Formaldehyde-free soft white rubber cement and preparation method thereof

Abstract

The invention discloses formaldehyde-free soft white adhesive cement and a preparation method thereof, and relates to the technical field of adhesive cement. The cleaning agent is prepared from the following raw materials in parts by mass: 57 to 67.5 parts of deionized water, 0.5 to 0.6 part of sodium bicarbonate, 90 to 108 parts of pre-emulsified liquid, 1 to 1.2 parts of ammonium persulfate, 3 to 4 parts of hybrid nano microspheres and 1.5 to 1.8 parts of propylene glycol methyl ether acetate. Wherein the pre-emulsion is prepared from the following raw materials in parts by mass: 45 to 54 parts of butyl acrylate, 20 to 24 parts of methyl methacrylate, 3 to 3.6 parts of acrylic acid, 5 to 6 parts of alpha-silane-terminated dynamic cross-linking agent, 15 to 18 parts of deionized water, 1 to 1.2 parts of sodium dodecyl benzene sulfonate and 1 to 1.2 parts of fatty alcohol-polyoxyethylene ether. According to the formaldehyde-free white adhesive cement disclosed by the invention, due to the introduction of the components such as the hybrid nano-microspheres and the alpha-silane-terminated dynamic crosslinking agent, the washing resistance, the flexibility after curing and the storage stability of the formaldehyde-free white adhesive cement are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to a formaldehyde-free soft white adhesive and its preparation method. Background Technology

[0002] White adhesive, as a type of water-based environmentally friendly adhesive, has core advantages such as convenient construction, wide bonding range, controllable cost, and good compatibility with substrates. Compared with traditional solvent-based adhesives, it is safer and is therefore widely used in textile printing, home building material bonding, handicrafts making, and environmentally friendly packaging.

[0003] However, white adhesive still has significant performance shortcomings in practical applications, restricting its expansion in mid-to-high-end scenarios: First, its washability is poor; when used for bonding textiles or daily necessities, it is prone to detachment and peeling after repeated washing. Second, its flexibility after curing is insufficient, easily causing the bonded substrate to harden and crack, especially with poor compatibility in flexible material processing. Third, its storage stability is weak; in low-temperature environments or during long-term static storage, it is prone to stratification and sedimentation, requiring re-stirring before use, which not only affects construction efficiency but may also reduce bonding quality. Fourth, it is prone to formaldehyde residue. Therefore, the washability, post-curing flexibility, and storage stability of existing white adhesive still need improvement, and the problem of formaldehyde residue remains to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a formaldehyde-free soft white adhesive and its preparation method, thereby solving the following technical problems: Existing white adhesive still has problems with poor washability, poor flexibility after curing, poor storage stability, and formaldehyde residue.

[0005] The objective of this invention can be achieved through the following technical solutions: A formaldehyde-free soft white adhesive, comprising the following raw materials in parts by weight: 57-67.5 parts deionized water, 0.5-0.6 parts sodium bicarbonate, 90-108 parts pre-emulsion, 1-1.2 parts ammonium persulfate, 3-4 parts hybrid nanospheres, and 1.5-1.8 parts propylene glycol methyl ether acetate; The pre-emulsion comprises the following raw materials in parts by weight: 45-54 parts butyl acrylate, 20-24 parts methyl methacrylate, 3-3.6 parts acrylic acid, 5-6 parts α-silane-terminated dynamic crosslinking agent, 15-18 parts deionized water, 1-1.2 parts sodium dodecylbenzene sulfonate, and 1-1.2 parts fatty alcohol polyoxyethylene ether. The hybrid nanospheres are prepared from titanium tetraisopropoxide, acetylacetone, tris(hydroxymethyl)aminomethane, dopamine hydrochloride, and tannic acid.

