Cationic acrylate binder and preparation method thereof

Abstract

The invention discloses a cationic acrylate binder and a preparation method thereof, and belongs to the field of binder preparation.The preparation method comprises the steps that methyl methacrylate, butyl acrylate, hydroxyethyl acrylate and hydroxypropyl acrylate are evenly mixed; then uniformly mixing the obtained acrylate mixed monomer, allyl alcohol polyoxyethylene polyoxypropylene ether and a cationic functional monomer to obtain a mixed system; and carrying out free radical polymerization reaction on the mixed system, polyvinyl alcohol and an initiator at 60-90 DEG C, cooling to room temperature, and regulating the pH value to be neutral to obtain the cationic acrylate binder. The cationic functional monomer can limit the movement of a polymer molecular chain, and a latex film is difficult to deform, so that the hardness is increased, meanwhile, particles of the polymer emulsion can carry positive charges and have good adhesive force on a substrate material with negative charges, such as paper and leather, the strength and water resistance of paper can be improved when the cationic functional monomer is applied to the paper, and the service life of the paper is prolonged. The method has a wide application prospect in the field of papermaking chemicals.

Description

Technical Field

[0001] The invention belongs to the field of adhesive preparation, and particularly relates to a cationic acrylate adhesive and a preparation method thereof. Background Art

[0002] Acrylic acid has many advantages as an adhesive. It can bond well with a variety of materials, such as metal, plastic, glass, etc. When used, it can be cured by initiating a polymerization reaction with an initiator. There are also light-cured types, and the curing speed can be adjusted. At the same time, it has good flexibility and can buffer the stress caused by thermal expansion and contraction of the bonded materials. However, due to the structural characteristics of the main chain and side groups of the acrylic acid polymer molecule, this type of adhesive has problems such as poor air permeability, insufficient adhesion, brittleness and hardening at low temperatures, and stickiness at high temperatures.

[0003] In order to develop an acrylic adhesive with excellent performance, the technicians have done a lot of work on the formulation. In view of the brittleness and hardness of acrylic esters at low temperatures, after adding an appropriate amount of dodecyl acrylate and dioctyl sebacate (plasticizer) with a low glass transition temperature (Tg), the acrylic adhesive can still maintain a certain elasticity at a low temperature of -20°C. The material after bending and bonding will not be brittle at the bonding site. For high-temperature stickiness, the technicians use cross-linking agents and inorganic fillers, with pentaerythritol triacrylate as the cross-linking agent. More cross-linking points can make it difficult for the polymer molecular chains to slide relative to each other at high temperatures, limiting the movement of the molecular chains. In this way, in a high-temperature environment, the adhesive can maintain good shape stability and reduce stickiness. Add high-temperature resistant inorganic fillers, such as talcum powder, to the adhesive. Talc powder can provide physical support for the adhesive at high temperatures, and the talcum powder particles dispersed in the adhesive can prevent the molecular chains from approaching each other at high temperatures and produce viscous flow. In a high temperature environment of 70°C, the surface of the acrylic adhesive with pentaerythritol triacrylate crosslinking agent and talcum powder still remains dry and there is no obvious sticky feeling when touching with fingers.

[0004] However, the problem of insufficient adhesion of acrylate adhesives has always limited their performance improvement and application. Technicians have introduced monomers containing functional groups such as carboxyl and hydroxyl groups, which can react chemically with the active sites on the surface of the substrate or form hydrogen bonds and other interactions, thereby enhancing adhesion. However, in a low-temperature and high-humidity environment, the drying speed of acrylate adhesives slows down and the film-forming process is incomplete, resulting in a poor bond between the adhesive and the substrate, reduced adhesion, and even whitening and falling off of the adhesive. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a cationic acrylate adhesive and a preparation method thereof, so as to solve the problems that the adhesive cannot form a good bond with a substrate, the adhesion is reduced, and even the adhesive turns white and falls off in a low-temperature and high-humidity environment. Polyvinyl alcohol is used as an emulsifier, allyl alcohol polyoxyethylene polyoxypropylene ether, DMC, MMA, BA, HEMA and HPA are subjected to free radical polymerization to form a cationic acrylate adhesive.

