaning effect is also relatively limited. Therefore, for natural fiber sponges, there is an urgent need to optimize and improve their performance. And in terms of the current process, there are also some processes that modify plant fibers to make them have the durability of synthetic fibers, but it only enhances the durability and is difficult to effectively retain the original advantages of natural fibers such as softness and high affinity. Summary of the Invention

[0005] To solve the problems that the existing synthetic fiber sponge products have better durability and cleaning ability, but poor safety and softness, while the natural fiber sponge products have good safety and softness, but limited cleaning ability, and the existing modified natural fiber sponge products also have many deficiencies, the present invention provides a sponge product and a preparation method thereof.

[0006] The main purpose of the present invention is:

[0007] 1. Directly construct a lightweight and high-structural-density sponge product with a synthetic fiber-like sponge using natural plant fibers as raw materials;

[0008] 2. The sponge product can maintain the safety and softness advantages of natural fiber sponges, and at the same time has good durability and cleaning ability;

[0009] 3. The preparation method is simple and efficient, suitable for industrial mass production.

[0010] To achieve the above objectives, the present invention adopts the following technical solutions.

[0011] A preparation method of a sponge product,

[0012] The method includes:

[0013] 1) Adding plant fibers to an aqueous hydrogen peroxide solution, swelling fully, and then filtering to separate the liquid to obtain pretreated fibers;

[0014] 2) Dispersing the pretreated fibers in water, adding acrylic acid monomers, stirring and reacting until floccules are formed, then quickly adding an alkali solution to adjust the pH value to 6-8, and adding water for volume expansion to form a gel sponge body;

[0015] 3) Placing the gel sponge body in methanol for displacement washing, and finally performing heat drying and solidification to obtain a solidified prefabricated sponge body;

[0016] 4) Placing the solidified prefabricated sponge body in excess water for ultrasonic washing until the sponge body is softened, then filtering and drying to obtain the sponge product.

[0017] Preferably,

[0018] The plant fibers in step 1) are wood fiber powder and / or bamboo fiber powder with a mesh number ≥ 80 meshes;

[0019] The concentration of the aqueous hydrogen peroxide solution in step 1) is 25-35 wt%;

[0020] The mass ratio of the plant fibers to the aqueous hydrogen peroxide solution in step 1) is 1: (2.75-3.25).

[0021] Preferably,

[0022] The full swelling in step 1) is carried out under the conditions of 20-25 °C for 30-60 min.

[0023] Preferably,

[0024] When dispersing the pretreated fibers in water in step 2), the mass ratio of the pretreated fibers to water is 1: (1.2-1.8);

[0025] In step 2), the amount of the acrylic monomer used is (0.8 - 1.2) g / g of the pretreated fiber.

[0026] Preferably,

[0027] In step 2), the reaction temperature during the stirring reaction process is controlled at 45 - 55 °C;

[0028] In step 2), the duration of the stirring reaction is 210 - 270 min.

[0029] Preferably,

[0030] In step 2), the lye is an aqueous sodium hydroxide solution with a concentration of 18 - 22 wt%;

[0031] In step 2), the amount of water used in the volume expansion process by adding water is (20 - 30) mL / g of the pretreated fiber.

[0032] Preferably,

[0033] In step 3), the heat drying and solidifying is carried out under the condition of 60 - 70 °C for 2 - 3 h.

[0034] Preferably,

[0035] In step 4), the excess water is water with a volume 3 - 5 times that of the solidified prefabricated sponge body.

[0036] A sponge product.

[0037] For the technical solution of the present invention, the most core technology lies in the combination of acrylic monomer and plant fiber, and the preparation of the sponge product is realized in a way similar to the modification of plant fiber. However, the difference is that the present invention only uses very few types of materials, greatly reducing the introduction of auxiliaries and regulators such as foaming agents and initiators, improving the safety and environmental protection of the sponge product, and at the same time largely retaining the original structural characteristics of the plant fiber, so that the plant fiber maintains good flexibility and the porous characteristics on the fiber surface, in order to improve the cleaning effect of the sponge product.

