White card for packaging, its preparation method and application

Abstract

The application belongs to the technical field of packaging paper, and discloses a white cardboard for packaging, a preparation method and application thereof. The white cardboard comprises, from bottom to top, a paper base material, a first coating layer, a second coating layer, a third coating layer and a fourth coating layer. The first coating layer and the third coating layer are the same in composition and are prepared from a first coating material. The first coating material comprises a water-based hydroxyl acrylic resin emulsion, a hydroxyl polydimethylsiloxane, modified sodium silicate, an additive A, an additive B and a solvent. The second coating layer and the fourth coating layer are the same in composition and are prepared from a second coating material. The second coating material comprises an amino resin emulsion, modified sodium silicate, an additive A, an additive B and a solvent. The modified sodium silicate is obtained by modifying nano-sodium silicate with a silane coupling agent, nano-silicon dioxide, polyethylene glycol and water. The white cardboard can simultaneously solve the problems of water vapor, oxygen and oil resistance, and has strong tolerance to high and low temperature food with high water content and is not prone to cracking.

Description

[0001] This application is a divisional application of the application filed on August 10, 2023, with application number 202311009161.2 and invention title "A white cardboard for packaging and its preparation method and application". Technical Field

[0002] This invention belongs to the field of packaging paper technology, and specifically relates to a white cardboard for packaging, its preparation method, and its application. Background Technology

[0003] There are many types of packaging paper, among which food packaging paper is used in extremely large quantities. Due to the requirements for food preservation and freshness, food packaging paper has special requirements. For example, it needs to be able to block oxygen, moisture, and oil, and it also needs to be strong enough to withstand tearing. Other fields may also have requirements for packaging paper that blocks oxygen, moisture, and oil.

[0004] In existing technologies, paper used for food packaging is typically made by coating white cardboard with polyethylene. While polyethylene has good resistance to water vapor, oxygen, and oil, it is difficult to degrade in nature and has poor environmental performance. Therefore, existing technologies are increasingly using coatings with water vapor, oxygen, and oil-resistant properties onto white cardboard. Although this method can solve the environmental problem, the paper prepared using this method has poor strength and is prone to cracking when used for food packaging, especially when dealing with foods with high or low temperatures and high moisture content.

[0005] Therefore, there is an urgent need to provide a new type of white cardboard for food packaging that can simultaneously solve the problems of water vapor, oxygen, and oil resistance, and has strong resistance to high and low temperature moisture content foods and is not easy to crack. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a white cardboard for packaging, its preparation method and application. The white cardboard of the present invention can simultaneously solve the problems of water vapor, oxygen, and oil resistance, and has strong resistance to high and low temperature moisture content foods, and is not easy to crack.

[0007] The inventive concept of this invention is as follows: The white cardboard of this invention comprises a paper substrate and four coatings on the surface of the paper substrate. The first and third coatings have the same composition, and the second and fourth coatings have the same composition. The first coating material for preparing the first coating comprises an aqueous hydroxyl acrylic resin emulsion, hydroxyl polydimethylsiloxane, modified sodium silicate, additive A, additive B, and a solvent. Additive B is mixed with the other components of the first coating during preparation to form the first coating material, which is then applied to the surface of the paper substrate. A spatial network structure is formed through the reaction of the aqueous hydroxyl acrylic resin emulsion and hydroxyl polydimethylsiloxane, and the modified sodium silicate is uniformly dispersed within this spatial network structure. The modified sodium silicate is obtained by modifying nano-sodium silicate with a silane coupling agent, nano-silica, polyethylene glycol, and water. The modified sodium silicate not only serves as a filler but also uniformly fills the spatial network structure formed by the reaction of the aqueous hydroxyl acrylic resin emulsion and hydroxyl polydimethylsiloxane, thus providing excellent waterproof, oxygen-proof, and oil-proof properties. The second coating consists of an amino resin emulsion, modified sodium silicate, additive A, additive B, and a solvent. Additive B is mixed with the remaining components during the preparation of the second coating. The modified sodium silicate is uniformly dispersed in the second coating (furthermore, due to the modification of sodium silicate in this invention, the modified sodium silicate can be uniformly dispersed in both the first and second coatings simultaneously), thereby providing better water vapor, oxygen, and oil resistance. Furthermore, the alternating combination of the first, second, third, and fourth coatings on the paper substrate surface not only significantly improves the water vapor, oxygen, and oil resistance of the white cardboard, but also enhances its resistance to high and low temperature moisture content foods, making it less prone to cracking.

