A modified neoprene latex and a method for preparing the same

Abstract

This invention belongs to the field of synthetic latex technology, specifically relating to a modified chloroprene latex and its preparation method. The preparation method includes the following steps: (1) preparing an emulsifier solution; (2) adding a reactive monomer and a silane coupling agent containing long, straight carbon chains with double bonds to the emulsifier solution for pre-emulsification; after a polymerization reaction of 2-4 hours, adding a silane coupling agent containing short, straight carbon chains with double bonds to continue the reaction for a period of time, followed by cooling and discharge. This preparation process is simple, low-cost, and easy to operate, which is beneficial for industrial production. The silane coupling agent containing short, straight carbon chains with double bonds has high reactivity, and the silane portion can greatly enhance the durability of the final adhesive film; the long carbon chains in the silane coupling agent containing long, straight carbon chains with double bonds can improve chain segment flexibility and act as internal plasticizers, improving compatibility with non-polar materials and increasing bonding strength.

Description

Technical Field

[0001] This invention belongs to the field of synthetic latex technology, specifically relating to a modified chloroprene latex and its preparation method. Background Technology

[0002] Chloroprene rubber, also known as chloroprene rubber, is mostly produced industrially using free radical emulsion polymerization technology. Its main chain structure is unsaturated, and the molecular chain contains a large number of electron-withdrawing chlorine atoms, resulting in high molecular chain regularity and easy crystallization. Therefore, chloroprene rubber possesses excellent comprehensive mechanical properties, fatigue resistance, oil resistance, aging resistance, flame retardancy, and electrical insulation, making it widely used in rubber hoses, wires and cables, conveying pipelines, air springs, and other applications.

[0003] Chloroprene rubber has polar chlorine atoms attached to its main chain, giving it good stability in most oils and acids, and superior oil resistance compared to styrene-butadiene rubber (SBR) and butyl rubber. Furthermore, chloroprene rubber is resistant to almost all corrosion except for highly oxidizing acids, exhibiting excellent chemical corrosion resistance. Simultaneously, chloroprene rubber possesses excellent flame retardant and aging resistance: due to the presence of polar chlorine atoms, it exhibits a quenching effect at high temperatures; and the presence of electron-withdrawing chlorine atoms reduces the activity of the carbon-carbon double bond, making it less susceptible to the effects of atmospheric heat, oxygen, ozone, and light, demonstrating excellent anti-aging, weather resistance, and ozone resistance. In addition, chloroprene rubber has excellent physical and mechanical properties: the polar chlorine atom groups increase the intermolecular forces, providing a self-reinforcing effect, and under external forces, it easily stretches and crystallizes, minimizing slippage between molecular chains, thus resulting in high physical and mechanical strength. Moreover, chloroprene rubber has excellent inter-adhesion properties, making it suitable as an adhesive. Neoprene rubber is widely used as an adhesive due to its high bonding strength and fast bonding speed in footwear manufacturing, wood bonding, metal adhesives and other fields.

[0004] Water-based chloroprene adhesives, due to their absence of organic solvents, non-toxicity, and non-polluting properties, are a strong alternative to solvent-based adhesives. Water-based chloroprene latex adhesives formulated primarily with chloroprene latex represent the future direction of chloroprene adhesive development. These adhesives combine the properties of solvent-based chloroprene adhesives with advantages they lack: good film-forming properties, flexible film, and resistance to impact and vibration; high cohesive strength and strong adhesion to polar materials; good resistance to ozone, oxidation, oil, flame, and weathering; convenient and safe to use, allowing for wet bonding; low cost; non-toxic, environmentally friendly, and harmless to health; non-flammable, posing no fire or explosion hazard. However, the adhesive stability of water-based chloroprene adhesives prepared using current technologies is still far inferior to that of solvent-based chloroprene adhesives, limiting their usage and application areas. Therefore, further research in this field is needed. Summary of the Invention

[0005] This invention provides a modified chloroprene latex and its preparation method. The preparation process is simple, low-cost, and easy to operate. The raw materials are readily available, which is conducive to industrial production. Furthermore, the adhesive prepared using this modified chloroprene latex has excellent mechanical properties and broad application prospects.

