A heat-resistant water whitening water-based pressure-sensitive latex emulsion and a preparation method thereof

Abstract

The application discloses a kind of heat-resistant white water whitening water-based pressure-sensitive latex emulsion and preparation method thereof.The preparation raw materials of the water-based pressure-sensitive latex emulsion include, emulsifier 0.1-2.0 parts, comonomer 100 parts, oil-soluble initiator 0.1-2.0 parts, deionized water 45-100 parts by weight.The initiator of the application uses oil-soluble thermal decomposition initiator, the macromolecular terminal generated by initiating polymerization reaction does not have special hydrophilic sulfate or sulfite radical, in addition, the molecular weight of polymerization reaction initiated by azo initiator is much smaller than that of polymerization initiated by peroxide, so that the glue film spreads more evenly, crosslinking is more compact, water molecules are difficult to penetrate, so the pressure-sensitive adhesive made by the emulsion coating film dried after the preparation of the application retains the original performance while improving water resistance.

Description

Technical Field

[0001] This invention relates to the field of pressure-sensitive adhesives, and more particularly to a water-based pressure-sensitive adhesive emulsion that is resistant to hot water whitening and its preparation method. Background Technology

[0002] Acrylic emulsion pressure-sensitive adhesives are copolymers of acrylic (esters), formed by copolymerizing acrylates and methacrylates, or by adding other monomers such as vinyl acetate, into a water-based adhesive. After two or three decades of rapid development, acrylic emulsion pressure-sensitive adhesives have been widely used in packaging, labeling, medical supplies, and other fields. The advantages of acrylic pressure-sensitive adhesives, such as low cost, safety, environmental friendliness, and anti-aging properties, have made them a key area of ​​development for pressure-sensitive adhesives. Through modification, the performance of acrylic emulsion pressure-sensitive adhesives has been further improved, expanding their application areas.

[0003] Although acrylic pressure-sensitive adhesives are becoming increasingly widely used, their poor water resistance limits their application in some industries and products. Therefore, it is of great significance to develop a safe, environmentally friendly, water-resistant, high-whitening, high-solids-content, and water-resistant water-based pressure-sensitive adhesive with good low-temperature initial adhesion and high-temperature storage stability.

[0004] It is generally believed that the poor water resistance of acrylic pressure-sensitive adhesives is due to the presence of hydrophilic groups on their molecular chains and the need for emulsifiers, which also contain hydrophilic groups. Therefore, to address these factors, it is advisable to select special comonomers with poor hydrophilicity (long-chain acrylic monomers, fluorinated and silicone monomers) and special emulsifiers (polymerizable emulsifiers), and to use internal and external crosslinking agents to block the hydrophilic hydroxyl or carboxyl groups to improve the water resistance of the pressure-sensitive adhesive. However, traditional initiator systems, whether persulfates or peroxides, will cause the polymer ends to have particularly hydrophilic sulfate or sulfite groups, affecting the water resistance of the pressure-sensitive adhesive. Patent publication number CN10250733A, "A Water-Resistant Whitening Fluorosilicone Modified Waterborne Pressure-Sensitive Adhesive and Polyethylene Protective Film," discloses a water-resistant whitening fluorosilicone modified waterborne pressure-sensitive adhesive for polyethylene films. This invention introduces siloxane monomers and fluorinated vinyl monomers to achieve a water-resistant whitening effect. However, fluorosilicone monomers are expensive, and the polymerization process uses reactive emulsifiers, significantly increasing the cost of the waterborne pressure-sensitive adhesive. Patents and literature concerning water-based pressure-sensitive adhesives with water-whitening resistance, such as Chen Lin and Lin Zhongxiang's "Water-resistant Whitening Acrylic Emulsion Pressure-sensitive Adhesive," synthesize pressure-sensitive adhesives using a low-temperature oxidation-reduction polymerization process. The resulting pressure-sensitive adhesive has a solid content of 35-45 wt%, exhibiting water-resistant whitening at 90℃ for 40 minutes without whitening. However, its low solid content leads to high energy consumption and low efficiency in actual production. Patent publication number CN 111205792 A, "A Water-resistant Whitening Water-based Pressure-sensitive Adhesive and its Preparation Method," discloses a water-resistant whitening water-based pressure-sensitive adhesive for polyethylene film. This method solves the problem of long-term water-resistant whitening by using a mixture of reactive and non-reactive emulsifiers and employing internal and external crosslinking technology. However, this method uses internal and external crosslinking agents, increasing costs and reducing the adhesiveness of the pressure-sensitive adhesive, sacrificing some performance characteristics. Summary of the Invention

