Water-based core-shell acrylic emulsion resistant to damp-heat aging as well as preparation method and application of water-based core-shell acrylic emulsion

Abstract

An acrylic emulsion particle formed by the acrylic emulsion is of a core-shell structure comprising a hard core and a soft shell, the hard core is a core seed emulsion, and the water-based core-shell acrylic emulsion is prepared from the following raw materials in parts by weight: 15-45 parts of the core seed emulsion; 10 to 30 parts of a hard monomer II; 35-55 parts of a soft monomer II; 1-8 parts of a functional monomer II; 3-10 parts of a reactive emulsifier II; 30 to 70 parts of deionized water II; 1-5 parts of an initiator II; and 0.5-6 parts of a neutralizer. The formed acrylic emulsion particle is of a core-shell structure comprising a hard core and a soft shell, the Tg value of the soft shell ranges from-50 DEG C to-35 DEG C, and the acrylic emulsion particle has good initial adhesion to glass beads, has certain pressure-sensitive performance and is suitable for bright silver hot pasting adhesive sticker. Under the conditions of high temperature and high humidity of 60 DEG C and 85%, the release force fluctuation is small, the release force is kept stable, and the problem of adhesive residue is avoided.

Description

Technical Field

[0001] The invention relates to the field of adhesives, and in particular to a water-based core-shell acrylic emulsion resistant to moisture and heat aging, and a preparation method and application thereof. Background Art

[0002] With the development of adhesive technology, hot-seal adhesive tapes are gradually widely used on shipping containers. However, in the hot and humid environment in summer, the peeling force of traditional hot-seal adhesive tapes will increase significantly, which is prone to residual adhesive problems and seriously affects the use. Therefore, it is very important to develop an acrylic adhesive that has almost the same peeling force at room temperature and in a hot and humid environment, and has good creep resistance to glass beads.

[0003] Chinese invention patent CN107446092B discloses an acrylic epoxy core-shell emulsion and a preparation method thereof, which combines an acrylic emulsion with an epoxy resin, makes up for the shortcomings of epoxy resin such as easy yellowing, poor moisture and heat resistance, and poor toughness, and improves the hardness and wear resistance of the acrylic emulsion. However, three emulsifications are required, and the three-polymerization preparation process is complicated. Chinese invention patent CN117567968A discloses a moisture and heat resistant acrylic glue and a preparation method thereof, wherein nano latex particles obtained by polymerization and micron latex particles formed by polymerization are bonded in pairs to obtain a moisture and heat resistant acrylic glue having a core-shell structure of small balls wrapped around large balls, and the glue has a moisture and heat resistant effect by increasing the crosslinking density and hydrophobicity of the glue and introducing a high thermal stability group. However, the reaction needs to be carried out under vacuum conditions, the reaction conditions are harsh, and the production cost is high. Summary of the invention

[0004] In order to develop an acrylic adhesive whose peeling force remains almost unchanged at room temperature and in a high temperature and high humidity environment and has good creep resistance to glass microbeads, the first aspect of the present invention provides an aqueous core-shell acrylic emulsion resistant to moisture and heat aging, wherein the acrylic latex particles formed by the acrylic emulsion are a core-shell structure comprising a hard core and a soft shell, wherein the hard core is a core seed emulsion, and the raw materials for preparing the core seed emulsion include, by weight, 30-55 parts of hard monomer I; 10-30 parts of soft monomer I; 0.5-6 parts of functional monomer I; 1-5 parts of reactive emulsifier I; 30-60 parts of deionized water I; 0.5-3 parts of buffer; and 0.5-4 parts of initiator I.

[0005] As a preferred embodiment, the raw materials for preparing the core seed emulsion include, by weight, 38-48 parts of hard monomer I; 12-25 parts of soft monomer I; 3.5-5 parts of functional monomer I; 1.5-3.5 parts of reactive emulsifier I; 50-60 parts of deionized water I; 0.5-1.2 parts of buffer; and 1.5-2.6 parts of initiator I.