[0006] This objective of the invention is achieved through the following technical solution:

[0007] A method for preparing modified chloroprene latex includes the following steps:

[0008] (1) Add nonionic emulsifier to deionized water to obtain emulsifier solution;

[0009] (2) Under heating conditions, chloroprene, methacrylic acid, acrylate and silane coupling agent containing long straight carbon chains with double bonds are added to the emulsifier solution while stirring to carry out pre-emulsification; the number of carbon atoms in the long straight carbon chains with double bonds is 8-18.

[0010] (3) After adding the initiator and polymerizing for 2-4 hours, add the silane coupling agent containing short straight carbon chains with double bonds and continue the reaction for a period of time before stopping the reaction and cooling down to discharge the material; the number of carbon atoms in the short straight carbon chains with double bonds is 2-4; the mass ratio of chloroprene, silane coupling agent containing long straight carbon chains with double bonds and silane coupling agent containing short straight carbon chains with double bonds is 100: (0.5-2): (3-6).

[0011] Existing technologies typically obtain carboxylated chloroprene latex main resins through copolymerization of chloroprene and methacrylic acid. The introduction of a small amount of carboxyl methacrylic acid monomers can improve the stability and adhesive properties of the latex. However, adding carboxyl methacrylic acid monomers during emulsion polymerization leads to a gradual increase in system viscosity. To address this issue, this invention specifically adds a certain amount of acrylate monomers. Acrylate monomers have high solubility in water, and the water-soluble initiator can initiate the copolymerization of water-soluble methacrylic acid and acrylate monomers, thus acting as a dispersive polymerization agent and helping to reduce system viscosity.

[0012] In the technical solution of this invention, chloroprene is the main monomer, providing core properties such as film-forming properties, weather resistance, ozone resistance, and flame retardancy. Methacrylic acid, as a functional monomer, provides carboxyl groups, significantly enhancing the adhesion of the adhesive to polar substrates (metals, ceramics, fibers) and serving as an active site for subsequent crosslinking. Acrylic esters, as soft monomers, can lower the glass transition temperature of the polymer, increase the flexibility and low-temperature resistance of the adhesive film, and regulate the balance between cohesive strength and tackiness.

[0013] Silane coupling agents containing double bonds participate in copolymerization, introducing silane groups into the polymer backbone or side chains via chemical bonds. Short carbon chains result in high reactivity, while the silane portion provides moisture-curing capability, significantly enhancing the water resistance, heat resistance, and durability of the final film. Long-chain double-bonded silane coupling agents also participate in copolymerization; the longer carbon chains improve chain flexibility, act as internal plasticizers, and improve compatibility with non-polar materials.

[0014] In one embodiment, the nonionic emulsifier in step (1) is one or more of polyvinyl alcohol, polyethylene glycol, sorbitan fatty acid ester, polyoxyethylene ether, hydroxyethyl cellulose, and hydroxymethyl cellulose. Specifically, the emulsifier can be dispersed in deionized water in advance, with a mass ratio of nonionic emulsifier to deionized water of (2.8-3.5):100. In particular, polyvinyl alcohol emulsifier with good water solubility can be used. The specific type of polyvinyl alcohol is not particularly limited, and any commonly used type in the art can be used. Further, polyvinyl alcohol with a lower cost, a degree of polymerization of 500-600, and a degree of alcoholysis of 87%-88% can be used.

[0015] In one embodiment, the heating temperature in step (2) is 35-45°C. Specifically, it can be 35°C, 36°C, 37°C, 38°C, 39°C, 40°C, 41°C, 42°C, 43°C, 44°C, or 45°C. A particularly suitable heating temperature is 38-42°C. Appropriate heating helps the emulsifier to adsorb and spread at the interface, but excessively high temperatures may cause the thermal motion of the emulsifier to be too intense, which may reduce its effective concentration at the interface.

[0016] In one embodiment, the acrylate in step (2) is one or more of methyl acrylate and methyl methacrylate. In particular, the acrylate is a mixture of methyl acrylate and methyl methacrylate. Due to differences in solubility and reactivity, the simultaneous addition of methyl acrylate and methyl methacrylate can promote the dispersion of the silane coupling agent and prevent the silane coupling agent monomer from self-polymerizing.

