Water-based silicic acid-based adhesive for PET (polyethylene terephthalate) film and BOPP (biaxially-oriented polypropylene) film

Abstract

The invention provides a water-based silicic acid-based adhesive for a PET (polyethylene terephthalate) film and a BOPP (biaxially-oriented polypropylene) film. Belongs to the field of adhesives. The paint comprises the following components: sodium silicate, cellulose acetate, tannic acid, epoxy resin, allyl glycidyl ether, diethanol amine, barium chloride and water. Through an inorganic rigid framework of sodium silicate, an organic cross-linked network of epoxy resin, interface enhancement of tannic acid and ionic cross-linking of barium chloride, the comprehensive performance of high bonding strength, water resistance, weather resistance, environment friendliness and no toxicity is achieved, and the adhesive is particularly suitable for connection of various different base materials such as PET films and BOPP films.

Description

Technical Field

[0001] The present invention belongs to the field of adhesives, and particularly relates to an aqueous silicate-based adhesive for PET films and BOPP films. Background Art

[0002] PET (polyethylene terephthalate) and BOPP (biaxially oriented polypropylene) are two high-performance plastic films widely used in the packaging, electronics, and industrial fields. PET films are known for their excellent mechanical strength, heat resistance (-70°C to 150°C), and high barrier properties (airtight, moisture-proof), and are commonly used in food packaging (such as beverage bottles, vacuum bags), electronic insulation materials (capacitors, cables), and aluminized film substrates. In contrast, BOPP films, with their high transparency, oil resistance, and low static electricity characteristics, are mainly used in flexible packaging (food bags, labels), tape substrates, and printed composite films (such as aluminized BOPP).

[0003] PET films and BOPP films themselves have excellent mechanical properties and barrier properties, but in actual applications, they often need to be compounded with other materials (such as paper, aluminum layers, PE films) to meet multifunctional requirements. Adhesives achieve the bonding of different materials through intermolecular bonding. For example, when a PET film needs to be combined with an aluminized layer, the adhesive can enhance the interfacial bonding force and prevent delamination. Summary of the Invention

[0004] The purpose of the present invention is to address the lack of a specialized adhesive when PET and BOPP substrates need to be compounded with other materials; and to propose an aqueous silicate-based adhesive.

[0005] To achieve the above purpose, the present invention provides an aqueous silicate-based adhesive, comprising the following components:

[0006]

[0007] And water.

[0008] The preparation method of the aforementioned aqueous silicate-based adhesive comprises the following steps:

[0009] S1 Tannic acid modification of epoxy resin: Mix tannic acid and allyl glycidyl ether and react to obtain a TA-AGE derivative;

[0010] Mix epoxy resin and diethanolamine and react to obtain a preliminarily modified epoxy resin;

[0011] Mix the preliminarily modified epoxy resin with TA-AGE, then add a catalyst and stir to react to form an epoxy resin emulsion;

[0012] S2 Preparation of silicate emulsion: Dissolve cellulose acetate in an organic solvent; then mix an aqueous sodium silicate solution with the cellulose acetate solution and stir to obtain a silicate emulsion;

[0013] S3 Blending, crosslinking and curing: Drop the epoxy resin emulsion into the silicate emulsion and continue the reaction; then add barium chloride and stir to form a colloid; then adjust the pH to weakly acidic to neutral with ammonia water and control the solid content; obtain the water-based silicate-based adhesive.

[0014] Preferably, in the step S1: The mixing reaction time of tannic acid and allyl glycidyl ether is at least 2 h, and the temperature is 82.5 ± 2.5 °C;

[0015] The mixing reaction time of epoxy resin and diethanolamine is at least 1.5 h, and the temperature is 72.5 ± 2.5 °C;

[0016] The mixing reaction time of the preliminarily modified epoxy resin and TA-AGE is at least 2 h, and the temperature is 62.5 ± 2.5 °C.

[0017] Preferably, in the step S1: The catalyst is an organic bismuth catalyst, and the addition amount is 0.5-0.7 wt% of the epoxy resin.

[0018] Preferably, in the step S2: The mass fraction of the sodium silicate aqueous solution is 35-55%; the mixing and stirring time of the sodium silicate aqueous solution and the cellulose acetate solution is at least 1.5 h, and the temperature is 72.5 ± 2.5 °C.

