Low-VOC styrene-butadiene latex raw material composition for food paper and preparation method of low-VOC styrene-butadiene latex raw material composition

Abstract

The invention provides a food paper low VOC styrene-butadiene latex raw material composition, which is composed of the following components by weight: 15-30 parts of butadiene, 10-20 parts of styrene, 5-15 parts of acrylate, 3-10 parts of methacrylate, 5-10 parts of a styrene-acrylic acid copolymer, 1-5 parts of an emulsifier, 0.1-2 parts of an initiator, and 0.1-1 part of a green catalyst. The green catalyst is selected from a bio-based catalyst or an inorganic catalyst. The method for preparing the low-VOC styrene-butadiene latex for the food paper from the raw material composition comprises the following steps: adding the components into a reactor, fully mixing, heating to 60-100 DEG C, reacting for 2-6 hours, washing a reaction product with water, and filtering with activated carbon, thereby obtaining the low-VOC styrene-butadiene latex for the food paper. By optimizing reaction conditions and monomers, the content of harmful substances is remarkably reduced while the high reaction conversion rate is guaranteed, a safe and healthy styrene-butadiene latex material selection is provided for the food packaging industry, and an effective solution is provided for meeting the dual requirements of modern consumers for food safety and environmental protection.

Description

Technical Field

[0001] The present invention relates to the technical field of styrene-butadiene latex preparation for papermaking, and particularly to a preparation method of low-VOC styrene-butadiene latex for food paper. Background Art

[0002] With the rapid development of the food packaging industry, consumers' attention to food safety and environmental protection has been increasing. Styrene-butadiene latex, as an important synthetic material, is widely used in fields such as food packaging, coatings, and adhesives. However, traditional styrene-butadiene latex may introduce various harmful substances during the preparation process, which not only affect the environment but also pose a threat to food safety. Therefore, it is particularly important to develop an efficient, safe, and environmentally friendly preparation method for styrene-butadiene latex.

[0003] In the production of styrene-butadiene latex, the reaction conversion rate and monomer residue are key indicators for evaluating its quality and safety. A high reaction conversion rate means that most of the raw materials participate in the reaction to form polymers, reducing the residue of unreacted monomers, thereby reducing the content of harmful substances in the product. Optimizing reaction conditions, such as adjusting reaction temperature, time, and pressure, can effectively improve the reaction conversion rate. For example, appropriately increasing the reaction temperature can accelerate the reaction rate of monomers, but too high a temperature may lead to side reactions. Therefore, determining the optimal reaction conditions through experiments can reduce the generation of harmful substances while ensuring a high conversion rate.

[0004] In terms of monomer selection, traditional styrene-butadiene latex usually uses organic monomers such as butadiene and styrene, which may remain in the final product after the polymerization reaction. To solve this problem, researchers have begun to explore the application of low-toxicity or bio-based monomers. For example, using bio-based butadiene or acrylate monomers to replace traditional monomers not only helps reduce the content of harmful substances in the product but also meets the requirements of sustainable development. In addition, using green catalysts and initiators can reduce the generation of by-products while improving the reaction efficiency, thereby further reducing the residue of unreacted monomers.

[0005] In the post-treatment stage, methods such as water washing and activated carbon filtration can effectively remove residual harmful components to ensure the safety of the final product. These measures not only improve the purity and safety of the latex but also make it more reliable in food packaging applications. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method of low-VOC styrene-butadiene latex for food paper to solve the above technical problems existing in the prior art.

[0007] The present invention is realized by adopting the following technical scheme:

[0008] A food paper low-VOC styrene-butadiene latex raw material composition is composed of the following components in parts by weight: 15-30 parts of butadiene, 10-20 parts of styrene, 5-15 parts of acrylate, 3-10 parts of methacrylate, 5-10 parts of styrene-acrylic copolymer, 1-5 parts of emulsifier, 0.1-2 parts of initiator, and 0.1-1 part of green catalyst, and the green catalyst is selected from bio-based catalysts or inorganic catalysts.

[0009] The acrylate is methyl acrylate or ethyl acrylate.

