A water-blocking paper bag and its preparation method and application

Abstract

The present invention discloses a water-blocking paper bag and a preparation method and application thereof, belonging to the technical field of paper packaging. The water-blocking paper bag comprises a paper layer and a water-blocking layer, wherein the water-blocking layer is on the inner side of the water-blocking paper bag; wherein the water-blocking layer comprises the following raw materials in parts by weight: 20 to 35 parts of methyl methacrylate, 10 to 15 parts of long-chain alkyl acrylate, 5 to 10 parts of divinylbenzene, 5 to 10 parts of modified polysiloxane, 1 to 2 parts of emulsifier, 0.5 to 1.5 parts of initiator, 2 to 4 parts of buffer and 40 to 60 parts of deionized water, wherein the modified polysiloxane contains an imide bond. The long-chain alkyl and the siloxane chain synergistically construct an effective barrier to the transmission of water molecules, thereby enhancing the ability of the water-blocking layer to resist the intrusion of external water; the dynamic imide bond and divinylbenzene in the modified polysiloxane can help form a microporous structure, which can effectively block water while allowing air molecules to pass relatively freely, thereby obtaining a water-blocking paper bag with good water-blocking property and certain air permeability.

Description

Technical Field

[0001] The invention belongs to the technical field of paper packaging, and in particular relates to a water-blocking paper bag and a preparation method and application thereof. Background Art

[0002] As people's awareness of environmental protection increases and consumers' requirements for product packaging safety and functionality increase, traditional plastic packaging has gradually exposed more and more problems, such as difficulty in degradation, environmental pollution and waste of resources. Paper-based paper bag packaging materials combine the advantages of paper's natural recyclability and are a more environmentally friendly and efficient alternative.

[0003] However, ordinary paper bags are not waterproof and are prone to cracking or breaking when exposed to water, which reduces their strength and makes them easy to be damaged. In order to solve this problem, the most common method is to apply one or more layers of waterproof coating on the surface of paper to prevent water from penetrating. However, it is found that the waterproof paper bags obtained by this method, due to the effect of the waterproof coating, the products inside the packaging, especially food or fruit, are difficult to evaporate during long-term storage. The air is difficult to exchange, which easily causes the internal products to deteriorate, is not conducive to product drying, and is not suitable for some food packaging that needs to maintain a certain humidity and prevent mildew. Summary of the invention

[0004] The object of the present invention is to provide a water-blocking paper bag and a preparation method and application thereof, so as to solve the problem that the paper bag has no waterproof property and is difficult to balance the air permeability.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a water-blocking paper bag, comprising a paper layer and a water-blocking layer, wherein the water-blocking layer is on the inner side of the paper bag; the water-blocking layer comprises the following raw materials in parts by weight:

[0007] 20-30 parts of acrylic acid;

[0008] 20-35 parts of methyl methacrylate;

[0009] 10-15 parts of long chain alkyl acrylate;

[0010] 5-10 parts of divinylbenzene;

[0011] 5-10 parts of modified polysiloxane;

[0012] 1-2 parts of emulsifier;

[0013] 0.5-1.5 parts of initiator;

[0014] 2-4 parts of buffer;

[0015] 40-60 parts of deionized water;

[0016] The modified polysiloxane contains an imine bond.

[0017] Preferably, the emulsifier includes a combination of one or more of ammonium succinate, alkylphenol polyoxyethylene ether, sodium lauryl sulfate and cetyltrimethylammonium bromide.

[0018] Preferably, the initiator comprises a combination of one or more of sodium persulfate, ammonium persulfate and hydrogen peroxide.

[0019] Preferably, the raw material of the paper layer includes one of kraft paper, white cardboard and black cardboard.

[0020] Preferably, the buffer is sodium bicarbonate.

[0021] By adopting the above technical solution, in the water-blocking layer of the water-blocking paper bag of the present invention, a plurality of acrylic monomers are compounded, which can help form a water-blocking layer with better mechanical strength, and is beneficial to prolonging the service life of the water-blocking paper bag.

