Anionic modified acrylic emulsion for paper and preparation method thereof

Abstract

The invention discloses an anionic modified acrylic emulsion for paper. The anionic modified acrylic emulsion comprises a hard monomer, a soft monomer, a functional monomer, a surfactant, an initiator, a residual free radical treating agent, a pH regulator and water, the invention correspondingly discloses a preparation method of the composition. The high-performance acrylate emulsion is prepared by designing and matching the dosages of the hard monomer, the soft monomer and the functional monomer and adopting a seed emulsion polymerization method, the emulsion is narrow and stable in particle size distribution and high in permeability to paper, the stiffness of the emulsion can be effectively improved when the emulsion is applied to the paper, and meanwhile green production, safety and environmental protection are achieved.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, and in particular relates to an anionic modified acrylic emulsion for paper and a preparation method thereof. Background Art

[0002] With the rapid development of social economy and the enhancement of people's environmental awareness, our requirements for decoration materials are getting higher and higher. Resin adhesives account for the largest proportion of the finishing materials of artificial boards. At present, the commonly used adhesives for decorative paper are trialdehyde glue (phenolic resin, urea-formaldehyde resin and melamine formaldehyde resin). Traditional trialdehyde glue will release free formaldehyde during the manufacture and application of furniture decoration and related wood products. At the same time, in order to reduce the free formaldehyde content and control production costs, the modification of trialdehyde glue will also bring some new problems. In order to reduce the harm of indoor furniture to human health, in recent years, the country has had higher requirements for the green development of indoor furniture and has new standards for safety and environmental protection. Therefore, the development of new formaldehyde-free adhesives has great research significance and social value.

[0003] Acrylic emulsion has many advantages. First, the polymerization reaction generally uses water as solvent, the raw materials are environmentally friendly, non-toxic, cheap and easy to obtain, and there is basically no addition and release of formaldehyde compounds, which will not have serious adverse effects on human health and the ecological environment; second, the emulsion polymerization reaction speed is fast, the polymerization system has low viscosity, fast heat dissipation, and safe production, which can save time and cost to a certain extent and improve production efficiency; finally, the emulsion has good storage stability, the product is easy to store and transport, and it does not need to be made on the spot, which also avoids the waste of resources to a certain extent. There are many types of acrylic acid series monomers, which contain some very polar functional groups, such as ester groups, carboxyl groups, hydroxyl groups, etc., which are easy to emulsion copolymerize with other monomers, and can prepare emulsion adhesives with various properties and meet different needs, and have extremely wide applications in different fields. However, at present, emulsion impregnation liquids have not been widely used in decorative paper. The main reason is that there is a problem of poor permeability when the emulsion is impregnated with decorative paper. The polyurethane impregnation adhesive developed by Wanhua Ecological Technology Co., Ltd. (CN110450239A) and the nanocellulose / nano Zn0 composite modified acrylic adhesive developed by Nanjing Forestry University (CN109680544A) can both achieve the formaldehyde-free treatment of decorative paper. However, the above-mentioned organic polymer resin adhesives are difficult to penetrate into the interior of the decorative base paper due to their high viscosity, large particle size, and high degree of cross-linking, and there are many problems. Summary of the invention

[0004] Purpose of the invention: In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide an anionic modified acrylic emulsion for paper and a preparation method thereof, aiming to develop high-performance water-based acrylic emulsion, synthesize and apply low-cost green acrylic emulsion adhesive for paper, effectively solve the problem of poor permeability of the emulsion to decorative paper, improve the stiffness of paper, and at the same time achieve green production, safety and environmental protection.

[0005] Technical solution: The anionic modified acrylic emulsion for paper described in the present invention includes a hard monomer, a soft monomer, a functional monomer, a surfactant, an initiator, a residual free radical treatment agent, a pH adjuster and water; the content of the above components is: the hard monomer accounts for 65 wt%~80 wt% of the total monomer amount, the soft monomer accounts for 15 wt%~30 wt% of the total monomer amount, the functional monomer accounts for 1 wt%~15 wt% of the total monomer amount, the surfactant accounts for 1 wt%~3 wt% of the total emulsion, the initiator accounts for 0~3 wt% of the total emulsion, the residual free radical treatment agent accounts for 0~3 wt% of the total monomer amount, the pH adjuster accounts for 0%~6 wt% of the total emulsion, and the solid content is 30 wt%~50 wt%.