[0006] Preferably, the preparation method of the terminal α-silane dynamic crosslinking agent is as follows: A1: Allyl glycidyl ether and benzophenone were added to 3-mercaptopropyltrimethoxysilane and reacted at 30°C under a nitrogen atmosphere and irradiated with 365nm ultraviolet light for 4-5 hours. Then, deionized water and acetic acid were added and stirred at 50°C for 1-1.5 hours. Then, the mixture was vacuumed at 50°C and -0.095MPa for 0.5-1 hours. Finally, unreacted monomers were removed by vacuum distillation at 100°C and -0.095MPa to obtain the α-hydroxysilane intermediate. A2: Polypropylene glycol is dehydrated under vacuum at 120℃ and -0.1MPa for 2-3 hours. After cooling to 60℃, isophorone diisocyanate and dibutyltin dilaurate are added under a nitrogen atmosphere and reacted at 80℃ for 2-2.5 hours. Then, the temperature is lowered to 40℃ and α-hydroxysilane intermediate is added and stirred for 1-2 hours. Finally, N,N'-bis(2-hydroxyethyl)ethylenediamine is added dropwise and reacted at 70℃ for 4-5 hours. After cooling, the terminal α-silane dynamic crosslinking agent is obtained.

[0007] Preferably, the mass ratio of 3-mercaptopropyltrimethoxysilane, allyl glycidyl ether, benzophenone, deionized water, and acetic acid in A1 is 11.9:7.12:0.1:1.5-2:0.1.

[0008] Preferably, the mass ratio of polypropylene glycol, isophorone diisocyanate, dibutyltin dilaurate, α-hydroxysilane intermediate, and N,N'-bis(2-hydroxyethyl)ethylenediamine in A2 is 100:26.6-33.3:0.05:4.65:1.5.

[0009] Preferably, the hybrid nanospheres are prepared by the following method: B1: Add tetraisopropoxide titanium to anhydrous ethanol and stir well, then add acetylacetone and ultrasonically disperse for 10-15 min to obtain titanium source precursor solution. B2: Add tris(hydroxymethyl)aminomethane to deionized water and stir for 20-30 min. Then adjust the pH to 8.5 with 1 mol / L hydrochloric acid. Add dopamine hydrochloride and tannic acid in sequence and stir in the dark for 20-30 min. Then add titanium source precursor solution dropwise at 0.1-0.2 mL / min at 2-4℃ and stir for 2-3 h. Raise the temperature to 25-30℃ and stir for 24-26 h. Filter with a 0.45 μm polyethersulfone filter membrane. Then transfer the filtrate to a dialysis bag (molecular weight cutoff 8000-14000 Da) and dialyze with deionized water for 72 h (changing the water every 8 h). Finally, freeze-dry at -50℃ for 24-30 h to obtain hybrid nanospheres.

[0010] Preferably, the ratio of anhydrous ethanol, tetraisopropoxide titanium, and acetylacetone in B1 is 20 mL: 1.7-1.8 g: 0.2 g.

[0011] Preferably, the ratio of deionized water, tris(hydroxymethyl)aminomethane, dopamine hydrochloride, tannic acid, and titanium source precursor solution in B2 is 400-420 mL: 1.21 g: 2 g: 1 g: 20 mL.

[0012] A method for preparing a formaldehyde-free soft white adhesive includes the following steps: S1: Mix butyl acrylate, methyl methacrylate, acrylic acid, and terminal α-silane dynamic crosslinking agent and stir for 10-20 min to obtain mixed monomers; S2: Add sodium dodecylbenzenesulfonate and fatty alcohol polyoxyethylene ether to deionized water in sequence and stir for 5-10 min. Then, while stirring, drop the mixed monomers at 2 mL / min and stir for 50-60 min to obtain a pre-emulsion. S3: Add ammonium persulfate to deionized water and stir well to obtain an initiator solution; S4: Add hybrid nanospheres to deionized water and ultrasonically disperse for 10-20 min, then stir for 10-20 min to obtain a microsphere solution; S5: Add sodium bicarbonate to deionized water and stir for 10-15 min. Then heat to 80℃ and keep warm for 5-7 min. Add pre-emulsion 1 and stir for 10-20 min. Add initiator solution 1 and stir at 80℃ for 30-50 min. Then add pre-emulsion 2 dropwise at 78-82℃ while stirring at 1.5 g / min. After 20-30 min of dropwise addition, add initiator solution 2 in two portions (once every 20 min). Then add microsphere solution dropwise at 1 mL / min and react at 80℃ for 80-90 min. After cooling to 45℃, add propylene glycol methyl ether acetate and stir for 30-40 min. Finally, adjust the pH to 7.0-7.5 with 10% sodium hydroxide aqueous solution and stir for 20-30 min. Filter through a 200-mesh filter to obtain formaldehyde-free soft white adhesive.