[0022] The acrylic monomers include long-chain alkyl acrylates. The long alkyl chain segments can help form a densely arranged hydrophobic barrier during the polymerization reaction, which can effectively prevent water molecules from contacting the inside of the water-blocking layer, thereby improving the water barrier properties of the paper bag. In addition, modified polysiloxanes are added to the water-blocking layer. The modified polysiloxanes themselves have very low surface energy and can cooperate with long-chain alkyl acrylates to build a more effective barrier to the transmission of water molecules. The long-chain alkyl groups will be entangled and intertwined to form a network-like structure. The modified polysiloxanes are intertwined in the network structure, which can not only regulate the network structure, but also fill in the pores inside the formed acrylic ester water-blocking layer, thereby improving the compactness of the water-blocking layer and enhancing the ability of the water-blocking layer to resist the intrusion of external water, thereby obtaining a water-blocking paper bag with strong water barrier properties.

[0023] Furthermore, the modified polysiloxane contains imine bonds. As a dynamic bond, the imine bond can form a microporous structure and an open channel inside the water-blocking layer, which can ensure the smooth passage of gas molecules without affecting the blocking effect on liquid water. In addition, the long alkyl chain of the long-chain alkyl acrylate can maintain the good flexibility of the water-blocking layer, which is more conducive to the formation of the microporous structure inside the water-blocking layer and the self-adjustment ability of the imine bond, which can effectively repair the minor damage that may occur to the water-blocking layer during use.

[0024] At the same time, divinylbenzene is also included in the water-blocking layer, which introduces a certain amount of carbon-carbon double bonds into the water-blocking layer, thereby improving the cross-linking of the water-blocking layer and helping to form a denser but not completely closed network structure, thereby effectively blocking moisture while allowing air molecules to pass relatively freely, thereby obtaining a water-blocking paper bag with good water-blocking properties and certain air permeability.

[0025] Preferably, the raw materials of the modified polysiloxane include octamethylcyclotetrasiloxane, aminosilane and benzaldehyde in a mass ratio of 1: (0.1-0.2): (0.05-0.1).

[0026] Preferably, the aminosilane includes one or more of aminopropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane.

[0027] Preferably, the modified polysiloxane is prepared according to the following method:

[0028] After mixing octamethylcyclotetrasiloxane and aminosilane, water and a catalyst are added, and the temperature is increased to 90-105°C in an inert gas atmosphere, and the reaction is carried out for 4-5 hours, and then a prepolymer is obtained by vacuum distillation; the prepolymer and benzaldehyde are added to a solvent, stirred for reaction for 4-6 hours, and modified polysiloxane is obtained by drying, centrifugal separation and precipitation.

[0029] Preferably, the catalyst comprises one or a combination of dimethyl sulfoxide and tetramethylammonium hydroxide pentahydrate.

[0030] Preferably, the inert gas atmosphere includes one of a nitrogen atmosphere and an argon atmosphere.

[0031] Preferably, the solvent comprises one of dichloromethane and toluene.

[0032] By adopting the above technical scheme, the present invention introduces amino groups on the siloxane chain after ring-opening hydrolysis prepolymerization, and then reacts with the aldehyde group of benzaldehyde to obtain a dynamic imine bond, so that the polysiloxane has certain dynamic covalent properties. When subjected to external effects, the network structure thereof can be adjusted through the formation and breaking of imine bonds, thereby improving the service life of the obtained water-blocking paper bag to a certain extent.

[0033] Most importantly, the dynamic imine bond can adjust itself to form partial microporous structures and open channels inside the water-blocking layer, allowing air molecules to pass through smoothly. Moreover, since polysiloxane itself has low surface energy and excellent hydrophobicity, it can effectively prevent moisture from penetrating into the water-blocking paper bag, ensuring good air permeability of the water-blocking paper bag without affecting the water-blocking effect of the water-blocking layer.