[0006] The present invention is achieved through the following technical solutions: A method for preparing a cationic acrylate adhesive comprises the following steps: S1, firstly, by weight percentage, 20%-45% of methyl methacrylate, 20%-45% of butyl acrylate, 5%-20% of hydroxyethyl acrylate and 5%-20% of hydroxypropyl acrylate are mixed evenly to form an acrylate mixed monomer, and then the acrylate mixed monomer, allyl alcohol polyoxyethylene polyoxypropylene ether and cationic functional monomer are mixed evenly, and the mass ratio of the acrylate mixed monomer to allyl alcohol polyoxyethylene polyoxypropylene ether is (1-40): (1-30), to obtain a mixed system; S2, subjecting the mixed system, polyvinyl alcohol and initiator to a free radical polymerization reaction at 60-90° C., adjusting the pH to neutral after cooling to room temperature, and obtaining a cationic acrylate adhesive.

[0007] Preferably, the cationic functional monomer in S1 is methacryloyloxyethyl trimethyl ammonium chloride, and the mass of methacryloyloxyethyl trimethyl ammonium chloride is 3%-15% of the total mass of the acrylic acid ester mixed monomer and allyl alcohol polyoxyethylene polyoxypropylene ether.

[0008] Preferably, the initiator described in S2 is azobisisobutyramidine hydrochloride or azobisisobutyronitrile, and the mass of the initiator is 0.1%-10% of the total mass of the acrylic acid ester mixed monomer and allyl alcohol polyoxyethylene polyoxypropylene ether.

[0009] Preferably, S2 simultaneously drops the mixed system and the initiator aqueous solution into a polyvinyl alcohol solution at 60-90° C., and after the dropping is completed, the mixture is kept warm and then cooled to room temperature. Finally, the pH of the obtained reaction solution is adjusted to neutral to obtain a cationic acrylate adhesive.

[0010] Furthermore, the mass fraction of the polyvinyl alcohol solution in S2 is 1%-20%, the degree of polymerization of the polyvinyl alcohol is between 300-3000, and the degree of alcoholysis is between 88%-98%.

[0011] Furthermore, in the initiator aqueous solution described in S2, the mass ratio of initiator to deionized water is (0.5-0.7):60.

[0012] Furthermore, the dropping time in S2 is controlled within 2-3 hours.

[0013] Furthermore, the insulation time after the dropwise addition in S2 is 2-3 hours.

[0014] Preferably, S2 uses 26% by mass of ammonia water to adjust the pH to neutral to obtain a cationic acrylate adhesive.

[0015] A cationic acrylate adhesive obtained by any one of the above-mentioned methods for preparing a cationic acrylate adhesive.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: The invention discloses a method for preparing a cationic acrylate adhesive, wherein polyvinyl alcohol is used as an emulsifier, and methyl methacrylate (MMA), butyl acrylate (BA), hydroxyethyl acrylate (HEMA) and hydroxypropyl acrylate (HPA) are used as acrylic monomers, and allyl alcohol polyoxyethylene polyoxypropylene ether and cationic functional monomers are used under the action of an initiator to undergo free radical polymerization reaction, and then the pH is adjusted to be neutral to obtain a cationic acrylate adhesive in the form of an emulsion. Polyvinyl alcohol has high mechanical properties and can increase the adhesion strength to the substrate under low temperature and high humidity environments. Allyl alcohol polyoxyethylene polyoxypropylene ether is a hydrophilic functional monomer. The addition of allyl alcohol polyoxyethylene polyoxypropylene ether helps to improve the flexibility of the acrylic adhesive molecular chain, because its molecular structure contains polyoxyethylene and polyoxypropylene segments, which are relatively soft and can give the adhesive better elasticity and flexibility at the molecular level, reduce the brittleness after curing, and make the adhesive less likely to crack when subjected to external forces; at the same time, allyl alcohol polyoxyethylene polyoxypropylene ether has good interfacial activity, which can reduce the surface tension between the emulsion and the substrate, so that the emulsion can better wet the substrate surface, increase the contact area between the two, and thus improve the adhesion. The introduction of polyvinyl alcohol molecular chains in monomer copolymerization significantly improves its mechanical properties and has good biocompatibility. Cationic functional monomers can limit the movement of polymer molecular chains, making it difficult for the latex film to deform, thereby increasing the hardness. At the same time, the particles of the polymer emulsion can be positively charged, and have good adhesion on negatively charged substrate materials, such as paper and leather. Application to paper can improve the strength and water resistance of paper, and has broad application prospects in the field of papermaking chemicals. The adhesive of the present invention can form a good bond with the substrate, and can also increase its adhesion to the fiber and improve its strength. The adhesive will not turn white or fall off. The raw materials used are non-toxic and pollution-free, which is more conducive to industrial production. The adhesive has good fluidity, uniform film formation, stable performance, easy use and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is a schematic diagram of the preparation principle of the cationic acrylate adhesive of the present invention.