[0010] The methacrylate is methyl methacrylate or ethyl methacrylate.

[0011] The styrene-acrylic copolymer preferably has a weight-average molecular weight (Mw) of 50,000-100,000, a degree of polymerization (DP) of 500-1000; a glass transition temperature (Tg) of 30-50 °C; and a particle size of 100-200 nm.

[0012] The emulsifier is selected from at least one of sodium dodecylbenzenesulfonate, polyoxyethylene-polyoxypropylene copolymer, and glycerol monostearate.

[0013] The initiator is selected from at least one of ammonium persulfate, azobisisobutyronitrile, or benzoyl peroxide.

[0014] The green catalyst is specifically selected from at least one of lipase, heteropolyacid, or molecular sieve.

[0015] The present invention further provides a preparation method of a food paper low-VOC styrene-butadiene latex. Using the above-mentioned food paper low-VOC styrene-butadiene latex raw material composition, it includes the following steps: adding each component in the food paper low-VOC styrene-butadiene latex raw material composition into a reactor and mixing well, heating to a reaction temperature of 60-100 °C, and reacting for 2-6 hours; the reaction product is washed with water and filtered through activated carbon to remove unreacted monomers and by-products, obtaining the food paper low-VOC styrene-butadiene latex.

[0016] The inventors have found through research that styrene-butadiene latex synthesized by using a special combination of monomers and cooperating with bio-based catalysts or inorganic catalysts can greatly reduce the residue of harmful substances and the VOC content. The specific mechanism is not very clear. The inventors speculate that on the one hand, it may be due to the use of a variety of low-toxicity monomers to replace traditional butadiene and styrene, and on the other hand, the use of bio-based catalysts or inorganic catalysts can reduce the generation of by-products, improve the reaction efficiency, and further reduce the residue of monomers. In addition, in the post-treatment stage, the combination of washing with water and activated carbon filtration can further remove residual harmful components and ensure the safety of the final product. Based on the above findings, the inventors have completed the present invention.

[0017] The reaction temperature is preferably 70-90°C. Within this temperature range, the conversion rate of the reaction is the highest, and at the same time, the generation of by-products is the least.

[0018] The styrene-butadiene latex with low VOC for food paper of the present invention has a residual monomer ≤ 12 mg / kg, VOC ≤ 1.2 ppm, and water resistance ≥ 12 N / cm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) By optimizing the reaction conditions, the conversion rate of the reaction is significantly improved, ensuring that most of the raw materials participate in the reaction and reducing the residue of unreacted monomers.

[0021] (2) By using high-purity raw materials and green catalysts, combined with an effective post-treatment process, the content of harmful components in the final product is significantly reduced, ensuring the safety of the latex.

[0022] (3) By using environmentally friendly alternative monomers and green catalysts, the negative impact on the environment is reduced, meeting the requirements of sustainable development.

[0023] (4) The final product has excellent properties such as adhesiveness, water resistance, and heat resistance, and can meet the requirements of various food packaging, having good market application prospects.

[0024] (5) The prepared styrene-butadiene latex meets the relevant food safety standards and can be safely applied to food packaging to ensure the health of consumers.

[0025] Through the optimization of reaction conditions and monomers, the styrene-butadiene latex provided by the present invention not only ensures a high reaction conversion rate but also significantly reduces the content of harmful substances, providing a safe and healthy material choice for the food packaging industry and an effective solution to meet the dual needs of modern consumers for food safety and environmental protection. Detailed Embodiments

[0026] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are only examples and do not limit the scope of the present invention. Those skilled in the art can think of other obvious variations. The basic principles defined in the following description can be applied to other embodiments, variations, improvements, equivalent solutions, and other technical solutions without departing from the spirit and scope of the present invention.

