阅读说明：本技术 一种水溶性低模量丙烯酸树脂粘合剂及其制备方法 (Water-soluble low-modulus acrylic resin adhesive and preparation method thereof ) 是由 蔡小川 席柳江 刘龙 刘海明 郭春成 向金林 黄玲 于 2020-11-25 设计创作，主要内容包括：本申请公开了一种水溶性低模量丙烯酸树脂粘合剂及其制备方法,水溶性低模量丙烯酸树脂粘合剂的玻璃化温度低于0℃,其储存状态是均质、澄明、稳定的水溶液,水溶液的pH值6～8,固含量5％～50％,粘度是10～200000cp；干燥后的水溶性低模量丙烯酸树脂粘合剂是固体；当温度高于0℃时,水溶性低模量丙烯酸树脂粘合剂的拉伸模量和弯曲模量低于100MPa；其制备方法,包括：将水溶性丙烯酸酯、水溶性低级醇、引发剂和纯水于反应容器中混合并充分搅拌后,得到澄明的水溶液,水溶液为反应液；将反应容器的温度升至50～80℃,反应2～8h,冷却收料。相较于现有技术而言,所述水溶性低模量丙烯酸树脂粘合剂是水溶液体系,小分子残留物少、稳定性好、储存条件要求更宽松、能够储存更长期限。(The application discloses a water-soluble low-modulus acrylic resin adhesive and a preparation method thereof, wherein the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is lower than 0 ℃, the water-soluble low-modulus acrylic resin adhesive is a homogeneous, clear and stable aqueous solution in a storage state, the pH value of the aqueous solution is 6-8, the solid content is 5-50%, and the viscosity is 10-200000 cp; the dried water-soluble low modulus acrylic resin binder is a solid; the tensile modulus and flexural modulus of the water-soluble low modulus acrylic resin binder are less than 100MPa when the temperature is above 0 ℃; the preparation method comprises the following steps: mixing water-soluble acrylate, water-soluble lower alcohol, an initiator and pure water in a reaction vessel, and fully stirring to obtain a clear aqueous solution, wherein the aqueous solution is a reaction solution; and (3) heating the temperature of the reaction container to 50-80 ℃, reacting for 2-8 h, cooling and collecting materials. Compared with the prior art, the water-soluble low-modulus acrylic resin adhesive is an aqueous solution system, has less micromolecule residues, good stability, more relaxed storage condition and longer shelf life.)

1. The water-soluble low-modulus acrylic resin adhesive is characterized in that the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is lower than 0 ℃, the water-soluble low-modulus acrylic resin adhesive is a homogeneous, clear and stable aqueous solution in a storage state, the pH value of the aqueous solution is 6-8, the solid content is 5-50%, and the viscosity is 10-200000 cp;

the water-soluble low modulus acrylic resin binder after drying is a solid;

the water-soluble low modulus acrylic resin binder has a tensile modulus and a flexural modulus of less than 100MPa when the temperature is above 0 ℃.

2. The water-soluble low-modulus acrylic resin adhesive as claimed in claim 2, wherein if the water-soluble low-modulus acrylic resin adhesive is capable of being dissolved in water again after being dried, the adhesive has a viscous state, and the viscous temperature is 55-95 ℃; if the adhesive is not re-soluble in water after drying, the adhesive does not have a viscous state.

3. The method for preparing a water-soluble low-modulus acrylic resin adhesive according to claim 1, comprising the steps of:

s101, mixing water-soluble acrylate, water-soluble lower alcohol, an initiator and pure water in a reaction container, and fully stirring to obtain a clear aqueous solution, wherein the aqueous solution is a reaction solution;

s102, raising the temperature of the reaction container to 50-80 ℃, reacting for 2-8 hours, cooling and collecting materials.

4. The method of claim 3, wherein the water-soluble acrylate comprises: hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2, 3-dihydroxypropyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, and 2, 3-dihydroxypropyl methacrylate.

