Curing-speed-stable chloroprene rubber for adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of chloroprene rubber preparation, and provides chloroprene rubber which is used for a two-component adhesive and is stable in curing speed as well as a preparation method and application of the chloroprene rubber. Chloroprene is taken as a basic material, and chloroprene rubber molecules are modified by functional monomers, so that groups which react with isocyanate are added to molecular chain segments of the chloroprene rubber molecules; and adding a reactive emulsifier to promote the functional monomer to enter latex particle molecules for reaction. The chloroprene rubber can be directly dissolved to be used for preparing a two-component adhesive solution, can react with an isocyanate curing agent without secondary grafting or addition of an auxiliary agent, and is stable in curing rate and better in controllability than imported carboxyl chloroprene rubber. A functional monomer is inserted into an active point of an existing polychloroprene macromolecular chain, reactive groups required by curing are increased, and the number of chloroprene rubber molecular functional groups is adjusted by controlling the addition amount of the functional monomer, so that the reaction rate of the chloroprene rubber adhesive and isocyanate is adjusted, and the curing time of the double-component adhesive is optimized.

Description

Technical Field

[0001] The invention belongs to the technical field of chloroprene rubber preparation, and particularly relates to chloroprene rubber for adhesive with stable curing speed and a preparation method thereof. Background Art

[0002] Chloroprene rubber crystallizes quickly and has strong cohesive force. The molecular structure contains highly electronegative chlorine atoms, which can provide the polarity required for bonding. It has good adhesion to a variety of materials and can be used to bond rubber to metal, rubber to rubber, fabric, plastic, wood, glass, leather, and other materials with high bonding strength.

[0003] Neoprene adhesives can be divided into one-component adhesives and two-component adhesives according to their components. One-component neoprene adhesives mainly utilize the crystallization characteristics of neoprene to obtain greater initial adhesion. Two-component neoprene adhesives are cured at room temperature through cross-linking reaction in combination with a curing agent, and can obtain higher strength in a short time. Two-component adhesives require the two components to be mixed evenly when used, and the process is more complicated than that of a single component, but their moisture resistance, bonding strength, and heat resistance are better than those of a single-component neoprene adhesive, and are suitable for applications that require rapid curing and bonding at room temperature.

[0004] Two-component chloroprene rubber adhesives mostly use isocyanate curing agents. Conventional chloroprene rubber mainly uses isocyanate groups to react with double bonds and active hydrogen atoms carried by 3,4 structural segments, but conventional chloroprene rubber has limited reactive groups, and it is difficult to quickly cure in a short time to obtain high strength. The Japanese patent "Japanese Publication of Patent No. 56-233 / 4" mixes chloroprene rubber and isocyanate and dissolves them in an organic solvent, and selects organic metal salts and tertiary amines as curing agents to improve the bonding strength and prepare adhesives that are not easy to yellow. Patent CN 116285775A "A high-performance chloroprene rubber adhesive and its preparation method" adds chloroprene rubber to an isocyanate crosslinking agent, and selects organic tin and zinc as catalysts to promote the crosslinking reaction and improve the high temperature resistance and bonding strength of the adhesive. It can be seen from the above patents that conventional chloroprene rubber is used to prepare two-component adhesives, and isocyanate curing agents are used. Catalysts need to be added to promote the crosslinking reaction, so the requirements for curing speed cannot be met.

[0005] Some patents increase the reactive groups in the adhesive by adding resin or di-monomer grafting to the chloroprene rubber glue to promote the reaction between the adhesive base liquid and the isocyanate curing agent. Patent CN 103031067 A "A fast-curing chloroprene rubber adhesive and its preparation method" uses general-purpose chloroprene rubber to prepare a fast-curing chloroprene rubber adhesive through a secondary reaction method of the glue liquid, overcoming the shortcomings of traditional chloroprene adhesives such as poor heat resistance and cold resistance, poor storage stability, and slow curing speed. Patent CN 1272520A "Normal temperature curing conveyor belt joint chloroprene rubber adhesive" uses copolymer modified chloroprene rubber and the addition of resin to prepare a two-component adhesive to shorten the curing time. At present, downstream customers mostly use carboxyl modified chloroprene rubber to prepare two-component adhesives, but its curing speed is too fast and unstable, resulting in too short an operating time for the adhesive. Summary of the invention

[0006] In view of the above problems, the present invention provides a chloroprene rubber with a stable curing speed for use in a two-component adhesive and a preparation method and application thereof. The preparation method of chloroprene rubber with a stable curing speed can be directly used in the preparation of a two-component adhesive to meet the needs of downstream customers.