[0008] In addition, citric acid is introduced into the second coating. Due to the polyhydroxyl and carbon skeleton characteristics of citric acid, when combined with amino resin emulsion and reacted with additive B, a network skeleton with a structure different from that of the first coating can be formed. This is more conducive to the dispersion of modified sodium silicate and to the formation of a certain interaction with the first coating in terms of structure, thereby better improving the waterproof, oxygen-proof, and oil-proof effects and the strong resistance to high and low temperature moisture-containing foods.

[0009] A first aspect of the present invention provides a white cardboard for packaging.

[0010] Specifically, a type of white cardboard for packaging includes, from bottom to top, a paper substrate, a first coating, a second coating, a third coating, and a fourth coating.

[0011] The first coating and the third coating have the same composition and are both made from the first coating material, which includes water-based hydroxyl acrylic resin emulsion, hydroxyl polydimethylsiloxane, modified sodium silicate, additive A, additive B, and solvent.

[0012] The second coating and the fourth coating have the same composition, both made from the second coating material, which includes an amino resin emulsion, modified sodium silicate, additive A, additive B, and solvent.

[0013] The modified sodium silicate is obtained by modifying nano-sodium silicate with silane coupling agent, nano-silica, polyethylene glycol, and water.

[0014] The auxiliary agent A includes sodium methylene dimethylbenzenesulfonate, defoamer, and dodecyl alcohol ester;

[0015] The auxiliary agent B includes isocyanate.

[0016] Preferably, additive A further includes an antibacterial agent and an antioxidant, used to improve the antibacterial and antioxidant properties of white cardboard.

[0017] Preferably, the auxiliary agent B further includes triethylenetetramine.

[0018] Preferably, the defoamer is polydimethylsiloxane.

[0019] Preferably, the modified sodium silicate is prepared by mixing silane coupling agent, nano silica, polyethylene glycol, water and nano sodium silicate in a weight ratio of (1-10):(3-15):(2-12):(30-80):(25-45) to obtain the modified sodium silicate.

[0020] Preferably, the modified sodium silicate is prepared by mixing silane coupling agent, nano silica, polyethylene glycol, water, and nano sodium silicate in a weight ratio of (4-10):(5-12):(3-12):(35-60):(30-40), at a mixing temperature of 40-60°C, at a stirring speed of 800-1200 rpm, and for 2-5 hours, thereby obtaining the modified sodium silicate.

[0021] Preferably, the silane coupling agent is selected from silane coupling agent KH560 or silane coupling agent KH570.

[0022] Preferably, the isocyanate is lysine diisocyanate.

[0023] Preferably, the solvent is water.

[0024] Preferably, the second coating also includes citric acid.

[0025] Preferably, the first coating comprises, by weight, 80 parts of water-based hydroxyl acrylic resin emulsion, 20-40 parts of hydroxyl polydimethylsiloxane, 60-80 parts of modified sodium silicate, 5-20 parts of additive A, 4-12 parts of additive B, and 100-200 parts of solvent.

[0026] More preferably, the first coating comprises, by weight, 80 parts of waterborne hydroxyl acrylic resin emulsion, 25-30 parts of hydroxyl polydimethylsiloxane, 65-70 parts of modified sodium silicate, 5-15 parts of additive A, 4-10 parts of additive B, and 100-180 parts of solvent.