5. The method for preparing a water-soluble low-modulus acrylic resin adhesive according to claim 3, wherein the water-soluble lower alcohol comprises: methanol, ethanol, n-propanol, isopropanol.

6. The method for preparing a water-soluble low-modulus acrylic resin adhesive according to claim 5, wherein the initiator is a water-soluble redox complex initiator; the water-soluble redox complex initiator comprises: an oxidizing agent and a reducing agent; the oxidizing agent comprises: sodium persulfate, ammonium persulfate, potassium persulfate; the reducing agent comprises: sodium sulfite, sodium bisulfite.

7. The method for preparing a water-soluble acrylic resin adhesive with low modulus as claimed in claim 6, wherein the weight ratio of the oxidant to the reducer is 1:3 to 3: 1.

8. The method for preparing a water-soluble acrylic resin adhesive with low modulus as claimed in claim 3, wherein the weight ratio of the water-soluble acrylate to the water-soluble lower alcohol is 1:3 to 10: 1.

9. The method for preparing a water-soluble acrylic resin adhesive with low modulus as claimed in claim 3, wherein the amount of said initiator is 0.05-1% of the amount of said water-soluble acrylic ester.

10. The method for preparing a water-soluble acrylic resin binder with low modulus as claimed in claim 3, wherein the reaction solution further comprises: a chain extender; the chain extender comprises: polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropyltriethoxysilane; the using amount of the chain extender is 0.05-20% of that of the water-soluble acrylate.

Technical Field

The application relates to the technical field of lithium battery adhesives, in particular to a water-soluble low-modulus acrylic resin adhesive and a preparation method thereof.

Background

Acrylic resin is a commonly used aqueous binder material. The synthetic monomers of the acrylic resin have wide selection range, and the water-based acrylic resin adhesive suitable for multiple purposes can be prepared by combining various monomers with different performances. Most of the acrylic resin synthetic monomers are insoluble in water and cannot prepare the aqueous acrylic resin adhesive in a solution polymerization form, so the aqueous acrylic resin adhesive on the market is usually prepared by an emulsion polymerization process and stored in a polymer emulsion form, and common varieties are pure acrylic emulsion, vinyl acetate-acrylic emulsion, styrene-acrylic emulsion, silicone-acrylic emulsion and the like.

However, adhesives of the emulsion type also present significant disadvantages. On the one hand, an emulsion is a thermodynamically unstable system, and polymer particles in the emulsion are continuously agglomerated with the lapse of time, thereby causing undesirable phenomena such as precipitation, gelation and the like, which are generally called "emulsion breaking". The demulsification can cause the structure of the emulsion to be gradually destroyed, the effective solid content is reduced, the performance of the emulsion is further deteriorated or even completely failed, and the demulsification is accelerated by overhigh or overlow temperature, mechanical agitation and impurities. On the other hand, the emulsion polymerization process is relatively complicated, and usually requires the addition of small molecular substances such as emulsifiers, co-emulsifiers and the like, which remain in the adhesive film or block after the adhesive is dried and cured, and the influence of such residues on the overall performance of the adhesive is adverse.

Compared with emulsion, the solution type water-based acrylic resin adhesive can well avoid the defects. The solution is a thermodynamically stable system and can therefore be stored for a long period of time, and the solution polymerization process is relatively simple, and it is not usually necessary to add small molecular substances which may cause residues in the polymerization formulation. The main component of the commonly used aqueous acrylic resin binders of the solution type is an acrylic acid (salt) -acrylamide copolymer, which is characterized by a high glass transition temperature, generally above 100 ℃. The adhesive has the defects of poor film forming property, low adhesive force and low bonding force due to the excessively high glass transition temperature, and is in a glass state at the common use temperature such as room temperature, and the like, so that the adhesive is in a rigid and easily-broken state in a macroscopic view, and the tensile modulus, the bending modulus and the like are usually more than 1GPa, so that the adhesive is not favorable for bonding of flexible adherends.