[0017] In one embodiment, the silane coupling agent containing a long straight carbon chain with double bonds in step (2) has the structural formula CH2=CH-X-Si-Y3, where X is a long straight carbon chain alkyl group with 6-16 carbon atoms, and Y is an alkoxy group with 1-4 carbon atoms. Specifically, the silane coupling agent containing a long straight carbon chain with double bonds is one or more of the following: octenyltrimethoxysilane, octenyltriethoxysilane, nonenyltrimethoxysilane, nonenyltriethoxysilane, decenyltrimethoxysilane, decenyltriethoxysilane, undecenyltrimethoxysilane, undecenyltriethoxysilane, dodecenyltrimethoxysilane, dodecenyltriethoxysilane, tetradecenyltrimethoxysilane, tetradecenyltriethoxysilane, hexadecenyltrimethoxysilane, and hexadecenyltriethoxysilane. The carbon-carbon double bonds in the silane coupling agent used in this invention are all on simple straight carbon chains. Compared with double-bonded silane coupling agents containing oxygen heteroatoms (such as methacryloyloxypropyltrimethoxysilane), it has better stability. In water-based emulsion polymerization, it is less prone to pre-hydrolysis and self-condensation, thereby greatly reducing the risk of latex thickening and gelation.

[0018] In one embodiment, the silane coupling agent containing a short straight carbon chain with double bonds in step (3) is one or more of vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane.

[0019] In one embodiment, the initiator in step (3) is one or more of potassium persulfate, ammonium persulfate, and dicumyl peroxide. Specifically, the initiator is added in the form of an aqueous solution with a concentration of 25-30 wt%. The total mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing a long straight carbon chain with double bonds, and silane coupling agent containing a short straight carbon chain with double bonds to the mass ratio of the initiator is 100:(0.1-10).

[0020] Specifically, the silane coupling agents containing short, straight carbon chains with double bonds and long, straight carbon chains with double bonds in this invention employ a stepwise addition process. By controlling the timing of the addition of different silanes, a functional group distribution with a specific sequence is constructed on the polymer growth chain. Silane coupling agents containing long, straight carbon chains with double bonds have lower activity; adding them in the early stages of the reaction can form segments rich in long-chain silanes. Adding silane coupling agents containing long, straight carbon chains with double bonds first can improve compatibility and provide internal toughening. Silane coupling agents containing long, straight carbon chains with double bonds have strong organic properties, better compatibility with rubber molecules, are easier to disperse in the polymer matrix, and are less prone to precipitation. When added in the early stages of polymerization, their double bonds can participate in copolymerization or grafting, introducing the long, flexible segments of the silane into the rubber molecular chain. This is equivalent to introducing a flexible spacer segment into the rubber network, which helps improve the flexibility, low-temperature compliance, and impact resistance of the film. Simultaneously, their siloxane ends provide a basic anchor point for the subsequent introduction of short-chain silanes. Silane coupling agents containing short, straight carbon chains with double bonds exhibit high reactivity, relatively higher siloxane content, and strong migration. When added after the initial reaction of silane coupling agents containing long, straight carbon chains with double bonds and a relatively stable system, they can rapidly migrate to the surface of latex particles and the material-substrate interface after final film formation. Their highly active siloxane ends can more effectively react with hydroxyl groups on the surface of inorganic substrates (such as glass, metal, and cement) to form strong chemical bonds, significantly improving adhesive strength. Stepwise addition of silane coupling agents with different chain lengths can prevent the crosslinked network from becoming too brittle, improving the toughness and low-temperature flexibility of the film. Specifically, silane coupling agents containing short, straight carbon chains with double bonds can be added after 2.5-3.5 hours of polymerization to better promote the dispersion of the silane coupling agent within the molecular chain.