[0027] In the present invention, if the instrument or raw material is not specified by the manufacturer, it is a conventional commercial instrument or raw material. The styrene-acrylic copolymer used in the examples is copolymerized from 50 wt% styrene, 10 wt% acrylic acid, 20 wt% methyl methacrylate, and 20 wt% butyl acrylate. The specific preparation method is as follows: In a reaction kettle, the monomers are mixed and 1% of the total amount of the monomer of sodium dodecyl sulfate as an emulsifier is added for pre-emulsification to form a stable emulsion. Then the temperature is raised to 70 °C, and 0.5 wt% of the total amount of the monomer of potassium persulfate as an initiator is added dropwise, and the reaction temperature is maintained at 70-75 °C for 5 hours. After the reaction is completed, it is cooled to room temperature and filtered to obtain. The obtained styrene-acrylic copolymer has a weight-average molecular weight of 82,500, a degree of polymerization of 720; a glass transition temperature of 41 °C; and a particle size of 162 nm.

[0028] In the examples of the present invention, if the detection indexes are not mentioned, the conventional detection methods in the art are used for detection.

[0029] Example 1

[0030] The formulation includes 15 parts of butadiene, 10 parts of styrene, 5 parts of methyl acrylate, 3 parts of methyl methacrylate, 5 parts of styrene-acrylic copolymer, 1 part of emulsifier (sodium dodecylbenzenesulfonate), 0.1 part of initiator (azobisisobutyronitrile), and 0.1 part of green catalyst (lipase CAL-B). The experimental steps are as follows: Under stirring conditions, butadiene, styrene, methyl acrylate, methyl methacrylate, and styrene-acrylic copolymer are added to the reaction kettle, and the emulsifier, initiator, and green catalyst are added to ensure thorough mixing. The reaction temperature is adjusted to 70 °C and the reaction is maintained for 3 hours. After the reaction is completed, unreacted monomers and harmful components are removed by washing with water and filtering with activated carbon. The latex finally obtained is detected, and its viscosity is 300 mPa·s, meeting the food safety standards.

[0031] Example 2

[0032] The formulation includes 20 parts of butadiene, 15 parts of styrene, 10 parts of methyl acrylate, 5 parts of ethyl methacrylate, 7 parts of styrene-acrylic copolymer, 3 parts of emulsifier (polyethylene-polypropylene copolymer), 0.5 part of initiator (ammonium persulfate), and 0.5 part of green catalyst (molecular sieve HZSM-5). The experimental steps are as follows: Butadiene, styrene, methyl acrylate, ethyl methacrylate, and styrene-acrylic copolymer are mixed in the reaction kettle, and the emulsifier, initiator, and green catalyst are added and stirred evenly. The reaction temperature is set at 80 °C and the reaction time is 4 hours. After completion, post-treatment is carried out, and purification is carried out by washing with water and filtering with activated carbon. The viscosity of the obtained latex is 500 mPa·s, meeting the relevant food safety standards.

[0033] Example 3

[0034] The formulation includes 25 parts of butadiene, 15 parts of styrene, 12 parts of ethyl acrylate, 4 parts of methyl methacrylate, 6 parts of styrene-acrylic acid copolymer, 2 parts of emulsifier (glycerol monostearate), 1 part of initiator (benzoyl peroxide), and 0.3 part of green catalyst (molecular sieve HZSM-5). The experimental procedure is as follows: After premixing the monomers and the emulsifier, add them into the reactor, then add the initiator and the green catalyst to ensure complete dissolution. Set the reaction temperature at 90 °C and the reaction time at 5 hours. After the reaction is completed, carry out post-treatment by washing with water and filtering with activated carbon. The viscosity of the final product is 800 mPa·s, and the test results meet the food safety standards.

[0035] Example 4

[0036] The formulation includes 27 parts of butadiene, 18 parts of styrene, 11 parts of ethyl acrylate, 6 parts of ethyl methacrylate, 8 parts of styrene-acrylic acid copolymer, 4 parts of emulsifier (polyoxyethylene-polyoxypropylene copolymer), 0.8 part of initiator (azobisisobutyronitrile), and 0.2 part of green catalyst (molecular sieve HZSM-5). The experimental procedure is as follows: Add each component into the reaction kettle according to the formulation, stir and mix them, then add the initiator and the green catalyst to ensure complete dissolution. Set the reaction temperature at 75 °C and the reaction time at 3.5 hours. After the reaction is completed, carry out post-treatment by washing with water and filtering with activated carbon. The viscosity of the final product is 1000 mPa·s, and the test results meet the food safety standards.