The reason why the above-mentioned drawbacks are caused in the solution-type aqueous acrylic resin adhesives is that water-soluble monomers such as acrylic acid and acrylamide are all "hard monomers", and these monomers cannot impart flexibility to the products. The flexible nature of the adhesive results from the high amount of "soft monomer" in the formulation (typically over 80% of the total monomer loading). However, common soft monomers such as butyl acrylate, isooctyl acrylate and the like are not soluble in water and cannot be applied to solution polymerization of aqueous systems. Therefore, if it is desired to prepare a solution-type aqueous acrylic resin adhesive having flexible, low modulus properties, the selection and use of water-soluble soft monomers is critical.

Monoesters of acrylic acid with dihydric and trihydric alcohols are one of a few water-soluble soft monomer types, and hydroxyethyl acrylate and hydroxypropyl acrylate are representative among them). The monoester can endow a polymerization product with lower glass transition temperature and good flexibility, and has good water solubility, for example, hydroxyethyl acrylate can be mutually dissolved with water in any proportion, and theoretically, the monoester is a soft monomer with good performance which can be used for preparing a solution type water-based acrylic resin adhesive. However, such monomers have a strong tendency to crosslink during polymerization, and when the amount is large, the product contains a high-density crosslinked structure, and macroscopically appears as an insoluble and infusible gel, and cannot be used as a binder. In general, monomers such as hydroxyethyl acrylate can be used only in a small amount as a crosslinking monomer in a polymerization formulation, and thus the properties such as flexibility and low modulus imparted thereto cannot be effectively expressed.

The crosslinking characteristic of the water-soluble soft monomer such as hydroxyethyl acrylate is caused by the combination of carbon-carbon double bonds and hydroxyl groups in the molecular structure. The carbon-carbon double bond is the main reaction site in the free radical polymerization process, and the hydroxyl group is a group with chain transfer capability, and in the free radical polymerization process, the hydroxyl group can abstract a free electron from a living radical so that the free radical is terminated, and the hydroxyl group is converted into a new free radical. Therefore, monomers such as hydroxyethyl acrylate actually contain two active sites for radical polymerization and can function as crosslinking monomers. Therefore, in general, a homopolymerization reaction of a monomer such as hydroxyethyl acrylate or a copolymerization reaction of a monomer containing a large amount of such a monomer in a formulation is accompanied by a severe gelation process, and a product in a solution state cannot be obtained.

Therefore, there is a need for a water-soluble acrylic resin binder with low modulus and a preparation method thereof, which can make the preparation process easy to control, make the prepared water-soluble acrylic resin binder with low modulus be an aqueous solution system, have less small molecular residue, good stability, more relaxed storage condition requirements, and be capable of being stored for a longer period of time, and thus, the technical problems to be solved by the technical personnel in the field are urgently needed.

Disclosure of Invention

In order to solve the technical problems, the present application provides a water-soluble low-modulus acrylic resin adhesive and a preparation method thereof, which can make the preparation process easy to control, and make the prepared water-soluble low-modulus acrylic resin adhesive be an aqueous solution system, and have the advantages of less micromolecule residues, good stability, more relaxed storage condition requirements, and longer shelf life.

The technical scheme provided by the application is as follows:

the water-soluble low-modulus acrylic resin adhesive provided by the invention has the advantages that the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is lower than 0 ℃, the water-soluble low-modulus acrylic resin adhesive is a homogeneous, clear and stable aqueous solution in a storage state, the pH value of the aqueous solution is 6-8, the solid content is 5-50%, and the viscosity is 10-200000 cp; the water-soluble low modulus acrylic resin binder after drying is a solid; the water-soluble low modulus acrylic resin binder has a tensile modulus and a flexural modulus of less than 100MPa when the temperature is above 0 ℃.

Further, in a preferred mode of the present invention, the tensile modulus and flexural modulus of the water-soluble low-modulus acrylic resin binder are less than 50 MPa.

