Low-solid-content temperature-resistant single-component chloroprene rubber adhesive and preparation method thereof

Abstract

The invention provides a low-solid-content and temperature-resistant single-component chloroprene rubber adhesive and a preparation method thereof. The single-component chloroprene rubber adhesive comprises modified chloroprene rubber, tackifying resin, an acid absorbent, an auxiliary agent and a solvent, the modified chloroprene rubber is prepared through an emulsion polymerization method, 2-chloro-1, 3-butadiene is used as a main monomer, a small amount of 2-hydroxyethyl acrylate is introduced for copolymerization, and hydroxyl functional groups are introduced into rubber molecules; by controlling the molar ratio of the two monomers, the polarity and the heat resistance of the system are improved, and meanwhile, good processability is considered; the tackifying resin is terpene phenol resin prepared by reacting alpha-pinene and phenol, and the initial adhesion and compatibility of the adhesive are further improved; the obtained single-component chloroprene rubber adhesive has the advantages of being low in solid content, good in construction performance, excellent in heat resistance and storage stability and the like, and is suitable for the field of electronic, electrical and industrial bonding.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, and in particular to a low-solids, heat-resistant, one-component chloroprene rubber and its preparation method. Background Technology

[0002] Neoprene rubber adhesives are widely used in footwear, leather, rubber products, metal composites, and industrial repair due to their excellent initial tack, adaptability to various substrates, and good oil and aging resistance. Among these, single-component neoprene rubber is particularly valuable in industrial production due to its ease of application and lack of on-site mixing requirements.

[0003] Existing one-component chloroprene rubber typically uses chloroprene rubber as the film-forming matrix, combined with tackifying resins such as terpene phenolic resins, petroleum resins, or phenolic resins. The adhesive interface is formed through solvent evaporation and the crystallization of the chloroprene rubber. The adhesive properties of this type of system mainly depend on the crystallization ability of the rubber and the physical compatibility between the resin and the rubber. Intermolecular forces are predominantly van der Waals forces, and the interfacial bonding energy is limited.

[0004] In practical applications, existing technologies generally suffer from the following shortcomings: On the one hand, in order to obtain higher heat resistance and bonding strength, it is usually necessary to increase the amount of chloroprene rubber and tackifying resin, which generally results in a higher solid content in the adhesive. This not only increases material costs, but also leads to increased viscosity of the adhesive, decreased workability, and prolonged solvent evaporation time, which is not conducive to high-speed and continuous production. On the other hand, in high-temperature environments, the rubber crystal structure and resin phase in traditional single-component chloroprene rubber systems are prone to softening or flow, and the interfacial bonding force decreases rapidly. This results in reduced heat-resistant peel strength and insufficient tack, making it difficult to meet the requirements of application scenarios with high temperature resistance.

[0005] To improve high-temperature resistance, existing technologies often employ the following approaches: First, increase the softening point of the tackifying resin or introduce high-rigidity phenolic resins. However, this approach often sacrifices initial tack and flexibility and can easily lead to decreased compatibility. Second, introduce crosslinking agents or reactive components to form a chemical crosslinking network. However, this can significantly shorten the shelf life, disrupt the stability of the single-component system, and even cause premature gelation or construction failure.

[0006] Therefore, how to improve the high-temperature resistance and adhesive strength of one-component chloroprene rubber without introducing chemical crosslinking, significantly increasing the solid content, or affecting storage stability and workability, especially maintaining good bonding performance under low solid content conditions, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] Purpose of the invention: The purpose of this invention is to provide a low-solids, high-temperature resistant single-component chloroprene rubber and its preparation method. By synergistically functionalizing chloroprene rubber and tackifying resin, functional groups that can form hydrogen bonds are introduced, and a stable and reversible intermolecular interaction network is constructed within the adhesive system, thereby significantly improving temperature resistance and bonding performance while reducing solids content.

[0008] The technical solution of this invention: In a first aspect, the present invention provides a low-solids, heat-resistant, single-component chloroprene rubber, wherein the raw material, based on 100% of the total weight of the chloroprene rubber, comprises the following components: Modified chloroprene rubber 7-9 wt%; 5-7 wt% tackifying resin; Acid absorbent 0.6-1.0 wt%; Additives 0.3-0.8 wt%; Filler 0-2.0wt%; Solvent balance; The modified chloroprene rubber uses 2-chloro-1,3-butadiene and 2-hydroxyethyl acrylate as its polymer monomers.