[0038] In this regard, the present invention first needs to effectively pretreat the plant fiber, and the pretreatment of the present invention is mainly carried out by treating it with an excessive amount of hydrogen peroxide aqueous solution at room temperature.

[0039] In this treatment process, the actual hydrogen peroxide plays a certain role as an initiator, which can make the plant fiber powder swell and expand to form filamentous fibers. At the same time, with the help of the strong oxidizing property of hydrogen peroxide, a large number of free radicals RO· are generated in the pretreatment system, thereby enabling the pretreated plant fiber to have a strong reactivity and be grafted with acrylic acid. This is also a relatively common pretreatment method used in the synthesis process of acrylic cellulose. However, for the present invention, unlike the common acrylic cellulose synthesis process which requires a pretreatment of at least 50 to 80 °C, the present invention needs to control the pretreatment temperature to be strictly within a relatively low range of 20 to 25 °C, because the use of low temperature combined with an excess of hydrogen peroxide aqueous solution can greatly improve the reactivity of the plant fiber, but can also avoid the generation of too many free radicals to stimulate the long-chain polymerization of acrylic monomers. The long-chain polymerization of acrylic monomers to form polyacrylic acid polymers with high polymerization degree and high crosslinking degree is not conducive to the preparation of the sponge product of the present invention.

[0040] This involves the second important technical point of the present invention, namely, the control of the acrylic acid polymerization process. To control the polymerization process and the properties of the polymerization product (and its derivatives, such as polyacrylic acid resin and sodium polyacrylate, etc.), the present invention firstly can directly use acrylic acid among a large number of acrylic acid monomers for free radical polymerization, because other acrylic acid monomers such as methyl methacrylate, ethyl acrylate or lauryl ester and other common acrylic acid monomers will cause the properties of the polymer to change, while the present invention needs to strictly control the crosslinking degree and polymer of the acrylic acid polymer, and these common monomers are not conducive to the control of the process.

[0041] In the reaction process between the pretreated fiber and acrylic acid of the present invention, the actual acrylic acid plays the role of "adhesive" to link the activated plant fiber with extremely strong reactivity, so that it can form a cross-linked flocculent while retaining the microstructure of the original plant fiber as much as possible, so that it maintains good affinity and flexibility to the human body. At the same time, the pretreated fiber after pretreatment also acts as an "initiator", which can promote its own grafting reaction with acrylic acid to cross-link and construct the basis of the sponge foam structure, and at the same time can stimulate acrylic acid to copolymerize to form a water-absorbent polymer, forming an interpenetrating network, and generating a supporting effect from the inside to the outside to expand the plant fiber outward to form a gel sponge with a certain hardness.

[0042] The subsequent treatment process is another important technical core of the present invention. During the research and development process, technicians found that under certain conditions, the polyacrylic acid fiber formed in the gel sponge is a polymer with very low polymerization degree and cross-linking degree, and the special polyacrylic acid fiber formed can be removed by "water washing", but before removal, it can play a good interpenetrating support role and overcome the thermal shrinkage problem of natural fiber sponge during the initial drying and curing process. Because whether it is wood fiber sponge or bamboo fiber sponge, or even higher-end bacterial cellulose sponge, it will produce irreversible volume shrinkage during the initial thermal drying process, and the thickness change rate before and after drying can even be as high as about 51-79%. This is mainly because the molecular structure of plant cellulose contains a large number of hydroxyl groups. These hydroxyl groups will form hydrogen bonds with water molecules in a wet state, making the fiber have a certain expansibility, but in the thermal drying process, the water is removed, and the hydrogen bonds between the cellulose molecular chains are rearranged, causing the molecular chains to become more compact and orderly. This structural change is irreversible, which leads to the shrinkage of the fiber sponge. Therefore, natural fiber sponges or foams need to be initially dried and solidified by freeze drying, which is costly, but this is obviously not suitable for the manufacture of cleaning sponges.