[0019] Preferably, in the step S3: The time for continuously reacting after dropping the epoxy resin emulsion into the silicate emulsion is at least 2 h, and the dropping time of the epoxy resin emulsion is not less than 80% of the continuous reaction time; the temperature is 60 ± 2.5 °C.

[0020] The time for adding barium chloride and stirring to form a colloid is at least 40 min, and the temperature is 50 ± 5 °C.

[0021] Adjust the pH with ammonia water, the pH value is 6.5-7.0; the solid content is 50-55%.

[0022] Functions of each component in the present invention:

[0023] Sodium silicate:

[0024] As an inorganic matrix, it provides the basic adhesiveness and high temperature resistance of the adhesive; the sodium silicate aqueous solution (water glass) forms a silica gel network through curing, enhancing the mechanical strength of the adhesive layer. It forms an organic-inorganic hybrid structure with cellulose acetate, improving the water resistance and durability of the adhesive layer.

[0025] Cellulose acetate:

[0026] As an organic toughening agent, it alleviates the brittleness of silicates and improves the flexibility and crack resistance of the adhesive layer; after being dissolved in an organic solvent and blended with sodium silicate emulsion, it improves the compatibility of the system and prevents inorganic phase agglomeration. Its film-forming property helps the adhesive to spread evenly on the surface of the substrate.

[0027] Tannic acid:

[0028] It reacts with allyl glycidyl ether to generate TA-AGE derivatives, introduces polyphenolic hydroxyl groups, and enhances the chemical crosslinking density with epoxy resin; the natural polyphenol structure provides antioxidant properties and prolongs the service life of the adhesive. It improves the wettability of polar substrates through hydrogen bonding.

[0029] Epoxy resin:

[0030] The three-dimensional network is formed by curing with diethanolamine, which significantly improves the tensile strength and chemical resistance of the adhesive layer. The epoxy group reacts with the surface active groups of the substrate (such as -OH, -COOH) to enhance the adhesion; and after being modified with tannic acid, the hydrolysis resistance of the epoxy resin is further improved.

[0031] Allyl glycidyl ether:

[0032] Bridging tannic acid and epoxy resin: its epoxy group reacts with tannic acid, and the allyl group participates in free radical polymerization to form an interpenetrating network; the long-chain allyl group reduces the cross-linking density and improves the toughness of the adhesive layer.

[0033] Diethanolamine:

[0034] As epoxy resin curing agent: secondary amine group and epoxy group open ring reaction, medium-speed curing to avoid stress in the glue layer. At the same time, maintain the weak alkalinity of the system and promote the stable cross-linking of sodium silicate.

[0035] Barium chloride:

[0036] Ba 2 + It forms insoluble barium silicate with silicate, which accelerates gelation and improves water resistance. Trace amounts of barium salts inhibit microbial growth and reduce adhesive layer degradation.

[0037] The present invention uses sodium silicate and cellulose acetate as main raw materials and combines water as dispersion medium, completely avoiding the VOCs emission problem of traditional solvent-based adhesives. The introduction of tannic acid as a natural polyphenol compound is in line with the development trend of bio-based materials.

[0038] The present invention forms an organic-inorganic hybrid network structure by grafting epoxy resin with tannic acid-allyl glycidyl ether (TA-AGE). This design not only retains the high bonding strength of epoxy resin, but also improves heat resistance through the rigid skeleton of silicate, effectively overcoming the pain points of low bonding strength and poor weather resistance of traditional water-based adhesives.

[0039] The addition of barium chloride in the present invention enhances the colloidal stability through ionic crosslinking, and diethanolamine as a curing agent can adjust the reaction activity.

[0040] Through the inorganic rigid framework of sodium silicate, the organic crosslinking network of epoxy resin, the interface enhancement of tannic acid and the ionic crosslinking of barium chloride, the present invention realizes the comprehensive properties of high bonding strength, water and weather resistance, environmental protection and non-toxicity, and is particularly suitable for connecting various different substrates such as PET film and BOPP film. Detailed implementation mode

[0041] For a better understanding of the present invention, the present invention will be further described below in combination with specific serial numbers. The terms used in the serial numbers are for describing specific specific implementation schemes and do not constitute a limitation on the protection scope of the present invention.