[0007] The present invention is realized by the following technical scheme: a method for preparing chloroprene rubber with stable curing speed for two-component adhesive, which uses chloroprene as a basic material, modifies chloroprene rubber molecules with functional monomers, and increases groups that react with isocyanate in its molecular chain segments; adds a reactive emulsifier to promote the functional monomer to enter the latex particle molecules for reaction; and adjusts the number of functional groups of chloroprene rubber molecules by controlling the amount of functional monomer added, thereby adjusting the reaction rate of chloroprene rubber adhesive with isocyanate and optimizing the curing time of the two-component adhesive.

[0008] The chloroprene is a mercaptan-regulated low-conversion chloroprene latex; the functional monomer is any one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, monobutyl maleate, monobutyl itaconate, hydroxymethyl acrylamide or N-methylmaleimide; the group that reacts with isocyanate is -OH, -COOH, -SH or -NH; the reactive emulsifier is any one of sodium vinyl sulfonate, sodium methacrylic acid, sodium propylene sulfonate, sodium acrylamidoisopropyl sulfonate, allyl nonylphenol polyoxyethylene ether sulfate or allyl polyether sulfate.

[0009] The specific method is: 60-85 parts of chloroprene rubber latex, 5-30 parts of functional monomers, 1-5 parts of emulsifiers, 0.05-0.15 parts of water-based initiators, and 0.5-2 parts of antioxidants. The chloroprene rubber latex, emulsifier, and antioxidant are mixed and stirred evenly according to the proportion. The mixed emulsion is heated to the reaction temperature of 40-60°C under nitrogen conditions, the initiator solution is added, the functional monomer is added, and the reaction is terminated after 4-6 hours. The latex is demulsified and dried into a film, which is the chloroprene rubber sample for two-component adhesive.

[0010] Furthermore, the chloroprene rubber latex is 65-80 parts and the functional monomer is 5-15 parts.

[0011] The water-based initiator is any one of potassium persulfate, sodium persulfate or ammonium persulfate; the antioxidant is a water-based composite antioxidant that can be directly added to latex.

[0012] The invention also provides chloroprene rubber which is used in a two-component adhesive and has a stable curing speed and is obtained by the preparation method.

[0013] The invention also provides application of the chloroprene rubber in the preparation of a two-component adhesive solution.

[0014] The chloroprene rubber prepared by the invention can be directly dissolved and used for the preparation of two-component adhesive solution, and can react with isocyanate curing agent without secondary grafting or adding auxiliary agent, and has stable curing rate and better controllability than imported carboxyl chloroprene rubber.

[0015] The present invention uses chloroprene latex as a basic material, and selects functional monomers to modify chloroprene rubber molecules so that groups that can react with isocyanate, such as -OH, -COOH, -SH, -NH, etc., are added to the molecular chain segments, so that the adhesive prepared from the chloroprene rubber has curing performance, and the group content can be effectively controlled by an emulsion grafting method involving a reactive emulsifier, thereby stabilizing the curing rate.

[0016] The emulsifier used in the present invention is a reactive emulsifier containing unsaturated double bonds that can participate in the polymerization reaction. The selected aqueous initiator can be added all at once, or can be added continuously or in batches. The antioxidant can be a water-based composite antioxidant that can be directly added to the latex, or a general composite antioxidant emulsion can be prepared by itself. The type and amount of the reactive emulsifier can be adjusted according to the ratio of functional monomers.

[0017] Usually, chloroprene rubber modification mostly uses chloroprene and dimonomer copolymerization method, such as dichloroprene, methacrylic acid, maleic acid, itaconic acid, etc. chloroprene monomer copolymerization, and dimonomer molecules are inserted into chloroprene rubber molecular chains. However, small molecule copolymerization is a macromolecular process, and the control of molecular chain structure is relatively difficult, thereby causing the copolymerization product performance to be unstable. The present invention adopts the insertion of functional monomers in the active points of existing polychloroprene macromolecular chains, increases the reactive groups required for curing, adds reactive emulsifiers, and the functional monomers react with the reactive emulsifiers. Relying on the emulsifying properties of the emulsifier, the functional monomers are easier to enter the latex particles and react with the macromolecular chains, and the feasibility of the reaction is increased. The functional monomers smoothly enter micelles and participate in grafting reactions, and the reactive active points are relatively fixed so that the reaction is relatively controllable. Then, by controlling the functional monomer addition amount, the quantity of the functional groups of the chloroprene rubber molecules can be adjusted, thereby adjusting the chloroprene adhesive and the isocyanate reaction rate, and optimizing the curing time of the two-component adhesive.