[0021] In one embodiment, the total mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent with long straight carbon chains containing double bonds, and silane coupling agent with short straight carbon chains containing double bonds to the mass ratio of nonionic emulsifier in step (3) is 100:(3.5-4.5). Sufficient emulsifier dosage is the fundamental guarantee for long-term latex storage (anti-settling, anti-stratification) and for withstanding shear forces during processing without demulsification. Insufficient emulsifier dosage leads to latex instability, easy stratification, skin formation, and gel formation. Excessive emulsifier dosage, while providing better stability, reduces free water in the system, resulting in a macroscopic increase in latex viscosity.

[0022] In one embodiment, the mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent with long straight carbon chains containing double bonds, and silane coupling agent with short straight carbon chains containing double bonds in step (3) is 100:(2-5):(10-15):(0.5-2):(3-6). In particular, each component may be added in the form of an aqueous solution.

[0023] In one embodiment, the reaction continues for 4-5 hours in step (3). In particular, the reaction can be stopped by adding a terminator and unreacted monomers can be removed by rotary evaporation.

[0024] On the other hand, the present invention also provides a modified chloroprene latex prepared by the above method, which can achieve superior technical effects with a very small amount of latex applied. This modified chloroprene latex can be used directly or after adding additives such as antioxidants, acid acceptors, stabilizers, fillers, tackifiers, pigments, colorants, wetting agents, defoamers, and thickeners.

[0025] Beneficial effects:

[0026] This invention provides a modified chloroprene latex and its preparation method. The preparation process is simple, low-cost, and easy to operate, with readily available raw materials, facilitating industrial production. Furthermore, the adhesive prepared using this modified chloroprene latex exhibits excellent mechanical properties. Chloroprene is the main monomer, providing core properties such as film-forming properties, weather resistance, ozone resistance, and flame retardancy. Methacrylic acid, as a functional monomer, provides carboxyl groups, significantly enhancing the adhesive's adhesion to polar substrates and serving as an active site for subsequent crosslinking. Acrylic esters, as soft monomers, can lower the polymer's glass transition temperature, increase the film's flexibility and low-temperature resistance, and balance cohesive strength and tackiness. A silane coupling agent containing double bonds participates in copolymerization, introducing silane groups into the polymer backbone or side chains via chemical bonds. Short-chain silane coupling agents exhibit high reactivity, with the silane portion providing moisture-curing capability, greatly enhancing the final film's water resistance, heat resistance, and durability. Long-chain silane coupling agents also participate in copolymerization. The long carbon chain can improve the flexibility of the chain segments, and can also play a role in internal plasticization and improve compatibility with non-polar materials, thereby improving the bond strength. Detailed Implementation

[0027] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention are described in detail below with reference to examples. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below. Unless otherwise specified, the types of raw materials and processes used in the following embodiments are the same.

[0028] Performance testing: Under parallel experimental conditions, 100 parts (solid component) of modified chloroprene latex prepared in each example or comparative example were mixed evenly with 25 parts of terpene phenolic tackifier, 0.2 parts of urethane modified polyether thickener and other main additives. After coating, drying and heat treatment, the peel strength of canvas-glass plate was tested (refer to JIS Z 0237:2009 for details).

[0029] Example 1

[0030] A method for preparing modified chloroprene latex includes the following steps:

[0031] (1) Polyvinyl alcohol was added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water was 2.8:100;

[0032] (2) At 39°C, chloroprene, methacrylic acid, acrylate and octenyltrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was methyl acrylate.

[0033] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has been going on for 2 hours, add vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 5 hours. Then stop the reaction, cool down and discharge the material. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:3.8. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:2:10:0.5:3. The peel strength was tested to be 4.0 kN / m.

[0034] Example 2

[0035] A method for preparing modified chloroprene latex includes the following steps:

[0036] (1) Polyvinyl alcohol was added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water was 3.2:100;

[0037] (2) At 42°C, chloroprene, methacrylic acid, acrylate and undecylenetrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was methyl methacrylate.

[0038] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has proceeded for 3.6 h, add vinyltriethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 4 h. Then stop the reaction, cool down, and discharge the material. The total mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:4.2. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:5:15:2:6. The peel strength was tested to be 5.3 kN / m.

