Moisture-proof coating liquid, moisture-proof coating paper containing moisture-proof coating liquid, preparation method of moisture-proof coating paper and packaging bag

Abstract

The invention belongs to the technical field of paper preparation, and particularly relates to moisture-proof coating liquid, moisture-proof coating paper containing the coating liquid, a preparation method and a packaging bag. The moisture-proof coating liquid comprises a surface coating liquid, and the surface coating liquid comprises 55-65 parts by weight of water, 15-25 parts by weight of polyacrylate, 5-15 parts by weight of polyurethane, 4-8 parts by weight of wax, 1-3 parts by weight of a water repellent agent and 1-3 parts by weight of other auxiliaries. The moisture-proof coating liquid provided by the invention can replace a plastic film to be coated on the surface of a paper base material to form a layer of compact moisture-proof coating, so that the paper has moisture-proof performance, and the paper with the moisture-proof performance is used for manufacturing a moisture-proof paper bag; compared with a paper bag formed by combining common paper / plastic films, the packaging material has the same effects of easiness in canning, easiness in exhausting and moisture prevention, and a packaging product is easy to recycle after being used and can directly enter a paper recycling and pulping system, so that the easy-to-recycle and easy-to-regenerate performance of the packaging material is greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of paper preparation, and in particular relates to a moisture-proof coating liquid, moisture-proof coated paper containing the coating liquid, a preparation method and a packaging bag. Background Art

[0002] Paper packaging products are increasingly being used in the packaging field due to their recyclable and easily degradable properties. Paper packaging bags have the characteristics of reasonable structure, high-speed filling, environmentally friendly materials, and beautiful appearance. With some special designs such as adding a plastic barrier layer, they can achieve functions such as barrier preservation and moisture-proof. They have been widely used in the fields of chemical industry, food, building materials, and medicine, especially for powder and granular materials, which can achieve clean, high-precision filling and highly automated operations throughout the entire process.

[0003] As the application fields of packaging products are further expanded, the requirements for packaging materials are getting higher and higher, especially some products have more stringent requirements on the moisture-proof performance of packaging materials. However, due to the poor barrier effect of paper against water vapor, the moisture-proof performance of paper packaging bags is limited. In the use scenarios with high moisture-proof requirements, it is necessary to add a layer of plastic film to achieve the moisture-proof effect of packaging. This kind of paper-plastic packaging product containing plastic greatly reduces the easy recycling and regeneration performance of the product, which is not in line with the sustainable development trend of the packaging industry. Summary of the invention

[0004] In order to solve the problem of poor moisture-proof effect and difficulty in recycling, the present invention provides a moisture-proof coating liquid and moisture-proof coated paper containing the coating liquid, a production process and a packaging bag. The present invention forms a moisture-proof coating layer by coating the moisture-proof coating liquid on the surface of paper, which can not only increase the moisture-proof function of the paper, but also enable the paper bag made of the moisture-proof coated paper to achieve the same moisture-proof effect as the plastic film without using the plastic film. At the same time, the coating attached to the surface of the paper can be directly put into the pulp recovery system for pulping and recycling after the paper packaging is used without affecting the pulping efficiency.

[0005] To achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0006] A moisture-proof coating liquid, wherein the moisture-proof coating liquid comprises a top coating liquid, and the top coating liquid comprises the following components in parts by weight:

[0007]

[0008] The moisture-proof coating liquid provided by the present invention can replace the plastic film and be coated on the surface of the paper substrate to form a dense moisture-proof coating layer, which plays a role in effectively blocking the penetration of water vapor, so that the coated paper has excellent moisture-proof performance, that is, the moisture-proof coated paper is obtained. The moisture-proof coated paper is used to make moisture-proof paper bags, which can not only achieve the same effect of easy canning, easy exhaust and moisture-proof as the paper bags made of the common paper / plastic film combination, but also the packaging products are easy to recycle after use and can directly enter the paper recycling pulping system, which greatly improves the easy recycling and easy regeneration performance of the packaging materials.