[0018] Figure 2 This is the infrared spectrum of the cationic acrylate emulsion obtained in Example 1 of the present invention.

[0019] Figure 3 This is a particle size diagram of the cationic acrylate emulsion obtained in Examples 1-4 of the present invention.

[0020] Figure 4 This is a stretching diagram of the cationic acrylate emulsion film obtained in Examples 1-4 of the present invention.

[0021] Figure 5 This is the TGA curve of the cationic acrylate latex film obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with embodiments. The description in this section is only exemplary and explanatory and should not have any limiting effect on the scope of protection of the present invention.

[0023] The key to improving the adhesion of acrylates is to improve the interaction between the adhesive and the surface of the adherend. Cationic groups can play a unique role in this. Cations carry a positive charge and can generate electrostatic attraction with many negatively charged groups on the surface of the adherend. This is similar to a microscopic magnetic force, pulling the adhesive and the adherend tightly together. Polyvinyl alcohol has excellent film-forming properties and can form a continuous, transparent, tough and strong film on the surface of an object. It has good adhesion and has strong adhesion to a variety of materials, such as paper, wood, fiber, glass, ceramics, etc. It has stable chemical properties, high chemical stability, good acid and alkali resistance, and can resist the erosion of chemical substances to a certain extent.

[0024] The present invention discloses a cationic acrylate adhesive, which comprises component I, component II, component III, a cationic functional monomer and an initiator; component I is polyvinyl alcohol (PVA), component II is allyl alcohol polyoxyethylene polyoxypropylene ether (polyether F-6), component III is an acrylate mixed monomer, the cationic functional monomer is methacryloyloxyethyl trimethylammonium chloride (DMC), and the initiator is an azo hydrochloride initiator, specifically azobisisobutyramidine hydrochloride or azobisisobutyronitrile. The mass ratio of component I, component II, and component III is (1-5): (1-30): (1-40); the mass of the cationic functional monomer (DMC) is 3-15% of the total mass of components II and III, and the mass of the initiator is 0.1-10% of the total mass of components II and III.

[0025] The degree of polymerization of polyvinyl alcohol (PVA) is between 300-3000, the degree of alcoholysis is between 88%-98%, and the mass concentration of its aqueous solution is between 1-20%.

[0026] Acrylate mixed monomers include methyl methacrylate (MMA), butyl acrylate (BA), hydroxyethyl acrylate (HEMA) and hydroxypropyl acrylate (HPA), of which methyl methacrylate accounts for 20%-45% of the total mass of the mixed monomers, butyl acrylate accounts for 20%-45% of the total mass of the mixed monomers, hydroxyethyl acrylate accounts for 5%-20% of the total mass of the mixed monomers, and hydroxypropyl acrylate accounts for 5%-20% of the total mass of the mixed monomers.

[0027] The present invention provides a method for preparing a cationic acrylate adhesive, taking the initiator azobisisobutylamidine hydrochloride V-50 as an example, the principle is as follows Figure 1 As shown, the following steps are included: (1) Dissolve polyvinyl alcohol in deionized water at 60-120°C to prepare a solution with a mass fraction of 1-20%.