[0042] In the detailed implementation mode, the experimental methods used are all conventional methods unless otherwise specified, and the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0043] The water used in the present invention is pure water.

[0044] The organobismuth catalyst used in the present invention is DY-20

[0045] Example 1 Preparation of water-based silicate adhesive, including the following steps:

[0046] S1 Weighing: Weigh the following components according to parts by mass:

[0047]

[0048] S2 Modification of epoxy resin with tannic acid:

[0049] Mix tannic acid and allyl glycidyl ether and react for 2 h at a temperature of 82.5 ± 2.5 °C; obtain TA-AGE derivative;

[0050] Mix epoxy resin and diethanolamine and add DY-20 and react for 1.5 h at a temperature of 72.5 ± 2.5 °C; obtain preliminarily modified epoxy resin;

[0051] Mix the preliminarily modified epoxy resin with TA-AGE, then add a catalyst and stir and react for 2 h at a temperature of 62.5 ± 2.5 °C; obtain an epoxy resin emulsion.

[0052] S3 Preparation of silicate emulsion:

[0053] Prepare an aqueous solution of sodium silicate with a mass fraction of 35% by adding water to sodium silicate; dissolve cellulose acetate in an appropriate amount of acetone; then mix the aqueous solution of sodium silicate with the cellulose acetate solution and stir at a temperature of 72.5 ± 2.5 °C for 1.5 h; obtain a silicate emulsion.

[0054] S4 Blending, crosslinking and curing: Slowly drip the epoxy resin emulsion into the silicate emulsion within 96 min, and then continue the reaction for 24 min; Keep stirring and the temperature at 60 ± 2.5 °C throughout the process;

[0055] Then add barium chloride and stir for 40 min to form a colloid; Then adjust the pH value to 6.5 and the solid content to 50% with ammonia water; Obtain the water-based silicate-based adhesive.

[0056] Example 2 Preparation of the water-based silicate-based adhesive, including the following steps:

[0057] S1 Weighing: Weigh the following components by mass parts:

[0058]

[0059] S2 Tannic acid modification of epoxy resin:

[0060] Mix tannic acid and allyl glycidyl ether and react for 2 h at a temperature of 82.5 ± 2.5 °C; Obtain the TA-AGE derivative;

[0061] Mix epoxy resin and diethanolamine and add DY-20 and react for 1.5 h at a temperature of 72.5 ± 2.5 °C; Obtain the preliminarily modified epoxy resin;

[0062] Mix the preliminarily modified epoxy resin with TA-AGE, then add a catalyst and stir and react for 2 h at a temperature of 62.5 ± 2.5 °C; Obtain the epoxy resin emulsion.

[0063] S3 Preparation of silicate emulsion:

[0064] Prepare an aqueous solution with a mass fraction of 45% by mixing sodium silicate with water; Dissolve cellulose acetate in an appropriate amount of acetone; Then mix the sodium silicate aqueous solution and the cellulose acetate solution and stir at a temperature of 72.5 ± 2.5 °C for 1.5 h; Obtain the silicate emulsion.

[0065] S4 Blending, crosslinking and curing: Slowly drip the epoxy resin emulsion into the silicate emulsion within 96 min, and then continue the reaction for 24 min; Keep stirring and the temperature at 60 ± 2.5 °C throughout the process;

[0066] Then add barium chloride and stir for 40 min to form a colloid; Then adjust the pH value to 6.5 and the solid content to 50% with ammonia water; Obtain the water-based silicate-based adhesive.

[0067] Example 3 Preparation of the water-based silicate-based adhesive, including the following steps:

[0068] S1 Weighing: Weigh the following components by mass parts:

[0069]

[0070] Tannic acid modification of S2 epoxy resin:

[0071] Mix tannic acid and allyl glycidyl ether and react for 2 h at a temperature of 82.5 ± 2.5 °C; obtain TA-AGE derivative;

[0072] Mix epoxy resin and diethanolamine and add DY-20 to react for 1.5 h at a temperature of 72.5 ± 2.5 °C; obtain preliminarily modified epoxy resin;

[0073] Mix the preliminarily modified epoxy resin with TA-AGE, then add a catalyst and stir to react for 2 h at a temperature of 62.5 ± 2.5 °C; obtain epoxy resin emulsion.