[0005] To overcome the shortcomings of poor water resistance in existing pressure-sensitive adhesives, the main objective of this invention is to provide a water-based pressure-sensitive adhesive emulsion that is resistant to water-induced whitening and its preparation method. By using a seed polymerization method, an oil-soluble initiator is used to replace the traditional water-soluble thermal decomposition initiator to initiate the polymerization reaction, thereby reducing the hydrophilicity of the polymer end groups and solving the problem of water-based pressure-sensitive adhesive whitening.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: A water-based pressure-sensitive adhesive latex that is resistant to hot water and whitens, wherein the raw materials for preparing the water-based pressure-sensitive adhesive latex include 0.1-2.0 parts of emulsifier, 100 parts of comonomer, 0.1-2.0 parts of oil-soluble initiator, and 45-100 parts of deionized water, by weight.

[0007] The oil-soluble initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptane, or dimethyl azobisisobutyrate.

[0008] The emulsifier is either an ionic emulsifier or a nonionic emulsifier.

[0009] The nonionic emulsifier is selected from at least one of reactive emulsifiers and non-reactive emulsifiers.

[0010] The reactive emulsifier is allyl fatty alcohol polyoxyethylene ether, and the non-reactive emulsifier is nonylphenol polyoxyethylene ether. The weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0011] The comonomer is selected from at least one of butyl acrylate, ethylene carbonate, octadecyl acrylate, acrylic acid, and hydroxybutyl acrylate.

[0012] The preparation method of the hot water resistant whitening water-based pressure-sensitive adhesive latex includes the following steps: S1: Take one-third of the weight of deionized water and put it into the emulsification kettle. Add half of the emulsifier and 95 parts of the comonomer according to 100 parts of the comonomer. Emulsify to obtain the emulsion. S2: Dissolve all the initiator with the remaining 5 parts of comonomer, add the other half of the emulsifier, and stir evenly with the remaining two-thirds of the weight of deionized water to make a stable pre-emulsion. Place it in a reaction vessel, heat it, and initiate the reaction at 65-70℃ to make a seed emulsion. S3: Add the emulsion described in step S1 to the seed emulsion described in step S2, and after the addition is completed, keep it warm and then cool it to room temperature; S4: After filtration, the hot water resistant whitening water-based pressure-sensitive latex is obtained.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: The initiator used in this invention is an oil-soluble thermal decomposition initiator. The macromolecules generated by the polymerization reaction do not have particularly hydrophilic sulfate or sulfite groups at their ends. In addition, the molecular weight of the polymers induced by azo initiators is much smaller than that of polymers induced by peroxides, resulting in more uniform film spreading, denser cross-linking, and difficulty for water molecules to penetrate. Therefore, the pressure-sensitive adhesive made from the emulsion coating film prepared by this invention retains its original properties while improving its water resistance after drying. Detailed Implementation

[0014] The embodiments described below are exemplary descriptions of primary experimental evidence and are not intended to limit the core content and application scope of this invention due to the amount of evidence. It should be noted that all these descriptions merely exemplify the concept, principles, and representative experimental evidence of the disclosed embodiments of this invention. Where the chain of evidence is complete, it is unnecessary to present all specific and extended details of the various embodiments listed in this invention.

[0015] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art to which this invention pertains.

[0016] The raw material emulsifier allyl fatty alcohol polyoxyethylene ether LGE-10 used in the following examples was purchased from Nanjing Qicheng New Material Co., Ltd., and the others were all commercially available products.