[0027] Preferably, the second coating comprises, by weight, 80 parts of amino resin emulsion, 40-55 parts of modified sodium silicate, 5-20 parts of additive A, 4-12 parts of additive B, and 100-200 parts of solvent.

[0028] More preferably, the second coating comprises 80 parts of amino resin emulsion, 10-20 parts of citric acid, 40-50 parts of modified sodium silicate, 5-15 parts of additive A, 4-10 parts of additive B, and 100-180 parts of solvent. Appropriate selection of the component amounts of the first and second coatings helps to improve the water vapor, oxygen, and oil resistance properties of the cardboard.

[0029] Preferably, a white cardboard for packaging comprises, from bottom to top, a paper substrate, a first coating, a second coating, a third coating, and a fourth coating;

[0030] The first coating and the third coating have the same composition, both made from the first coating material. The first coating material, by weight, includes 80 parts of water-based hydroxyl acrylic resin emulsion, 20-40 parts of hydroxyl polydimethylsiloxane, 60-80 parts of modified sodium silicate, 5-20 parts of additive A, 4-12 parts of additive B, and 100-200 parts of solvent.

[0031] The second coating and the fourth coating have the same composition and are both made from the second coating material. The second coating material, by weight, includes 80 parts of amino resin emulsion, 10-20 parts of citric acid, 40-50 parts of modified sodium silicate, 5-15 parts of additive A, 4-10 parts of additive B, and 100-180 parts of solvent.

[0032] The modified sodium silicate is prepared by mixing silane coupling agent, nano silica, polyethylene glycol, water, and nano sodium silicate in a weight ratio of (4-10):(5-12):(3-12):(35-60):(30-40), at a temperature of 40-60°C, at a stirring speed of 800-1200 rpm, and for 2-5 hours, thereby obtaining the modified sodium silicate.

[0033] The auxiliary agent A includes sodium methylene dimethylbenzenesulfonate, defoamer, and dodecyl alcohol ester;

[0034] The auxiliary agent B includes isocyanate.

[0035] Preferably, the paper substrate is commercially available white cardboard, i.e., conventional white cardboard. For example, a specification of 200-300g / m². 2 White cardstock. Specifically, for example, 210g / m². 2 230g / m 2 250g / m 2 280g / m 2 White cardstock.

[0036] A second aspect of the present invention provides a method for preparing white cardboard for packaging.

[0037] Specifically, a method for preparing white cardboard for packaging includes the following steps:

[0038] Take the components for preparing the first coating, mix the components, and obtain the first coating;

[0039] Take the components for preparing the second coating, mix the components, and obtain the second coating;

[0040] Take a paper substrate, coat the surface of the paper substrate with a first coating and a second coating in sequence, then coat the surface with the first coating and the second coating again, and then heat and cure to obtain the white cardboard.

[0041] Preferably, the preparation method of the first coating is as follows: weigh waterborne hydroxyl acrylic resin emulsion, hydroxyl polydimethylsiloxane, modified sodium silicate, additive A and solvent according to the proportion, stir and mix at a stirring speed of 800-1500 rpm for 30-60 minutes, and then add additive B and mix to obtain the first coating.

[0042] Preferably, the preparation method of the second coating is as follows: weigh out amino resin emulsion, citric acid, modified sodium silicate, additive A and solvent according to the proportion, stir and mix at a stirring speed of 600-1500 rpm for 20-50 minutes, and then add additive B and mix to obtain the second coating.

[0043] Preferably, the amount of the first and second coatings applied each time is 3-15 g / m². 2 Preferred concentration: 4-12 g / m 2 .

[0044] Preferably, the heating and curing temperature is 90-150℃, and the heating and curing time is 8-15 minutes.

[0045] A third aspect of the present invention provides an application of white cardboard.

[0046] The above-mentioned white cardboard has applications in the packaging field. The white cardboard of this invention can be used in any packaging field where there are requirements for paper to be waterproof, oxygen-proof, or oil-proof.