[0028] (2) Mix methyl methacrylate, butyl acrylate, hydroxypropyl acrylate, hydroxyethyl acrylate, allyl alcohol polyoxyethylene polyoxypropylene ether and methacryloyloxyethyl trimethylammonium chloride and mix well.

[0029] (3) Dissolve 0.5-0.7 g of initiator in 60 g of deionized water to prepare an initiator aqueous solution.

[0030] (4) At 60-90° C., the solutions prepared in steps (2) and (3) are slowly added dropwise to the polyvinyl alcohol solution at the same time (i.e., the temperature of the polyvinyl alcohol solution is maintained at 60-90° C.). The addition time is controlled to be 2-3 h. After the addition is completed, the temperature is kept for 2-3 h, and then the temperature is cooled to room temperature. The pH is adjusted to neutral with 26% by mass ammonia water to obtain a cationic acrylate adhesive.

[0031] Example 1 2 g of polyvinyl alcohol was dissolved in deionized water at 90°C to prepare a solution with a mass fraction of 10%, and the solution was cooled to 80°C.

[0032] Weigh 35g MMA, 20g BA, 10g HPA, 5g HEMA, 20g polyether F-6, and 4.74g DMC and mix them evenly. The amount of DMC added is 5%. Dissolve 0.5 g of azobisisobutyramidine hydrochloride in 60 g of deionized water to prepare an aqueous solution; At 80°C, the two solutions were added dropwise to the polyvinyl alcohol solution through a constant pressure funnel to ensure that they were all added at the same time. The addition time was controlled within 2 hours. After the addition was completed, the solution was kept warm for 2 hours and then cooled to room temperature. The pH was adjusted to neutral with 26% by mass ammonia water to obtain an acrylate adhesive.

[0033] Example 2 2 g of polyvinyl alcohol was dissolved in deionized water at 90°C to prepare a solution with a mass fraction of 10%, and the solution was cooled to 80°C.

[0034] Weigh 35g MMA, 20g BA, 10g HPA, 5g HEMA, 20g polyether F-6, and 7.83g DMC and mix them evenly. The amount of DMC added is 8%. Dissolve 0.5 g of azobisisobutyramidine hydrochloride in 60 g of deionized water to prepare an aqueous solution; At 80°C, the two solutions were added dropwise to the polyvinyl alcohol solution through a constant pressure funnel to ensure that they were all added at the same time. The addition time was controlled within 2 hours. After the addition was completed, the solution was kept warm for 2 hours and then cooled to room temperature. The pH was adjusted to neutral with 26% by mass ammonia water to obtain an acrylate adhesive.

[0035] Example 3 2 g of polyvinyl alcohol was dissolved in deionized water at 90°C to prepare a solution with a mass fraction of 10%, and the solution was cooled to 80°C.

[0036] Weigh 35g MMA, 20g BA, 10g HPA, 5g HEMA, 20g polyether F-6, and 10g DMC and mix them evenly. The amount of DMC added is 10%; Dissolve 0.7 g of azobisisobutyramidine hydrochloride in 60 g of deionized water to prepare an aqueous solution; At 80°C, the two solutions were added dropwise to the polyvinyl alcohol solution through a constant pressure funnel to ensure that they were all added at the same time. The addition time was controlled within 2 hours. After the addition was completed, the solution was kept warm for 2 hours and then cooled to room temperature. The pH was adjusted to neutral with 26% by mass ammonia water to obtain an acrylate adhesive.

[0037] Example 4 2 g of polyvinyl alcohol was dissolved in deionized water at 90°C to prepare a solution with a mass fraction of 10%, and the solution was cooled to 80°C.