[0074] S3 Preparation of silicate emulsion:

[0075] Adjust sodium silicate with water to form an aqueous solution with a mass fraction of 35%; dissolve cellulose acetate in an appropriate amount of acetone; then mix the sodium silicate aqueous solution with the cellulose acetate solution and stir at a temperature of 72.5 ± 2.5 °C for 1.5 h; obtain silicate emulsion.

[0076] S4 Co-blending crosslinking and curing: Slowly drop the epoxy resin emulsion into the silicate emulsion within 96 min, and then continue to react for 24 min; keep stirring and the temperature at 60 ± 2.5 °C throughout the process;

[0077] Then add barium chloride and stir for 40 min to form a colloid; then adjust the pH value to 7.0 and the solid content to 55% with ammonia water; obtain water-based silicate-based adhesive.

[0078] Preparation of the water-based silicate-based adhesive in Example 4 includes the following steps:

[0079] S1 Weighing: Weigh the following components by mass parts:

[0080]

[0081] S2 Preparation of silicate emulsion:

[0082] Adjust sodium silicate with water to form an aqueous solution with a mass fraction of 35%; dissolve cellulose acetate in an appropriate amount of acetone; then mix the sodium silicate aqueous solution with the cellulose acetate solution and stir at a temperature of 72.5 ± 2.5 °C for 1.5 h; obtain silicate emulsion.

[0083] S3 Co-blending crosslinking and curing:

[0084] Dissolve epoxy resin in an appropriate amount of acetone; slowly drop the epoxy resin emulsion into the silicate emulsion within 96 min, and then continue to react for 24 min; keep stirring and the temperature at 60 ± 2.5 °C throughout the process;

[0085] Then add barium chloride and stir for 40 min to form a colloid; then adjust the pH value to 7.0 and the solid content to 55% with ammonia water; obtain the water-based silicate-based adhesive.

[0086] Example 5 Preparation of water-based silicate-based adhesive, including the following steps:

[0087] S1 Weighing: Weigh the following components by mass parts:

[0088]

[0089] S2 Tannic acid modification of epoxy resin:

[0090] Mix tannic acid and allyl glycidyl ether and react for 2 h at a temperature of 82.5 ± 2.5 °C; obtain TA-AGE derivative;

[0091] Mix epoxy resin and diethanolamine and add DY-20 and react for 1.5 h at a temperature of 72.5 ± 2.5 °C; obtain the preliminarily modified epoxy resin;

[0092] Mix the preliminarily modified epoxy resin with TA-AGE, then add a catalyst and stir and react for 2 h at a temperature of 62.5 ± 2.5 °C; obtain the epoxy resin emulsion.

[0093] S3 Preparation of silicate emulsion:

[0094] Adjust sodium silicate with water to form an aqueous solution with a mass fraction of 35%; obtain the silicate emulsion.

[0095] S4 Co-blending crosslinking and curing: Slowly drop the epoxy resin emulsion into the silicate emulsion within 96 min, and then continue to react for 24 min; keep stirring and the temperature at 60 ± 2.5 °C throughout the process;

[0096] Then add barium chloride and stir for 40 min to form a colloid; then adjust the pH value to 6.5 and the solid content to 50% with ammonia water; obtain the water-based silicate-based adhesive.

[0097] Performance test:

[0098] Test the bonding performance of the above examples. Clean the surface of the silica gel, and then coat the adhesive on the surface of the substrate respectively, bake until the adhesive liquid is cured, and then obtain the coating layer. Test the peel strength and tensile strength of the coating layer prepared above at room temperature; among them, use a universal tensile machine for testing. The T-peel strength adopts "GB / T 2791-1995 Test method for T-peel strength of adhesives Flexible material to flexible material", and the tensile speed: 300 mm / s for testing; the tensile strength adopts "GB / T7124-2008 Determination of tensile shear strength of adhesives (Rigid material to rigid material)" gauge: 100 mm; tensile speed: 10 m / s for testing.