[0009] In some embodiments, the molar ratio of 2-chloro-1,3-butadiene to 2-hydroxyethyl acrylate is 95-99:1-5; further, the molar ratio of 2-chloro-1,3-butadiene to 2-hydroxyethyl acrylate is 98.0-98.8:1.2-2.0.

[0010] In some embodiments, the modified chloroprene rubber has a molecular weight of 1.0 × 10⁻⁶. 5 -1.5×10 5 g / mol.

[0011] In some embodiments, the method for preparing the modified chloroprene rubber includes the following steps: S1: Add deionized water to the reactor, add emulsifier and stir to dissolve, and adjust the pH of the system to 10.0-11.5 with alkali; S2: Add 2-chloro-1,3-butadiene and 2-hydroxyethyl acrylate, and emulsify by stirring at low temperature; S3: Introduce nitrogen gas, add an initiator, and heat the reaction. Add a molecular weight regulator to control the molecular weight. S4: After the reaction is complete, add a terminator, cool, adjust the pH to neutral, filter, and obtain modified chloroprene rubber.

[0012] In some embodiments, the emulsification temperature of the low-temperature stirring emulsification described in S2 is 5-10°C, and the stirring time is 20-40 min.

[0013] In some embodiments, the initiator in S3 is one or more combinations of potassium persulfate and ammonium persulfate, the reaction temperature of the heating reaction is 40-55°C, and the reaction time is 4-8 h; the molecular weight regulator is one or more combinations of dodecyl mercaptan and tert-dodecyl mercaptan.

[0014] In some embodiments, the terminator in S4 is either hydroquinone or a hydroxylamine salt, and the cooling temperature is 25-30°C.

[0015] In some embodiments, the number-average molecular weight Mn of the tackifying resin is 600-1200.

[0016] In some embodiments, the polymerizable monomers of the tackifying resin are α-pinene, phenol, and N-vinylpyrrolidone.

[0017] In some embodiments, the molar ratio of α-pinene, phenol, and N-vinylpyrrolidone is 65-75:20-30:2-8; further, the molar ratio of α-pinene, phenol, and N-vinylpyrrolidone is 70:25:5.

[0018] In some embodiments, the method for preparing the tackifying resin includes the following steps: S1: Add phenol to the reaction vessel, heat to dissolve, then add α-pinene, stir evenly, then add N-vinylpyrrolidone, and continue stirring until homogeneous; S2: Heat the system and add an acidic catalyst; heat again and maintain the temperature for reaction; after the reaction is complete, cool down, add a weak base to neutralize, filter, and obtain the tackifying resin.

[0019] In some embodiments, the heating temperature in S1 is 50-60°C, the stirring time is 20-30 min, and the stirring time is continued for 10-20 min.

[0020] In some embodiments, the system in S2 is heated to 70-80°C, and the acidic catalyst is one or more combinations of p-toluenesulfonic acid or oxalic acid; the holding temperature is 130-150°C, and the reaction is carried out for 2-4 hours; the cooling temperature is below 90°C, and the weak base is one or more combinations of triethylamine or sodium carbonate.

[0021] In some embodiments, the acid absorbent is selected from one or more combinations of magnesium oxide, zinc oxide, calcium oxide, magnesium carbonate, calcium carbonate, and hydrotalcite. The acid absorbent can absorb HCl released by chloroprene rubber during storage or under high-temperature conditions; inhibit molecular chain degradation and viscosity abrupt changes; and prevent acid-catalyzed damage to the hydroxyl / amide / urea groups in the tackifying resin.

[0022] In some embodiments, the additive is selected from one or more combinations of antioxidants, dispersants and wetting agents, rheology modifiers, and defoamers.

[0023] In some embodiments, the filler is selected from one or more combinations of light calcium carbonate, precipitated barium sulfate, kaolin, talc, fumed silica, micronized mica, and flake talc. The filler is not mandatory; its function is to fine-tune high-temperature resistance to flow, improve thixotropy, and reduce costs.

[0024] In some embodiments, the solvent is selected from a variety of combinations of methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, butyl acetate, isopropyl acetate, toluene, xylene, and aromatic solvent oils. For example, a mixture of methyl ethyl ketone, butyl acetate, and toluene in a mass ratio of 40:30:30 can be used.