[0017] Traditional emulsion polymerization uses water as the reaction medium. Under the action of an emulsifier, monomers diffuse into latex particles, and the reaction takes place within the latex particles, initiated by a water-soluble initiator. Typically, emulsion polymerization using oil-soluble initiators results in the reaction occurring in large droplets rather than within the latex particles, leading to emulsion instability, demulsification, and the inability to obtain a stable product. This invention overcomes this problem by utilizing a compounded emulsifier and employing a seed emulsion polymerization method to prepare water-based pressure-sensitive adhesive latexes.

[0018] Example 1 Example 1 provides a water-resistant whitening water-based pressure-sensitive adhesive latex, which, by weight, comprises the following raw materials: 0.6 parts of emulsifier nonylphenol polyoxyethylene ether (NP-10), 0.2 parts of emulsifier allyl fatty alcohol polyoxyethylene ether (LGE-10), 100 parts of comonomer, 0.30 parts of initiator (AIBN), and 100 parts of deionized water.

[0019] The emulsifier is a reactive emulsifier (LGE-10) and a non-reactive emulsifier (NP-10); the weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0020] The comonomers include, by weight, 91 parts butyl acrylate, 7.0 parts ethylene carbonate (V10), 1.0 part octadecyl acrylate, and 1.0 part acrylic acid, mixed evenly.

[0021] The initiator is azobisisobutyronitrile (AIBN). The preparation method of the hot water resistant whitening water-based pressure-sensitive adhesive latex includes the following steps: S1: Take one-third of the weight of deionized water and put it into the emulsification kettle, add half of the emulsifier and 95 parts of comonomer (comonomer is calculated as 100 parts), emulsify, and obtain the emulsion. S2: Dissolve all the initiator with the remaining 5 parts of comonomer, add the other half of the emulsifier, and stir evenly with the remaining two-thirds of the weight of deionized water. Use a high-pressure homogenizer to form a stable pre-emulsion, place it in a reaction vessel, raise the temperature, and initiate the reaction at 65-70℃ to prepare a seed emulsion.

[0022] S3: Add the emulsion from step S1 dropwise to the seed emulsion from step S2, keep warm for 2 hours after the addition is complete, and then cool down to room temperature; S4: Filter the material to obtain the hot water resistant whitening water-based pressure-sensitive latex.

[0023] Example 2 Example 2 provides a water-resistant whitening water-based pressure-sensitive adhesive latex, which, by weight, comprises 0.6 parts of emulsifier (NP-10), 0.2 parts of emulsifier (LGE-10), 100 parts of comonomer, 0.30 parts of initiator (AIBN), and 100 parts of deionized water.

[0024] The emulsifier is a reactive emulsifier (LGE-10) and a non-reactive emulsifier (NP-10); the weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0025] The comonomers include, by weight, 91 parts butyl acrylate, 7.0 parts ethylene carbonate (V10), 1.0 part octadecyl acrylate, and 1.0 part hydroxybutyl acrylate; The initiator is azobisisobutyronitrile (AIBN). The preparation method of the hot water resistant whitening water-based pressure-sensitive adhesive latex is the same as in Example 1.

[0026] Example 3 Example 3 provides a water-resistant whitening water-based pressure-sensitive adhesive latex, which, by weight, comprises 0.6 parts of emulsifier (NP-10), 0.2 parts of emulsifier (LGE-10), 100 parts of comonomer, 2.0 parts of initiator (AIBN), and 100 parts of deionized water.

[0027] The emulsifier is a reactive emulsifier (LGE-10) and a non-reactive emulsifier (NP-10); the weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0028] The comonomers include, by weight, 91 parts butyl acrylate, 7.0 parts ethylene carbonate (V10), 1.0 part octadecyl acrylate, and 1.0 part acrylic acid; The initiator is azobisisobutyronitrile (AIBN). The preparation method of the hot water resistant whitening water-based pressure-sensitive adhesive latex is the same as in Example 1.

[0029] Example 4 Example 4 provides a water-resistant whitening water-based pressure-sensitive adhesive latex, which, by weight, comprises 0.6 parts of emulsifier (NP-10), 0.2 parts of emulsifier (LGE-10), 100 parts of comonomer, 2.0 parts of initiator (AIBN), and 100 parts of deionized water.

