Water-based adhesive special for stone paper packaging box and preparation method thereof

Abstract

The application relates to the technical field of adhesives, and discloses a water-based adhesive special for stone paper packaging boxes and a preparation method thereof.The water-based adhesive comprises 30-40 parts by weight of a pigment filler, 0.2-0.35 parts by weight of a dispersing agent, 20-27 parts by weight of polyvinyl alcohol, 2.4-5 parts by weight of a cationized end isocyanate curing agent and 30-48 parts by weight of carboxyl styrene-butadiene latex.The end position of the cationized end isocyanate curing agent contains four isocyanate curing sites, forms a better curing crosslinking reaction with the polyvinyl alcohol, and is beneficial to improving the bonding performance and mechanical strength of the adhesive curing product.The curing agent contains a cationic group, can form electrostatic interaction with a carboxyl sodium anion group of the carboxyl styrene-butadiene latex, is beneficial to increasing the cohesion of the adhesive curing product, and thus improves the peeling strength and bonding performance of the adhesive, so that the adhesive has higher peeling strength and tensile strength.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adhesive, in particular to a water-based adhesive special for stone paper packaging box and a preparation method thereof. BACKGROUND

[0002] Stone paper is mainly composed of high molecular resin such as polyethylene and calcium carbonate, and is a new type of environmental protection material between paper and plastic, which has wide application in packaging materials, wall paper and the like. The stone paper can be glued with adhesive to make materials such as packaging box with excellent performance and low cost. Traditional stone paper adhesive includes polyvinyl alcohol, carboxyl styrene butadiene latex, acrylic resin, alkyd resin and the like. Chinese patent CN104559897B discloses a special adhesive for stone paper and a preparation method thereof, which uses alkyd resin, seaweed glue powder and reinforcing fiber as raw materials, and realizes fast adhesion of stone paper through connection of microfibers by the penetration of alkyd resin and the tackifying effect of seaweed glue powder. However, the hot sealing temperature of the adhesive is high, and the stone paper is prone to thermal deformation. Moreover, the adhesive does not improve the tensile property, which is not conducive to improving the mechanical property of stone paper material. SUMMARY

[0003] The present application solves the problem of poor adhesion and mechanical property of traditional polyvinyl alcohol and styrene butadiene rubber adhesive.

[0004] The technical scheme of the present application is as follows: a water-based adhesive includes 30-40 parts by weight of color filler, 0.2-0.35 parts by weight of dispersant, 20-27 parts by weight of polyvinyl alcohol, 2.4-5 parts by weight of cationic end isocyanate curing agent and 30-48 parts by weight of carboxyl styrene butadiene latex.

[0005] Preferably, the preparation method of the water-based adhesive is as follows:

[0006] (1) polyvinyl alcohol is added to water, heated to 90-95℃, and dissolved by stirring to obtain a polyvinyl alcohol solution.

[0007] (2) sodium hydroxide is added to the carboxyl styrene butadiene latex to adjust the pH to neutral, then the polyvinyl alcohol solution, color filler and dispersant are added, and shearing dispersion is performed, and finally the cationic end isocyanate curing agent is added to obtain the water-based adhesive.

[0008] Preferably, the preparation method of the cationic end isocyanate curing agent is as follows:

[0009] (1) dichloro polyethylene glycol and N-methyl diethanolamine with a molar ratio of 1:(4-6) are added to ethanol, heated to 70-80℃ (water bath temperature), stirred and condensed refluxed for 24-30h, concentrated under reduced pressure, and the product is precipitated in diethyl ether, filtered and dried to obtain cationic polyethylene glycol.

[0010] (2) adding cationic polyethylene glycol (dried to remove water before use), diisocyanate, dibutyl tin dilaurate in a molar ratio of 1: (4.8-5.4): (0.02-0.026) to a solvent, heating to 65-80℃ (water bath temperature) in a nitrogen atmosphere, stirring and condensing reflux reaction for 2-3h, concentrating under reduced pressure to obtain cationic terminal isocyanate curing agent. The preparation reaction formula is:

[0011]

[0012] Preferably, the solvent in (2) is acetone or tetrahydrofuran.