[0006] Furthermore, as a preferred embodiment, the hard monomer is selected from one or more of methyl methacrylate, vinyl acetate, acrylonitrile, styrene, ethyl methacrylate, isobutyl methacrylate, methyl acrylate, and acrylamide.

[0007] Furthermore, as a preferred embodiment, the soft monomer is selected from one or more of butyl acrylate, ethyl acrylate, and isooctyl acrylate.

[0008] Furthermore, as a preferred embodiment, the functional monomer is selected from one or more of acrylic acid, methacrylic acid, sodium methacrylic acid sulfonate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and glycidyl methacrylate.

[0009] Furthermore, as a preferred embodiment, the surfactant is one or more of sodium dodecyl sulfate, ammonium dodecyl sulfate, and fatty alcohol polyoxyethylene ether.

[0010] Furthermore, as a preferred embodiment, the initiator is one or more of ammonium persulfate, potassium persulfate, and sodium bisulfite.

[0011] Furthermore, as a preferred embodiment, the residual free radical treatment agent is a thiol compound.

[0012] Furthermore, as a more preferred embodiment, the residual free radical treatment agent is 2-mercaptoethanol or dodecyl mercaptan.

[0013] Furthermore, as a preferred embodiment, the pH adjuster is one or more of sodium hydroxide, triethylamine, triethanolamine, and ammonia water.

[0014] The present invention also provides a method for preparing the anionic modified acrylic emulsion for paper, comprising the following steps: Step (1) mixing the initiator and water according to a ratio and fully dissolving them to obtain a solution a; Step (2) stirring and mixing the hard monomer, the soft monomer and the functional monomer to obtain a mixed monomer solution b; Step (3) pure water, surfactant and pH adjuster are stirred and mixed according to the proportion, and after they are fully dissolved, solution b is slowly added under strong stirring to obtain pre-emulsion c; Step (4) Add 1 / 5 of the pre-emulsion c into a four-necked flask, start stirring, add 1 / 3 of the initiator aqueous solution a when the temperature is 50-65°C, maintain the temperature at 60-65°C until blue light appears, and continue the reaction for 20-50 minutes to prepare the seed emulsion d; Step (5) Based on the seed emulsion d, the temperature is raised to 65°C-70°C, and the remaining pre-emulsion c and the initiator aqueous solution a are added continuously in two ways at the same time, and the addition time is controlled within 2-4 hours; After the step (6) is completed, the temperature is kept at 65°C to 70°C for 1-2 hours, and then the initiator is added and the temperature is kept at 65°C to 70°C for another 1-2 hours; In step (7), a residual monomer treatment agent is added to remove free radicals, the mixture is stirred at 65°C to 70°C for 30-40 minutes, the mixture is cooled to 40-50°C and filtered, and a pH adjuster is added to the filtrate to adjust the pH of the emulsion to 8-9, thereby obtaining an anionic modified acrylic emulsion.

[0015] Beneficial Effects

[0016] (1) The anionic modified acrylic emulsion for paper prepared by the present invention uses water as a solvent, does not contain any formaldehyde compounds, and has a simple and safe preparation process; (2) The present invention prepares a high-performance water-based acrylic emulsion by rationally matching hard monomers, soft monomers and functional monomers, thereby improving the permeability of the emulsion to paper and the stiffness of paper, while achieving green production, safety and environmental protection; the prepared acrylic emulsion has excellent performance, strong permeability to paper, and improves the stiffness of paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the infrared spectrum of the anionic modified acrylic ester emulsion prepared by the scheme of the present invention. DETAILED DESCRIPTION

[0018] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with embodiments, the purpose of which is to understand the contents of the present invention in detail rather than to limit the present invention.