[0030] The emulsifier is a reactive emulsifier (LGE-10) and a non-reactive emulsifier (NP-10); the weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0031] The comonomers include, by weight, 91 parts butyl acrylate, 7.0 parts ethylene carbonate (V10), 1.0 part octadecyl acrylate, and 1.0 part hydroxybutyl acrylate; The initiator is azobisisobutyronitrile (AIBN). The preparation method of the hot water resistant whitening water-based pressure-sensitive adhesive latex is the same as in Example 1.

[0032] Example 5 Example 5 provides a water-resistant whitening water-based pressure-sensitive adhesive latex, which, by weight, comprises 0.075 parts of emulsifier (NP-10), 0.025 parts of emulsifier (LGE-10), 100 parts of comonomer, 0.1 parts of initiator (AIBN), and 45 parts of deionized water.

[0033] The emulsifier is a reactive emulsifier (LGE-10) and a non-reactive emulsifier (NP-10); the weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0034] The comonomers include, by weight, 91 parts butyl acrylate, 7.0 parts ethylene carbonate (V10), 1.0 part octadecyl acrylate, and 1.0 part hydroxybutyl acrylate; The initiator is azobisisobutyronitrile (AIBN). The preparation method of the hot water resistant whitening water-based pressure-sensitive adhesive latex is the same as in Example 1.

[0035] Example 6 Example 6 provides a water-resistant whitening water-based pressure-sensitive adhesive latex, which, by weight, comprises 1.5 parts of emulsifier (NP-10), 0.5 parts of emulsifier (LGE-10), 100 parts of comonomer, 2.0 parts of initiator (AIBN), and 100 parts of deionized water.

[0036] The emulsifier is a reactive emulsifier (LGE-10) and a non-reactive emulsifier (NP-10); the weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0037] The comonomers include, by weight, 91 parts butyl acrylate, 7.0 parts ethylene carbonate (V10), 1.0 part octadecyl acrylate, and 1.0 part hydroxybutyl acrylate; The initiator is azobisisobutyronitrile (AIBN). The preparation method of the hot water resistant whitening water-based pressure-sensitive adhesive latex is the same as in Example 1.

[0038] In the above embodiments, the initiator is azobisisobutyronitrile (AIBN). One or more of azobisisoheptanetron (ABVN) and dimethyl azobisisobutyrate (AIBME) can be used as initiators, which is a conventional alternative in the art.

[0039] In the above embodiments, the emulsifiers are reactive emulsifiers (LGE-10) and non-reactive emulsifiers, both of which are nonionic emulsifiers. The present invention can also use reactive or non-reactive emulsifiers alone. Ionic emulsifiers can also be used in the present invention.

[0040] Comparative Example 1 Comparative Example 1 provides an aqueous pressure-sensitive adhesive latex, the raw materials for which, by weight, are: 0.6 parts of emulsifier (NP-10), 0.2 parts of emulsifier (LGE-10), 100 parts of comonomer, 0.30 parts of initiator (APS), and 100 parts of deionized water.

[0041] The emulsifier is a reactive emulsifier (LGE-10) and a non-reactive emulsifier (NP-10); the weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0042] The comonomers include, by weight, 91 parts butyl acrylate, 7.0 parts ethylene carbonate (V10), 1.0 part octadecyl acrylate, and 1.0 part acrylic acid; The initiator is ammonium persulfate (APS); The preparation method of the water-based pressure-sensitive adhesive includes the following steps: S1: Take one-third of the weight of deionized water and put it into an emulsification kettle. Add emulsifier and comonomer (comonomer is calculated in 100 parts). Emulsify to obtain an emulsion. S2: Add one-third by weight of deionized water to the reactor, heat to 80 degrees Celsius, and then add the initiator APS.

[0043] S3: Add the emulsion from step S1 dropwise to the reactor, keep it warm after the addition is complete, and then cool it down to room temperature; S4: Filter the material to obtain water-based pressure-sensitive latex.

[0044] Comparative Example 2 Comparative Example 2 provides an aqueous pressure-sensitive adhesive latex, the raw materials for which, by weight, are: 0.6 parts of emulsifier (NP-10), 0.2 parts of emulsifier (LGE-10), 100 parts of comonomer, 0.30 parts of initiator (APS), and 100 parts of deionized water.