[0018] According to the "grafting to the main chain" mechanism, the initiator free radical initiates the functional monomer, the functional monomer combines with the reactive emulsifier, the functional monomer enters the micelle to extract the chlorine atom in the polymer, and finally the free radicals couple to obtain the functional monomer modified polychloroprene. The polychloroprene molecules containing functional groups can react with the isocyanate group -NCO, and the content of functional groups determines the degree of reaction. The inferred polymerization mechanism is as follows: . DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and the disclosure and materials cited therein are hereby incorporated by reference.

[0021] Technical equivalents to the specific embodiments described that are apparent to those skilled in the art using no more than routine experimentation are intended to be encompassed by this application.

[0022] The experimental methods in the following examples are all conventional methods unless otherwise specified. The instruments and equipment used in the following examples are all conventional laboratory instruments and equipment unless otherwise specified; the experimental materials used in the following examples are all purchased from conventional biochemical reagent stores unless otherwise specified.

[0023] Example 1: Weigh 240 g of chloroprene rubber latex, 6 g of sodium methacrylic acid sulfonate, and 12.4 g of antioxidant EB7301-1 in proportion, place them in a four-necked round-bottom bottle and stir evenly. Under nitrogen protection, the emulsion is heated to 40°C for reaction, an initiator solution is added, 15 g of functional monomer monobutyl maleate is added, the reaction is terminated after 5 hours, the latex is demulsified and dried into a film, and a chloroprene rubber sample for adhesive is obtained.

[0024] Example 2: Weigh 240 g of chloroprene rubber latex, 6 g of sodium methacrylic acid sulfonate, and 12.4 g of antioxidant EB7301-1 in proportion, place them in a four-necked round-bottom bottle and stir evenly. Under nitrogen protection, the emulsion is heated to 50°C for reaction, an initiator solution is added, 15 g of functional monomer hydroxypropyl methacrylate is added, the reaction is terminated after 5 hours, the latex is demulsified and dried into a film, and a chloroprene rubber sample for adhesive is obtained.

[0025] Example 3: Weigh 240 g of chloroprene rubber latex, 6 g of allyl polyether sulfate, and 12.4 g of antioxidant EB7301-1 in proportion, place them in a four-necked round-bottom bottle and stir evenly. Under nitrogen protection, the emulsion is heated to 40°C for reaction, an initiator solution is added, 15 g of functional monomer hydroxymethyl acrylamide is added, the reaction is terminated after 5 hours, the latex is demulsified and dried into a film, and a chloroprene rubber sample for adhesive is obtained.

[0026] Example 4: Weigh 240 g of chloroprene rubber latex, 6 g of allyl polyether sulfate, and 12.4 g of antioxidant EB7301-1 in proportion, place in a four-necked round-bottom bottle and stir evenly, under nitrogen protection, heat the emulsion to 40°C for reaction, add initiator solution, add 15 g of functional monomer hydroxymethyl acrylamide, and terminate the reaction after 6 hours. Demulsify the latex and dry it into a film to obtain a chloroprene rubber sample for adhesive.

[0027] Example 5: Weigh 240 g of chloroprene rubber latex, 15 g of sodium methacrylic acid sulfonate, and 12.4 g of antioxidant EB7301-1 in proportion, place them in a four-necked round-bottom bottle and stir evenly. Under nitrogen protection, the emulsion is heated to 40°C for reaction, an initiator solution is added, 45 g of functional monomer monobutyl maleate is added, the reaction is terminated after 5 hours, the latex is demulsified and dried into a film, and a chloroprene rubber sample for adhesive is obtained.

[0028] Example 6: Weigh 240 g of chloroprene rubber latex, 6 g of sodium methacrylic acid sulfonate, and 12.4 g of antioxidant EB7301-1 in proportion, place them in a four-necked round-bottom bottle and stir evenly. Under nitrogen protection, heat the emulsion to 40°C for reaction, add initiator solution, add 15 g of functional monomer monobutyl maleate, and terminate the reaction after 4 hours. Demulsify the latex and dry it into a film to obtain a chloroprene rubber sample for adhesive.

[0029] Example 7: Weigh 240 g of chloroprene rubber latex, 9 g of sodium methacrylic acid sulfonate, and 12.4 g of antioxidant EB7301-1 in proportion, place in a four-necked round-bottom bottle and stir evenly, under nitrogen protection, heat the emulsion to 40°C for reaction, add initiator solution, add 30 g of functional monomer monobutyl maleate, and terminate the reaction after 5 hours. Demulsify the latex and dry it into a film to obtain a chloroprene rubber sample for adhesive.