[0039] Example 3

[0040] A method for preparing modified chloroprene latex includes the following steps:

[0041] (1) Polyvinyl alcohol is added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water is 3:100;

[0042] (2) At 41°C, chloroprene, methacrylic acid, acrylate and undecylenetrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was methyl acrylate.

[0043] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has been going on for 3 hours, add vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 4.5 hours. Then stop the reaction, cool down, and discharge the material. The mass ratio of the total mass of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:4. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:3:12:1.2:4.5. The peel strength was tested to be 4.7 kN / m.

[0044] Example 4

[0045] A method for preparing modified chloroprene latex includes the following steps:

[0046] (1) Polyvinyl alcohol was added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water was 2.8:100;

[0047] (2) At 40°C, chloroprene, methacrylic acid, acrylate and octenyltrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, are added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate is a mixture of methyl acrylate and methyl methacrylate in a molar ratio of 1:1.

[0048] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has proceeded for 2.2 h, add vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 5 h. Then stop the reaction, cool down, and discharge the material. The mass ratio of the total mass of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:3.9. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:2.2:14.5:2:3.2. The peel strength was tested to be 4.8 kN / m.

[0049] Example 5

[0050] A method for preparing modified chloroprene latex includes the following steps:

[0051] (1) Polyvinyl alcohol is added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water is 3:100;

[0052] (2) At 41°C, chloroprene, methacrylic acid, acrylate and undecylenetrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was methyl methacrylate.

[0053] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has been going on for 3 hours, add vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 4.5 hours. Then stop the reaction, cool down and discharge the material. The total mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:4. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:3:12:1.2:4.5. The peel strength was tested to be 4.5 kN / m.

[0054] Example 6

[0055] A method for preparing modified chloroprene latex includes the following steps:

[0056] (1) Polyvinyl alcohol was added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water was 2.9:100;

[0057] (2) At 40°C, chloroprene, methacrylic acid, acrylate and undecylenetrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, are added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate is a mixture of methyl acrylate and methyl methacrylate in a molar ratio of 0.5:1.

[0058] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has proceeded for 2.8 h, add vinyltriethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 4.3 h. Then stop the reaction, cool down, and discharge the material. The total mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:3.9. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:3:11:1:4. The peel strength was tested to be 4.4 kN / m.

[0059] Example 7

[0060] A method for preparing modified chloroprene latex includes the following steps:

[0061] (1) Polyvinyl alcohol is added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water is 3:100;

[0062] (2) At 41°C, chloroprene, methacrylic acid, acrylate and undecylenetrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was a mixture of methyl acrylate and methyl methacrylate in a molar ratio of 5:1.

[0063] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After 4 hours of polymerization, add vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 4.5 hours. Then stop the reaction, cool down, and discharge the material. The total mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:4. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:3:12:1.2:4.5. The peel strength was tested to be 4.7 kN / m.

[0064] Example 8

[0065] A method for preparing modified chloroprene latex includes the following steps:

[0066] (1) Polyvinyl alcohol was added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water was 3.1:100;

[0067] (2) At 41°C, chloroprene, methacrylic acid, acrylate and octenyltrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was a mixture of methyl acrylate and methyl methacrylate in a molar ratio of 2:1.

[0068] (3) Potassium persulfate (added as a 27wt% aqueous solution) was added as an initiator. After polymerization for 3.4 h, vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, was added and the reaction continued for another 4.8 h before stopping the reaction and cooling down to discharge the product. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol was 100:1:4.1. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds was 100:4:14:1.8:5. The peel strength was tested to be 4.9 kN / m.

[0069] Example 9

[0070] A method for preparing modified chloroprene latex includes the following steps:

[0071] (1) Polyvinyl alcohol was added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water was 2.8:100;

[0072] (2) At 42°C, chloroprene, methacrylic acid, acrylate and undecylenetrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was methyl methacrylate.

[0073] (3) Potassium persulfate (added as a 27wt% aqueous solution) was added as an initiator. After polymerization for 2.3 h, vinyltriethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, was added and the reaction continued for another 4.7 h before stopping the reaction and cooling down to discharge the product. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol was 100:1:4.2; the mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds was 100:3.5:12.6:1.3:4.8. The peel strength was tested to be 4.3 kN / m.