[0013] Preferably, the mass ratio of deionized water to ammonium persulfate in S3 is 2-2.5:1-1.2; The mass ratio of hybrid nanospheres added to the deionized water described in S4 is 5:3-4.

[0014] Preferably, the mass ratio of deionized water, sodium bicarbonate, preemulsion 1, initiator solution 1, preemulsion 2, initiator solution 2, microsphere solution, and propylene glycol methyl ether acetate in S5 is 50-60:0.5-0.6:20-24:1.5-1.8:70-84:1.5-1.9:8-9:1.5-1.8.

[0015] The beneficial effects of this invention are: This invention provides a formaldehyde-free soft white adhesive and its preparation method. The invention improves the washability, post-curing flexibility, and storage stability of the white adhesive simultaneously by means of the following method, while reducing the formaldehyde residue.

[0016] (1) The raw materials for the synthesis of the α-silane dynamic crosslinking agent of the present invention do not contain formaldehyde or formaldehyde-releasing groups, and the synthesis route does not actively introduce formaldehyde sources; at the same time, it replaces the urea-formaldehyde, melamine-formaldehyde and other aldehyde-containing crosslinking systems that may be contained in traditional adhesives, thus effectively avoiding increasing the formaldehyde content of the product and ensuring the formaldehyde-free characteristics of the adhesive. The flexible polyoxypropylene glycol segments in the molecular structure of the α-silane dynamic crosslinking agent can be embedded in the crosslinking network of acrylate polymers, reducing the entanglement density of molecular chains and improving the mobility of chain segments, thereby improving the elongation at break of the cured film; the silane groups in the α-silane dynamic crosslinking agent can be hydrolyzed to form siloxane bonds with dynamic exchange characteristics. Under the action of external force, these dynamic bonds can break and recombine, which helps to disperse stress and avoid cracks in the adhesive film, so cracks are not easy to occur when folding. The silanol groups generated from the hydrolysis of silane groups in the α-silane-terminated dynamic crosslinking agent can undergo condensation reactions with acrylate molecules and hydroxyl groups on the surface of hybrid nanospheres to form a covalent crosslinking network. Simultaneously, the urea and urethane groups of the polyurethane segments can form hydrogen bonds with acrylates, constructing a dual stable structure of covalent crosslinking and hydrogen bonding. This resists the penetration and stripping of water molecules during washing, preventing film swelling and detachment, and contributing to improved wash resistance. The silane groups in the α-silane-terminated dynamic crosslinking agent exhibit a mild hydrolysis rate in the emulsion, making it less prone to latex particle aggregation and flocculation due to rapid hydrolysis and crosslinking. Its polyurethane segments may provide some auxiliary effect on the electrostatic or steric stability of latex particles through interfacial adsorption, reducing particle aggregation. The flexibility of the polyurethane segments and the hydrophilic groups after silane hydrolysis can improve the hydrophilic-hydrophobic balance on the latex particle surface, contributing to long-term storage stability.

[0017] (2) The raw materials for the synthesis of the hybrid nanospheres of this invention are all free of formaldehyde and are not prone to decomposition or reaction to generate formaldehyde during preparation and storage. At the same time, the interaction between the microspheres and the adhesive matrix is ​​mainly physical entanglement and hydrogen bonding, which can effectively avoid inducing the degradation of other components and the release of formaldehyde. The uniform distribution of the hybrid nanospheres in the acrylate matrix can alleviate the stress concentration problem. The abundant polar groups on the surface of the microspheres can form strong hydrogen bonds with the polymer chains and interact with the silanol groups of the terminal α-silane dynamic crosslinking agent. In the later curing or heat treatment, a condensation reaction may further occur to form covalent bonds and construct a dynamic crosslinking network. When the adhesive film is under stress, the dynamic crosslinking bonds can break and recombine, release stress, and improve the elongation at break. The microspheres enhance the modulus through a rigid inorganic core and improve the compatibility with the matrix through the surface organic layer, thereby improving the strength while avoiding the increase of brittleness and helping to optimize the flexibility of the adhesive. The hydrogen bonds and potential covalent bonds formed between hybrid nanospheres and the acrylate matrix and silane crosslinking agent can increase the crosslinking density of the adhesive film, reduce the permeation rate of water molecules during washing, and reduce the swelling and peeling of polymer chains. The inorganic titanium oxide network of the hybrid nanospheres can enhance the friction resistance and tensile strength of the adhesive film, making it less prone to damage and peeling under the mechanical action of repeated washing. At the same time, the increased density of the adhesive film after microsphere filling can reduce the risk of interfacial delamination between the adhesive film and the substrate. The polyphenol groups on the surface of the microspheres are hydrophilic and can form an adsorption layer with sodium dodecylbenzenesulfonate and fatty alcohol polyoxyethylene ether in the aqueous phase, preventing the microspheres from agglomerating through steric hindrance and inhibiting the aggregation and sedimentation of acrylate emulsion particles. The addition of nanospheres can increase the viscosity of the system and inhibit particle aggregation and sedimentation through steric hindrance, thereby improving storage stability. As a nanofiller, the microspheres can restrict the movement of polymer chain segments, and the interaction between the polar groups on their surface and the polymer helps to mitigate the fluctuations in the rheological properties of the system caused by temperature changes.