[0034] Preferably, the long-chain alkyl acrylate includes a combination of one or more of octadecyl acrylate, octadecyl methacrylate, dodecyl acrylate, dodecyl methacrylate, hexadecyl acrylate and isodecyl acrylate.

[0035] By adopting the above technical solution, the alkyl chain of the long-chain alkyl acrylate is longer and has a stronger non-polar effect. When the water-blocking component is coated on the surface of the paper raw material, it tends to migrate outward and is enriched on the surface of the water-blocking layer, so that the water-blocking layer presents a lower surface energy and exhibits better water-blocking properties. It can also cooperate with the silicon-oxygen chain of the modified polysiloxane in the water-blocking layer to construct a densely arranged hydrophobic barrier, effectively achieving the effect of blocking the passage of water molecules. Moreover, the addition of long-chain alkyl acrylate can improve the flexibility of the water-blocking layer, which is conducive to the dynamic imine bond in the modified polysiloxane to smoothly self-adjust and form micro-channels that are only used for air to pass through, so that the obtained water-blocking paper bag has good water-blocking properties and a certain good air permeability.

[0036] At the same time, the addition of long-chain alkyl acrylate can adjust the interaction between itself and other components, help improve the combination between the water-blocking layer and the paper layer, and increase the bonding force between the water-blocking layer and the paper layer. When the amount of long-chain alkyl acrylate added is reduced, this bonding effect also decreases, and the effect of improving the water-blocking performance of the water-blocking layer also decreases; when the amount of long-chain alkyl acrylate added is increased, not only will the water-blocking layer become too hydrophobic, the adhesion of the water-blocking layer will be greatly reduced, and the mechanical properties will also be affected. In addition, the hydrophobic barrier formed will be too dense, and the network structure formed by the entanglement between the alkyl chains will be arranged more tightly, which will seriously restrict the free movement between other components and cause resistance to the microporous structure formed by the imine bond, which is not conducive to the interaction of gases.

[0037] In a second aspect, the present invention provides a method for preparing a water-blocking paper bag, comprising the following process steps:

[0038] S1. Weigh acrylic acid, methyl methacrylate, long-chain alkyl acrylate, divinylbenzene, modified polysiloxane, emulsifier, buffer and deionized water according to corresponding mass parts, and stir and mix at room temperature for 0.5 to 1 hour to obtain a pre-emulsion;

[0039] S2. In a nitrogen atmosphere, the pre-emulsion temperature was raised to 90-95°C, the initiator was added while stirring, the mixture was kept warm for 2-3 hours, and the mixture was naturally cooled to room temperature to obtain a water-blocking component;

[0040] S3. coating the water-blocking component on one side of the paper raw material, drying it to form a water-blocking layer, and drying it at 30-40° C. to obtain a water-blocking paper bag.

[0041] In a third aspect, the present invention provides an application of a water-blocking paper bag, which is applied to food packaging, fruit bagging and medical machinery packaging.

[0042] By adopting the above technical scheme, the water-blocking paper bag obtained by the present invention has excellent water-blocking performance, which can effectively prevent the products inside the paper bag from being eroded by water vapor, causing corrosion or deterioration of the products. In addition, the water-blocking paper bag of the present invention has a certain degree of air permeability, which can allow air to interact effectively and keep the internal products dry, so as to better store the products.

[0043] Beneficial effects of the present invention:

[0044] 1. The water-blocking paper bag of the present invention comprises a water-blocking layer and a paper layer, wherein a long-chain alkyl acrylate is added to the water-blocking layer, and the long alkyl group can cooperate with the siloxane chain in the modified polysiloxane to construct a more effective barrier to the transmission of water molecules, which can effectively prevent water molecules from contacting the inside of the water-blocking layer, thereby enhancing the ability of the water-blocking layer to resist the intrusion of external moisture, and obtaining a water-blocking paper bag with strong water-blocking properties.