[0074] Example 10

[0075] A method for preparing modified chloroprene latex includes the following steps:

[0076] (1) Polyvinyl alcohol is added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water is 3:100;

[0077] (2) At 41°C, chloroprene, methacrylic acid, acrylate and undecylenetrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was a mixture of methyl acrylate and methyl methacrylate in a molar ratio of 5:1.

[0078] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has been going on for 3 hours, add vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 4.5 hours. Then stop the reaction, cool down, and discharge the material. The mass ratio of the total mass of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:4. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:3:12:1.2:4.5. The peel strength was tested to be 5.1 kN / m.

[0079] Comparative Example 1

[0080] A method for preparing modified chloroprene latex includes the following steps:

[0081] (1) Polyvinyl alcohol is added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water is 3:100;

[0082] (2) At 41°C, chloroprene, methacrylic acid, acrylate and vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was a mixture of methyl acrylate and methyl methacrylate in a molar ratio of 5:1.

[0083] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has been going on for 3 hours, add undecenyltrimethoxysilane, a silane coupling agent containing long straight carbon chains with double bonds, and continue the reaction for another 4.5 hours. Then stop the reaction, cool down and discharge the material. The total mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:4. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:3:12:1.2:4.5. The peel strength was tested to be 2.9 kN / m.

[0084] Comparative Example 2

[0085] A method for preparing modified chloroprene latex includes the following steps:

[0086] (1) Polyvinyl alcohol is added to deionized water to obtain an emulsifier solution; the mass ratio of polyvinyl alcohol to deionized water is 3:100;

[0087] (2) At 41°C, chloroprene, methacrylic acid, acrylate and undecylenetrimethoxysilane, a silane coupling agent containing a long straight carbon chain with double bonds, were added to the emulsifier solution while stirring to carry out pre-emulsification; the acrylate was a mixture of methyl acrylate and methyl methacrylate in a molar ratio of 5:1.

[0088] (3) Add potassium persulfate as an initiator (added in the form of a 27wt% aqueous solution). After the polymerization reaction has been going on for 3 hours, add vinyltrimethoxysilane, a silane coupling agent containing short straight carbon chains with double bonds, and continue the reaction for another 4.5 hours. Then stop the reaction, cool down, and discharge the material. The total mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds to potassium persulfate and polyvinyl alcohol is 100:1:4. The mass ratio of chloroprene, methacrylic acid, propylene ester, silane coupling agent containing long straight carbon chains with double bonds, and silane coupling agent containing short straight carbon chains with double bonds is 100:3:12:4.5:1.2. The peel strength was tested to be 3.3 kN / m.

[0089] As can be seen from the above embodiments and comparative examples, the present invention provides a modified chloroprene latex and its preparation method. This preparation process is simple, low-cost, and easy to operate, with readily available raw materials. Chloroprene is the main monomer, providing core properties such as film-forming properties and weather resistance. Methacrylic acid, as a functional monomer, provides carboxyl groups, significantly enhancing the adhesion of the adhesive to polar substrates and serving as an active site for subsequent crosslinking. Acrylic esters, as soft monomers, can lower the polymer's glass transition temperature, increase the film's flexibility and low-temperature resistance, and regulate the balance between cohesive strength and tackiness. Meanwhile, silane coupling agents containing double bonds participate in copolymerization, introducing silane groups into the polymer backbone or side chains via chemical bonds.

[0090] Specifically, compared to Example 10, Comparative Example 1 first added a silane coupling agent containing short, straight carbon chains with double bonds. When this silane coupling agent bonded to the polymer chain, its short and rigid structure created significant steric hindrance in the local molecular chain. The subsequently added silane coupling agent molecules with large, long, flexible chains then struggled to approach and react chemically with the active sites of the polymer chain. As a result, most of the long, flexible silane coupling agent could only physically mix within the system, failing to achieve the desired chemical bonding and internal toughening effects, thus affecting the improvement of bond strength. Compared to Example 10, Comparative Example 2 used too much silane coupling agent containing long, straight carbon chains with double bonds, while using too little silane coupling agent containing short, straight carbon chains with double bonds. Excessive use of silane coupling agents containing long, straight carbon chains with double bonds not only leads to material softening and reduced load-bearing capacity, but also causes excessive long-chain silane molecules to surround the active reaction sites, forming spatial and physical barriers, ultimately resulting in an incomplete cross-linking network of the material, which further exacerbates the decrease in strength. On the other hand, using less silane coupling agents containing short, straight carbon chains with double bonds makes it difficult to construct a silicon-oxygen reinforced network, resulting in lower bonding strength.