[0043] However, in the technical solution of the present invention, the plant fiber-acrylic cellulose network composed of plant fiber and acrylic acid and the polyacrylic acid fiber network form an interpenetrating support, which can inhibit the narrowing and shrinkage of the cellulose molecular chain during the heat drying process, and the surface of the polyacrylic acid fiber also contains abundant carboxyl hydroxyl groups, which can effectively stabilize the arrangement of the cellulose molecular chains through hydrogen bonding. After the initial heat drying, the plant cellulose tends to be stable, which can effectively maintain the light and flexible state of the sponge product.

[0044] Therefore, the present invention needs to ensure that in step 2), two main reaction processes, namely, grafting of plant fiber with acrylic acid and short-chain polymerization of acrylic acid, can occur. Therefore, in addition to controlling the aforementioned plant fiber pretreatment process, attention must also be paid to the reaction temperature. The present invention adopts a lower reaction temperature in order to suppress the long-chain polymerization of acrylic acid as much as possible.

[0045] After completing the initial heat drying and solidification of the gel sponge, the present invention further uses excess water for ultrasonic dissolution to achieve the "dissolution" of the low-polymerization degree and low-crosslinking degree acrylic acid polymer, so that it is converted into a low-viscosity colloid state or even almost completely dissolved, and separated from the sponge product, thereby realizing the preparation of the target sponge product.

[0046] The beneficial effects of the present invention are:

[0047] The present invention can achieve the preparation of a natural fiber-like sponge with very few raw material additives, endowing it with the characteristics of high affinity and high softness of natural sponges, while enhancing its durability and cleaning power. The preparation process is simple, efficient, greener and safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 Figure 1 is a 20x optical microscope photograph of a commercially available wood pulp sponge in a dry state;

[0049] Figure 2 Figure 2 is a 20x optical microscope photograph of a commercially available wood pulp sponge after water absorption;

[0050] Figure 3 Figure 3 is a 20x optical microscope photograph of the sponge product prepared in Example 1 of the present invention in a dry state;

[0051] Figure 4 Figure 4 is a 20x optical microscope photograph of the sponge product prepared in Example 1 of the present invention after water absorption;

[0052] Figure 5 Figure 5 is an SEM characterization diagram of the sponge product prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0053] The present invention will be further clearly and detailedly described below with reference to specific examples. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following descriptions are usually only a part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0054] Unless otherwise specified, the raw materials used in the embodiments of the present invention are all commercially available or raw materials that can be obtained by those skilled in the art; unless otherwise specified, the methods used in the embodiments of the present invention are all methods mastered by those skilled in the art.

[0055] Example 1

[0056] A method for preparing a sponge product,

[0057] The method includes:

[0058] 1) Mix 80-mesh wood fiber powder and 120-mesh bamboo fiber powder in a mass ratio of 1:1, add them to an aqueous hydrogen peroxide solution with a mass concentration of 30 wt% that is 3 times their mass, and fully impregnate and swell at 22 ± 1 °C for 50 min, then filter to separate the liquid to obtain pretreated fibers;

[0059] 2) Disperse the pretreated fibers into pure water with a mass 1.5 times that of the fibers, add acrylic acid with the same mass as the pretreated fibers, stir and react at 50 °C for 4 h until a flocculent substance is formed, then quickly add a 20 wt% aqueous sodium hydroxide solution within 2 min to adjust the pH value to 6.8, and add pure water for volume expansion according to the ratio of 25 mL of pure water per gram of pretreated fibers, and cut into block-shaped cuboids to obtain a gel sponge;

[0060] 3) Immerse the gel sponge in anhydrous methanol and perform ultrasonic treatment for 15 min for solvent replacement immersion washing, and finally perform thermal drying at 65 °C for 2.5 h to complete solidification to obtain a solidified prefabricated sponge;

[0061] 4) Place the solidified prefabricated sponge in pure water with a volume 5 times that of the sponge and perform ultrasonic immersion washing for 60 min, repeat the ultrasonic immersion washing 3 times until the sponge is completely softened, then filter and dry at 60 °C for 12 min to obtain a sponge product.