[0045] The emulsifier is a reactive emulsifier (LGE-10) and a non-reactive emulsifier (NP-10); the weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:3.

[0046] The comonomers include, by weight, 91 parts butyl acrylate, 7.0 parts ethylene carbonate (V10), 1.0 part octadecyl acrylate, and 1.0 part hydroxybutyl acrylate; The initiator is ammonium persulfate (APS); The preparation method of the hot water resistant whitening waterborne pressure-sensitive adhesive latex is the same as that of Comparative Example 1.

[0047] Example 7 Performance Test Water whitening resistance grade: The water-resistant whitening water-based pressure-sensitive adhesive described in the example is applied to a 23-micron thick PET film using a wire bar coater. The film is then immersed in a 60-degree water bath for 24 hours and 48 hours. The changes in the appearance of the film are observed after immersion. The film is recorded as follows: transparent with no change is recorded as A; slightly blurry but not white is recorded as B; slightly white is recorded as C; and severely white and opaque is recorded as D. The test results are shown in Table 1.

[0048] Table 1 Performance Tests

[0049] The test results above show that the pressure-sensitive adhesive made from the emulsion of this invention has significantly improved hot water resistance.

[0050] The above embodiments only describe a portion of the specific implementation methods of the present invention in detail, and are not limited to the embodiments disclosed herein. Furthermore, the substantive content protected by the present invention is not limited thereto. Any other modifications, equivalent substitutions, improvements, etc., made based on the principles and techniques of the present invention without departing from its design scope are all within the protection scope of the present invention.

Claims

1. A water-based pressure-sensitive adhesive latex resistant to hot water whitening, characterized in that, The raw materials for preparing the water-based pressure-sensitive adhesive latex, by weight, include 0.1-2.0 parts of emulsifier, 100 parts of comonomer, 0.1-2.0 parts of oil-soluble initiator, and 45-100 parts of deionized water.

2. The water-based pressure-sensitive adhesive latex with heat-resistant whitening properties according to claim 1, characterized in that, The oil-soluble initiator is selected from one or more of azobisisobutyronitrile, azobisisoheptane, or dimethyl azobisisobutyrate.

3. The water-based pressure-sensitive adhesive latex with heat-resistant whitening properties according to claim 1, characterized in that, The emulsifier is either an ionic emulsifier or a nonionic emulsifier.

4. The water-based pressure-sensitive adhesive latex with heat-resistant whitening properties according to claim 3, characterized in that, The nonionic emulsifier is selected from at least one of reactive emulsifiers and non-reactive emulsifiers.

5. The water-based pressure-sensitive adhesive latex with heat-resistant whitening properties according to claim 4, characterized in that, The reactive emulsifier is allyl fatty alcohol polyoxyethylene ether, and the non-reactive emulsifier is nonylphenol polyoxyethylene ether. The weight ratio of the reactive emulsifier to the non-reactive emulsifier is 1:

3.

6. The water-based pressure-sensitive adhesive latex with heat-resistant whitening properties according to claim 1, characterized in that, The comonomer is selected from at least one of butyl acrylate, ethylene carbonate, octadecyl acrylate, acrylic acid, and hydroxybutyl acrylate.

7. The method for preparing the water-based pressure-sensitive adhesive latex with hot water resistance and whitening as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Take one-third of the weight of deionized water and put it into the emulsification kettle. Add half of the emulsifier and 95 parts of the comonomer according to 100 parts of the comonomer. Emulsify to obtain the emulsion. S2: Dissolve all the initiator with the remaining 5 parts of comonomer, add the other half of the emulsifier, and stir evenly with the remaining two-thirds of the weight of deionized water to make a stable pre-emulsion. Place it in a reaction vessel, heat it, and initiate the reaction at 65-70℃ to make a seed emulsion. S3: Add the emulsion described in step S1 to the seed emulsion described in step S2, and after the addition is completed, keep it warm and then cool it to room temperature; S4: After filtration, the hot water resistant whitening water-based pressure-sensitive latex is obtained.

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