Further, in a preferred embodiment of the present invention, the solid content is preferably 10% to 35%, and the viscosity is preferably 1000 to 100000 cp.

Further, in a preferred embodiment of the present invention, if the water-soluble low-modulus acrylic resin adhesive is dried and then can be dissolved in water again, the adhesive has a viscous state, and the viscous temperature is 55 to 95 ℃; if the adhesive is not re-soluble in water after drying, the adhesive does not have a viscous state.

Another technical scheme provided by the application is as follows:

the invention provides a preparation method of a water-soluble low-modulus acrylic resin adhesive, which comprises the following steps:

s101, mixing water-soluble acrylate, water-soluble lower alcohol, an initiator and pure water in a reaction container, and fully stirring to obtain a clear aqueous solution, wherein the aqueous solution is a reaction solution;

s102, raising the temperature of the reaction container to 50-80 ℃, reacting for 2-8 hours, cooling and collecting materials.

Further, in a preferred mode of the present invention, the water-soluble acrylate includes: hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2, 3-dihydroxypropyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, and 2, 3-dihydroxypropyl methacrylate.

Further, in a preferred mode of the present invention, the water-soluble acrylate is hydroxyethyl acrylate.

Further, in a preferred mode of the present invention, the water-soluble lower alcohol includes: methanol, ethanol, n-propanol, isopropanol.

Further, in a preferred mode of the present invention, the water-soluble lower alcohol is isopropyl alcohol.

Further, in a preferred mode of the present invention, the initiator is a water-soluble redox complex initiator including: oxidant and reducer.

Further, in a preferred mode of the present invention, the oxidizing agent includes: sodium persulfate, ammonium persulfate, potassium persulfate; the reducing agent comprises: sodium sulfite, sodium bisulfite.

Further, in a preferred embodiment of the present invention, the weight ratio of the oxidizing agent to the reducing agent is 1:3 to 3: 1.

Further, in a preferred embodiment of the present invention, the weight ratio of the water-soluble acrylate to the water-soluble lower alcohol is 1:3 to 10: 1.

Further, in a preferred embodiment of the present invention, the weight ratio of the water-soluble acrylate to the water-soluble lower alcohol is 1:1 to 3: 1.

Further, in a preferred embodiment of the present invention, the amount of the initiator is 0.05% to 1% of the amount of the water-soluble acrylate.

Further, in a preferred embodiment of the present invention, the reaction solution further includes: a chain extender; the chain extender comprises: polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropyltriethoxysilane; the using amount of the chain extender is 0.05-20% of that of the water-soluble acrylate.

The invention provides a technical scheme, compared with the prior art, the invention provides a water-soluble low-modulus acrylic resin adhesive and a preparation method thereof, the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is lower than 0 ℃, the water-soluble low-modulus acrylic resin adhesive is a homogeneous, clear and stable aqueous solution in a storage state, the pH value of the aqueous solution is 6-8, the solid content is 5-50%, and the viscosity is 10-200000 cp; the water-soluble low modulus acrylic resin binder after drying is a solid; the tensile modulus and flexural modulus of the water-soluble low modulus acrylic resin binder are less than 100MPa when the temperature is above 0 ℃; the preparation method of the water-soluble low-modulus acrylic resin adhesive comprises the following steps: s101, mixing water-soluble acrylate, water-soluble lower alcohol, an initiator and pure water in a reaction container, and fully stirring to obtain a clear aqueous solution, wherein the aqueous solution is a reaction solution; s102, raising the temperature of the reaction container to 50-80 ℃, reacting for 2-8 hours, cooling and collecting materials. Compared with the prior art, the preparation method of the water-soluble low-modulus acrylic resin adhesive has the advantages that the preparation process is easy to control, the prepared water-soluble low-modulus acrylic resin adhesive is an aqueous solution system, small molecular residues are few, the stability is good, the storage condition requirement is looser, and the water-soluble low-modulus acrylic resin adhesive can be stored for a longer period of time. In addition, in the preparation process of the water-soluble low-modulus acrylic resin adhesive, the lower alcohol is used as a chain transfer agent, so that the cross-linking reaction caused by the transfer of free radicals to monomers in the polymerization process of water-soluble acrylate monomers can be effectively inhibited, the reaction process is stable and controllable, and the generation of gel is avoided. On the other hand, the lower alcohol also plays a role of a solvent, and the residual lower alcohol can volatilize along with water in the drying and curing process of the adhesive, so that the residual micromolecular substances after the adhesive is cured are effectively avoided; the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is below 0 ℃, the water-soluble low-modulus acrylic resin adhesive has low-modulus mechanical characteristics after drying and curing, is easy to generate elastic or plastic deformation under stress, has better film forming property and adhesive force, and is suitable for bonding various base materials, especially soft base materials due to the characteristics of flexibility, folding resistance and easy deformation under stress.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or be indirectly disposed on the other element; when an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "first," "second," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, refer to an orientation or positional relationship that is indicative of but not limiting of the present application, merely to facilitate the description of the application and to simplify the description, and that it is not intended to indicate or imply that the device or element so referred to must have a particular orientation, be constructed and operated in a particular orientation.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "plurality" or "a plurality" means two or more unless specifically limited otherwise.