[0047] Preferably, the application is in the field of food packaging.

[0048] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0049] (1) The white cardboard of the present invention comprises a paper substrate and four coatings on the surface of the paper substrate, wherein the first and third coatings have the same composition, and the second and fourth coatings have the same composition. The first coating for preparing the first coating comprises an aqueous hydroxyl acrylic resin emulsion, hydroxyl polydimethylsiloxane, modified sodium silicate, additive A, additive B, and solvent. It is coated on the surface of the paper substrate, and a spatial network structure is formed by the reaction of the aqueous hydroxyl acrylic resin emulsion and hydroxyl polydimethylsiloxane, and the modified sodium silicate is uniformly dispersed in the formed spatial network structure. The modified sodium silicate is obtained by modifying nano-sodium silicate with silane coupling agent, nano-silica, polyethylene glycol, and water; the modified sodium silicate can not only be used as a filler, but also the modified sodium silicate can be uniformly filled in the spatial network structure formed by the reaction of the aqueous hydroxyl acrylic resin emulsion and hydroxyl polydimethylsiloxane, thereby playing a good role in waterproofing, oxygen protection, and oil protection. The second coating is composed of an amino resin emulsion, modified sodium silicate, additive A, additive B, and solvent. Modified sodium silicate is uniformly dispersed in the second coating (furthermore, due to the modification of sodium silicate in this invention, the modified sodium silicate can be uniformly dispersed in both the first and second coatings simultaneously), thereby achieving better water vapor, oxygen, and oil resistance. Moreover, the alternating combination of the first, second, third, and fourth coatings on the paper substrate surface not only significantly improves the water vapor, oxygen, and oil resistance of the white cardboard, but also enhances its resistance to high and low temperature moisture content foods, making it less prone to cracking.

[0050] (2) Citric acid is also introduced into the second coating. Due to the polyhydroxyl and carbon skeleton characteristics of citric acid, combined with amino resin emulsion and additive B, it can form a network skeleton with a structure different from that of the first coating. This is more conducive to the dispersion of modified sodium silicate and to the formation of a certain interaction with the first coating in terms of structure, thereby better improving the waterproof, oxygen-proof, and oil-proof effects and the strong tolerance to high and low temperature water-containing foods. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the structure of the white cardboard prepared in Example 1 of the present invention. Detailed Implementation

[0052] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0053] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0054] Example 1: Preparation of white cardboard

[0055] A type of white cardboard for packaging, comprising, from bottom to top, a paper substrate, a first coating, a second coating, a third coating, and a fourth coating;

[0056] The first and third coatings have the same composition, both made from the first coating material. The first coating material, by weight, consists of 80 parts of water-based hydroxyl acrylic resin emulsion, 22 parts of hydroxyl polydimethylsiloxane, 65 parts of modified sodium silicate, 6 parts of additive A (1 part of sodium methylene dimethylbenzenesulfonate, 4 parts of polydimethylsiloxane, 1 part of dodecyl alcohol ester), 6 parts of additive B (6 parts of lysine diisocyanate), and 180 parts of solvent (water).

[0057] The second and fourth coatings have the same composition, both made from the second coating material. The second coating material, by weight, consists of 80 parts of amino resin emulsion, 45 parts of modified sodium silicate, 5 parts of additive A (1 part of sodium methylene dimethylbenzenesulfonate, 3 parts of polydimethylsiloxane, 1 part of dodecyl alcohol ester), 5 parts of additive B (5 parts of lysine diisocyanate), and 180 parts of solvent (water).

[0058] The preparation process of modified sodium silicate is as follows: silane coupling agent KH560, nano silica, polyethylene glycol, water and nano sodium silicate are mixed in a weight ratio of 5:8:7:50:30. The mixing temperature is 50℃, the stirring speed is 1000 rpm, and the mixing time is 2 hours to obtain modified sodium silicate.

[0059] The paper substrate has a specification of 230g / m². 2 White cardstock.