[0009] Furthermore, the topcoat solution comprises the following components in parts by weight:

[0010]

[0011] As a preferred embodiment, the moisture-proof coating liquid further comprises a primer liquid, and the primer liquid comprises the following components in parts by weight:

[0012]

[0013] The moisture-proof coating liquid provided by the present invention further includes a primer liquid. Applying the primer liquid before applying the top coating liquid on the surface of the paper substrate can make the surface of the paper substrate smoother, thereby reducing the amount of top coating liquid used, thereby achieving the purpose of achieving better moisture-proof effect while saving costs.

[0014] Furthermore, the primer solution comprises the following components in parts by weight:

[0015]

[0016] In the present invention, in the primer, the other additives are one or both of leveling agents or defoamers; in the topcoat, the other additives are one or more of siloxane-based organosilicon additives, leveling agents or defoamers.

[0017] The present invention also provides a moisture-proof coated paper, wherein the moisture-proof coated paper comprises a paper substrate 1 and a moisture-proof coating 2, wherein the moisture-proof coating 2 is a top coating 21 formed by coating the surface of the paper substrate 1 with a top coating liquid of the moisture-proof coating liquid.

[0018] As a preferred embodiment, the present invention also provides another moisture-proof coated paper, the moisture-proof coated paper includes a paper substrate 1 and a moisture-proof coating 2, the moisture-proof coating 2 includes a top coating 21 and a base coating 22, the base coating 22 is formed by coating the base coating liquid of the moisture-proof coating liquid on the surface of the paper substrate 1, and the top coating 21 is formed by coating the top coating liquid of the moisture-proof coating liquid on the surface of the base coating 22.

[0019] The present invention also provides a method for preparing the moisture-proof coated paper, wherein the preparation method comprises:

[0020] The top coating liquid is evenly coated on the surface of the paper substrate 1, and after drying, a top coating layer 21 is formed, namely, the moisture-proof coating layer 2, to obtain the moisture-proof coated paper.

[0021] The present invention also provides another method for preparing moisture-proof coated paper, wherein the preparation method comprises:

[0022] 1) firstly uniformly coating the primer liquid on the surface of the paper substrate 1, and forming a primer layer 22 after drying;

[0023] 2) The top coating liquid is then evenly coated on the surface of the base coating 22, and after drying, a top coating 21 is formed. The top coating 21 and the base coating 22 together constitute a moisture-proof coating 2, and the moisture-proof coated paper is obtained.

[0024] In the present invention, the paper substrate 1 is selected from a paper having a gram weight of 50 to 150 g / m 2 , preferably 60 to 120 g / m 2 of paper.

[0025] The absolute dry coating weight of the primer layer 22 is 1 to 15 g / m 2 The best thickness is between 2 and 10 g / m 2 between;

[0026] The absolute dry coating amount of the top coating 21 is 1 to 15 g / m 2 The best thickness is between 2 and 10 g / m 2 between.

[0027] In the present invention, the coating can be carried out by transfer coating methods such as anilox roller coating, air knife coating, curtain coating, etc.

[0028] The present invention further provides a packaging bag, wherein the packaging bag is made of the moisture-proof coated paper of the present invention.

[0029] Preferably, it is a packaging bag composed of two layers of paper, or a packaging bag composed of three layers or more of paper, wherein the moisture-proof coating of the packaging bag composed of two layers of paper is placed on the inner side of the outer layer of paper or the outer side of the inner layer of paper;

[0030] For packaging bags made of three or more layers of paper, the moisture-proof coating is placed on one side of the middle paper.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] (1) The moisture-proof coating liquid provided by the present invention can replace plastic film and be coated on the surface of a paper substrate to form a dense moisture-proof coating layer, thereby giving the paper moisture-proof properties, thereby replacing the commonly used plastic film to play the moisture-proof function of packaging paper bags;

[0033] (2) Using the functional coating method, the functional coated paper packaging bag can achieve a moisture-proof effect similar to that of conventional PE film;

[0034] (3) The use of moisture-proof coated paper technology can achieve limited reduction in plastic packaging. The product is easy to recycle and regenerate. After use, the packaged product can directly enter the pulping system for re-pulping without the need for additional separation operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic diagram of the structure of the moisture-proof coating paper provided in Examples 1-3 of the present invention;

[0036] Figure 2 A schematic diagram of the structure of the moisture-proof coating paper provided in Examples 4-6 of the present invention;

[0037] Figure 3 This is a test chart of the moisture-proof effect of a whole bag of water putty powder for building materials. DETAILED DESCRIPTION

[0038] The following are specific embodiments of the present invention, and the embodiments are intended to further describe the present invention rather than to limit the present invention.