It should be understood that the disclosure of the present application, which is to be read and understood by those skilled in the art, is not to be limited to the details of construction and arrangement of parts so defined, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed.

The water-soluble low-modulus acrylic resin adhesive and the preparation method thereof have the advantages that the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is lower than 0 ℃, the water-soluble low-modulus acrylic resin adhesive is a homogeneous, clear and stable aqueous solution in a storage state, the pH value of the aqueous solution is 6-8, the solid content is 5-50%, and the viscosity is 10-200000 cp; the water-soluble low modulus acrylic resin binder after drying is a solid; the tensile modulus and flexural modulus of the water-soluble low modulus acrylic resin binder are less than 100MPa when the temperature is above 0 ℃; the preparation method of the water-soluble low-modulus acrylic resin adhesive comprises the following steps: s101, mixing water-soluble acrylate, water-soluble lower alcohol, an initiator and pure water in a reaction container, and fully stirring to obtain a clear aqueous solution, wherein the aqueous solution is a reaction solution; s102, raising the temperature of the reaction container to 50-80 ℃, reacting for 2-8 hours, cooling and collecting materials.

The embodiment of the invention provides a water-soluble low-modulus acrylic resin adhesive and a preparation method thereof, wherein the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is lower than 0 ℃, the water-soluble low-modulus acrylic resin adhesive is a homogeneous, clear and stable aqueous solution in a storage state, the pH value of the aqueous solution is 6-8, the solid content is 5-50%, and the viscosity is 10-200000 cp; the water-soluble low modulus acrylic resin binder after drying is a solid; the tensile modulus and flexural modulus of the water-soluble low modulus acrylic resin binder are less than 100MPa when the temperature is above 0 ℃; the preparation method of the water-soluble low-modulus acrylic resin adhesive comprises the following steps: s101, mixing water-soluble acrylate, water-soluble lower alcohol, an initiator and pure water in a reaction container, and fully stirring to obtain a clear aqueous solution, wherein the aqueous solution is a reaction solution; s102, raising the temperature of the reaction container to 50-80 ℃, reacting for 2-8 hours, cooling and collecting materials. Compared with the prior art, the preparation method of the water-soluble low-modulus acrylic resin adhesive has the advantages that the preparation process is easy to control, the prepared water-soluble low-modulus acrylic resin adhesive is an aqueous solution system, small molecular residues are few, the stability is good, the storage condition requirement is looser, and the water-soluble low-modulus acrylic resin adhesive can be stored for a longer period of time.