[0038] Weigh 35g MMA, 20g BA, 10g HPA, 5g HEMA, 20g polyether F-6, and 13.45g DMC and mix them evenly. The amount of DMC added is 13%; Dissolve 0.5 g of azobisisobutyramidine hydrochloride in 60 g of deionized water to prepare an aqueous solution; At 80°C, the two solutions were added dropwise to the polyvinyl alcohol solution through a constant pressure funnel to ensure that they were all added at the same time. The addition time was controlled within 2 hours. After the addition was completed, the solution was kept warm for 2 hours and then cooled to room temperature. The pH was adjusted to neutral with 26% by mass ammonia water to obtain an acrylate adhesive.

[0039] Figure 2 In the infrared spectrum, at 3348cm -1 The broad strong absorption peak is the hydroxyl (-OH) stretching vibration absorption peak; 2946cm -1 The weak absorption peak at 1233 cm is the stretching vibration absorption peak of methyl (CH). -1 The bending vibration absorption peak also appeared at 2832cm, and the functional group region and the fingerprint region corroborated each other, indicating the existence of fatty ether (COC). -1 There is an absorption peak at 1730cm -1 and 1150 cm -1 The presence of absorption peaks at 1635cm -1 The absorption peak is the bending vibration absorption peak of water molecules (-OH), and liquid infrared contains water. -1 YesN + There is no characteristic absorption peak of C=C in the (CH3)3 bending vibration absorption peak in the polymer, which preliminarily indicates that the monomers have reacted. The structure in the spectrum is consistent with the structural characteristics of cationic acrylic emulsion.

[0040] Figure 3 The intensity of the ordinate in the particle size spectrum (histogram) refers to the light scattering intensity. Particles of different sizes in the emulsion will scatter the incident light to varying degrees, and what the instrument detects is the intensity of these scattered lights. The larger the particle size, the higher the scattered light intensity, and the scattered light intensity is proportional to the sixth power of the particle size. When analyzing the particle size distribution of the emulsion, the intensity can intuitively reflect the contribution of emulsion particles of different sizes to light scattering. The relative content of emulsion particles of different sizes in the system can be understood by the proportion of the scattered light intensity corresponding to each particle size to the total intensity. The cumulative undersize rate (curve) on the ordinate refers to the mass or quantity percentage of particles smaller than a certain particle size in all particles. Taking mass as an example, if the cumulative undersize value is 50%, it means that the mass of emulsion particles smaller than this particle size accounts for half of the total mass of the emulsion, which can clearly show the distribution range of the emulsion particle size and the proportion of particles in different particle size ranges. The cumulative undersize curve can quickly tell the particle size range in which most of the particles in the emulsion are located, which is of great significance for evaluating the uniformity of the emulsion particle size and quality control. From Figure 3It can be seen that different DMC addition amounts affect the particle size of the emulsion. The particle size of the emulsion increases with the increase of the DMC addition amount. The average particle size of the emulsion is 147.2 nm, 129 nm, 251.4 nm, and 260 nm, respectively, and the dispersion index (PDI) of the emulsion is 0.091, 0.062, 0.130, and 0.129, respectively. With the continuous increase of the DMC addition amount, the PDI also gradually increases, and the dispersibility of the emulsion gradually decreases. This is because the addition of DMC changes the kinetic process of the polymerization reaction. DMC participates in the polymerization reaction, resulting in a change in the reaction rate. The polymerization reaction rate becomes faster, and the newly generated polymer has no time to be evenly dispersed, so it is easy to aggregate together, causing the PDI to gradually increase and the particle size to increase. On the other hand, with the continuous increase of the DMC addition amount, the particle size of the emulsion gradually increases. This is because the presence of DMC affects the stability of the system. It changes the surface charge distribution of the emulsion system, reduces the electrostatic repulsion between the originally stable colloid particles, and makes it easier to aggregate after collision between particles, resulting in a gradual increase in particle size.