[0060] Figure 1 This is a schematic diagram of the structure of the white cardboard prepared in Embodiment 1 of the present invention. In the diagram, 100 represents the paper substrate, 200 represents the first coating, 300 represents the second coating, 400 represents the third coating, and 500 represents the fourth coating.

[0061] A method for preparing white cardboard for packaging includes the following steps:

[0062] Weigh out the water-based hydroxyl acrylic resin emulsion, hydroxyl polydimethylsiloxane, modified sodium silicate, additive A, and solvent according to the proportion. Stir and mix at a stirring speed of 1000 rpm for 40 minutes. Then add additive B and mix to obtain the first coating.

[0063] Weigh out the amino resin emulsion, modified sodium silicate, additive A, and solvent according to the proportion, stir and mix at a stirring speed of 700 rpm for 40 minutes, then add additive B and mix to obtain the second coating.

[0064] Take paper substrate (specification 230g / m²) 2 White cardboard), the first coating (coating amount of 8g / m²) is sequentially applied to the surface of the paper substrate. 2 ), second coating (coating amount 6g / m 2 Then apply the first coating (coating amount 8g / m²). 2 ), second coating (coating amount 6g / m 2 The process involves alternating between the first and second coatings, drying at 80°C for 10 minutes, and then maintaining the temperature at 130°C for 13 minutes to produce white cardboard.

[0065] Example 2: Preparation of white cardboard

[0066] A type of white cardboard for packaging, comprising, from bottom to top, a paper substrate, a first coating, a second coating, a third coating, and a fourth coating;

[0067] The first and third coatings have the same composition, both made from the first coating material. The first coating material, by weight, consists of 80 parts of water-based hydroxyl acrylic resin emulsion, 22 parts of hydroxyl polydimethylsiloxane, 65 parts of modified sodium silicate, 6 parts of additive A (1 part of sodium methylene dimethylbenzenesulfonate, 4 parts of polydimethylsiloxane, 1 part of dodecyl alcohol ester), 6 parts of additive B (6 parts of lysine diisocyanate), and 180 parts of solvent (water).

[0068] The second and fourth coatings have the same composition, both made from the second coating material. The second coating material, by weight, consists of 80 parts amino resin emulsion, 16 parts citric acid, 45 parts modified sodium silicate, 5 parts additive A (1 part sodium methylene dimethylbenzenesulfonate, 3 parts polydimethylsiloxane, 1 part dodecyl alcohol ester), 5 parts additive B (5 parts lysine diisocyanate), and 180 parts solvent (water).

[0069] The preparation process of modified sodium silicate is as follows: silane coupling agent KH560, nano silica, polyethylene glycol, water and nano sodium silicate are mixed in a weight ratio of 5:8:7:50:30. The mixing temperature is 50℃, the stirring speed is 1000 rpm, and the mixing time is 2 hours to obtain modified sodium silicate.

[0070] The paper substrate has a specification of 230g / m². 2 White cardstock.

[0071] A method for preparing white cardboard for packaging includes the following steps:

[0072] Weigh out the water-based hydroxyl acrylic resin emulsion, hydroxyl polydimethylsiloxane, modified sodium silicate, additive A, and solvent according to the proportion. Stir and mix at a stirring speed of 1000 rpm for 40 minutes. Then add additive B and mix to obtain the first coating.

[0073] Weigh out the amino resin emulsion, citric acid, modified sodium silicate, additive A, and solvent according to the proportion, stir and mix at a stirring speed of 700 rpm for 40 minutes, then add additive B and mix to obtain the second coating.

[0074] Take paper substrate (specification 230g / m²) 2 White cardboard), the first coating (coating amount of 8g / m²) is sequentially applied to the surface of the paper substrate. 2 ), second coating (coating amount 6g / m 2 Then apply the first coating (coating amount 8g / m²). 2 ), second coating (coating amount 6g / m 2 The process involves alternating between the first and second coatings, drying at 80°C for 10 minutes, and then maintaining the temperature at 130°C for 13 minutes to produce white cardboard.