[0018] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] Unless otherwise specified, the following information pertains to some of the raw materials used in the following embodiments and comparative examples of this invention: Polypropylene glycol (PPG1000) was purchased from Wuhan Kanos Technology Co., Ltd.

[0021] Example 1: A method for preparing a formaldehyde-free soft white adhesive is as follows: S1: 7.12 g allyl glycidyl ether and 0.1 g benzophenone were added to 11.9 g 3-mercaptopropyltrimethoxysilane and reacted at 30 °C under a nitrogen atmosphere and irradiated with 365 nm ultraviolet light for 4 h. Then, 1.5 mL deionized water and 0.1 g acetic acid were added and stirred at 50 °C for 1 h. Then, the mixture was evacuated at 50 °C and -0.095 MPa for 0.5 h. Finally, unreacted monomers were removed by vacuum distillation at 100 °C and -0.095 MPa to obtain the α-hydroxysilane intermediate. S2: 100g of polypropylene glycol (PPG1000) was dehydrated under vacuum at 120℃ and -0.1MPa for 2h. After cooling to 60℃, 26.6g of isophorone diisocyanate and 0.05g of dibutyltin dilaurate were added under nitrogen protection and reacted at 80℃ for 2h. Then, the temperature was lowered to 40℃ and 4.65g of α-hydroxysilane intermediate was added and stirred for 1h. Finally, 1.5g of N,N'-bis(2-hydroxyethyl)ethylenediamine was added dropwise and reacted at 70℃ for 4h. After cooling, the α-silane-terminated dynamic crosslinking agent was obtained. S3: Add 1.7g of tetraisopropoxide titanium to 20mL of anhydrous ethanol and stir for 20min. Then add 0.2g of acetylacetone and sonicate for 10min to obtain titanium source precursor solution. S4: Add 1.21 g of tris(hydroxymethyl)aminomethane to 400 mL of deionized water and stir for 20 min. Then adjust the pH to 8.5 with 1 mol / L hydrochloric acid. Add 2 g of dopamine hydrochloride and 1 g of tannic acid in sequence and stir in the dark for 20 min. Then, while stirring at 2 °C, add 20 mL of titanium source precursor solution dropwise at 0.1 mL / min and stir for 2 h. Raise the temperature to 25 °C and stir for 24 h. Filter the solution through a 0.45 μm polyethersulfone membrane. Then transfer the filtrate to a dialysis bag (molecular weight cutoff 8000-14000 Da) and dialyze with deionized water for 72 h (changing the water every 8 h). Finally, freeze-dry at -50 °C for 24 h to obtain hybrid nanospheres. S5: Mix 45g butyl acrylate, 20g methyl methacrylate, 3g acrylic acid, and 5g terminal α-silane dynamic crosslinking agent and stir for 10 minutes to obtain a mixed monomer; S6: Add 1g sodium dodecylbenzenesulfonate and 1g fatty alcohol polyoxyethylene ether to 15g deionized water and stir for 5min. Then, while stirring, add 73g mixed monomer dropwise at 2mL / min and stir for 50min to obtain a pre-emulsion. S7: Add 1g of ammonium persulfate to 2g of deionized water and stir for 10min to obtain the initiator solution; S8: Add 3g of hybrid nanospheres to 5g of deionized water and ultrasonically disperse for 10min, then stir for 10min to obtain a microsphere solution; S9: Add 0.5g sodium bicarbonate to 50g deionized water and stir for 10min. Then heat to 80℃ and keep warm for 5min. Add 20g pre-emulsion and stir for 10min. Add 1.5g initiator solution and stir at 80℃ for 30min. Then add 70g pre-emulsion dropwise at 78℃ with stirring at 1.5g / min. After 20min of dropwise addition, add 1.5g initiator solution in two portions (once every 20min). Then add 8g microsphere solution dropwise at 1mL / min and react at 80℃ for 80min. After cooling to 45℃, add 1.5g propylene glycol methyl ether acetate and stir for 30min. Finally, adjust the pH to 7 with 10% sodium hydroxide aqueous solution. After stirring for 20min, filter through a 200-mesh filter to obtain formaldehyde-free soft white adhesive.