Example 1

60g of pure water, 30g of isopropanol, 30g of hydroxyethyl acrylate and 0.15g of ammonium persulfate-sodium sulfite composite initiator are put into a three-necked bottle provided with an electric stirring device and a reflux condenser pipe, wherein the ammonium persulfate-sodium sulfite composite initiator comprises: ammonium persulfate 0.1g and sodium sulfite 0.05 g. Fully stirring until all materials are completely dissolved, keeping stirring, raising the reaction temperature to 65 ℃, reacting for 6 hours, cooling and collecting materials.

The water-soluble low-modulus acrylic resin adhesive obtained actually contained 25.1% of solids. The state was a pale yellow clear solution with a viscosity of about 75 cp. The dried and cured adhesive is a brown yellow rosin-shaped solid at room temperature, rapidly absorbs moisture and is sticky when placed in the air, is easily subjected to plastic deformation under stress, and can be rapidly re-dissolved in water. When the temperature is raised to about 65 ℃, the solid adhesive is gradually converted into fluid.

Preparation example 2:

compared with example 1, the amount of pure water was changed to 90g, the amount of hydroxyethyl acrylate was changed to 60g, the amount of initiator was changed to 0.3g (containing 0.2g of ammonium persulfate and 0.1g of sodium sulfite), and 0.3g of chain extender KH570 was added, and the rest was the same as in preparation example 1.

The water-soluble low-modulus acrylic resin adhesive obtained was found to contain 33.5% by weight. The state was a pale yellow clear solution with a viscosity of about 200 cp. The dried and cured adhesive is a brown yellow semitransparent silica gel-like solid at room temperature, has high elasticity of rubber, is not sticky when placed in air, and is easy to elastically deform under stress. Gradually swells in water, and completely dissolves after standing for about 24 hours. When the temperature is raised to about 55 ℃, the solid adhesive begins to become soft gradually, but still has high elasticity. When the temperature is raised to about 90 ℃, the solid adhesive is gradually converted into fluid.

Specifically, in the examples of the present invention, the tensile modulus and flexural modulus of the water-soluble low-modulus acrylic resin binder were less than 50 MPa.

Specifically, in the embodiment of the present invention, the solid content is preferably 10% to 35%, and the viscosity is preferably 1000 to 100000 cp.

Specifically, in the embodiment of the invention, if the water-soluble low-modulus acrylic resin adhesive can be dissolved in water again after being dried, the adhesive has a viscous state, and the viscous flow temperature is 55-95 ℃; if the adhesive is not re-soluble in water after drying, the adhesive does not have a viscous state.

Specifically, in embodiments of the present invention, the water-soluble acrylate comprises: hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2, 3-dihydroxypropyl acrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, and 2, 3-dihydroxypropyl methacrylate.

Specifically, in an embodiment of the present invention, the water-soluble acrylate is hydroxyethyl acrylate.

Specifically, in embodiments of the present invention, the water-soluble lower alcohols include: methanol, ethanol, n-propanol, isopropanol.

Specifically, in the embodiment of the present invention, the water-soluble lower alcohol is isopropyl alcohol.

Specifically, in an embodiment of the present invention, the initiator is a water-soluble redox complex initiator including: oxidant and reducer.

Specifically, in an embodiment of the present invention, the oxidizing agent includes: sodium persulfate, ammonium persulfate, potassium persulfate; the reducing agent comprises: sodium sulfite, sodium bisulfite.

Specifically, in the embodiment of the invention, the weight ratio of the oxidizing agent to the reducing agent is 1: 3-3: 1.

Specifically, in the embodiment of the invention, the weight ratio of the water-soluble acrylate to the water-soluble lower alcohol is 1: 3-10: 1.

Specifically, in the embodiment of the invention, the weight ratio of the water-soluble acrylate to the water-soluble lower alcohol is 1:1 to 3: 1.

Specifically, in the embodiment of the present invention, the amount of the initiator is 0.05% to 1% of the amount of the water-soluble acrylate.

Specifically, in an embodiment of the present invention, the reaction solution further includes: a chain extender; the chain extender comprises: polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, gamma-methacryloxypropyltrimethoxysilane, gamma-methacryloxypropyltriethoxysilane; the using amount of the chain extender is 0.05-20% of that of the water-soluble acrylate.