[0025] In a second aspect, the present invention provides a method for preparing the above-mentioned low-solids-content, heat-resistant single-component chloroprene rubber, specifically comprising the following steps: Step 1: Add the modified chloroprene rubber to the solvent and disperse it evenly to obtain a modified chloroprene rubber solution; Step 2: Add the tackifying resin to the solvent and disperse it evenly to obtain a tackifying resin solution; Step 3: Slowly add the tackifying resin solution obtained in step S2 to the modified chloroprene rubber solution described in step S1, and heat and stir to disperse evenly; Step 4: Add the acid absorbent, filler, and additives to the above mixture in sequence, and continue stirring to disperse. Step 5: Add solvent to obtain the single-component chloroprene rubber product.

[0026] In some embodiments, the heating temperature for heating, stirring and dispersing in step 3 is 30-50°C, and the stirring time is 30-90 min.

[0027] Using the above preparation method, a reversible physical cross-linking network is constructed inside the adhesive by simultaneously introducing functional groups that can form hydrogen bonds into the modified chloroprene rubber and the modified tackifying resin. This network partially dissociates under high temperature conditions to absorb thermal stress and inhibit flow, and reforms after cooling. Thus, it can still maintain high temperature resistance, high initial tack and high peel strength under low solid content conditions, while maintaining good storage stability and workability.

[0028] Beneficial effects: Compared with existing technologies, the low-solids, high-temperature resistant single-component chloroprene rubber provided by this invention, through synergistic functionalization modification of chloroprene rubber and tackifying resin, constructs a reversible physical crosslinking network dominated by hydrogen bonding within the adhesive system. This significantly improves the high-temperature resistance and bonding stability of the adhesive without introducing chemical crosslinking agents. The hydroxyl, amide, or urea functional groups introduced into the modified chloroprene rubber and modified tackifying resin can form high-density hydrogen bond connections at room temperature, improving the cohesive strength and interfacial bonding of the adhesive layer. In high-temperature environments, some hydrogen bonds undergo reversible dissociation to absorb thermal stress and inhibit adhesive layer flow and loss of tack. After cooling, the hydrogen bonds reform, thus maintaining long-term bonding reliability.

[0029] Furthermore, through the aforementioned physical cross-linking mechanism, this invention effectively reduces the overall solid content of the adhesive to 15-20% while ensuring temperature resistance and adhesive performance. This significantly reduces the amount of polymer materials used, lowers the system viscosity, improves coating and application performance, and offers significant cost advantages and economic benefits. The system is a single-component structure, requiring no on-site mixing or heat curing, exhibits good storage stability, and is suitable for industrial bonding applications with high requirements for heat resistance, workability, and cost control. Detailed Implementation

[0030] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0031] Unless otherwise specified, all chemical reagents used in this invention are commercially available analytical grade reagents.

[0032] Example 1 of the preparation of modified chloroprene rubber S1: Add 1000 mL of deionized water to the reactor, add 25 g of disproportionated rosin sodium and stir to dissolve, and adjust the pH of the system to 10.0 with sodium hydroxide solution; S2: Add 195g of 2-chloro-1,3-butadiene and 5g of 2-hydroxyethyl acrylate at 10℃, with a molar ratio of 98:2 (±0.3), and stir and emulsify at 10℃ for 30min; S3: Purge with nitrogen for 30 min, add 1.0 g potassium persulfate, and heat to 50℃ for 8 h. Add 0.3 g dodecyl mercaptan to control the molecular weight. S4: After the reaction is complete, hydroquinone is added, and after cooling, the pH is adjusted to 7. After coagulation, filtration and washing, modified chloroprene rubber #1 is obtained.

[0033] Example 2 of preparation of modified chloroprene rubber The preparation steps of Modified Chloroprene Rubber Preparation Example 2 are basically the same as those of Modified Chloroprene Rubber Preparation Example 1, except that the added masses of 2-chloro-1,3-butadiene and 2-hydroxyethyl acrylate are 184.5 g and 15.5 g, respectively, so that the molar ratio of 2-chloro-1,3-butadiene to 2-hydroxyethyl acrylate is 94:6. Modified Chloroprene Rubber #2 was thus prepared.