[0022] Example 2: A method for preparing a formaldehyde-free soft white adhesive is as follows: S1: 7.12 g allyl glycidyl ether and 0.1 g benzophenone were added to 11.9 g 3-mercaptopropyltrimethoxysilane and reacted at 30 °C under a nitrogen atmosphere and irradiated with 365 nm ultraviolet light for 4.5 h. Then, 1.8 mL deionized water and 0.1 g acetic acid were added and stirred at 50 °C for 1.2 h. Then, the mixture was evacuated at 50 °C and -0.095 MPa for 0.8 h. Finally, unreacted monomers were removed by vacuum distillation at 100 °C and -0.095 MPa to obtain α-hydroxysilane intermediate. S2: 100g of polypropylene glycol (PPG1000) was dehydrated under vacuum at 120℃ and -0.1MPa for 2.5h. After cooling to 60℃, 30g of isophorone diisocyanate and 0.05g of dibutyltin dilaurate were added under nitrogen protection and reacted at 80℃ for 2.3h. Then, the temperature was lowered to 40℃ and 4.65g of α-hydroxysilane intermediate was added and stirred for 1.5h. Finally, 1.5g of N,N'-bis(2-hydroxyethyl)ethylenediamine was added dropwise and reacted at 70℃ for 4.5h. After cooling, the α-silane-terminated dynamic crosslinking agent was obtained. S3: Add 1.75g ​​of tetraisopropoxide titanium to 20mL of anhydrous ethanol and stir for 25min. Then add 0.2g of acetylacetone and sonicate for 13min to obtain titanium source precursor solution. S4: Add 1.21 g of tris(hydroxymethyl)aminomethane to 410 mL of deionized water and stir for 25 min. Then adjust the pH to 8.5 with 1 mol / L hydrochloric acid. Add 2 g of dopamine hydrochloride and 1 g of tannic acid in sequence and stir in the dark for 25 min. Then, while stirring at 3 °C, add 20 mL of titanium source precursor solution dropwise at 0.15 mL / min and stir for 2.5 h. After heating to 27 °C and stirring for 25 h, filter through a 0.45 μm polyethersulfone filter membrane. Then transfer the filtrate to a dialysis bag (molecular weight cutoff 8000-14000 Da) and dialyze with deionized water for 72 h (changing the water every 8 h). Finally, freeze-dry at -50 °C for 27 h to obtain hybrid nanospheres. S5: Mix 49.5g butyl acrylate, 22g methyl methacrylate, 3.3g acrylic acid, and 5.5g terminal α-silane dynamic crosslinking agent and stir for 15 minutes to obtain mixed monomers; S6: Add 1.1g sodium dodecylbenzenesulfonate and 1.1g fatty alcohol polyoxyethylene ether to 16.5g deionized water and stir for 8min. Then, while stirring, add 80.3g mixed monomer dropwise at 2mL / min and stir for 55min to obtain a pre-emulsion. S7: Add 1.1g of ammonium persulfate to 2.3g of deionized water and stir for 15min to obtain the initiator solution; S8: Add 3.5g of hybrid nanospheres to 5g of deionized water and ultrasonically disperse for 15min, then stir for 15min to obtain a microsphere solution; S9: Add 0.55g sodium bicarbonate to 55g deionized water and stir for 13min. Then heat to 80℃ and keep warm for 6min. Add 22g pre-emulsion and stir for 15min. Add 1.57g initiator solution and stir at 80℃ for 40min. Then add 77g pre-emulsion dropwise at 80℃ while stirring at 1.5g / min. After 25min of dropwise addition, add 1.7g initiator solution in two portions (once every 20min). Then add 8.5g microsphere solution dropwise at 1mL / min and react at 80℃ for 85min. After cooling to 45℃, add 1.6g propylene glycol methyl ether acetate and stir for 35min. Finally, adjust the pH to 7.2 with 10% sodium hydroxide aqueous solution. After stirring for 25min, filter through a 200-mesh filter to obtain formaldehyde-free soft white adhesive.