[0045] 2. In the water-blocking layer of the water-blocking paper bag of the present invention, the modified polysiloxane contains a dynamic imine bond, which can form a microporous structure and an open channel inside the water-blocking layer, and under the coordination of the flexible action of the long-chain alkyl group, it is more conducive to the self-adjustment of the imine bond and the formation of micropores. Divinylbenzene is also added to the water-blocking layer, which can improve the cross-linking property of the water-blocking layer and help form a more compact but not completely closed network structure, so that it can effectively block moisture while allowing air molecules to pass relatively freely, so that it can be applied to the packaging and storage of products that need to be waterproof but also need to be kept dry. DETAILED DESCRIPTION

[0046] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] Preparation Example

[0048] Preparation Example 1: A modified polysiloxane is prepared according to the following method:

[0049] After mixing 100 g of octamethylcyclotetrasiloxane and 15 g of aminopropylmethyldiethoxysilane, 2.5 g of water and 1.2 g of tetramethylammonium hydroxide pentahydrate were added, the temperature was raised to 100° C. in an argon atmosphere, the reaction was carried out for 4 hours, and then a prepolymer was obtained by vacuum distillation; the prepolymer and 7 g of benzaldehyde were added to 250 mL of dichloromethane, the reaction was stirred for 5 hours, and the modified polysiloxane was obtained by drying, centrifugal separation and precipitation.

[0050] Preparation Example 2, a modified polysiloxane, is different from Preparation Example 1 only in that the added amount of aminopropylmethyldiethoxysilane is 10 g; the added amount of benzaldehyde is 5 g.

[0051] Preparation Example 3, a modified polysiloxane, is different from Preparation Example 1 only in that the added amount of aminopropylmethyldiethoxysilane is 20 g; the added amount of benzaldehyde is 10 g.

[0052] Preparation Example 4, a modified polysiloxane, is different from Preparation Example 1 only in that the amount of benzaldehyde added is 2 g.

[0053] Preparation Example 5, a modified polysiloxane, is different from Preparation Example 1 only in that the amount of benzaldehyde added is 15 g.

[0054] Preparation Example 6, a modified polysiloxane, prepared according to the following method:

[0055] After mixing 100 g of octamethylcyclotetrasiloxane and 15 g of aminopropylmethyldiethoxysilane, 2.5 g of water and 1.2 g of tetramethylammonium hydroxide pentahydrate were added, the temperature was raised to 100° C. in an argon atmosphere, and the reaction was performed for 4 hours, and then the modified polysiloxane was obtained by vacuum distillation, drying, centrifugal separation and precipitation.

[0056] Example

[0057] Example 1, a water-blocking paper bag is prepared according to the following process steps:

[0058] S1. Weigh 25 parts of acrylic acid, 30 parts of methyl methacrylate, 12 parts of octadecyl acrylate, 8 parts of divinylbenzene, 8 parts of the modified polysiloxane prepared in Preparation Example 1, 2 parts of sodium lauryl sulfate, 3 parts of sodium bicarbonate and 50 parts of deionized water, and stir and mix at room temperature for 0.5h to obtain a pre-emulsion;

[0059] S2. In a nitrogen atmosphere, the pre-emulsion temperature was raised to 95 ° C, 1 part of ammonium persulfate was added while stirring, the mixture was kept warm for 2 h, and naturally cooled to room temperature to obtain a water-blocking component;

[0060] S3. The water-blocking component is coated on one side of the paper raw material, and dried to form a water-blocking layer, and then dried at 35° C. to obtain a water-blocking paper bag, wherein the water-blocking layer is located on the inner side of the water-blocking paper bag.

[0061] Embodiment 2 and Embodiment 3 are water-blocking paper bags. The only difference from Embodiment 1 is that the raw material ratio of the water-blocking layer is adjusted, as shown in Table 1:

[0062]

[0063] Wherein, Example 2 and Example 3 both use the modified polysiloxane prepared in Preparation Example 1.