Comparative example 3

20g of sodium acrylate, 8g of acrylamide, 0.15g of an initiator (containing 0.1g of ammonium persulfate and 0.05g of sodium sulfite) and 70g of pure water were put into a three-necked flask equipped with an electric stirrer and a reflux condenser, and sufficiently stirred until the materials were completely dissolved. Keeping stirring and heating to 65 ℃, reacting for 6 hours, cooling and collecting.

The actual content of the obtained water-soluble low-modulus acrylic resin adhesive was 29.9%. The adhesive is light yellow transparent solution with the viscosity of about 500 cp. The adhesive after drying and curing is a light yellow transparent rigid solid at room temperature, is hard and brittle, slightly sticky after being placed in the air for 1h, and hardly deforms under stress. Gradually dissolved in water. Significant softening of the binder solids was not observed at temperatures up to about 200 ℃.

Test example 4

Glass transition temperature (Tg) test: the testing was performed using DSC.

And (3) testing the peel strength: respectively blade-coating the adhesive on the surfaces of a polyethylene film and a copper foil with the thickness of about 10 mu m by using a wire rod, and drying at 55-60 ℃ to obtain an adhesive film coating with the thickness of 2-3 mu m. The peel strength of the coatings was tested as described in GB/T2792-2014.

Tensile modulus and flexural modulus testing: the dry cured adhesive was trimmed to test bars and tested for tensile modulus as described in GB/T1040.3-2007 and flexural modulus as described in GB/T9341-2008.

The test results are shown in the following table:

from the above, the water-soluble low-modulus acrylic resin adhesive and the preparation method thereof relate to the embodiment of the invention, the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is lower than 0 ℃, the water-soluble low-modulus acrylic resin adhesive is a homogeneous, clear and stable aqueous solution in a storage state, the pH value of the aqueous solution is 6-8, the solid content is 5-50%, and the viscosity is 10-200000 cp; the water-soluble low modulus acrylic resin binder after drying is a solid; the tensile modulus and flexural modulus of the water-soluble low modulus acrylic resin binder are less than 100MPa when the temperature is above 0 ℃; the preparation method of the water-soluble low-modulus acrylic resin adhesive comprises the following steps: s101, mixing water-soluble acrylate, water-soluble lower alcohol, an initiator and pure water in a reaction container, and fully stirring to obtain a clear aqueous solution, wherein the aqueous solution is a reaction solution; s102, raising the temperature of the reaction container to 50-80 ℃, reacting for 2-8 hours, cooling and collecting materials. Compared with the prior art, the preparation method of the water-soluble low-modulus acrylic resin adhesive has the advantages that the preparation process is easy to control, the prepared water-soluble low-modulus acrylic resin adhesive is an aqueous solution system, small molecular residues are few, the stability is good, the storage condition requirement is looser, and the water-soluble low-modulus acrylic resin adhesive can be stored for a longer period of time. In addition, in the preparation process of the water-soluble low-modulus acrylic resin adhesive, the lower alcohol is used as a chain transfer agent, so that the cross-linking reaction caused by the transfer of free radicals to monomers in the polymerization process of water-soluble acrylate monomers can be effectively inhibited, the reaction process is stable and controllable, and the generation of gel is avoided. On the other hand, the lower alcohol also plays a role of a solvent, and the residual lower alcohol can volatilize along with water in the drying and curing process of the adhesive, so that the residual micromolecular substances after the adhesive is cured are effectively avoided; the glass transition temperature of the water-soluble low-modulus acrylic resin adhesive is below 0 ℃, the water-soluble low-modulus acrylic resin adhesive has low-modulus mechanical characteristics after drying and curing, is easy to generate elastic or plastic deformation under stress, has better film forming property and adhesive force, and is suitable for bonding various base materials, especially soft base materials due to the characteristics of flexibility, folding resistance and easy deformation under stress.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.