[0023] Example 3: A method for preparing a formaldehyde-free soft white adhesive is as follows: S1: 7.12 g allyl glycidyl ether and 0.1 g benzophenone were added to 11.9 g 3-mercaptopropyltrimethoxysilane and reacted at 30 °C under a nitrogen atmosphere and irradiated with 365 nm ultraviolet light for 5 h. Then, 2 mL deionized water and 0.1 g acetic acid were added and stirred at 50 °C for 1.5 h. Then, the mixture was vacuum-sealed at 50 °C and -0.095 MPa for 1 h. Finally, unreacted monomers were removed by vacuum distillation at 100 °C and -0.095 MPa to obtain the α-hydroxysilane intermediate. S2: 100g of polypropylene glycol (PPG1000) was dehydrated under vacuum at 120℃ and -0.1MPa for 3h. After cooling to 60℃, 33.3g of isophorone diisocyanate and 0.05g of dibutyltin dilaurate were added under nitrogen protection and reacted at 80℃ for 2.5h. Then, the temperature was lowered to 40℃ and 4.65g of α-hydroxysilane intermediate was added and stirred for 2h. Finally, 1.5g of N,N'-bis(2-hydroxyethyl)ethylenediamine was added dropwise and reacted at 70℃ for 5h. After cooling, the α-silane-terminated dynamic crosslinking agent was obtained. S3: Add 1.8 g of tetraisopropoxide titanium to 20 mL of anhydrous ethanol and stir for 30 min. Then add 0.2 g of acetylacetone and sonicate for 15 min to obtain titanium source precursor solution. S4: Add 1.21 g of tris(hydroxymethyl)aminomethane to 420 mL of deionized water and stir for 30 min. Then adjust the pH to 8.5 with 1 mol / L hydrochloric acid. Add 2 g of dopamine hydrochloride and 1 g of tannic acid in sequence and stir in the dark for 30 min. Then, while stirring at 4 °C, add 20 mL of titanium source precursor solution dropwise at 0.2 mL / min and stir for 3 h. After heating to 30 °C and stirring for 26 h, filter through a 0.45 μm polyethersulfone filter membrane. Then transfer the filtrate to a dialysis bag (molecular weight cutoff 8000-14000 Da) and dialyze with deionized water for 72 h (changing the water every 8 h). Finally, freeze-dry at -50 °C for 30 h to obtain hybrid nanospheres. S5: Mix 54g butyl acrylate, 24g methyl methacrylate, 3.6g acrylic acid, and 6g terminal α-silane dynamic crosslinking agent and stir for 20 minutes to obtain mixed monomers; S6: Add 1.2g sodium dodecylbenzenesulfonate and 1.2g fatty alcohol polyoxyethylene ether to 18g deionized water and stir for 10min. Then, while stirring, add 87.6g mixed monomer dropwise at 2mL / min and stir for 60min to obtain a pre-emulsion. S7: Add 1.2g of ammonium persulfate to 2.5g of deionized water and stir for 20min to obtain an initiator solution; S8: Add 4g of hybrid nanospheres to 5g of deionized water and ultrasonically disperse for 20min, then stir for 20min to obtain a microsphere solution; S9: Add 0.6g of sodium bicarbonate to 60g of deionized water and stir for 15min. Then heat to 80℃ and keep warm for 7min. Add 24g of pre-emulsion and stir for 20min. Add 1.8g of initiator solution and stir at 80℃ for 50min. Then add 84g of pre-emulsion dropwise at 82℃ while stirring at 1.5g / min. After 30min of dropwise addition, add 1.9g of initiator solution in two portions (once every 20min). Then add 9g of microsphere solution dropwise at 1mL / min and react at 80℃ for 80-90min. After cooling to 45℃, add 1.8g of propylene glycol methyl ether acetate and stir for 40min. Finally, adjust the pH to 7.5 with 10% sodium hydroxide aqueous solution and stir for 30min. Filter through a 200-mesh filter to obtain formaldehyde-free soft white adhesive.