[0062] Among them, the sizes of the gel sponge, the solidified prefabricated sponge and the target product sponge are measured and recorded, and the volume shrinkage rates during the solidification process and during the drying process after washing away the internal support acrylic polymer network are calculated. Only taking the thickness as the standard, in step 2) of this example, the cutting process controls the average thickness of the gel sponge to be about 3.8 cm, the average thickness of the solidified prefabricated sponge obtained after thermal drying and solidification is about 3.65 cm, and the average thickness of the finally obtained sponge product is about 3.58 cm. It can be seen that the natural fiber-like sponge product of the present invention has extremely high structural stability, will not shrink excessively due to water loss, and after 100 saturated water absorption and drying cycles, the average thickness of the sponge product still remains at 3.53 cm, that is, the thickness change rate ≤ 1.39%. It shows very excellent structural stability and excellent durability.

[0063] In addition, during the above cycle process, the present invention also performs optical microscopic characterization on the dry state and the sponge after water absorption (after saturated water absorption, the water is squeezed out until it no longer drips, but the touch still remains significantly wet, the same below), and compares it with a commercially available cleaning wood pulp sponge. The optical microscopic characterization diagram of the cleaning wood pulp sponge in the dry state is as Figure 1 shown, and the optical microscopic characterization diagram of the cleaning wood pulp sponge after water absorption is as Figure 2 shown. From Figure 1 and Figure 2It can be clearly seen from the comparison that obvious structural changes occur in the commercially available wood pulp sponge in the dry state and after water absorption. After water absorption, the plant fibers "swell" due to hydrogen bonding, but shrink again after drying and water loss. Inevitably, structural collapse will occur during use. For example, in the saturated water absorption and drying cycle test, the thickness change rate of the commercially available cleaning wood pulp sponge reaches about 8.3% after 80 cycles, and this thickness change is irreversible. The optical micrographs of the sponge product of the present invention in the dry state and after water absorption are respectively as Figure 3 and Figure 4 shown. There is almost no change in its structure in the dry state and after water absorption, which also shows its extremely high structural stability. Moreover, the results of the water absorption-drying cycle test also show that the sponge product of the present invention has extremely strong durability. In addition, the sponge product prepared in this example was characterized by an electron microscope, and the characterized structure is as Figure 5 shown. It can be clearly seen from Figure 5 that the fibers of the sponge product of the present invention retain the surface porosity of natural plant fibers, which endows it with ultra-high water absorption that synthetic fibers do not have. At the same time, it also shows that although the preparation process of the present invention seems to be similar to the preparation process of modified cellulose, the structure of the plant fibers themselves is still largely retained, which ensures its good affinity and water absorption.

[0064] Based on the above, the common properties of the sponge product were also characterized and compared with commercially available wood pulp sponges and synthetic fiber sponges respectively. The sponges used in the comparison are of the same size specification. The characterization results are shown in the following table.

[0065] Table 1: Results of performance standards.

[0066]

[0067] In the table: Due to the dry hardening characteristics of the wood pulp sponge, the tensile strength and elongation at break are both tested and characterized under the condition of water absorption; the thousand-time wear rate is to immerse one side of the sponge to be tested in pure water, and press a 3 kg counterweight on the wetted surface on a platform of the same material (304 stainless steel platform), and reciprocate friction 1000 times at the same rate, with a single friction distance of 10 cm. Measure and record the mass before and after friction and calculate the mass loss rate after friction, which is recorded as the thousand-time wear rate.