[0064] Example 4 is a water-blocking paper bag, which is different from Example 1 only in that octadecyl acrylate is replaced by an equal amount of dodecyl methacrylate.

[0065] Example 5, a water-blocking paper bag, is different from Example 1 only in that the modified polysiloxane prepared in Preparation Example 1 is replaced by an equal amount of the modified polysiloxane prepared in Preparation Example 2.

[0066] Example 6, a water-blocking paper bag, is different from Example 1 only in that the modified polysiloxane prepared in Preparation Example 1 is replaced by an equal amount of the modified polysiloxane prepared in Preparation Example 3.

[0067] Example 7, a water-blocking paper bag, is different from Example 1 only in that the modified polysiloxane prepared in Preparation Example 1 is replaced by an equal amount of the modified polysiloxane prepared in Preparation Example 4.

[0068] Example 8, a water-blocking paper bag, is different from Example 1 only in that the modified polysiloxane prepared in Preparation Example 1 is replaced by an equal amount of the modified polysiloxane prepared in Preparation Example 5.

[0069] Comparative Example

[0070] Comparative Example 1 is a water-blocking paper bag, which is different from Example 1 only in that octadecyl acrylate is replaced by an equal amount of methacrylate.

[0071] Comparative Example 2 is a water-blocking paper bag, which is different from Example 1 only in that the added amount of octadecyl acrylate is 5 parts.

[0072] Comparative Example 3 is a water-blocking paper bag, which is different from Example 1 only in that the added amount of octadecyl acrylate is 20 parts.

[0073] Comparative Example 4 is a water-blocking paper bag, which is different from Example 1 only in that octadecyl acrylate is not added.

[0074] Comparative Example 5 is a water-blocking paper bag, which is different from Example 1 only in that divinylbenzene is not added.

[0075] Comparative Example 6 is a water-blocking paper bag, which is different from Example 1 only in that the modified polysiloxane prepared in Preparation Example 1 is replaced by an equal amount of the modified polysiloxane prepared in Preparation Example 6.

[0076] Comparative Example 7 is a water-blocking paper bag, which is different from Example 1 only in that the amount of the modified polysiloxane prepared in Preparation Example 1 added is 2 parts.

[0077] Comparative Example 8 is a water-blocking paper bag, which is different from Example 1 only in that the added amount of the modified polysiloxane prepared in Preparation Example 1 is 15 parts.

[0078] Comparative Example 9 is a water-blocking paper bag, which is different from Example 1 only in that the modified polysiloxane prepared in Preparation Example 1 is replaced by an equal amount of polydimethylsiloxane.

[0079] Comparative Example 10 is a water-blocking paper bag, which is different from Example 1 only in that the modified polysiloxane prepared in Preparation Example 1 is not added.

[0080] Performance testing

[0081] 1. Water barrier test: According to the relevant records in GB / T 1540-2002 "Determination of water absorption of paper and paperboard - Cobber method", the water absorption of the water-blocking paper bags obtained in the examples and comparative examples was tested to characterize the water barrier performance of the obtained paper bags;

[0082] 2. Air permeability test: According to the relevant records in GB / T 458-2008 "Determination of air permeability of paper and paperboard", the air permeability of the water-blocking paper bags obtained in the examples and comparative examples was tested.

[0083] The above test results are shown in Table 2:

[0084]

[0085] According to Table 2, in combination with Example 1, Example 7, Example 8 and Comparative Example 6, it can be seen that the water absorption of Example 7, Example 8 and Comparative Example 6 has increased slightly, and the air permeability has decreased, especially the air permeability of Comparative Example 6 has decreased significantly. The reason is that compared with Example 1, Example 7, Example 8 and Comparative Example 6 change the content of dynamic imine bonds in the modified polysiloxane. When the imine bonds are reduced, the ability of the molecular chains to deform decreases, the network entanglement effect between the long-chain alkyl acrylate decreases, and the ability of the hydrophobic barrier decreases, resulting in a slight decrease in water resistance. When the imine bonds increase, the binding force between the modified polysiloxane molecular chains increases, and the content of polar groups increases, which is not conducive to the improvement of water resistance. In Comparative Example 6, the amino group is not converted into a dynamic imine bond. Due to the addition of polar groups, the binding force between the molecular chains is enhanced, which is difficult to move and cannot form a microporous structure or an open channel structure, which finally leads to a significant decrease in the air permeability of the material.