[0024] Comparative Example 1: Compared with Example 1, this comparative example only did not add "terminal α-silane dynamic crosslinking agent" in the preparation process of S5. All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, formaldehyde-free soft white adhesive was obtained.

[0025] Comparative Example 2: Compared with Example 1, this comparative example only omits the addition of "microsphere solution" in the preparation process of S9. All other steps and parameters are the same, and will not be repeated here. The final result is a formaldehyde-free soft white adhesive.

[0026] Performance testing: Formaldehyde content determination: According to GB 18583-2008 standard, the formaldehyde content (g / kg) of the formaldehyde-free soft white adhesive prepared in Examples 1-3 and Comparative Examples 1-2 of this invention was determined, and the test results are shown in Table 1.

[0027] Determination of flexibility: The elongation at break (%) of the cured film (thickness 0.5 mm) made from the formaldehyde-free soft white adhesive prepared in Examples 1-3 and Comparative Examples 1-2 of this invention and whether there are cracks when folded at 180° were determined. The test results are shown in Table 1.

[0028] Determination of washability: Referring to GB / T 3921-2008 standard, formaldehyde-free soft white adhesive was evenly coated onto the surface of a standard cotton fabric at a coating amount of 200 g / m². 2After curing, the sample was dried in an oven at 80℃ for 30 minutes. Then, a 5cm×10cm sample was cut and sewn to the lining fabric according to standard requirements to obtain the sample. The samples made of formaldehyde-free soft white adhesive prepared in Examples 1-3 and Comparative Examples 1-2 were tested for delamination, stickiness, and peeling after 50 standard water washes. The test results are shown in Table 1.

[0029] Table 1: Performance test results of Examples 1-3 and Comparative Examples 1-2 Determination of storage stability: The samples were sealed and stored at 0℃ and 40℃ for 90 days respectively. After 180 days of storage, the presence of stratification, flocculation, and precipitation, as well as the viscosity change rate (%) after 180 days of storage, were tested. The storage stability of the samples made from the formaldehyde-free soft white adhesive prepared in Examples 1-3 and Comparative Examples 1-2 of this invention was determined according to the above method. The test results are shown in Table 2.

[0030] Table 1: Storage stability test results of Examples 1-3 and Comparative Examples 1-2 Data Analysis: As can be seen from Table 1, the formaldehyde-free soft white adhesive prepared in the embodiments of the present invention has excellent washability, curing flexibility, and storage stability.

[0031] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A formaldehyde-free soft white adhesive, characterized in that, The raw materials include the following parts by weight: 57-67.5 parts deionized water, 0.5-0.6 parts sodium bicarbonate, 90-108 parts pre-emulsion, 1-1.2 parts ammonium persulfate, 3-4 parts hybrid nanospheres, and 1.5-1.8 parts propylene glycol methyl ether acetate; The pre-emulsion comprises the following raw materials in parts by weight: 45-54 parts butyl acrylate, 20-24 parts methyl methacrylate, 3-3.6 parts acrylic acid, 5-6 parts α-silane-terminated dynamic crosslinking agent, 15-18 parts deionized water, 1-1.2 parts sodium dodecylbenzene sulfonate, and 1-1.2 parts fatty alcohol polyoxyethylene ether. The hybrid nanospheres are prepared from tetraisopropoxide titanium, acetylacetone, tris(hydroxymethyl)aminomethane, dopamine hydrochloride, and tannic acid.

2. The formaldehyde-free soft white adhesive according to claim 1, characterized in that, The preparation method of the terminal α-silane dynamic crosslinking agent is as follows: A1: Allyl glycidyl ether and benzophenone were added to 3-mercaptopropyltrimethoxysilane and reacted at 30°C under nitrogen atmosphere and irradiated with 365nm ultraviolet light for 4-5 hours. Then, deionized water and acetic acid were added and stirred at 50°C for 1-1.5 hours. Then, the mixture was evacuated at 50°C and -0.095MPa for 0.5-1 hours. Finally, unreacted monomers were removed by vacuum distillation to obtain α-hydroxysilane intermediate. A2: Polypropylene glycol is dehydrated under vacuum at 120℃ and -0.1MPa for 2-3 hours. After cooling to 60℃, isophorone diisocyanate and dibutyltin dilaurate are added under a nitrogen atmosphere and reacted at 80℃ for 2-2.5 hours. Then, the temperature is lowered to 40℃ and α-hydroxysilane intermediate is added and stirred for 1-2 hours. Finally, N,N'-bis(2-hydroxyethyl)ethylenediamine is added dropwise and reacted at 70℃ for 4-5 hours. After cooling, the terminal α-silane dynamic crosslinking agent is obtained.