[0030] Example 8: Weigh 240 g of chloroprene rubber latex, 6 g of sodium methacrylic acid sulfonate, and 12.4 g of antioxidant EB7301-1 in proportion, place in a four-necked round-bottom bottle and stir evenly. Under nitrogen protection, heat the emulsion to 50°C for reaction, add initiator solution, add 8 g of functional monomer hydroxypropyl methacrylate, and terminate the reaction after 5 hours. Demulsify the latex and dry it into a film to obtain a chloroprene rubber sample for adhesive.

[0031] Example 9: Weigh 240 g of chloroprene rubber latex and 2.4 g of antioxidant EB7301-1 in proportion, place in a four-necked round-bottom bottle and stir evenly, under nitrogen protection, heat the emulsion to 40°C for reaction, add initiator solution, add 30 g of functional monomer monobutyl maleate, and terminate the reaction after 5 hours. Demulsify the latex and dry it into a film to obtain a chloroprene rubber sample for adhesive.

[0032] Example 10: Weigh 240 g of chloroprene rubber latex and 2.4 g of antioxidant EB7301-1 in proportion, place in a four-necked round-bottom bottle and stir evenly, under nitrogen protection, heat the emulsion to 50°C for reaction, add initiator solution, add 30 g of functional monomer hydroxypropyl methacrylate, and terminate the reaction after 5 hours. Demulsify the latex and dry it into a film to obtain a chloroprene rubber sample for adhesive.

[0033] Example 11: Weigh 240 g of chloroprene rubber latex, 6 g of sodium methacrylic acid sulfonate, and 12.4 g of antioxidant EB7301-1 in proportion, place in a four-necked round-bottom bottle and stir evenly. Under nitrogen protection, heat the emulsion to 40°C for reaction, add initiator solution, add 15 g of functional monomer monobutyl maleate, and terminate the reaction after 10 hours. Demulsify the latex and dry it into a film to obtain a chloroprene rubber sample for adhesive.

[0034] Example 12: Weigh 240 g of chloroprene rubber latex, 6 g of allyl polyether sulfate, and 12.4 g of antioxidant EB7301- according to proportion, place in a four-necked round-bottom bottle and stir evenly. Under nitrogen protection, heat the emulsion to 40°C for reaction, add initiator solution, add 15 g of functional monomer hydroxymethyl acrylamide, and terminate the reaction after 10 hours. Demulsify the latex and dry it into a film to obtain a chloroprene rubber sample for adhesive.

[0035] Comparative Example 1: A rubber sample is prepared by adjusting low conversion rate chloroprene rubber latex with conventional mercaptan, i.e. conventional mercaptan-regulated chloroprene rubber.

[0036] Comparative Example 2: Imported carboxyl chloroprene rubber, model is Japan Tosoh 570.

[0037] Experimental example: Dry glue samples prepared by different schemes for the preparation of two-component chloroprene adhesives were dissolved in toluene in proportion to prepare glue liquid, and curing agent was added in proportion to investigate the curing rate. The curing reaction is the cross-linking reaction between the glue liquid and the curing agent. As the reaction progresses, the viscosity of the glue liquid changes significantly, from a liquid flow state to a solid elastic colloid, and finally becomes a solid hard object, that is, completely cured. Therefore, the state and rate of the curing reaction can be judged according to the change in the viscosity of the glue liquid. The experimental data are shown in Table 1.

[0038] Table 1: Experimental data The viscosity is measured using a Brookfield viscometer at 25°C, and the viscosity unit is mPa.s.

[0039] Comparative Example 1 shows that conventional chloroprene rubber has limited reaction with curing agent, and the viscosity of the glue increases after 4 hours, but the viscosity of the glue is still low after 8 hours, and there is fluidity but no curing. Comparative Example 2 shows that the imported carboxyl chloroprene rubber has a very fast curing speed, and the glue has no fluidity after 30 minutes. The samples prepared from the selected functional monomers in Examples 1-12 have a large change in viscosity after curing for 2 hours. The comparison of Examples 1 / 5 / 7 and 2 / 8 respectively shows that the curing rate of the glue is significantly different when the amount of functional monomer added is different; the curing rate is also accelerated when the amount of functional monomer added increases. Therefore, in the actual reaction, the curing speed can be adjusted and stabilized by adjusting the appropriate proportion of functional monomer addition. Examples 3 / 4 / 12 and 1 / 6 / 11 respectively show that appropriately increasing the reaction time can promote the complete reaction of the functional monomer. When the functional monomer reacts completely, increasing the reaction time will not increase the curing rate. Examples 9 / 10 are colloid samples without adding reactive emulsifiers. The viscosity of the colloid solution changes more significantly than that of comparative example 1, but the data are not as good as the effects of other examples, which proves that reactive emulsifiers have a certain promoting effect on the preparation of the colloid samples of the present invention.