[0068] It can be clearly seen from the above characterization results that the sponge product of the present invention has a lower density compared to commercially available wood pulp sponges, with an obvious low-density characteristic. Its tensile strength and elongation at break are significantly better than those of commercially available wood pulp sponges, that is, natural fiber sponges, and are close to those of synthetic fiber sponges. Moreover, the difference between the dry hardness and the water absorption hardness is small, and the water absorption hardness is much higher than that of commercially available wood pulp sponges, and is already relatively close to that of commercially available synthetic fiber sponges. This endows it with very excellent cleaning ability because the hardness of the sponge after water absorption is a key parameter determining its cleaning ability. Regarding the previous wear rate, due to the flexibility of natural plant fibers themselves, its wear rate is much lower than that of synthetic fiber sponges, similar to that of commercially available wood pulp sponges, and the wear debris is not the plastic component of synthetic fiber sponges, but the safer natural fiber component. This makes the sponge product of the present invention also have extremely high use safety.

[0069] Example 2

[0070] A preparation method of a sponge product,

[0071] The method includes:

[0072] 1) Mix 80-mesh wood fiber powder and 120-mesh bamboo fiber powder in a mass ratio of 2:1, add them to an aqueous hydrogen peroxide solution with a mass concentration of 30 wt% that is 3 times their mass, fully immerse and swell at 22 ± 1 °C for 50 min, and then filter to separate the liquid to obtain pretreated fibers;

[0073] 2) Disperse the pretreated fibers in pure water with a mass 1.5 times that of the pretreated fibers, add acrylic acid with the same mass as the pretreated fibers, stir and react at 50 °C for 4 h until flocculates are formed, then quickly add a 20 wt% sodium hydroxide aqueous solution within 2 min to adjust the pH value to 7.0, and add pure water for volume expansion according to the ratio of 25 mL of pure water per gram of pretreated fibers, and cut into block-shaped cuboids to obtain a gel sponge body;

[0074] 3) Immerse the gel sponge body in anhydrous methanol and perform ultrasonic treatment for 15 min for solvent replacement leaching, and finally perform thermal drying at 65 °C for 2.5 h to complete solidification to obtain a solidified prefabricated sponge body;

[0075] 4) Place the solidified prefabricated sponge body in pure water with a volume 5 times that of the sponge body and perform ultrasonic leaching for 60 min, repeat the ultrasonic leaching 3 times until the sponge body is completely softened, then filter and dry at 60 °C for 12 min to obtain the sponge product.

[0076] Perform the same characterization on the sponge product prepared in this example as in Example 1. The characterization results are shown in the following table.

[0077] Table 2: Performance standard results.

[0078]

[0079] It can be clearly seen from the above characterization results that the sponge products prepared in this example also have good performance, good durability and cleaning ability, and at the same time have the safety of natural fiber sponges.

[0080] Comparative Example 1

[0081] A preparation method of a sponge product,

[0082] The method includes:

[0083] 1) Mix 80-mesh wood fiber powder and 120-mesh bamboo fiber powder in a mass ratio of 1:1, add them to an aqueous hydrogen peroxide solution with a mass concentration of 30 wt% three times its mass, and fully impregnate and swell at 55 ± 1.5 °C for 50 min, then filter to separate the liquid to obtain pretreated fibers;

[0084] 2) Disperse the pretreated fibers in pure water with a mass 1.5 times that of the pretreated fibers, add acrylic acid with the same mass as the pretreated fibers, stir and react at 50 °C for 4 h until flocs are formed, then quickly add a 20 wt% sodium hydroxide aqueous solution within 2 min to adjust the pH value to 6.8, and add pure water in a ratio of 25 mL of pure water per gram of pretreated fibers for volume expansion, and cut into block-shaped cuboids to obtain a gel sponge body;

[0085] 3) Immerse the gel sponge body in anhydrous methanol and perform ultrasonic treatment for 15 min for solvent replacement washing, and finally perform thermal drying at 65 °C for 2.5 h to complete solidification to obtain a solidified prefabricated sponge body;

[0086] 4) Place the solidified prefabricated sponge body in pure water with a volume 5 times that of the sponge body and perform ultrasonic washing for 60 min, repeat the ultrasonic washing 3 times until the sponge body is completely softened, then filter and dry at 60 °C for 12 min to obtain a sponge product.