[0037] Example 5

[0038] The formulation includes 30 parts of butadiene, 20 parts of styrene, 15 parts of methyl acrylate, 10 parts of methyl methacrylate, 10 parts of styrene-acrylic acid copolymer, 5 parts of emulsifier (sodium dodecylbenzenesulfonate), 2 parts of initiator (ammonium persulfate), and 1 part of green catalyst (molecular sieve HZSM-5). The experimental procedure is as follows: Add butadiene, styrene, methyl acrylate, methyl methacrylate, and styrene-acrylic acid copolymer into the reactor, then add the emulsifier, the initiator, and the green catalyst, and stir well. Adjust the reaction temperature to 100 °C and keep the reaction for 6 hours. After the reaction is completed, carry out post-treatment to remove unreacted components by washing with water and filtering with activated carbon. The viscosity of the finally obtained latex is 1500 mPa·s, and after testing, it meets all food safety standards.

[0039] Comparative Example 1

[0040] Prepare styrene-butadiene latex with a traditional formulation as follows:

[0041] The formulation includes 45 parts of butadiene, 35 parts of styrene, 5 parts of emulsifier (sodium dodecylbenzenesulfonate), and 2 parts of initiator (ammonium persulfate). The experimental procedure is as follows: Add butadiene and styrene into the reactor, then add the emulsifier and the initiator, and stir well. Adjust the reaction temperature to 100 °C and maintain the reaction for 6 hours. After the reaction is completed, perform post-treatment by washing with water and filtering with activated carbon to remove unreacted components. The final latex viscosity obtained is 2200 mPa·s. After testing, the monomer residues and VOC exceed the standards and do not meet the food safety standards.

[0042] Comparative Example 2

[0043] Styrene-acrylic copolymer was not added, and the others were the same as in Example 5. The specific process is as follows:

[0044] The formulation includes 30 parts of butadiene, 20 parts of styrene, 15 parts of acrylate, 10 parts of methacrylate, 5 parts of emulsifier (sodium dodecylbenzenesulfonate), 2 parts of initiator (ammonium persulfate), and 1 part of green catalyst (zeolite HZSM-5). The experimental procedure is as follows: Add butadiene, styrene, acrylate, and methacrylate into the reactor, then add the emulsifier, the initiator, and the green catalyst, and stir well. Adjust the reaction temperature to 100 °C and maintain the reaction for 6 hours. After the reaction is completed, perform post-treatment by washing with water and filtering with activated carbon to remove unreacted components. The final latex viscosity obtained is 1900 mPa·s. After testing, the monomer residues and VOC exceed the standards and do not meet the food safety standards.

[0045] Comparative Example 3

[0046] The product was not filtered with activated carbon, and the others were the same as in Example 5. The specific process is as follows:

[0047] The formulation includes 30 parts of butadiene, 20 parts of styrene, 15 parts of acrylate, 10 parts of methacrylate, 10 parts of styrene-acrylic copolymer, 5 parts of emulsifier (sodium dodecylbenzenesulfonate), 2 parts of initiator (ammonium persulfate), and 1 part of green catalyst (bio-based catalyst). The experimental procedure is as follows: Add butadiene, styrene, acrylate, methacrylate, and styrene-acrylic copolymer into the reactor, then add the emulsifier, the initiator, and the green catalyst, and stir well. Adjust the reaction temperature to 100 °C and maintain the reaction for 6 hours. After the reaction is completed, perform post-treatment by washing with water to remove unreacted components. The final latex viscosity obtained is 1500 mPa·s. After testing, the monomer residues and VOC exceed the standards and do not meet the food safety standards.

[0048] The following tests were conducted on the samples of each example and comparative example:

[0049] 1. Residual monomer detection

[0050] Gas chromatography (GC) is used: Take the sample and dilute it in a suitable solvent, analyze the sample using a gas chromatograph, set appropriate temperature programs and chromatographic conditions, and calculate the content of residual monomers according to the standard curve.