[0039] Example 1

[0040] This embodiment provides a moisture-proof coating liquid, wherein the moisture-proof coating liquid includes a top coating liquid, and the top coating liquid includes the following components:

[0041]

[0042]

[0043] in:

[0044] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0045] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0046] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0047] This embodiment further provides a moisture-proof coated paper, such as Figure 1 As shown, the moisture-proof coated paper comprises a paper substrate 1 and a moisture-proof coating 2, wherein the moisture-proof coating 2 is a top coating 21 formed by coating the top coating liquid described in this embodiment on the surface of the paper substrate 1. The preparation method thereof is as follows:

[0048] 1) Select a weight of 80g / m 2 The stretchable paper is used as the paper substrate 1;

[0049] 2) The top coating liquid is evenly coated on the surface of the paper substrate 1 by an anilox roller coating method, with a coating speed of 100 m / min and a coating amount of 8 g / m 2 After drying, a top coating 21 is formed, namely, a moisture-proof coating 2, to obtain the moisture-proof coated paper.

[0050] This embodiment also provides a packaging bag, which is composed of three layers of paper, wherein the paper is the moisture-proof coated paper of this embodiment as the middle second layer of paper, and the moisture-proof coating is placed on the outer layer of the second layer of paper and is prepared according to a conventional method. Specifically, it is a packaging bag composed of two layers of paper (i.e., moisture-proof coated paper), or a packaging bag composed of three or more layers of paper, wherein the moisture-proof coating of the packaging bag composed of two layers of paper is placed on the inner side of the outer layer of paper or the outer side of the inner layer of paper;

[0051] For packaging bags made of three or more layers of paper, the moisture-proof coating is placed on one side of the middle paper.

[0052] Through various test examples, this application document fully demonstrates the excellent performance of moisture-proof coated paper, especially its significant advantages when applied to packaging bags. Test Example 1 successfully demonstrated the controllability of water vapor transmission rate (WVTR) by adjusting the coating amount, which is crucial to ensure the moisture-proof effect of the items in the packaging bag. For example, the WVTR of sample 2 is significantly lower than 100g / m 2 24h. This result shows that even in a high humidity environment, the packaging bag made of the moisture-proof coated paper of the present application can effectively prevent the articles from absorbing moisture and agglomerating.

[0053] Test Example 2 further verifies the moisture-proof effect of the moisture-proof coated paper bag of the present invention in practical applications. Compared with the conventional packaging bag of three layers of paper plus one layer of PE film, the three-layer moisture-proof coated paper bag of the present invention shows a similar whole bag water absorption weight gain rate in the accelerated aging test, which proves that its moisture-proof performance in practical applications is comparable to or even better than that of the prior art.

[0054] Test Examples 3 and 4 highlight the moisture-proof performance of the preferred samples of the present invention by comparing the WVTR of different samples. In particular, the WVTR of Sample 4 is much lower than that of Sample 3. This comparison emphasizes the scientificity and accuracy of the present invention in material selection and coating process.

[0055] From the data in Table 2, we can see that no matter what type of base paper is, after being treated with the moisture-proof coating of the present invention, its moisture-proof performance is significantly improved. In particular, in Example 3, the WVTR of the moisture-proof coated paper is only 27 g / m 2 24h, which is an excellent result among similar products. In practical applications, different moisture-proof coating papers can be selected according to the moisture-proof performance requirements of different packaged items to effectively protect the safety and stability of the items during the shelf life.