[0087] Perform the same characterization on the sponge products prepared in this example as in Example 1. The characterization results are shown in the following table.

[0088] Table 3: Performance standard results.

[0089]

[0090] From the above characterization results, compared with Example 1, almost all properties of this example have been improved except for the thousand - time wear rate. However, this is not actually what the present invention requires. Because in the product prepared in this example, the mass ratio of the product quality to the mass of the plant fibers used (total mass of wood fiber powder and bamboo fiber powder) is approximately 1.37:1, while in Example 1, the mass ratio of the product quality to the mass of the plant fibers used (total mass of wood fiber powder and bamboo fiber powder) is approximately 1.09:1. It can be seen that the sponge product prepared in this example contains a large amount of acrylic polymers and their derivatives, which does not meet the purpose of the natural - fiber - like sponge with high use safety and environmental friendliness to be prepared by the present invention. Its thousand - time wear rate has also increased significantly, indicating that it contains more synthetic fiber components that are prone to wear and fall off.

[0091] This is mainly because the excessive pretreatment temperature causes more free radicals to be formed in the pretreated fibers, resulting in the polymerization of acrylic acid to form long chains and a higher degree of cross - linking. During the subsequent "water washing" process, the removal difficulty increases, and it is even impossible to remove. This does not conform to the original intention of the present invention.

[0092] Comparative Example 2

[0093] A preparation method of a sponge product,

[0094] The method includes:

[0095] 1) Mix 80 - mesh wood fiber powder and 120 - mesh bamboo fiber powder in a mass ratio of 1:1, add them to an aqueous hydrogen peroxide solution with a mass concentration of 30 wt% three times their mass, and fully immerse and swell at 22 ± 1 °C for 50 min, then filter to separate the liquid to obtain pretreated fibers;

[0096] 2) Disperse the pretreated fibers in pure water with a mass 1.5 times that of the pretreated fibers, add acrylic monomers with the same mass as the pretreated fibers (acrylic acid and lauryl methacrylate are mixed in a mass ratio of 1:0.1), stir and react at 50 °C for 4 h until a flocculent substance is formed. Then, quickly add a 20 wt% sodium hydroxide aqueous solution within 2 min to adjust the pH value to 6.8, and add pure water for volume expansion according to the ratio of 25 mL of pure water per gram of pretreated fiber, and cut into block - shaped cuboids to obtain a gel sponge body;

[0097] 3) Immerse the gel sponge body in anhydrous methanol and perform ultrasonic treatment for 15 min for solvent replacement leaching, and finally perform thermal drying at 65 °C for 2.5 h to complete solidification to obtain a solid - shaped pre - formed sponge body;

[0098] 4) Place the solid - shaped pre - formed sponge body in pure water with a volume 5 times that of the sponge body and perform ultrasonic leaching for 60 min, repeat the ultrasonic leaching 3 times until the sponge body is completely softened, then filter and dry at 60 °C for 12 min to obtain the sponge product.

[0099] The sponge product prepared in this example was characterized in the same manner as in Example 1. The characterization results are shown in the following table.

[0100] Table 4: Performance criteria results.

[0101]

[0102] It can be clearly seen from the above characterization results that the sponge product prepared in this example is similar to the product of Comparative Example 1, and its performance is actually better than that of the product of Example 1 in many aspects. However, similarly, the mass ratio of its product mass to the mass of the plant fiber used (total mass of wood fiber powder and bamboo fiber powder) is about 1.41:1, which is even higher than that of Comparative Example 1. This is mainly due to the use of lauryl methacrylate as one of the monomers in this example, which significantly improves the water resistance of acrylic polymers and their derivatives, making them difficult to remove by washing, and also leaving more synthetic fiber components, which does not meet the original intention of the research and development of the present invention.