[0051] 2. VOC Detection

[0052] Gas chromatography - mass spectrometry (GC - MS) is used: Take the sample and prepare the sample pretreatment, analyze the volatile organic compounds (VOCs) in the sample using GC - MS, record the peak areas, and quantitatively analyze the content of VOCs by comparing with reference substances.

[0053] 3. Water Resistance Detection

[0054] Immersion test is used: Coat the latex sample on standard paper, cut it into specified dimensions after drying. Immerse the sample in water for 24 hours, observe and record the changes in the sample (such as peeling, foaming, etc.). Evaluate the water resistance by measuring the adhesion strength.

[0055] The specific test results are shown in Table 1.

[0056] Table 1 Sample Test Data

[0057]

[0058] It can be seen from the test results that the embodiments of the present invention are superior to the comparative examples in terms of residual monomers, volatile organic compounds (VOCs), and water resistance. The content of residual monomers in the embodiments is significantly lower than that in the comparative examples, showing better safety and environmental protection. In addition, the embodiments have stronger water resistance, indicating better performance in practical applications.

[0059] Those skilled in the art should understand that the above embodiments are only examples and do not limit the present invention. The object of the present invention has been fully and effectively achieved. The functions and structural principles of the present invention have been demonstrated and explained in the embodiments. Without departing from the above - mentioned principles, the embodiments of the present invention can have any deformation or modification.

Claims

1. A low-VOC styrene-butadiene latex raw material composition for food paper, characterized in that: The invention is composed of the following components in parts by weight: 15-30 parts of butadiene, 10-20 parts of styrene, 5-15 parts of acrylate, 3-10 parts of methacrylate and 5-10 parts of styrene-acrylic acid copolymer, 1-5 parts of emulsifier, 0.1-2 parts of initiator and 0.1-1 parts of green catalyst, wherein the green catalyst is selected from bio-based catalyst or inorganic catalyst.

2. The low-VOC styrene-butadiene latex raw material composition for food paper according to claim 1, characterized in that: The acrylate is methyl acrylate or ethyl acrylate.

3. The low-VOC styrene-butadiene latex raw material composition for food paper according to claim 1, characterized in that: The methacrylate is methyl methacrylate or ethyl methacrylate.

4. The low-VOC styrene-butadiene latex raw material composition for food paper according to claim 1, characterized in that: The weight average molecular weight of the styrene-acrylic acid copolymer is 50,000-100,000, the degree of polymerization is 500-1,000, the glass transition temperature is 30-50° C., and the particle size is 100-200 nm.

5. The low-VOC styrene-butadiene latex raw material composition for food paper according to claim 1, characterized in that: The emulsifier is selected from at least one of sodium dodecylbenzene sulfonate, polyoxyethylene-polyoxypropylene copolymer, and glycerol monostearate.

6. The low-VOC styrene-butadiene latex raw material composition for food paper according to claim 1, characterized in that: The initiator is selected from at least one of ammonium persulfate, azobisisobutyronitrile or benzoyl peroxide.

7. The low-VOC styrene-butadiene latex raw material composition for food paper according to claim 1, characterized in that: The green catalyst is selected from at least one of lipase, heteropoly acid or molecular sieve.

8. A method for preparing low-VOC styrene-butadiene latex for food paper, characterized in that: The method comprises the following steps: adding the components of the low-VOC styrene-butadiene latex raw material composition for food paper according to any one of claims 1 to 7 into a reactor and mixing them thoroughly, heating the reactor to a reaction temperature of 60-100° C., and reacting the mixture for 2-6 hours; washing the reaction product with water, filtering the reaction product with activated carbon to remove unreacted monomers and by-products, and obtaining the low-VOC styrene-butadiene latex for food paper.

9. The method according to claim 8, characterized in that The reaction temperature is 70-90°C.

10. The low VOC styrene-butadiene latex for food paper prepared by the method of claim 8 or 9, characterized in that: Residual monomer ≤12mg / kg, VOC ≤1.2ppm, water resistance ≥12N / cm.

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