[0013] Preferably, the diisocyanate in (2) is toluene-2,4-diisocyanate, isophorone diisocyanate or diphenylmethane 4,4'-diisocyanate.

[0014] Preferably, the color filler is any one of calcium carbonate, barium sulfate, kaolin, titanium dioxide.

[0015] Preferably, the dispersant is sodium hexametaphosphate or sodium polycarboxylate dispersant.

[0016] Preferably, the water-based adhesive is applied to the stone paper packaging box.

[0017] The beneficial technical effects of the present application: using dichloro polyethylene glycol and N-methyl diethanolamine to react to obtain cationic polyethylene glycol, the terminal hydroxyl group reacts with diisocyanate to obtain cationic terminal isocyanate curing agent. Further, carboxyl styrene butadiene rubber and polyvinyl alcohol are used as the main agent of the adhesive, and fillers, dispersants, curing agents, etc. are added to obtain a water-based adhesive for stone paper packaging boxes. The terminal position of the cationic terminal isocyanate curing agent contains four isocyanate curing sites, which forms better curing crosslinking reaction with polyvinyl alcohol, which is beneficial to improve the bonding performance and mechanical strength of the adhesive curing product.

[0018] The cationic terminal isocyanate curing agent of the present application contains a cationic group, which allows the polyvinyl alcohol-isocyanate curing crosslinking product to form electrostatic interaction with the sodium carboxylate anion group of the carboxyl styrene butadiene latex, which is beneficial to increase the cohesion of the adhesive curing product, thereby improving the peel strength and bonding performance of the adhesive, and the adhesive has higher peel strength and tensile strength.

[0019] The terminal isocyanate curing agent of the present application contains a flexible polyether molecular chain, which has a good toughening effect on the adhesive, thereby improving the elongation at break and toughness.

[0020] The curing temperature of the adhesive of the present application is low, the bonding and construction are convenient, and the problem of thermal deformation of stone paper caused by high curing temperature is avoided. DETAILED DESCRIPTION

[0021] The specific embodiments of the present application are further described below. It should be noted that the description of these embodiments is intended to assist in understanding the present application, but is not intended to limit the present application. Furthermore, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0022] The following polyvinyl alcohol type is 1788, purchased from Guangzhou Huihui Chemical Co., Ltd. Carboxyl styrene latex, solid content 50±2%, purchased from Jining Fanghe Chemical Co., Ltd. Sodium polycarboxylate dispersant, type DP5040, purchased from Nanjing Chuhai New Material Technology Co., Ltd.

[0023] The dichloro polyethylene glycol was prepared according to the method of the journal “Chemical Engineering of High Schools” Vol. 31 No. 6, December 2017, “Process research on synthesis of chloro polyethylene glycol by reaction of polyethylene glycol and thionyl chloride”. 30 mmol of polyethylene glycol 2000 was added to 100 mL of toluene, 180 mmol of thionyl chloride and 180 mmol of pyridine were added dropwise in an ice water bath, then stirred at 40°C for 18 h, and then concentrated under reduced pressure to remove thionyl chloride and most of the toluene until a large amount of precipitate was precipitated. After filtration, the filtrate was concentrated under reduced pressure to obtain dichloro polyethylene glycol. The structural formula is

[0024] Example 1:

[0025] (1) 5 mmol of dichloro polyethylene glycol, 26 mmol of N-methyl diethanolamine were added to 100 mL of ethanol, heated to 70°C, stirred and condensed reflux for 30 h, concentrated under reduced pressure, and the product was precipitated in diethyl ether, filtered and dried to obtain cationic polyethylene glycol.

[0026] (2) 10 mmol of dry cationic polyethylene glycol, 52 mmol of toluene-2,4-diisocyanate, and 0.22 mmol of dibutyltin dilaurate were added to 20 mL of acetone, heated to 70°C under nitrogen atmosphere, stirred and condensed reflux for 3 h, and then concentrated under reduced pressure to obtain a cationic isocyanate curing agent.