[0103] Comparative Example 3

[0104] A method for preparing a sponge product,

[0105] The method comprises:

[0106] 1) 80 mesh wood fiber powder and 120 mesh bamboo fiber powder were mixed in a mass ratio of 1:1, added into a 30 wt% hydrogen peroxide aqueous solution, fully immersed and swollen at 22±1 ℃ for 50 min, and then the liquid was separated by filtration to obtain pretreated fiber;

[0107] 2) The pretreated fibers were dispersed in pure water 1.5 times their mass, and acrylic acid of the same mass as the pretreated fibers was added. The mixture was stirred at 65 °C for 4 h to form flocs. A 20 wt% aqueous sodium hydroxide solution was quickly added within 2 min to adjust the pH value to 6.8. Pure water was added at a ratio of 25 mL of pure water per gram of pretreated fibers to expand the volume, and the pretreated fibers were cut into block-shaped rectangular blocks to obtain a gel sponge.

[0108] 3) The gel sponge was immersed in anhydrous methanol and ultrasonically treated for 15 min to perform solvent replacement and washing, and finally, it was thermally dried at 65°C for 2.5 h to complete solidification, thereby obtaining a solid prefabricated sponge;

[0109] 4) The solid prefabricated sponge was placed in pure water with a volume 5 times its own for ultrasonic immersion for 60 min. The ultrasonic immersion was repeated 3 times until the sponge was completely softened, and then filtered and dried at 60 °C for 12 min to obtain a sponge product.

[0110] The sponge product prepared in this example was characterized in the same manner as in Example 1. The characterization results are shown in the following table.

[0111] Table 5: Performance criteria results.

[0112]

[0113] It can be clearly seen from the above characterization results that the sponge product prepared in this example is similar to the products of Comparative Examples 1 and 2, and its performance in many properties is actually close to or even better than the product of Example 1, but similarly, the mass ratio of its product mass to the mass of the plant fiber used (total mass of wood fiber powder and bamboo fiber powder) is about 1.18:1, which is much higher than that of Example 1. This is mainly due to the use of a higher free radical polymerization reaction temperature in this example, which increases the chain length and polymer of the acrylic acid polymer and its derivatives, making it difficult to wash and remove, and also leaves more synthetic fiber components, which does not meet the original intention of the research and development of the present invention.

[0114] Comparative Example 4

[0115] A method for preparing a sponge product,

[0116] The method comprises:

[0117] 1) 80 mesh wood fiber powder and 120 mesh bamboo fiber powder were mixed in a mass ratio of 1:1, added into a 30 wt% hydrogen peroxide aqueous solution, fully immersed and swollen at 22±1 ℃ for 50 min, and then the liquid was separated by filtration to obtain pretreated fiber;

[0118] 2) The pretreated fibers were dispersed in pure water 1.5 times their weight, and acrylic acid 0.2 times the weight of the pretreated fibers was added. The mixture was stirred at 50 °C for 4 h to form flocs. A 20 wt% sodium hydroxide aqueous solution was quickly added within 2 min to adjust the pH value to 6.8. Pure water was added at a ratio of 25 mL of pure water per gram of pretreated fibers to expand the volume, and the pretreated fibers were cut into block-shaped rectangular blocks to obtain a gel sponge.

[0119] 3) The gel sponge was immersed in anhydrous methanol and ultrasonically treated for 15 min to perform solvent replacement and washing, and finally, it was thermally dried at 65°C for 2.5 h to complete solidification, thereby obtaining a solid prefabricated sponge;

[0120] 4) The solid prefabricated sponge was placed in pure water with a volume 5 times its own for ultrasonic immersion for 60 min. The ultrasonic immersion was repeated 3 times until the sponge was completely softened, and then filtered and dried at 60 °C for 12 min to obtain a sponge product.