[0056] In summary, the moisture-proof coated paper and packaging bags made from it in this application provide moisture-proof protection that exceeds that of traditional materials while maintaining the recyclability and environmental protection characteristics of paper. This not only improves the practicality and durability of the packaging bags, but also provides a new solution for sustainable development and environmentally friendly packaging.

[0057] The packaging bag achieves its unique functionality by using the moisture-proof coating paper specially prepared in this embodiment. This packaging bag not only utilizes the excellent moisture-proof performance of the moisture-proof coating paper, but also enhances its application flexibility and diversity. The moisture-proof coating paper can be directly used to make packaging bags. This method is simple and fast and is suitable for application scenarios that have certain requirements for moisture-proof performance.

[0058] As a preferred embodiment, it is a packaging bag composed of two layers of paper (i.e., moisture-proof coated paper), or a packaging bag composed of three layers or more of paper, wherein the moisture-proof coating of the packaging bag composed of two layers of paper is placed on the inner side of the outer layer of paper or the outer side of the inner layer of paper;

[0059] For packaging bags made of three or more layers of paper, the moisture-proof coating is placed on one side of the middle paper.

[0060] Not only the moisture-proof effect is taken into consideration, but also the environmental protection properties and recyclability of the material are taken into account. By selecting specific topcoat and primer liquids, and precisely controlling the coating process, the packaging bag of this application significantly improves its moisture-proof performance while maintaining the original recyclability of the paper. In addition, by adjusting the coating amount, the water vapor transmission rate (WVTR) of the packaging bag can be flexibly adjusted to meet the moisture-proof requirements of different products.

[0061] Furthermore, Examples 1 and 2 to 6 show the moisture-proof coated paper prepared under different conditions and their applications, proving that the packaging bag of the present application has wide applicability and high technical adaptability. Through these examples, it can be seen that the packaging bag of the present application can be customized according to specific needs in practical applications, and whether it is a single-layer moisture-proof coated paper bag or a packaging bag made of multi-layer moisture-proof coated paper, it can provide reliable moisture-proof protection and ensure the quality and stability of the packaged contents.

[0062] Example 2

[0063] This embodiment provides a moisture-proof coating liquid, wherein the moisture-proof coating liquid includes a top coating liquid, and the top coating liquid includes the following components:

[0064]

[0065] in:

[0066] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0067] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0068] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0069] This embodiment further provides a moisture-proof coated paper, the structure of which is the same as that of embodiment 1. Figure 1 The preparation method is as follows:

[0070] 1) Select kraft paper with a gram weight of 60 g / m2 as the paper substrate 1;

[0071] 2) The top coating liquid is evenly coated on the surface of the paper substrate 1 by air knife coating, and the coating amount is 2 g / m 2 After drying, a top coating 21 is formed, namely, a moisture-proof coating 2, to obtain the moisture-proof coated paper.

[0072] This embodiment also provides a packaging bag, wherein the packaging paper is prepared from the moisture-proof coated paper of this embodiment according to a conventional method.

[0073] Example 3

[0074] This embodiment provides a moisture-proof coating liquid, wherein the moisture-proof coating liquid includes a top coating liquid, and the top coating liquid includes the following components:

[0075]

[0076] in:

[0077] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0078] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0079] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0080] This embodiment further provides a moisture-proof coated paper, the structure of which is the same as that of embodiment 1. Figure 1 The preparation method is as follows:

[0081] 1) Choose a weight of 120g / m 2 The stretchable paper is used as the paper substrate 1;

[0082] 2) The top coating liquid is evenly coated on the surface of the paper substrate 1 by curtain coating, and the coating amount is 10 g / m 2 After drying, a top coating 21 is formed, namely, a moisture-proof coating 2, to obtain the moisture-proof coated paper.

[0083] This embodiment also provides a packaging bag, wherein the packaging paper is prepared from the moisture-proof coated paper of this embodiment according to a conventional method.