[0041] 25g of the prepared cationic acrylate adhesive was poured onto a polytetrafluoroethylene plate, dried at 80°C, cut into dumbbell shapes, and the tensile strength of the film was measured. The effect of different DMC addition amounts on the strength of the latex film is shown in Figure 2. Figure 4 As shown. Figure 4 It can be seen that as the amount of DMC increases, the strain gradually decreases, the plasticity decreases, the stress gradually increases, and the hardness of the latex film increases. This is because DMC can participate in the polymerization reaction and introduce cationic structural units. These structural units restrict the movement of the polymer molecular chain, just like adding some fixed piles to the originally flexible molecular chain. After the movement of the molecular chain is restricted, the latex film is difficult to deform, thereby increasing the hardness.

[0042] from Figure 5 It can be seen that with the increase of temperature, the mass loss of the binder presents three different stages and finally reaches a state of equilibrium; the mass fraction shows a trend of first slowly decreasing, then accelerating, and then gradually stabilizing. In the first stage when the temperature does not exceed 250°C, the mass of the binder changes by 3.36%, which is the evaporation of water; in the stage when the temperature does not exceed 300°C, a small amount of side chain groups on the molecular chain are pyrolyzed; in the third stage, when the temperature does not exceed 410°C, the mass loss rate is significantly accelerated, and the mass change is as high as 64.5%, which is mainly manifested by the breakage of the main chain segment of the binder.

Claims

1. A method for preparing a cationic acrylate adhesive, characterized in that: The following steps are involved: S1, firstly, by weight percentage, 20%-45% of methyl methacrylate, 20%-45% of butyl acrylate, 5%-20% of hydroxyethyl acrylate and 5%-20% of hydroxypropyl acrylate are mixed evenly to form an acrylate mixed monomer, and then the acrylate mixed monomer, allyl alcohol polyoxyethylene polyoxypropylene ether and cationic functional monomer are mixed evenly, and the mass ratio of the acrylate mixed monomer to allyl alcohol polyoxyethylene polyoxypropylene ether is (1-40): (1-30), to obtain a mixed system; S2, subjecting the mixed system, polyvinyl alcohol and initiator to a free radical polymerization reaction at 60-90° C., adjusting the pH to neutral after cooling to room temperature, and obtaining a cationic acrylate adhesive.

2. The method for preparing a cationic acrylate adhesive according to claim 1, wherein: The cationic functional monomer in S1 is methacryloyloxyethyl trimethyl ammonium chloride, and the mass of methacryloyloxyethyl trimethyl ammonium chloride is 3%-15% of the total mass of the acrylic ester mixed monomer and allyl alcohol polyoxyethylene polyoxypropylene ether.

3. The method for preparing a cationic acrylate adhesive according to claim 1, characterized in that: The initiator described in S2 is azobisisobutyramidine hydrochloride or azobisisobutyronitrile, and the mass of the initiator is 0.1%-10% of the total mass of the acrylic ester mixed monomer and allyl alcohol polyoxyethylene polyoxypropylene ether.

4. The method for preparing a cationic acrylate adhesive according to claim 1, characterized in that: S2 simultaneously adds the mixed system and the initiator aqueous solution to a polyvinyl alcohol solution at 60-90°C, and after the addition is completed, the solution is kept warm and then cooled to room temperature. Finally, the pH of the resulting reaction solution is adjusted to neutral to obtain a cationic acrylate adhesive.

5. The method for preparing a cationic acrylate adhesive according to claim 4, characterized in that: The mass fraction of the polyvinyl alcohol solution in S2 is 1%-20%.

6. The method for preparing a cationic acrylate adhesive according to claim 4, characterized in that: In the initiator aqueous solution described in S2, the mass ratio of initiator to deionized water is (0.5-0.7):

60.

7. The method for preparing a cationic acrylate adhesive according to claim 4, characterized in that: The dripping time in S2 is controlled at 2-3h.

8. The method for preparing a cationic acrylate adhesive according to claim 4, characterized in that: The insulation time after the addition of S2 is completed is 2-3 hours.

9. The method for preparing a cationic acrylate adhesive according to claim 1, characterized in that: S2 uses 26% by mass of ammonia water to adjust the pH to neutral to obtain a cationic acrylate adhesive.

10. A cationic acrylate adhesive obtained by the preparation method of the cationic acrylate adhesive according to any one of claims 1 to 9.

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