[0027] (3) 200 g of polyvinyl alcohol was added to 1.2 L of water, heated to 95°C, and stirred to dissolve to obtain a polyvinyl alcohol solution; sodium hydroxide was added to 480 g of carboxyl styrene latex to adjust the pH to neutral, then the polyvinyl alcohol solution was added, 300 g of titanium white powder, 2 g of sodium polycarboxylate dispersant, and sheared and dispersed, and finally 24 g of cationic isocyanate curing agent was added to obtain a water-based adhesive.

[0028] Example 2:

[0029] (1) To 150 mL of ethanol, add 5 mmol of dichloro polyethylene glycol, 30 mmol of N-methyl diethanolamine, heat to 75 °C, stir and condense reflux reaction for 30 h, reduce pressure concentration, product is added to diethyl ether for precipitation, filtration, drying, to get cationic polyethylene glycol.

[0030] (2) To 30 mL of tetrahydrofuran, add 10 mmol of dry cationic polyethylene glycol, 48 mmol of isophorone diisocyanate, 0.2 mmol of dibutyl tin dilaurate, heat to 80 °C in nitrogen atmosphere, stir and condense reflux reaction for 2 h, reduce pressure concentration, to get cationic end isocyanate curing agent.

[0031] (3) To 1.5 L of water, add 220 g of polyvinyl alcohol, heat to 90 °C, stir and dissolve, to get polyvinyl alcohol solution; To 420 g of carboxyl styrene-butadiene latex, add sodium hydroxide, adjust pH to neutral, then add polyvinyl alcohol solution, 340 g of calcium carbonate, 2.8 g of sodium polycarboxylate dispersant, shear dispersion, finally add 32 g of cationic end isocyanate curing agent, to get water-based adhesive.

[0032] Example 3:

[0033] (1) To 100 mL of ethanol, add 5 mmol of dichloro polyethylene glycol, 20 mmol of N-methyl diethanolamine, heat to 70 °C, stir and condense reflux reaction for 30 h, reduce pressure concentration, product is added to diethyl ether for precipitation, filtration, drying, to get cationic polyethylene glycol.

[0034] (2) To 30 mL of acetone, add 10 mmol of dry cationic polyethylene glycol, 54 mmol of diphenylmethane 4,4'-diisocyanate, 0.26 mmol of dibutyl tin dilaurate, heat to 70 °C in nitrogen atmosphere, stir and condense reflux reaction for 3 h, reduce pressure concentration, to get cationic end isocyanate curing agent.

[0035] (3) To 1.6 L of water, add 250 g of polyvinyl alcohol, heat to 95 °C, stir and dissolve, to get polyvinyl alcohol solution; To 370 g of carboxyl styrene-butadiene latex, add sodium hydroxide, adjust pH to neutral, then add polyvinyl alcohol solution, 360 g of kaolin, 3 g of sodium polycarboxylate dispersant, shear dispersion, finally add 40 g of cationic end isocyanate curing agent, to get water-based adhesive.

[0036] Example 4:

[0037] (1) To 100 mL of ethanol, add 5 mmol of dichloro polyethylene glycol, 30 mmol of N-methyl diethanolamine, heat to 80°C, stir and condense reflux reaction for 24 h, concentrate under reduced pressure, precipitate the product in diethyl ether, filter, dry, and obtain the cationic polyethylene glycol.

[0038] (2) To 30 mL of tetrahydrofuran, add 10 mmol of dry cationic polyethylene glycol, 52 mmol of toluene-2,4-diisocyanate, 0.22 mmol of dibutyltin dilaurate, heat to 80°C under nitrogen atmosphere, stir and condense reflux reaction for 2 h, concentrate under reduced pressure, and obtain the cationic end isocyanate curing agent.