[0084] Example 4

[0085] This embodiment provides a moisture-proof coating liquid, wherein the moisture-proof coating liquid includes a top coating liquid and a bottom coating liquid, and the top coating liquid includes the following components:

[0086]

[0087] In topcoat:

[0088] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0089] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0090] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0091] The primer solution comprises the following components in parts by weight:

[0092]

[0093] Primer:

[0094] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0095] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0096] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0097] This embodiment further provides a moisture-proof coated paper, such as Figure 2 As shown, the moisture-proof coated paper comprises a paper substrate 1 and a moisture-proof coating 2, wherein the moisture-proof coating 2 comprises a top coating 21 and a base coating 22, wherein the base coating 22 is formed by coating the base coating liquid of this embodiment on the surface of the paper substrate 1, and the top coating 21 is formed by coating the top coating liquid of this embodiment on the surface of the base coating 22. The preparation method thereof is as follows:

[0098] 1) Selecting a stretch paper with a grammage of 50 g / m2 as the paper substrate 1;

[0099] 2) The primer solution is firstly evenly coated on the surface of the paper substrate 1 by an anilox roller coating method, with a coating speed of 100 m / min and a coating amount of 2 g / m 2 , forming a primer layer 22 after drying;

[0100] 3) The top coating liquid is then evenly coated on the surface of the base coating 22 by an anilox roller coating method, with a coating speed of 100 m / min and a coating amount of 1 g / m 2 After drying, a top coating 21 is formed. The top coating 21 and the base coating 22 together constitute a moisture-proof coating 2, thus obtaining the moisture-proof coated paper.

[0101] This embodiment also provides a packaging bag, wherein the packaging paper is prepared from the moisture-proof coated paper of this embodiment according to a conventional method.

[0102] Example 5

[0103] This embodiment provides a moisture-proof coating liquid, wherein the moisture-proof coating liquid includes a top coating liquid and a bottom coating liquid, and the top coating liquid includes the following components:

[0104]

[0105] In topcoat:

[0106] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0107] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0108] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0109] The primer solution comprises the following components in parts by weight:

[0110]

[0111] Primer:

[0112] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0113] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0114] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0115] This embodiment further provides a moisture-proof coated paper, the structure of which is the same as that of embodiment 4. Figure 2 The preparation method is as follows:

[0116] 1) Selecting kraft paper with a gram weight of 150 g / m2 as the paper substrate 1;

[0117] 2) First, the primer liquid is evenly coated on the surface of the paper substrate 1 by air knife coating, and the coating amount is 10g / m 2 , forming a primer layer 22 after drying;

[0118] 3) The top coating liquid is then evenly coated on the surface of the base coating 22 by air knife coating, and the coating amount is 12 g / m 2 After drying, a top coating 21 is formed. The top coating 21 and the base coating 22 together constitute a moisture-proof coating 2, thus obtaining the moisture-proof coated paper.

[0119] This embodiment also provides a packaging bag, wherein the packaging paper is prepared from the moisture-proof coated paper of this embodiment according to a conventional method.

[0120] Example 6

[0121] This embodiment provides a moisture-proof coating liquid, wherein the moisture-proof coating liquid includes a top coating liquid and a bottom coating liquid, and the top coating liquid includes the following components:

[0122]

[0123] In topcoat:

[0124] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0125] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0126] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0127] The primer solution comprises the following components in parts by weight:

[0128]

[0129]

[0130] Primer:

[0131] The polyacrylate is at least one of the following: polystyrene-butyl acrylate, poly(isooctyl acrylate), poly(butyl acrylate), ethyl acrylate, isopropyl acrylate, n-pentyl acrylate, methyl methacrylate, methyl acrylate, n-pentyl methacrylate;

[0132] The water repellent is at least one of the following: amino resin water repellent, glyoxal water repellent or polyamide polyurea water repellent.

[0133] The other additives are at least one of the following: siloxane-based silicone additives, leveling agents and defoaming agents; the siloxane-based silicone additives are at least one of the following: polydimethylsiloxane (PDMS), siloxane polyether copolymers, alkoxysilanes, aminosilanes or hydroxy silicone oils; the leveling agent is at least one of the following: acrylate leveling agents, polyurethane leveling agents, modified silicone leveling agents or polyether-modified polysiloxane leveling agents; the defoaming agent is at least one of the following: siloxane defoaming agents, polyether defoaming agents, mineral oil defoaming agents or silicone polyether copolymer defoaming agents.