[0006] As a preferred embodiment, the raw materials for preparing the aqueous core-shell acrylic emulsion include, by weight: 15-45 parts of core seed emulsion; 10-30 parts of hard monomer II; 35-55 parts of soft monomer II; 1-8 parts of functional monomer II; 3-10 parts of reactive emulsifier II; 30-70 parts of deionized water II; 1-5 parts of initiator II; and 0.5-6 parts of neutralizer.

[0007] As a preferred embodiment, the raw materials for preparing the aqueous core-shell acrylic emulsion include, by weight: 20-40 parts of core seed emulsion; 12-20 parts of hard monomer II; 43-55 parts of soft monomer II; 3.5-4.5 parts of functional monomer II; 3.8-5.5 parts of reactive emulsifier II; 45-59 parts of deionized water II; 2.6-4.5 parts of initiator II; and 2.5-5.3 parts of neutralizer.

[0008] As a preferred embodiment, the hard monomer I and the hard monomer II are both selected from at least one of methyl methacrylate and styrene.

[0009] As a preferred embodiment, the soft monomer I and the soft monomer II are both selected from at least one of isooctyl acrylate, butyl acrylate and ethyl acrylate.

[0010] As a preferred embodiment, the functional monomer I and the functional monomer II are both selected from at least one of acrylic acid, methacrylic acid, glycidyl acrylate and glycidyl methacrylate.

[0011] As a preferred embodiment, the functional monomer I is a combination of methacrylic acid and glycidyl methacrylate in a weight ratio of (2.5-3):(1-2).

[0012] As a preferred embodiment, the reactive emulsifier I and reactive emulsifier II are both selected from at least one of sodium acrylamide isopropyl sulfonate, special alcohol ether sulfate containing allyl group, sodium salt of alcohol ether sulfosuccinate containing double bond, and allyl polyether sulfate type anionic surfactant.

[0013] As a preferred embodiment, the reactive emulsifier I and the reactive emulsifier II are allyl-containing special alcohol ether sulfates.

[0014] As a preferred embodiment, the initiator I and the initiator II are both selected from at least one of an aqueous solution of ammonium persulfate and an aqueous solution of sodium persulfate.

[0015] As a preferred embodiment, the buffer is sodium bicarbonate or ammonium bicarbonate, and the neutralizer is aqueous ammonia.

[0016] As a preferred embodiment, the glass transition temperature of the hard core is 60 to 80°C, and the glass transition temperature of the soft shell is -50 to -35°C.

[0017] The inventor found in the experiment that the peeling force of traditional acrylic adhesives will increase significantly in high temperature and high humidity environments, resulting in residual glue problems, affecting normal use. The inventor prepared a core-shell structured polymer material with a hard core and a soft shell. At room temperature, the shell Tg value is between -50 and -35°C, which has good initial adhesion to glass beads and certain pressure-sensitive properties, making it suitable for bright silver hot-stick adhesive tape. Under the conditions of 60°C and 85%, the shell Tg value of the resin is between 60 and 80°C, and most of the polymer segments of the core layer resin have not yet begun to creep. After a week of constant temperature and humidity at 60°C and 85%, the peeling force does not change much, and the core layer hard segment material is used as the cohesive strength point, making it difficult for the resin to have residual glue and other phenomena, effectively solving the problem of oily resin. Under high temperature and humidity at 60°C and 85%, the molecular segments can easily creep and completely wet the substrate, so that the peeling force fluctuates greatly, the peeling force rises sharply, and even residual glue problems occur.

[0018] In addition, the core-shell structured self-adhesive polymer prepared by the inventor does not use alkylphenol polyoxyethylene ether as an emulsifier, is an environmentally friendly emulsifier, has no migration of small molecule emulsifiers, and further improves the ability to resist moisture and heat aging.