[0039] (3) To 1.8 L of water, add 270 g of polyvinyl alcohol, heat to 90°C, stir and dissolve to obtain a polyvinyl alcohol solution; to 300 g of carboxyl styrene-butadiene latex, add sodium hydroxide to adjust the pH to neutral, then add the polyvinyl alcohol solution, 400 g of barium sulfate, 3.5 g of dispersant sodium hexametaphosphate, shear and disperse, and finally add 50 g of the cationic end isocyanate curing agent to obtain the water-based adhesive.

[0040] Comparative Example 1

[0041] (1) To 1.2 L of water, add 200 g of polyvinyl alcohol, heat to 95°C, stir and dissolve to obtain a polyvinyl alcohol solution; to 480 g of carboxyl styrene-butadiene latex, add sodium hydroxide to adjust the pH to neutral, then add the polyvinyl alcohol solution, 300 g of titanium white, 2 g of sodium polycarboxylate dispersant, shear and disperse to obtain the water-based adhesive.

[0042] Comparative Example 2

[0043] (1) To 20 mL of acetone, add 10 mmol of dry polyethylene glycol 2000, 26 mmol of toluene-2,4-diisocyanate, and 0.22 mmol of dibutyltin dilaurate, heat to 70°C under nitrogen atmosphere, stir and condense reflux reaction for 3 h, concentrate under reduced pressure, and obtain the end isocyanate curing agent. The structural formula is as follows:

[0044]

[0045] (2) To 1.2 L of water, add 200 g of polyvinyl alcohol, heat to 95°C, stir and dissolve to obtain a polyvinyl alcohol solution; to 480 g of carboxyl styrene-butadiene latex, add sodium hydroxide to adjust the pH to neutral, then add the polyvinyl alcohol solution, 300 g of titanium white, 2 g of sodium polycarboxylate dispersant, shear and disperse, and finally add 24 g of the end isocyanate curing agent to obtain the water-based adhesive.

[0046] Comparative Example 3

[0047] (1) To 100 mL of ethanol, add 5 mmol of dichloro polyethylene glycol, 26 mmol of 3-dimethylamino-1-propanol, heat to 70°C, stir and condense reflux reaction for 30 h, reduce pressure concentration, add the product to ether for precipitation, filter, dry, to obtain cationic polyethylene glycol. The structural formula is as follows:

[0048]

[0049] (2) To 20 mL of acetone, add 10 mmol of dry cationic polyethylene glycol, 52 mmol of toluene-2,4-diisocyanate, 0.22 mmol of dibutyltin dilaurate, heat to 70°C under nitrogen atmosphere, stir and condense reflux reaction for 3 h, reduce pressure concentration, to obtain cationic end isocyanate curing agent. The structural formula is as follows:

[0050] (3) To 1.2 L of water, add 200 g of polyvinyl alcohol, heat to 95°C, stir to dissolve, to obtain polyvinyl alcohol solution; to 480 g of carboxyl styrene-butadiene latex, add sodium hydroxide, adjust pH to neutral, then add polyvinyl alcohol solution, 300 g of titanium white, 2 g of polycarboxylic acid sodium dispersant, shear dispersion, finally add 24 g of cationic end isocyanate curing agent, to obtain water-based adhesive.

[0051] The peel strength of the adhesive is tested according to GB / T 2791-1995 method, the test substrate is stone paper to stone paper. The curing temperature is 70°C, the curing time is 4 h, and the curing is placed at room temperature for 24 h.

[0052] The peel strength is introduced into a mold, cured at 70°C for 6 h, and placed at room temperature for 24 h, to obtain adhesive film, the tensile properties are tested according to GB / T 528-2009 method.

[0053] Table 1 adhesive performance test

[0054]

[0055] The peel strength of Comparative Example 1 is only 8.4 N / cm, and the tensile strength and elongation at break of the adhesive cured film are low, and the mechanical properties are poor. The cationic terminal isocyanate curing agent is added in Examples 1-4, and the terminal position of the curing agent contains four isocyanate curing sites, which forms better curing crosslinking reaction with polyvinyl alcohol, and is conducive to improving the bonding properties and mechanical strength of the adhesive cured product. At the same time, the terminal isocyanate curing agent contains cationic groups, which can form electrostatic interaction with the carboxyl sodium anion groups of the carboxylated styrene-butadiene latex, which is conducive to increasing the cohesive force of the adhesive cured product, thereby improving the peel strength and bonding properties of the adhesive, and the adhesive has higher peel strength and tensile strength. And the terminal isocyanate curing agent contains a flexible polyether molecular chain, which has a good toughening effect on the adhesive, thereby improving the elongation at break and toughness.