[0040] The present invention adopts the canvas T-type peeling method according to the GB / T2791-1995 standard, and detects the peeling strength at room temperature. The servo tensile machine model is high-speed rail AI-3000, and the peeling speed is 5cm / min. Data Table 2 is the comparative example and the canvas peeling strength and heat resistance data of the embodiment. Comparative Example 1 shows that the 30min peeling strength of conventional chloroprene rubber is only 0.2KN / m, the peeling strength is 4.0 KN / m after being placed for 48h, and the heat resistance temperature is 50°C. Comparative Example 2 The 30min peeling strength of carboxyl chloroprene rubber can reach 1.8KN / m, the 2h peeling strength is 5.2KN / m, the peeling strength is 6.5 KN / m after being placed for 48h, and the heat resistance temperature can reach 90°C. The embodiment shows that the rubber sample prepared by the method described in the present invention has a significant improvement in the 30min and 2h peeling strengths compared with conventional chloroprene rubber, and the 48h peeling strength and heat resistance are better than conventional chloroprene rubber, and the performance of some rubber samples is comparable to that of carboxyl chloroprene rubber.

[0041] Table 2: Stripping data The peeling test method is carried out in accordance with GB / T 2791-1995 standard, and the unit of peeling strength is KN / m.

[0042] According to the above experimental results, the 30min and 2h peel strengths of the rubber samples prepared by the method of the present invention are significantly improved compared with conventional chloroprene rubber, and the 48h peel strength and heat resistance are better than those of conventional chloroprene rubber, and some rubber sample properties are comparable to those of carboxyl chloroprene rubber. It can be directly dissolved for the preparation of two-component adhesive liquid, and can react with isocyanate curing agents without secondary grafting or adding additives, and the curing rate is stable, and the controllability is better than that of imported carboxyl chloroprene rubber.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing chloroprene rubber with a stable curing speed for use in a two-component adhesive, characterized in that: Using chloroprene as the base material, the chloroprene rubber molecules are modified with functional monomers to increase the groups that react with isocyanate in the molecular segments; reactive emulsifiers are added to promote the functional monomers to enter the latex particle molecules for reaction; and by controlling the amount of functional monomers added, the number of functional groups in the chloroprene rubber molecules is adjusted, thereby adjusting the reaction rate between the chloroprene adhesive and isocyanate and optimizing the curing time of the two-component adhesive.

2. The preparation method according to claim 1, characterized in that: The chloroprene is a mercaptan-regulated low-conversion chloroprene latex; the functional monomer is any one of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, monobutyl maleate, monobutyl itaconate, hydroxymethyl acrylamide or N-methylmaleimide; the group that reacts with isocyanate is -OH, -COOH, -SH or -NH; the reactive emulsifier is any one of sodium vinyl sulfonate, sodium methacrylic acid, sodium propylene sulfonate, sodium acrylamidoisopropyl sulfonate, allyl nonylphenol polyoxyethylene ether sulfate or allyl polyether sulfate.

3. The preparation method according to claim 1, characterized in that: The specific method is: 60-85 parts of chloroprene rubber latex, 5-30 parts of functional monomers, 1-5 parts of emulsifiers, 0.05-0.15 parts of water-based initiators, and 0.5-2 parts of antioxidants. The chloroprene rubber latex, emulsifier, and antioxidant are mixed and stirred evenly according to the proportion. The mixed emulsion is heated to the reaction temperature of 40-60°C under nitrogen conditions, the initiator solution is added, the functional monomer is added, and the reaction is terminated after 4-6 hours. The latex is demulsified and dried into a film, which is the chloroprene rubber sample for two-component adhesive.

4. The preparation method according to claim 3, characterized in that: The amount of the chloroprene rubber latex is 65-80 parts.

5. The preparation method according to claim 3, characterized in that: The functional monomer is 5-15 parts.

6. The preparation method according to claim 3, characterized in that: The water-based initiator is any one of potassium persulfate, sodium persulfate or ammonium persulfate; the antioxidant is a water-based composite antioxidant that can be directly added to latex.

7. A chloroprene rubber having a stable curing speed and used in a two-component adhesive obtained by the preparation method according to any one of claims 1 to 3.

8. Use of the chloroprene rubber according to claim 4 in the preparation of a two-component adhesive solution.

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