[0019] The second aspect of the present invention provides a method for preparing a water-based core-shell acrylic emulsion resistant to moist heat aging, comprising the following steps:

[0020] S1 Put hard monomer I, soft monomer I, functional monomer I, reactive emulsifier I, deionized water I, and buffer into a reaction kettle, heat to 70-90°C, stir, add initiator I, stir for 2-3h, and obtain a core seed emulsion;

[0021] S2: put hard monomer II, soft monomer II, functional monomer II, reactive emulsifier II and deionized water II into an emulsifying kettle and stir for 0.5-2h to obtain a milky white dispersion;

[0022] S3: The reactor is heated to 80-88°C, and the reactor contains 15-45 parts by weight of the core seed emulsion prepared in step S1. Stirring is started, and the milky white dispersion and initiator II are added dropwise at the same time. After 3-5 hours of dropping, the dropping is completed, and the temperature is raised to 85-90°C, kept warm for 1-3 hours, cooled to 40°C, a neutralizer is added, and the material is filtered to obtain an aqueous core-shell acrylic emulsion resistant to moisture and heat aging.

[0023] The third aspect of the present invention provides an application of a water-based core-shell acrylic emulsion resistant to moist heat aging, which is applied to self-adhesive products.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The aqueous core-shell acrylic emulsion resistant to moisture and heat aging of the present invention forms acrylic latex particles with a core-shell structure comprising a hard core and a soft shell, the Tg value of the soft shell is within the range of -50 to -35°C, has good initial adhesion to glass microbeads, has certain pressure-sensitive properties, and is suitable for bright silver hot-stick tape self-adhesives.

[0026] (2) The water-based core-shell acrylic emulsion resistant to moisture and heat aging of the present invention has little fluctuation in peeling force under high temperature and high humidity conditions of 60° C. and 85%, and the peeling force remains stable without the problem of residual adhesive.

[0027] (3) The water-based core-shell acrylic emulsion resistant to moisture and heat aging of the present invention adopts a special alcohol ether sulfate reactive emulsifier containing allyl group, and does not introduce alkylphenol polyoxyethylene ether as an emulsifier. The polymerization reaction is more environmentally friendly and there is no migration of small molecule emulsifier, which further improves the ability of moisture and heat aging resistance.

[0028] (4) The water-based core-shell acrylic emulsion resistant to moisture and heat aging of the present invention first synthesizes a core seed emulsion, and then free radical polymerization (secondary polymerization) is carried out inside the latex particles of the core seed emulsion. The latex particles grow up to form a core-shell emulsion polymerization. Only two polymerizations are required, and the reaction process is simple, efficient, and simple in process.

[0029] (5) The water-based core-shell acrylic emulsion resistant to moisture and heat aging of the present invention is an environmentally friendly water-based acrylic emulsion and does not use environmental pollutants such as alkylphenol polyoxyethylene ether and nonylphenol polyoxyethylene ether, thus being green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the structure of the acrylic latex particles prepared in Example 1.

[0031] In the picture: 1. Hard core; 2. Soft shell. DETAILED DESCRIPTION

[0032] Example 1

[0033] A water-based core-shell acrylic emulsion resistant to moisture and heat aging, wherein acrylic latex particles formed by the acrylic emulsion are a core-shell structure comprising a hard core and a soft shell, wherein the hard core is a core-seed emulsion, and the raw materials for preparing the core-seed emulsion include, by weight, 45 parts of a hard monomer I; 25 parts of a soft monomer I; 4.5 parts of a functional monomer I; 1.5 parts of a reactive emulsifier I; 55 parts of deionized water I; 1.2 parts of a buffer; and 2.6 parts of an initiator I.

[0034] The raw materials for preparing the aqueous core-shell acrylic emulsion include, by weight: 30 parts of core seed emulsion; 15 parts of hard monomer II; 50 parts of soft monomer II; 3.5 parts of functional monomer II; 4.1 parts of reactive emulsifier II; 45 parts of deionized water II; 4.5 parts of initiator II; and 3.4 parts of neutralizer.