[0134] This embodiment further provides a moisture-proof coated paper, the structure of which is the same as that of embodiment 4. Figure 2 The preparation method is as follows:

[0135] 1) Select a weight of 100g / m 2 The stretchable paper is used as the paper substrate 1;

[0136] 2) First, the primer liquid is evenly coated on the surface of the paper substrate 1 by curtain coating, and the coating amount is 5g / m 2 , forming a primer layer 22 after drying;

[0137] 3) The top coating liquid is then evenly coated on the surface of the base coating 22 by curtain coating, and the coating amount is 5 g / m 2 After drying, a top coating 21 is formed. The top coating 21 and the base coating 22 together constitute a moisture-proof coating 2, thus obtaining the moisture-proof coated paper.

[0138] This embodiment also provides a packaging bag, wherein the packaging paper is prepared from the moisture-proof coated paper of this embodiment according to a conventional method.

[0139] Test Example 1

[0140] This test example investigates the moisture-proof performance of moisture-proof coated paper with different coating amounts.

[0141] Test method: select a weight of 80g / m 2 The stretchable paper is used as the paper substrate 1, the primer liquid described in Example 4 is coated on the surface of the paper substrate 1, and the primer layer 22 is formed after drying; the top coating liquid described in Example 4 is then coated on the surface of the primer layer 22, and the top coating layer 21 is formed after drying; the primer liquid and the top coating liquid are both coated by an anilox roller metering rod coating, and the coating speed is 100 m / min. The primer layer 22 and the top coating layer 21 together constitute the moisture-proof coating layer 2. The absolute dry coating amounts of the primer layer 22 and the top coating layer 21 are shown in the table, and moisture-proof coated papers with different coating amounts are obtained.

[0142] Moisture resistance test: At a temperature of 38°C and a humidity of 90% RH, the total number of grams of water vapor that permeates per square meter of paper in 24 hours is measured at the left, middle and right positions of the paper, i.e. the water vapor transmission rate (WVTR, g / m 2 ·24h) to evaluate the moisture-proof performance of moisture-proof coated paper. The results are shown in Table 1:

[0143] Table 1

[0144]

[0145] From the results in Table 1, it can be seen that packaging products made of materials with a water vapor transmission rate of less than 100 can effectively prevent packaging materials such as mortar, building materials putty powder, etc. from getting damp and agglomerating, ensuring stable performance during the product warranty period. The results of Test Example 1 show that under the same material and coating conditions, the water vapor transmission rate related to moisture resistance can be adjusted by adjusting the coating amount. The larger the coating amount, the smaller the water vapor transmission rate.

[0146] Test Example 2

[0147] This test example investigates the moisture-proof effect of a whole bag of water-based putty powder for building materials.

[0148] Test moisture-proof coated paper bag: The moisture-proof coated paper of sample 1 of the above test example 1 is used as the middle layer of a three-layer paper bag to prepare a moisture-proof coated paper bag;

[0149] Comparative moisture-proof coated paper bag: the weight is 80g / m 2 The stretch paper and PE film are used to make a three-layer paper plus a layer of PE film packaging bag as a comparison sample with the three-layer paper moisture-proof paper bag.

[0150] Test on moisture-proof effect of whole bag of building materials water putty powder: After the test moisture-proof coated paper bags and control moisture-proof paper bags were filled with water-based putty for construction on the production line, the water absorption and weight gain rate of the whole bag were tested at 38°C and 90% humidity for 41 days. The results are shown in the figure. Figure 2 As shown:

[0151] Figure 2 The results show that the water absorption weight gain rate of the whole bag of the three-layer moisture-proof coated paper bag of the present invention and the control moisture-proof coated paper bag of three papers and one film is similar, indicating that the moisture-proof coated paper bag of the present invention has the same moisture-proof effect as conventional products.