[0086] Combining Example 1 and Comparative Example 1, it can be seen that the air water absorption of Comparative Example 1 is significantly increased. The reason is that in Comparative Example 1, short-chain acrylate is used to replace long-chain alkyl acrylate, and a hydrophobic barrier cannot be constructed on the surface during the formation of the water-blocking layer, making it difficult to directly block the invasion of water molecules. In addition, the flexibility of the material is also reduced, and the effect of the entangled network structure with the modified polysiloxane is also reduced, resulting in a decrease in the air permeability and water barrier properties of the obtained water-blocking layer.

[0087] Combining Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 4, it can be seen that the air water absorption of Comparative Example 2, Comparative Example 3 and Comparative Example 4 has increased, and the air permeability has decreased. The reason is that the amount of long-chain alkyl acrylate added in Comparative Example 2 is reduced, resulting in a decrease in the arrangement effect of the hydrophobic barrier in the obtained water-blocking layer, and the water barrier property is reduced accordingly. The amount of long-chain alkyl acrylate added in Comparative Example 3 is increased, resulting in the hydrophobic barrier in the obtained water-blocking layer being too dense, and the network structure formed by the entanglement between the alkyl chains is arranged more tightly, which seriously restricts the free movement between other components, causing resistance to the microporous structure formed by the imine bond, and the air permeability of the obtained water-blocking paper bag is significantly reduced. In Comparative Example 4, no long-chain alkyl acrylate is added. On the one hand, the water barrier property is significantly reduced, and on the other hand, the lack of the flexibility of the long-chain alkyl group hinders the formation of the microporous structure, and the air permeability of the obtained paper bag is also reduced.

[0088] Combining Example 1 and Comparative Example 5, it can be seen that the air permeability of Comparative Example 5 is reduced. The reason is that the only difference between Comparative Example 5 and Example 1 is that divinylbenzene is not added in Comparative Example 5. Compared with Example 1, the cross-linked structure of the water-blocking layer formed in Comparative Example 5 is not properly adjusted, and the water-blocking layer cannot be helped to form a denser but not completely closed network structure, allowing the ability of air molecules to pass relatively freely to decrease, and the air permeability of the obtained water-blocking paper bag decreases.

[0089] Combining Example 1 and Comparative Example 9, it can be seen that the air permeability of Comparative Example 9 is significantly reduced. The reason is that the polysiloxane of Comparative Example 9 has not been modified and lacks the regulating effect of dynamic imine, and the air permeability is significantly reduced. However, compared with Comparative Example 5, Comparative Example 9 lacks the introduction of amino polar groups, and the bonding force and cross-linking density between the water-blocking layers will decrease, resulting in an increase in the air permeability compared to Comparative Example 5. At the same time, compared with Comparative Example 5, the decrease in the content of polar groups leads to a slight increase in the water absorption of Comparative Example 9.