[0035] The hard monomer I is styrene, the soft monomer I is butyl acrylate, the functional monomer I is a combination of acrylic acid and glycidyl acrylate, with a weight ratio of 2.5:2. The reactive emulsifier I is a special alcohol ether sulfate containing allyl, with a brand name of NRS-10. The buffer is sodium bicarbonate, and the initiator I is ammonium persulfate.

[0036] The hard monomer II is styrene; the soft monomer II is isooctyl acrylate; the functional monomer II is methacrylic acid; the reactive emulsifier II is a special alcohol ether sulfate containing allyl group, with the brand name NRS-10; the initiator II is sodium persulfate; and the neutralizer is ammonia water.

[0037] A method for preparing a water-based core-shell acrylic emulsion resistant to moisture and heat aging comprises the following steps:

[0038] S1: Put hard monomer I, soft monomer I, functional monomer I, reactive emulsifier I, deionized water I and buffer into a reaction kettle, heat to 80°C, stir, add initiator I, stir for 2.5h, and obtain core seed emulsion;

[0039] S2: put hard monomer II, soft monomer II, functional monomer II, reactive emulsifier II and deionized water II into an emulsifying kettle and stir for 1.5 hours to obtain a milky white dispersion;

[0040] S3: heat the reactor to 85°C, the reactor contains 30 parts by weight of the core seed emulsion prepared in step S1, start stirring, and simultaneously drop the milky white dispersion and initiator II. After 4 hours of dropping, the dropping is completed, heat to 90°C, keep warm for 2 hours, cool to 40°C, add a neutralizer, filter the material, and obtain a water-based core-shell acrylic emulsion resistant to moisture and heat aging.

[0041] The structure of acrylic latex particles formed by the prepared acrylic emulsion is shown in Figure 1 .

[0042] Example 2

[0043] A water-based core-shell acrylic emulsion resistant to moisture and heat aging, wherein acrylic latex particles formed by the acrylic emulsion are a core-shell structure comprising a hard core and a soft shell, wherein the hard core is a core-seed emulsion, and the raw materials for preparing the core-seed emulsion include, by weight, 38 parts of a hard monomer I; 12 parts of a soft monomer I; 3.5 parts of a functional monomer I; 3.5 parts of a reactive emulsifier I; 50 parts of deionized water I; 0.5 parts of a buffer; and 1.5 parts of an initiator I.

[0044] The raw materials for preparing the aqueous core-shell acrylic emulsion include, by weight: 30 parts of core seed emulsion; 20 parts of hard monomer II; 55 parts of soft monomer II; 4.5 parts of functional monomer II; 5.5 parts of reactive emulsifier II; 59 parts of deionized water II; 2.6 parts of initiator II; and 5.3 parts of neutralizer.

[0045] The hard monomer I is styrene, the soft monomer I is butyl acrylate, the functional monomer I is a combination of methacrylic acid and glycidyl methacrylate, with a weight ratio of 2.5:1. The reactive emulsifier I is a special alcohol ether sulfate containing allyl, with a brand name of NRS-10. The buffer is ammonium bicarbonate, and the initiator I is ammonium persulfate.

[0046] The hard monomer II is methyl methacrylate; the soft monomer II is isooctyl acrylate; the functional monomer II is acrylic acid; the reactive emulsifier II is a special alcohol ether sulfate containing allyl group, with the brand name NRS-10; the initiator II is ammonium persulfate; and the neutralizer is ammonia water.

[0047] A method for preparing a water-based core-shell acrylic emulsion resistant to moisture and heat aging comprises the following steps:

[0048] S1 Put hard monomer I, soft monomer I, functional monomer I, reactive emulsifier I, deionized water I, and buffer into a reaction kettle, heat to 80°C, stir, add initiator I, stir for 2h, and obtain core seed emulsion;

[0049] S2: put hard monomer II, soft monomer II, functional monomer II, reactive emulsifier II and deionized water II into an emulsifying kettle and stir for 1 hour to obtain a milky white dispersion;

[0050] S3: heat the reactor to 80°C, the reactor contains 30 parts by weight of the core seed emulsion prepared in step S1, start stirring, and simultaneously drop the milky white dispersion and initiator II. After 3 hours of dropping, the dropping is completed, heat to 85°C, keep warm for 3 hours, cool to 40°C, add a neutralizer, filter the material, and obtain a water-based core-shell acrylic emulsion resistant to moisture and heat aging.