[0099] The results are shown in Table 1.

[0100] Table 1

[0101] Serial number T-peel strength / (N / mm) Tensile strength / Mpa Example 1 0.050 223 Example 2 0.053 246 Example 3 0.047 258 Example 4 0.034 168 Example 5 0.042 203

[0102] As can be seen from Table 1, in Example 4, tannic acid, allyl glycidyl ether and DY-20 were not used, and the epoxy resin was not modified, resulting in the weakest crosslinking degree and interfacial bonding strength; in Example 5, cellulose acetate was lacking, and the uniformity of the adhesive layer was poor, leading to a decrease in cohesive strength, but the TA-AGE modification still retained some crosslinking advantages. In Example 3, the addition amounts of cellulose acetate, epoxy resin and tannic acid were all the highest; the modification of tannic acid-allyl glycidyl ether enhanced the crosslinking density of the epoxy resin, and at the same time, the high content of cellulose acetate could improve the cohesive force of the adhesive layer; however, the relatively high addition amount might lead to a too thick adhesive layer, and the loss of cohesive strength might be relatively large, resulting in a partial decrease in the T-peel strength.

[0103] The above detailed description is a specific description of one of the feasible embodiments of the present invention, and this embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or change made without departing from the present invention shall be included within the scope of the technical solution of the present invention.

Claims

1. An aqueous silicate-based adhesive, characterized in that, It includes the following components:

2. The preparation method of the aqueous silicate-based adhesive according to claim 1, characterized in that, It includes the following steps: S1 Tannic acid modification of epoxy resin: Mix tannic acid and allyl glycidyl ether and react to obtain TA-AGE derivative; Mix epoxy resin and diethanolamine and react to obtain preliminarily modified epoxy resin; Mix the preliminarily modified epoxy resin with TA-AGE, then add a catalyst and stir to react to form an epoxy resin emulsion; S2 Preparation of silicate emulsion: Dissolve cellulose acetate in an organic solvent; then mix an aqueous sodium silicate solution and a cellulose acetate solution and stir to obtain a silicate emulsion; S3 Blending, cross-linking and curing: Drop the epoxy resin emulsion into the silicate emulsion and continuously react; then add barium chloride and stir to form a colloid; then adjust the pH to weakly acidic to neutral with ammonia water and control the solid content to obtain an aqueous silicate-based adhesive.

3. The preparation method of the aqueous silicate-based adhesive according to claim 2, characterized in that, In the step S1: The mixing reaction time of tannic acid and allyl glycidyl ether is at least 2 h, and the temperature is 82.5 ± 2.5 °C; The mixing reaction time of epoxy resin and diethanolamine is at least 1.5 h, and the temperature is 72.5 ± 2.5 °C; The mixing reaction time of the preliminarily modified epoxy resin and TA-AGE is at least 2 h, and the temperature is 62.5 ± 2.5 °C.

4. The preparation method of the aqueous silicate-based adhesive according to claim 2, characterized in that, In the step S1: The catalyst is an organic bismuth catalyst, and the addition amount is 0.5-0.7 wt% of the epoxy resin.

5. The preparation method of the aqueous silicate-based adhesive according to claim 2, characterized in that, In the step S2: The mass fraction of the aqueous sodium silicate solution is 35-55%; the mixing and stirring time of the aqueous sodium silicate solution and the cellulose acetate solution is at least 1.5 h, and the temperature is 72.5 ± 2.5 °C.

6. The preparation method of the aqueous silicate-based adhesive according to claim 3, characterized in that, In the step S3: The continuous reaction time of dropping the epoxy resin emulsion into the silicate emulsion is at least 2 h, and the dropping time of the epoxy resin emulsion is not less than 80% of the continuous reaction time; the temperature is 60 ± 2.5 °C.

7. The preparation method of the aqueous silicate-based adhesive according to claim 3, characterized in that, In the step S3: The time for adding barium chloride and stirring to form a colloid is at least 40 min, and the temperature is 50 ± 5 °C.

8. The preparation method of the aqueous silicate-based adhesive according to claim 3, characterized in that, In the step S3: The pH is adjusted with ammonia water, and the pH value is 6.5-7.0; the solid content is 50-55%.

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