[0121] The sponge product prepared in this example was characterized in the same manner as in Example 1. The characterization results are shown in the following table.

[0122] Table 6: Performance standard results.

[0123]

[0124] It can be clearly seen from the above characterization results that the sponge products prepared in this example perform more similarly to the performance of wood pulp sponges in terms of performance. The density and tensile strength increase compared to Example 1, the elongation at break decreases compared to Example 1, and there is a large gap between the dry hardness and the water absorption hardness, showing an obvious dry hardening phenomenon. This is mainly because the present invention uses less acrylic monomer, which only plays the role of an "adhesive", and the mass ratio of its product quality to the mass of the plant fibers used (the total mass of wood fiber powder and bamboo fiber powder) is about 1.08:1, close to Example 1. During the preparation process, in step 2) of this example, the average thickness of the gel sponge body is controlled to be about 3.8 cm during the cutting process, the average thickness of the solidified prefabricated sponge body obtained after heat drying and solidification is about 3.01 cm, and the average thickness of the finally obtained sponge product is about 2.93 cm. The thickness shrinkage rate is much higher than that of Example 1, reaching about 22.9%. Combining with the aforementioned Comparative Examples 1 to 3, it can be clearly seen that the present invention adopts the form of appropriately using acrylic acid and controlling its proper polymerization, which can play a supporting role during the heat drying and solidification process. At the same time, the polymers and their derivatives formed under appropriate polymerization conditions can be easily washed off with water to ensure that the sponge products of the present invention have the characteristics similar to natural fiber sponges but also have better use performance.

Claims

1. A method for preparing a sponge product, characterized in that: The method comprises: 1) adding plant fiber into aqueous hydrogen peroxide solution to fully swell the fiber, and then filtering and separating the liquid to obtain pretreated fiber; 2) Dispersing the pretreated fibers in water, adding acrylic acid monomer, stirring and reacting until flocs are formed, then quickly adding alkali solution to adjust the pH value to 6-8 and adding water to expand the volume into a gel sponge; 3) placing the gel sponge in methanol for displacement immersion and finally performing heat drying to solidify, thereby obtaining a solid prefabricated sponge; 4) placing the solid prefabricated sponge in excess water and ultrasonically washing it until the sponge softens, then filtering and drying it to obtain a sponge product; Step 1) The sufficient swelling is performed by swelling and immersing at 20 to 25°C for 30 to 60 minutes; Step 2) the acrylic acid monomer is used in an amount of (0.8-1.2) g / g pretreated fiber; Step 2) the reaction temperature during the stirring reaction is controlled to be 45-55°C; Step 2) The stirring reaction time is 210 to 270 min.

2. The method for preparing a sponge product according to claim 1, characterized in that: Step 1) the plant fiber is wood fiber powder and / or bamboo fiber powder with a mesh size of ≥80 mesh; Step 1) The concentration of the aqueous hydrogen peroxide solution is 25-35 wt%; In step 1), the mass ratio of the plant fiber to the aqueous hydrogen peroxide solution is 1:(2.75-3.25).

3. The method for preparing a sponge product according to claim 1, characterized in that: In step 2), when the pretreated fibers are dispersed in water, the mass ratio of the pretreated fibers to water is 1:(1.2-1.8).

4. The method for preparing a sponge product according to claim 1, characterized in that: Step 2) the alkali solution is a sodium hydroxide aqueous solution with a concentration of 18 to 22 wt%; In step 2), the amount of water added for volume expansion is (20-30) mL / g pretreated fiber.

5. The method for preparing a sponge product according to claim 1, characterized in that: Step 3) The heat drying solidification is carried out at 60-70°C for 2-3 hours.

6. The method for preparing a sponge product according to claim 1, characterized in that: Step 4) The excess water is 3 to 5 times the volume of the solid preformed sponge.

7. A sponge product obtained by the method according to any one of claims 1 to 6.

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