[0152] Test Example 3

[0153] In this test example, the compositions of the top coating liquid and the base coating liquid of the moisture-proof coating liquid were screened.

[0154]

[0155] In the above test table, two typical samples 3 and 4 are listed, and the coating amounts of the primer and topcoat are different. The primer and topcoat alone show obvious moisture-proof performance. Under the same coating amount, the topcoat material has better moisture-proof performance. Compared with sample 1 and sample 2, the combination of primer and topcoat has better synergistic advantages. The present application prefers the primer and topcoat to synergistically form a moisture-proof coating;

[0156] Test Example 4

[0157] This test example examines the moisture-proof properties of the base paper before being coated with a moisture-proof coating and the moisture-proof coated paper obtained after the coating in each embodiment of the present invention.

[0158] The moisture-proof performance testing method is the same as that of Test Example 1, and the results are shown in Table 2:

[0159] Table 2

[0160]

[0161]

[0162] It can be seen from the results in Table 2 that after the moisture-proof coating provided by the present invention is coated on the surface of the base paper, the paper has good moisture-proof performance, and the moisture-proof performance of the moisture-proof coating comprising two layers of the base coating and the top coating is better than the moisture-proof performance of only comprising a single layer of the top coating.

Claims

1. A moisture-proof coating liquid, characterized in that: The moisture-proof coating liquid includes a top coating liquid, and the top coating liquid includes the following components in parts by weight:

2. The moisture-proof coating liquid according to claim 1, characterized in that: The topcoat liquid comprises the following components in parts by weight:

3. The moisture-proof coating liquid according to claim 1 or 2, characterized in that: The moisture-proof coating liquid also includes a primer, and the primer includes the following components in parts by weight:

4. The moisture-proof coating liquid according to claim 3, characterized in that: The primer solution comprises the following components in parts by weight:

5. The moisture-proof coating liquid according to claim 4, characterized in that: In the primer, the other additives are one or both of a leveling agent or a defoaming agent; In the topcoat liquid, the other additives are one or more of siloxane organic silicon additives, leveling agents or defoaming agents.

6. A moisture-proof coated paper, characterized in that: The moisture-proof coated paper comprises a paper substrate (1) and a moisture-proof coating (2), wherein the moisture-proof coating (2) is a top coating (21) formed by coating the surface of the paper substrate (1) with a top coating liquid of the moisture-proof coating liquid according to claim 1 or 2.

7. A moisture-proof coated paper, characterized in that: The moisture-proof coated paper comprises a paper substrate (1) and a moisture-proof coating (2), wherein the moisture-proof coating (2) comprises a top coating (21) and a base coating (22), wherein the base coating (22) is formed by coating a base coating liquid of the moisture-proof coating liquid according to any one of claims 3 to 5 on the surface of the paper substrate (1), and the top coating (21) is formed by coating a top coating liquid of the moisture-proof coating liquid according to any one of claims 3 to 5 on the surface of the base coating (22).

8. A method for preparing moisture-proof coated paper according to claim 6, characterized in that: The preparation method is: The top coating liquid is evenly coated on the surface of the paper substrate (1), and after drying, a top coating layer (21) is formed, namely, a moisture-proof coating layer (2), thereby obtaining the moisture-proof coated paper; The preparation method is: 1) firstly uniformly coating the primer liquid on the surface of the paper substrate (1) and forming a primer layer (22) after drying; 2) The top coating liquid is then evenly coated on the surface of the base coating (22), and after drying, a top coating (21) is formed. The top coating (21) and the base coating (22) together constitute a moisture-proof coating (2), thus obtaining the moisture-proof coated paper.

9. A packaging bag, characterized in that: The packaging bag is made of the moisture-proof coated paper according to claim 6 or 7.

10. A packaging bag according to claim 9, characterized in that: It is a packaging bag composed of two layers of paper, or a packaging bag composed of three layers or more of paper, wherein the moisture-proof coating of the packaging bag composed of two layers of paper is placed on the inner side of the outer layer of paper or the outer side of the inner layer of paper; For packaging bags made of three or more layers of paper, the moisture-proof coating is placed on one side of the middle paper.

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