[0034] Example of chloroprene rubber preparation The preparation steps for the chloroprene rubber preparation example are basically the same as those for the modified chloroprene rubber preparation example 1, except that the added masses of 2-chloro-1,3-butadiene and 2-hydroxyethyl acrylate are 200 g and 0 g, respectively. Chloroprene rubber was thus prepared.

[0035] Example 1 of preparation of tackifying resin S1: Add 60 g of phenol to the reactor, heat to 55℃ to dissolve, then add 137 g of α-pinene, stir for 30 min until homogeneous, then add 11 g of N-vinylpyrrolidone, and continue stirring until homogeneous; S2: Heat the system to 80°C and add 10g of p-toluenesulfonic acid; heat again to 120°C and keep the reaction at that temperature for 2 hours; after the reaction is complete, cool down to 80°C, add sodium carbonate to neutralize, filter, and obtain tackifying resin #1.

[0036] Example 2 of preparation of tackifying resin The preparation steps of tackifying resin preparation example 2 are basically the same as those of tackifying resin preparation example 1, except that the molar ratios of α-pinene, phenol, and N-vinylpyrrolidone added are 154.3 g and 45.7 g, respectively, resulting in a molar ratio of 70:30:0 for α-pinene, phenol, and N-vinylpyrrolidone. Modified chloroprene rubber #2 was thus prepared.

[0037] Example Step 1: Add the modified chloroprene rubber to the solvent, and swell and disperse it evenly at 35°C to obtain a modified chloroprene rubber solution; Step 2: Add the tackifying resin to the solvent and disperse it evenly at 50°C to obtain a tackifying resin solution; Step 3: Slowly add the tackifying resin solution obtained in step S2 to the modified chloroprene rubber solution in step S1, and heat and stir at 50°C for 90 min to disperse evenly; Step 4: Add the acid absorbent, filler, and additives to the above mixture in sequence, and continue stirring to disperse. Step 5: Replenish the solvent to control the total solid content of the final one-component chloroprene rubber at 15-20 wt%, and obtain the finished one-component chloroprene rubber product.

[0038] The raw materials and their weight fractions used in the examples are shown in Table 1.

[0039] Table 1 Formulation table for each embodiment

[0040] Comparative Example The preparation method of the comparative example is basically the same as that of the example, except that the formulation of the comparative example is shown in Table 2.

[0041] Table 2 Formulations for each comparative example

[0042] Performance testing: 1. The single-component chloroprene rubber products obtained in the examples and comparative examples were subjected to high-temperature heat aging treatment at 130°C for 720 hours. The tensile strength of the fresh single-component chloroprene rubber products and the single-component chloroprene rubber products after heat aging treatment were tested respectively. The tensile strength test method was in accordance with GB / T528-2009 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber". The test results are shown in Table 3.

[0043] 2. The single-component chloroprene rubber product prepared above is dried and pulverized in the same manner for later use. 10g of each pulverized product is weighed and added to 100g of a mixed solvent (toluene:ethyl acetate = 7:3, mass ratio). The mixture is stirred at 300rpm at 25℃, and the time required to achieve uniformity with no visible gel particles is recorded.

[0044] 3. Apply the rubber solution obtained above onto the PET film using a 100μm doctor blade; observe whether stringing, blade skipping, or uneven surface occurs during the coating process.

[0045] Table 3 Test Results

[0046] The test results of the examples show that the chloroprene rubber product using the technical solution provided in this application has good high-temperature resistance. Through the comparison of Example 2 and Comparative Examples 1 and 3, it can be seen that when the modified chloroprene rubber and tackifying resin provided by this invention are used, a reversible physical cross-linking network mainly based on hydrogen bonding is constructed between the two in the adhesive system. This significantly improves the high-temperature resistance and bonding stability of the adhesive without the introduction of chemical cross-linking agents. Without either of them, this effect cannot be achieved, thus giving the chloroprene rubber good high-temperature resistance.

[0047] A comparison of Example 2 and Comparative Example 2 shows that when the molar ratio of 2-chloro-1,3-butadiene to 2-hydroxyethyl acrylate exceeds 95:5, the resulting modified chloroprene rubber exhibits deteriorated processing properties such as slow dissolution rate, high system viscosity, and easy stringing during coating due to the higher hydroxyl content and enhanced intermolecular hydrogen bonding. In contrast, when the molar ratio is 98:2, the rubber system balances polarity and fluidity, and the processing stability is significantly improved, making it more suitable for the industrial preparation and application of single-component chloroprene rubber.