3. The formaldehyde-free soft white adhesive according to claim 2, characterized in that, The mass ratio of 3-mercaptopropyltrimethoxysilane, allyl glycidyl ether, benzophenone, deionized water, and acetic acid in A1 is 11.9:7.12:0.1:1.5-2:0.

1.

4. The formaldehyde-free soft white adhesive according to claim 2, characterized in that, The mass ratio of polypropylene glycol, isophorone diisocyanate, dibutyltin dilaurate, α-hydroxysilane intermediate, and N,N'-bis(2-hydroxyethyl)ethylenediamine in A2 is 100:26.6-33.3:0.05:4.65:1.

5.

5. The formaldehyde-free soft white adhesive according to claim 1, characterized in that, The method for preparing the hybrid nanospheres is as follows: B1: Add tetraisopropoxide titanium to anhydrous ethanol and stir well, then add acetylacetone and ultrasonically disperse for 10-15 min to obtain titanium source precursor solution. B2: Add tris(hydroxymethyl)aminomethane to deionized water and stir for 20-30 min. Then adjust the pH to 8.5, add dopamine hydrochloride and tannic acid, and stir in the dark for 20-30 min. Then add titanium source precursor solution dropwise while stirring at 2-4℃ and stir for 2-3 h. Raise the temperature to 25-30℃ and stir for 24-26 h, then filter. Then dialyze the filtrate and finally freeze-dry to obtain hybrid nanospheres.

6. The formaldehyde-free soft white adhesive according to claim 5, characterized in that, The ratio of anhydrous ethanol, tetraisopropoxide titanium, and acetylacetone described in B1 is 20 mL: 1.7-1.8 g: 0.2 g.

7. The formaldehyde-free soft white adhesive according to claim 5, characterized in that, The ratio of deionized water, tris(hydroxymethyl)aminomethane, dopamine hydrochloride, tannic acid, and titanium source precursor solution in B2 is 400-420 mL: 1.21 g: 2 g: 1 g: 20 mL.

8. A method for preparing a formaldehyde-free soft white adhesive according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Mix butyl acrylate, methyl methacrylate, acrylic acid, and terminal α-silane dynamic crosslinking agent to obtain a mixed monomer; S2: Add sodium dodecylbenzenesulfonate and fatty alcohol polyoxyethylene ether to deionized water in sequence and stir for 5-10 min. Then, while stirring, dropwise add the mixed monomers and stir for 50-60 min to obtain a pre-emulsion. S3: Add ammonium persulfate to deionized water and stir well to obtain an initiator solution; S4: Add hybrid nanospheres to deionized water and ultrasonically disperse for 10-20 min, then stir for 10-20 min to obtain a microsphere solution; S5: Add sodium bicarbonate to deionized water and stir well. Then heat to 80℃ and keep warm for 5-7 minutes. Then add pre-emulsion 1 and stir for 10-20 minutes. Then add initiator solution 1 and stir at 80℃ for 30-50 minutes. Then add pre-emulsion 2 and initiator solution 2 dropwise at 78-82℃. Then add microsphere solution dropwise and react at 80℃ for 80-90 minutes. After cooling to 45℃, add propylene glycol methyl ether acetate and stir for 30-40 minutes. Finally, adjust the pH to 7.0-7.5, stir for 20-30 minutes, and filter to obtain formaldehyde-free soft white adhesive.

9. The method for preparing formaldehyde-free soft white adhesive according to claim 8, characterized in that, The mass ratio of deionized water to ammonium persulfate in S3 is 2-2.5:1-1.2; The mass ratio of hybrid nanospheres added to the deionized water described in S4 is 5:3-4.

10. The method for preparing formaldehyde-free soft white adhesive according to claim 8, characterized in that, The mass ratio of deionized water, sodium bicarbonate, preemulsion 1, initiator solution 1, preemulsion 2, initiator solution 2, microsphere solution, and propylene glycol methyl ether acetate in S5 is 50-60:0.5-0.6:20-24:1.5-1.8:70-84:1.5-1.9:8-9:1.5-1.8.

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