[0091] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described; these embodiments not explicitly stated should also be considered within the scope of this specification. Although the present invention has been described in detail above with general descriptions and specific embodiments, some modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing modified chloroprene latex, characterized in that, Includes the following steps: (1) Add nonionic emulsifier to deionized water to obtain emulsifier solution; (2) Under heating conditions, chloroprene, methacrylic acid, acrylate and silane coupling agent containing long straight carbon chains with double bonds are added to the emulsifier solution while stirring to carry out pre-emulsification; The number of carbon atoms in the long straight carbon chain containing double bonds is 8-18; (3) After adding the initiator and polymerizing for 2-4 hours, add the silane coupling agent containing short straight carbon chains with double bonds and continue the reaction for a period of time before stopping the reaction and cooling down to discharge the material; the number of carbon atoms in the short straight carbon chains with double bonds is 2-4; the mass ratio of chloroprene, silane coupling agent containing long straight carbon chains with double bonds and silane coupling agent containing short straight carbon chains with double bonds is 100: (0.5-2): (3-6).

2. A process for the preparation of a modified chloroprene latex as claimed in claim 1, characterized in that, In step (1), the nonionic emulsifier is one or more of the following: polyvinyl alcohol, polyethylene glycol, sorbitan fatty acid ester, polyoxyethylene ether, hydroxyethyl cellulose, and hydroxymethyl cellulose.

3. A process for the preparation of a modified chloroprene latex as claimed in claim 1, wherein, In step (2), the acrylate is one or more of methyl acrylate and methyl methacrylate.

4. A process for the preparation of a modified chloroprene latex as claimed in claim 1, wherein, In step (2), the silane coupling agent containing a long straight carbon chain with double bonds is one or more of the following: octenyltrimethoxysilane, octenyltriethoxysilane, nonenyltrimethoxysilane, nonenyltriethoxysilane, decenyltrimethoxysilane, decenyltriethoxysilane, undecenyltrimethoxysilane, undecenyltriethoxysilane, dodecenyltrimethoxysilane, dodecenyltriethoxysilane, tetradecenyltrimethoxysilane, tetradecenyltriethoxysilane, hexadecenyltrimethoxysilane, and hexadecenyltriethoxysilane.

5. The process for preparing a modified neoprene latex according to claim 1, wherein the process is characterized by, In step (3), the silane coupling agent containing a short straight carbon chain with double bonds is one or more of vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane.

6. A process for the preparation of a modified neoprene latex as claimed in claim 1, wherein, In step (3), the initiator is one or more of potassium persulfate, ammonium persulfate, and dicumyl peroxide.

7. The method for preparing a modified chloroprene latex as described in claim 1, characterized in that, In step (3), the total mass ratio of chloroprene, methacrylic acid, acrylate, silane coupling agent with long straight carbon chain containing double bond and silane coupling agent with short straight carbon chain containing double bond to nonionic emulsifier is 100: (3.5-4.5).

8. A process for the preparation of a modified neoprene latex as claimed in claim 1, wherein, In step (3), the mass ratio of chloroprene, methacrylic acid, acrylate, silane coupling agent with long straight carbon chain containing double bond, and silane coupling agent with short straight carbon chain containing double bond is 100: (2-5): (10-15): (0.5-2): (3-6).

9. A process for the preparation of a modified chloroprene latex as claimed in claim 1, wherein, The reaction time in step (3) is 4-5 hours.

10. A modified chloroprene latex characterized in that, It is prepared by the method of any one of claims 1-9 for the preparation of a modified chloroprene latex.