[0075] Example 3: Preparation of white cardboard

[0076] A type of white cardboard for packaging, comprising, from bottom to top, a paper substrate, a first coating, a second coating, a third coating, and a fourth coating;

[0077] The first and third coatings have the same composition, both made from the first coating material. The first coating material, by weight, consists of 80 parts of water-based hydroxyl acrylic resin emulsion, 30 parts of hydroxyl polydimethylsiloxane, 75 parts of modified sodium silicate, 8 parts of additive A (1 part of sodium methylene dimethylbenzenesulfonate, 5 parts of polydimethylsiloxane, and 2 parts of dodecyl alcohol ester), 8 parts of additive B (6 parts of lysine diisocyanate and 2 parts of triethylenetetramine), and 200 parts of solvent (water).

[0078] The second and fourth coatings have the same composition, both made from the second coating material. The second coating material, by weight, consists of 80 parts amino resin emulsion, 40 parts modified sodium silicate, 5 parts additive A (1 part sodium methylene dimethylbenzenesulfonate, 3 parts polydimethylsiloxane, 1 part dodecyl alcohol ester), 6 parts additive B (5 parts lysine diisocyanate, 1 part triethylenetetramine), and 180 parts solvent (water).

[0079] The preparation process of modified sodium silicate is as follows: silane coupling agent KH570, nano silica, polyethylene glycol, water, and nano sodium silicate are mixed in a weight ratio of 5:10:8:55:35. The mixing temperature is 55℃, the stirring speed is 1000 rpm, and the mixing time is 2.5 hours to obtain modified sodium silicate.

[0080] The paper substrate has a specification of 230g / m². 2 White cardstock.

[0081] A method for preparing white cardboard for packaging includes the following steps:

[0082] Weigh out the water-based hydroxyl acrylic resin emulsion, hydroxyl polydimethylsiloxane, modified sodium silicate, additive A, and solvent according to the proportion. Stir and mix at a stirring speed of 1000 rpm for 40 minutes. Then add additive B and mix to obtain the first coating.

[0083] Weigh out the amino resin emulsion, modified sodium silicate, additive A, and solvent according to the proportion, stir and mix at a stirring speed of 700 rpm for 40 minutes, then add additive B and mix to obtain the second coating.

[0084] Take paper substrate (specification 230g / m²) 2 White cardboard), the first coating (coating amount of 10g / m²) is sequentially applied to the surface of the paper substrate. 2 ), second coating (coating amount 8g / m 2 Then apply the first coating (coating amount is 10g / m²). 2 ), second coating (coating amount 8g / m 2 The process involves alternating between the first and second coatings, drying at 85°C for 10 minutes, and then maintaining the temperature at 135°C for 11 minutes to produce white cardboard.

[0085] Example 4: Preparation of white cardboard

[0086] A type of white cardboard for packaging, comprising, from bottom to top, a paper substrate, a first coating, a second coating, a third coating, and a fourth coating;

[0087] The first and third coatings have the same composition, both made from the first coating material. The first coating material, by weight, consists of 80 parts of water-based hydroxyl acrylic resin emulsion, 32 parts of hydroxyl polydimethylsiloxane, 72 parts of modified sodium silicate, 8 parts of additive A (1 part of sodium methylene dimethylbenzenesulfonate, 5 parts of polydimethylsiloxane, and 2 parts of dodecyl alcohol ester), 8 parts of additive B (6 parts of lysine diisocyanate and 2 parts of triethylenetetramine), and 200 parts of solvent (water).

[0088] The second and fourth coatings have the same composition, both made from the second coating material. The second coating material, by weight, consists of 80 parts amino resin emulsion, 13 parts citric acid, 41 parts modified sodium silicate, 5 parts additive A (1 part sodium methylene dimethylbenzenesulfonate, 3 parts polydimethylsiloxane, 1 part dodecyl alcohol ester), 6 parts additive B (5 parts lysine diisocyanate, 1 part triethylenetetramine), and 180 parts solvent (water).