[0056] Compared with Example 1, Comparative Example 2 reacts with conventional polyethylene glycol and toluene-2,4-diisocyanate to obtain a terminal isocyanate curing agent with only two isocyanate curing sites at the terminal position. The curing crosslinking reaction performance with polyvinyl alcohol is low, and the curing effect is poor. And it does not contain cationic groups, and cannot form electrostatic interaction with the carboxylated styrene-butadiene latex, the cohesive force of the adhesive cured product is low, resulting in poor peel strength and tensile properties of the adhesive. The terminal position of the cationic terminal isocyanate curing agent of Comparative Example 3 contains only two isocyanate curing sites, and the curing crosslinking reaction performance with polyvinyl alcohol is low, and the curing effect is poor, resulting in lower peel strength and tensile properties of the adhesive than Example 1.

Claims

1. An aqueous adhesive, characterized by, The water-based adhesive comprises 30-40 parts by weight of color fillers, 0.2-0.35 parts by weight of dispersants, 20-27 parts by weight of polyvinyl alcohol, 2.4-5 parts by weight of cationic terminal isocyanate curing agents, and 30-48 parts by weight of carboxyl styrene-butadiene latex. The preparation method of the cationic terminal isocyanate curing agent is as follows: (1) adding dichloro polyethylene glycol and N-methyl diethanolamine into ethanol, and reacting, after the reaction, reducing pressure concentration, adding the product into diethyl ether for precipitation, filtering, and drying to obtain cationic polyethylene glycol; (2) adding dry cationic polyethylene glycol, diisocyanate, and dibutyltin dilaurate into a solvent, and reacting in a nitrogen atmosphere, after the reaction, reducing pressure concentration to obtain the cationic terminal isocyanate curing agent; The molar ratio of dichloro polyethylene glycol and N-methyl diethanolamine in the step (1) is 1:(4-6); The molar ratio of cationic polyethylene glycol, diisocyanate, and dibutyltin dilaurate in the step (2) is 1:(4.8-5.4):(0.02-0.026).

2. The aqueous adhesive according to claim 1, characterized in that, The reaction in the step (1) is stirred and refluxed at 70-80℃ for 24-30 hours.

3. The aqueous adhesive of claim 1, wherein The solvent in the step (2) is acetone or tetrahydrofuran.

4. The aqueous adhesive of claim 1, wherein The diisocyanate is toluene-2,4-diisocyanate, isophorone diisocyanate, or diphenylmethane 4,4'-diisocyanate.

5. The aqueous adhesive of claim 1, wherein The reaction in the step (2) is stirred and refluxed at 65-80℃ for 2-3 hours.

6. The aqueous adhesive of claim 1, wherein, The color fillers are any one of calcium carbonate, barium sulfate, kaolin, and titanium white; and the dispersants are sodium hexametaphosphate or sodium polycarboxylate dispersant.

7. A process for the preparation of the aqueous adhesive according to any one of claims 1 to 6, characterized in that, The preparation method is as follows: (1) adding polyvinyl alcohol into water, heating to 90-95℃, and stirring and dissolving to obtain a polyvinyl alcohol solution; (2) adding sodium hydroxide into carboxyl styrene-butadiene latex, adjusting the pH to neutral, then adding the polyvinyl alcohol solution, color fillers, and dispersants, shearing and dispersing, and finally adding the cationic terminal isocyanate curing agent to obtain the water-based adhesive.

8. Application of the water-based adhesive prepared by the preparation method of claim 7 in stone paper packaging boxes.

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