[0048] The present invention can also be implemented in various other ways. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A low-solids, heat-resistant, one-component chloroprene rubber, characterized in that, Based on the total weight of chloroprene rubber (100%), the raw materials consist of the following components: Modified chloroprene rubber 7-9 wt%; 5-7 wt% tackifying resin; Acid absorbent 0.6-1.0 wt%; Additives 0.3-0.8 wt%; Filler 0-2.0wt%; Solvent balance; The modified chloroprene rubber uses 2-chloro-1,3-butadiene and 2-hydroxyethyl acrylate as its polymer monomers.

2. The single-component chloroprene rubber according to claim 1, characterized in that, The molar ratio of 2-chloro-1,3-butadiene to 2-hydroxyethyl acrylate is 95-99:1-5.

3. The single-component chloroprene rubber according to claim 1 or 2, characterized in that, The molar ratio of 2-chloro-1,3-butadiene to 2-hydroxyethyl acrylate is 98.0-98.8:1.2-2.

0.

4. The single-component chloroprene rubber according to claim 1, characterized in that, The preparation method of the modified chloroprene rubber includes the following steps: S1: Add deionized water to the reactor, add emulsifier and stir to dissolve, and adjust the pH of the system to 10.0-11.5 with alkali; S2: Add 2-chloro-1,3-butadiene and 2-hydroxyethyl acrylate, and emulsify by stirring at low temperature; S3: Introduce nitrogen gas, add an initiator, and heat the reaction. Add a molecular weight regulator to control the molecular weight. S4: After the reaction is complete, add a terminator, cool, adjust the pH to neutral, filter, and obtain modified chloroprene rubber.

5. The single-component chloroprene rubber according to claim 4, characterized in that, S2 The emulsification temperature for low-temperature stirring and emulsification is 5-10℃, and the stirring time is 20-40 min; S3 The initiator is one or more combinations of potassium persulfate and ammonium persulfate, the reaction temperature for the heating reaction is 40-55℃, and the reaction time is 4-8 h; The molecular weight regulator is one or more combinations of dodecyl mercaptan and tert-dodecyl mercaptan; S4 The terminator is one of hydroquinone or hydroxylamine salt, and the cooling temperature is 25-30℃.

6. The single-component chloroprene rubber according to claim 1, characterized in that, The polymer monomers of the tackifying resin are α-pinene, phenol, and N-vinylpyrrolidone.

7. The single-component chloroprene rubber according to claim 6, characterized in that, The molar ratio of α-pinene, phenol and N-vinylpyrrolidone is 65-75:20-30:2-8.

8. The single-component chloroprene rubber according to claim 1, characterized in that, The method for preparing the tackifying resin includes the following steps: S1: Add phenol to the reaction vessel, heat to dissolve, then add α-pinene, stir evenly, then add N-vinylpyrrolidone, and continue stirring until homogeneous; S2: Heat the system and add an acidic catalyst; heat again and maintain the temperature for reaction; after the reaction is complete, cool down, add a weak base to neutralize, filter, and obtain the tackifying resin.

9. The single-component chloroprene rubber according to claim 8, characterized in that, The heating temperature in S1 is 50-60℃, the stirring time is 20-30 min, and the stirring time is continued for 10-20 min; the system heating temperature in S2 is 70-80℃, and the acidic catalyst is one or more combinations of p-toluenesulfonic acid or oxalic acid; the heat preservation temperature is 130-150℃, and the reaction time is 2-4 h; the cooling temperature is below 90℃, and the weak base is one or more combinations of triethylamine or sodium carbonate.

10. The method for preparing the single-component chloroprene rubber according to any one of claims 1-9, characterized in that, Specifically, the following steps are included: Step 1: Add the modified chloroprene rubber to the solvent and disperse it evenly to obtain a modified chloroprene rubber solution; Step 2: Add the tackifying resin to the solvent and disperse it evenly to obtain a tackifying resin solution; Step 3: Slowly add the tackifying resin solution obtained in step S2 to the modified chloroprene rubber solution described in step S1, and heat and stir to disperse evenly; Step 4: Add the acid absorbent, filler, and additives to the above mixture in sequence, and continue stirring to disperse. Step 5: Add solvent to obtain the single-component chloroprene rubber product.

Images