[0089] The preparation process of modified sodium silicate is as follows: silane coupling agent KH570, nano silica, polyethylene glycol, water and nano sodium silicate are mixed in a weight ratio of 5:9:9:55:35. The mixing temperature is 55℃, the stirring speed is 1000 rpm, and the mixing time is 2.5 hours to obtain modified sodium silicate.

[0090] The paper substrate has a specification of 230g / m². 2 White cardstock.

[0091] A method for preparing white cardboard for packaging includes the following steps:

[0092] Weigh out the water-based hydroxyl acrylic resin emulsion, hydroxyl polydimethylsiloxane, modified sodium silicate, additive A, and solvent according to the proportion. Stir and mix at a stirring speed of 1000 rpm for 40 minutes. Then add additive B and mix to obtain the first coating.

[0093] Weigh out the amino resin emulsion, citric acid, modified sodium silicate, additive A, and solvent according to the proportion, stir and mix at a stirring speed of 700 rpm for 40 minutes, then add additive B and mix to obtain the second coating.

[0094] Take paper substrate (specification 230g / m²) 2 White cardboard), the first coating (coating amount of 10g / m²) is sequentially applied to the surface of the paper substrate. 2 ), second coating (coating amount 8g / m 2 Then apply the first coating (coating amount is 10g / m²). 2 ), second coating (coating amount 8g / m 2 The process involves alternating between the first and second coatings, drying at 85°C for 10 minutes, and then maintaining the temperature at 135°C for 11 minutes to produce white cardboard.

[0095] Comparative Example 1

[0096] Compared with Example 1, the only difference in Comparative Example 1 is that in the first coating of Comparative Example 1, an equal amount of water-based hydroxyl acrylic resin emulsion was used instead of hydroxyl polydimethylsiloxane, while the other components and processes were the same as in Example 1.

[0097] Comparative Example 2

[0098] Compared with Example 1, the only difference in Comparative Example 2 is that, in the first and second coatings of Comparative Example 2, the nano-sodium silicate is not modified, but an equal amount of nano-sodium silicate is used instead of modified sodium silicate. The remaining components and processes are the same as in Example 1.

[0099] Comparative Example 3

[0100] Compared with Example 1, the preparation process of white cardboard in Comparative Example 3 is as follows: Take paper substrate (specification 230g / m²) 2 White cardboard), the first coating (coating amount of 8g / m²) is sequentially applied to the surface of the paper substrate. 2 First coating (coating amount 8g / m) 2 Then apply a second coating (coating amount 6g / m²). 2 ), second coating (coating amount 6g / m 2 The first and second coatings are applied without alternation, then dried at 80°C for 10 minutes, and then kept at 130°C for 13 minutes to obtain white cardboard. The first and second coatings in Comparative Example 3 are the same as those in Example 1.

[0101] Product effectiveness test

[0102] 1. Water vapor, oxygen, and oil repellency tests

[0103] The white cardboard prepared in Examples 1-2 and Comparative Examples 1-3 were placed at 25°C and 80% relative humidity for 24 hours and 60 hours, and the water vapor transmission rate and oxygen transmission rate of the white cardboard were tested.

[0104] The oil-resistant performance test involved making a cup shape out of white cardboard, filling it with soybean oil (the soybean oil was in contact with the fourth coating of the white cardboard), and letting it stand at 0℃ and 40℃ for 12 hours each, and repeating this process 8 times. The test was conducted to observe whether the white cardboard was penetrated by the soybean oil (the penetration level was divided into four levels: large penetration, medium penetration, small penetration, and no penetration, which were respectively recorded as level D, level C, level B, and level A, with level A corresponding to no penetration and the best oil-resistant effect). The results are shown in Table 1.