[0051] Example 3

[0052] A water-based core-shell acrylic emulsion resistant to moisture and heat aging, wherein acrylic latex particles formed by the acrylic emulsion are a core-shell structure comprising a hard core and a soft shell, wherein the hard core is a core-seed emulsion, and the raw materials for preparing the core-seed emulsion include, by weight, 48 parts of a hard monomer I; 22 parts of a soft monomer I; 5 parts of a functional monomer I; 2.5 parts of a reactive emulsifier I; 60 parts of deionized water I; 0.9 parts of a buffer; and 2 parts of an initiator I.

[0053] The raw materials for preparing the aqueous core-shell acrylic emulsion include, by weight: 30 parts of core seed emulsion; 12 parts of hard monomer II; 43 parts of soft monomer II; 4 parts of functional monomer II; 3.8 parts of reactive emulsifier II; 52 parts of deionized water II; 3.2 parts of initiator II; and 2.5 parts of neutralizer.

[0054] The hard monomer I is styrene, the soft monomer I is ethyl acrylate, and the functional monomer I is a combination of methacrylic acid and glycidyl methacrylate, with a weight ratio of 3:2. The reactive emulsifier I is a special alcohol ether sulfate containing allyl, with a brand name of NRS-10. The buffer is ammonium bicarbonate, and the initiator I is ammonium persulfate.

[0055] The hard monomer II is methyl methacrylate; the soft monomer II is isooctyl acrylate; the functional monomer II is acrylic acid; the reactive emulsifier II is a special alcohol ether sulfate containing allyl group, with the brand name NRS-10; the initiator II is ammonium persulfate; and the neutralizer is ammonia water.

[0056] A method for preparing a water-based core-shell acrylic emulsion resistant to moisture and heat aging comprises the following steps:

[0057] S1: Put hard monomer I, soft monomer I, functional monomer I, reactive emulsifier I, deionized water I and buffer into a reaction kettle, heat to 80°C, stir, add initiator I, stir for 3h, and obtain core seed emulsion;

[0058] S2: put hard monomer II, soft monomer II, functional monomer II, reactive emulsifier II and deionized water II into an emulsifying kettle and stir for 2 hours to obtain a milky white dispersion;

[0059] S3: heat the reactor to 88°C, the reactor contains 30 parts by weight of the core seed emulsion prepared in step S1, start stirring, and simultaneously drop the milky white dispersion and initiator II. After 5 hours of dropping, the dropping is completed, heat to 90°C, keep warm for 1 hour, cool to 40°C, add a neutralizer, filter the material, and obtain a water-based core-shell acrylic emulsion resistant to moisture and heat aging.

[0060] Comparative Example 1

[0061] An oily acrylic resin was purchased from Foshan Huangfeng Huacheng Coating Technology Development Co., Ltd., with the brand name S63.

[0062] Performance Testing

[0063] 1. Solid content: Use an aluminum foil box with a mass of M to weigh glue with a mass of M1, put it in a 150℃ oven for 30 minutes, and weigh it as M2. Its solid content = (M2-M) / M1×100%

[0064] 2. Viscosity: measured at 25°C using a rotational viscometer NDJ-5S.

[0065] 3. Appearance: Visually inspect the appearance of the prepared emulsion.

[0066] 4. Tg: tested by differential scanning calorimetry.

[0067] 5. Peeling force at room temperature: Test the peeling force at room temperature 25°C and 40%.

[0068] 6. High temperature and high humidity peeling strength: Test the peeling strength after aging for one week at 60℃ and 85%.

[0069] The peel force test method is as follows:

[0070] 1) Cut the sample into 25mm wide strips; 2) Perform a 180° peel test on a universal tensile testing machine (Beidou Precision Instruments); the pulling rate is 300mm / min;

[0071] The test results are shown in Table 1.