[0090] Combining Example 1, Comparative Example 7, Comparative Example 8 and Comparative Example 10, it can be seen that the air permeability of Comparative Example 7, Comparative Example 8 and Comparative Example 10 decreases, and the water absorption increases. The reason is that the amount of modified polysiloxane added is changed in Comparative Example 7, Comparative Example 8 and Comparative Example 10, and the amount of modified polysiloxane added is reduced. It can be clearly seen that with the reduction of polysiloxane, the water barrier performance of the water barrier layer decreases, and no modified polysiloxane is added in Comparative Example 10, and the water barrier performance decreases more significantly, and the content of modified polysiloxane is reduced or not added, lacking the regulating effect of dynamic imine on the water barrier layer, and the reduction of microporous structure will lead to a decrease in the ability of the water barrier layer to allow air molecules to pass through, and a decrease in air permeability. Comparative Example 8 increases the amount of modified polysiloxane added, so the water absorption does not increase too significantly, but due to the increase in polysiloxane molecular chains, the arrangement density of the cross-linked network structure formed in the water barrier layer increases, which is not conducive to the improvement of air permeability.

[0091] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0092] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A water-blocking paper bag, comprising a paper layer and a water-blocking layer, characterized in that: The water-blocking layer is on the inner side of the paper bag; the water-blocking layer comprises the following raw materials in parts by weight: 20-30 parts of acrylic acid; 20-35 parts of methyl methacrylate; 10-15 parts of long chain alkyl acrylate; 5-10 parts of divinylbenzene; 5-10 parts of modified polysiloxane; 1-2 parts of emulsifier; 0.5-1.5 parts of initiator; 2-4 parts of buffer; 40-60 parts of deionized water; The modified polysiloxane contains an imine bond; The raw materials of the modified polysiloxane include octamethylcyclotetrasiloxane, aminosilane and benzaldehyde in a mass ratio of 1: (0.1-0.2): (0.05-0.1).

2. The water-blocking paper bag according to claim 1, characterized in that: The aminosilane includes one or more of aminopropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane.

3. The water-blocking paper bag according to claim 1, characterized in that: The modified polysiloxane is prepared according to the following method: After mixing octamethylcyclotetrasiloxane and aminosilane, water and a catalyst are added, and the temperature is increased to 90-105°C in an inert gas atmosphere, and the reaction is carried out for 4-5 hours, and then a prepolymer is obtained by vacuum distillation; the prepolymer and benzaldehyde are added to a solvent, stirred for reaction for 4-6 hours, and modified polysiloxane is obtained by drying, centrifugal separation and precipitation.

4. The water-blocking paper bag according to claim 1, characterized in that: The long-chain alkyl acrylate includes a combination of one or more of octadecyl acrylate, octadecyl methacrylate, dodecyl acrylate, dodecyl methacrylate, hexadecyl acrylate and isodecyl acrylate.

5. The water-blocking paper bag according to claim 1, characterized in that: The emulsifier includes one or more combinations of ammonium succinate, alkylphenol polyoxyethylene ether, sodium lauryl sulfate and hexadecyltrimethylammonium bromide.

6. The water-blocking paper bag according to claim 1, characterized in that: The initiator includes a combination of one or more of sodium persulfate, ammonium persulfate and hydrogen peroxide.

7. The water-blocking paper bag according to claim 1, characterized in that: The raw material of the paper layer includes one of kraft paper, white card paper and black card paper.

8. A method for preparing a water-blocking paper bag according to any one of claims 1 to 7, characterized in that: The process steps include: S1. Weigh acrylic acid, methyl methacrylate, long-chain alkyl acrylate, divinylbenzene, modified polysiloxane, emulsifier, buffer and deionized water according to corresponding mass parts, and stir and mix at room temperature for 0.5 to 1 hour to obtain a pre-emulsion; S2. In a nitrogen atmosphere, the pre-emulsion temperature was raised to 90-95°C, the initiator was added while stirring, the mixture was kept warm for 2-3 hours, and the mixture was naturally cooled to room temperature to obtain a water-blocking component; S3. coating the water-blocking component on one side of the paper raw material, drying it to form a water-blocking layer, and drying it at 30-40° C. to obtain a water-blocking paper bag.

9. An application of a water-blocking paper bag according to any one of claims 1 to 7, characterized in that: The water-blocking paper bag is applied to food packaging, fruit bagging and medical machinery packaging.

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