[0105] Table 1

[0106]

[0107] As can be seen from Table 1, the white cardboard prepared in Examples 1-2 of this invention exhibits excellent barrier properties against water vapor, oxygen, and oil, significantly outperforming Comparative Examples 1-3. This indicates that the use of hydroxyl polydimethylsiloxane, the modification method of nano-sodium silicate, and the coating sequence of the coating on the paper substrate surface (in Comparative Example 3, changing the coating sequence of the first and second coatings resulted in only one contact interface between the first and second coatings, thus reducing the water vapor, oxygen, and oil resistance of the white cardboard) all significantly affect the water vapor, oxygen, and oil resistance of the white cardboard.

[0108] 2. High and low temperature water resistance test

[0109] Take the white cardboard from Examples 1-2 and Comparative Example 2, fold it into a paper cup, put 0°C ice water (the water is in contact with the fourth coating of the white cardboard) into the paper cup and leave it for 12 hours (the ice water temperature is kept at 0°C during the placement). Then pour out the ice water, put in 100°C water, and leave it for another 12 hours (the water temperature is kept at 100°C during the placement). Pour out the water again, and continue to put 0°C ice water into the paper cup and leave it for another 12 hours. Repeat this cycle until the paper cup shows signs of wet cracking. Count the number of cycles of adding 0°C ice water and 100°C water when the paper cup shows signs of wet cracking. The results are shown in Table 2.

[0110] Table 2

[0111]

[0112] As can be seen from Table 2, the white cardboard of the paper cups in Examples 1-2 of the present invention exhibits significantly better high and low temperature water resistance than that of Comparative Example 2. Furthermore, the results of Examples 1-2 show that adding citric acid to the second coating significantly improves the high and low temperature water resistance of the white cardboard.

[0113] The properties of the white cardboard in Examples 3-4 are similar to those in Examples 1-2.

Claims

1. A type of white cardstock, characterized in that, From bottom to top, it includes paper substrate, first coating, second coating, third coating, and fourth coating; The first coating and the third coating have the same composition, both made from the first coating material. The first coating material, by weight, consists of the following components: 80 parts of water-based hydroxyl acrylic resin emulsion, 20-40 parts of hydroxyl polydimethylsiloxane, 60-80 parts of modified sodium silicate, 5-20 parts of additive A, 4-12 parts of additive B, and 100-200 parts of solvent. The second coating and the fourth coating have the same composition, both made from the second coating material. The second coating material, by weight, consists of the following components: 80 parts of amino resin emulsion, 10-20 parts of citric acid, 40-50 parts of modified sodium silicate, 5-15 parts of additive A, 4-10 parts of additive B, and 100-180 parts of solvent. The modified sodium silicate is prepared by mixing silane coupling agent, nano silica, polyethylene glycol, water, and nano sodium silicate in a weight ratio of (4-10):(5-12):(3-12):(35-60):(30-40), at a temperature of 40-60°C, at a stirring speed of 800-1200 rpm, and for 2-5 hours, thereby obtaining the modified sodium silicate. The auxiliary agent A includes sodium methylene dimethylbenzenesulfonate, defoamer, dodecyl alcohol ester, antibacterial agent and antioxidant; The auxiliary agent B includes isocyanate.

2. The white cardboard according to claim 1, characterized in that, The auxiliary agent B also includes triethylenetetramine.

3. The white cardboard according to claim 1, characterized in that, The defoamer is polydimethylsiloxane.

4. The method for preparing white cardboard according to any one of claims 1-3, characterized in that, Includes the following steps: Take the components for preparing the first coating, mix the components, and obtain the first coating; Take the components for preparing the second coating, mix the components, and obtain the second coating; Take a paper substrate, coat the surface of the paper substrate with a first coating and a second coating in sequence, then coat the surface with the first coating and the second coating again, and then heat and cure to obtain the white cardboard.

5. The preparation method according to claim 4, characterized in that, The application amount of the first and second coatings is 3-15 g / m² each time. 2 .

6. The application of white cardboard as described in any one of claims 1-3 in the packaging field.

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