[0072] Table 1

[0073]

Claims

1. A water-based core-shell acrylic emulsion resistant to moisture and heat aging, characterized in that: The acrylic latex particles formed by the acrylic emulsion are a core-shell structure including a hard core and a soft shell, wherein the hard core is a core-seed emulsion, and the raw materials for preparing the core-seed emulsion include, by weight, 30-55 parts of a hard monomer I; 10-30 parts of a soft monomer I; 0.5-6 parts of a functional monomer I; 1-5 parts of a reactive emulsifier I; 30-60 parts of deionized water I; 0.5-3 parts of a buffer; and 0.5-4 parts of an initiator I.

2. The aqueous core-shell acrylic emulsion resistant to moist heat aging according to claim 1, characterized in that: The raw materials for preparing the aqueous core-shell acrylic emulsion include, by weight: 15-45 parts of core seed emulsion; 10-30 parts of hard monomer II; 35-55 parts of soft monomer II; 1-8 parts of functional monomer II; 3-10 parts of reactive emulsifier II; 30-70 parts of deionized water II; 1-5 parts of initiator II; and 0.5-6 parts of neutralizer.

3. The aqueous core-shell acrylic emulsion resistant to moist heat aging according to claim 2, characterized in that: The hard monomer I and the hard monomer II are both selected from at least one of methyl methacrylate and styrene.

4. The aqueous core-shell acrylic emulsion resistant to moist heat aging according to claim 2, characterized in that: The soft monomer I and the soft monomer II are both selected from at least one of isooctyl acrylate, butyl acrylate and ethyl acrylate.

5. The aqueous core-shell acrylic emulsion resistant to moist heat aging according to claim 2, characterized in that: The functional monomer I and the functional monomer II are both selected from at least one of acrylic acid, methacrylic acid, glycidyl acrylate and glycidyl methacrylate.

6. The water-based core-shell acrylic emulsion resistant to moist heat aging according to claim 2, characterized in that: The reactive emulsifier I and reactive emulsifier II are both selected from at least one of sodium acrylamide isopropyl sulfonate, special alcohol ether sulfate containing allyl group, sodium salt of alcohol ether sulfosuccinate containing double bond, and allyl polyether sulfate type anionic surfactant.

7. The water-based core-shell acrylic emulsion resistant to moist heat aging according to claim 2, characterized in that: The initiator I and the initiator II are both selected from at least one of an aqueous solution of ammonium persulfate and an aqueous solution of sodium persulfate.

8. The water-based core-shell acrylic emulsion resistant to moist heat aging according to claim 1, characterized in that: The glass transition temperature of the hard core is 60 to 80°C, and the glass transition temperature of the soft shell is -50 to -35°C.

9. A method for preparing the water-based core-shell acrylic emulsion resistant to moist heat aging according to any one of claims 2 to 8, characterized in that: The following steps are involved: S1 Put hard monomer I, soft monomer I, functional monomer I, reactive emulsifier I, deionized water I, and buffer into a reaction kettle, heat to 70-90°C, stir, add initiator I, stir for 2-3h, and obtain a core seed emulsion; S2: put hard monomer II, soft monomer II, functional monomer II, reactive emulsifier II and deionized water II into an emulsifying kettle and stir for 0.5-2h to obtain a milky white dispersion; S3: The reactor is heated to 80-88°C, and the reactor contains 15-45 parts by weight of the core seed emulsion prepared in step S1. Stirring is started, and the milky white dispersion and initiator II are added dropwise at the same time. After 3-5 hours of dropping, the dropping is completed, and the temperature is raised to 85-90°C, kept warm for 1-3 hours, cooled to 40°C, a neutralizer is added, and the material is filtered to obtain an aqueous core-shell acrylic emulsion resistant to moisture and heat aging.

10. An application of the water-based core-shell acrylic emulsion resistant to moist heat aging according to any one of claims 2 to 8, characterized in that: Used in self-adhesive products.

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