[0019] Unless otherwise specified, the reagents and raw materials used in the examples and comparative examples of the present invention are conventionally commercially available.

[0020] Embodiment 1:

[0021] In the anionic modified acrylic emulsion for paper described in this embodiment, the mass fractions of each component are: 80 mass fractions of hard monomer, 15 mass fractions of soft monomer, 5 mass fractions of functional monomer, 1.6 mass fractions of surfactant, 0.4 mass fractions of initiator, 0.05 mass fractions of residual free radical treatment agent, 1 mass fraction of pH adjuster, and 126 mass fractions of water.

[0022] The hard monomer is a mixture of methyl methacrylate, vinyl acetate and acrylonitrile, the soft monomer is butyl acrylate, the functional monomer is a mixture of acrylic acid and sodium methacrylic acid sulfonate, the surfactant is sodium dodecyl sulfate, the initiator is ammonium persulfate, the residual monomer treatment agent is dodecyl mercaptan, and the pH adjuster is triethanolamine.

[0023] The specific preparation process is as follows: 0.4 parts of ammonium persulfate and 40 parts of water are mixed to obtain solution a; 80 parts of mixed hard monomers (70 parts of methyl methacrylate, 7 parts of vinyl acetate and 3 parts of acrylonitrile), 15 parts of butyl acrylate, and 5 parts of functional monomers (3 parts of acrylic acid and 2 parts of sodium methacrylic acid) are mixed to obtain solution b; 1.6 parts of sodium dodecyl sulfate, 1 part of pH regulator and water are mixed and stirred, and after fully dissolved, solution b is slowly added under strong stirring to obtain pre-emulsion c; 1 / 5 of pre-emulsion c is added to a four-necked flask, and the mixture is stirred and stirred. Start stirring, when the temperature is 60℃, add 1 / 3 of the initiator aqueous solution a, keep the temperature at 60℃ until blue light appears, and continue the reaction for 30min to prepare the seed emulsion d; raise the temperature to 65℃, and continuously add the remaining pre-emulsion c and solution a at the same time, and control the dropping time to 3h. After the dropping is completed, keep warm at 65℃ for 2h, add 0.05 parts of dodecyl mercaptan to remove free radicals, keep warm at 65℃ and stir for 30min, cool to 45℃, filter, adjust the pH to 8~9, and obtain anionic modified acrylate emulsion, in which water accounts for 55% of the total emulsion.

[0024] Embodiment 2:

[0025] The present embodiment has the same formula as that of the embodiment 1, except that the difference lies in the temperature and time for preparing the emulsion. In step (4), the temperature of the initiator aqueous solution a is 50°C, the reaction temperature is 60°C, and the reaction is continued for 50 minutes when blue light appears to prepare the seed emulsion; in step (5), the temperature is raised to 65°C based on the seed emulsion d, and the dropwise addition time is controlled within 4 hours; in step (6), after the monomer is dropwise added, the reaction temperature is 65°C, kept warm for 2 hours, and then the initiator is added, and kept warm at 65°C for another 2 hours; in step (7), the residual monomer treatment temperature is 65°C, kept warm and stirred for 40 minutes, and filtered after the temperature drops below 40°C.

[0026] Embodiment 3:

[0027] The present embodiment has the same formula as that of the embodiment 1, except that the difference lies in the temperature and time for preparing the emulsion. In step (4), the temperature of the initiator aqueous solution a is 65°C, the reaction temperature is 65°C, and the reaction is continued for 20 minutes when blue light appears to prepare the seed emulsion; in step (5), the temperature is raised to 70°C based on the seed emulsion d, and the dropwise addition time is controlled within 2 hours; in step (6), after the monomer dropwise addition is completed, the reaction temperature is 70°C, and the temperature is kept for 1 hour, and then the initiator is added, and the temperature is kept at 70°C for another 1 hour; in step (7), the residual monomer treatment temperature is 70°C, the temperature is kept and stirred for 30 minutes, and then filtered after the temperature drops below 50°C.

[0028] Embodiment 4:

[0029] This embodiment is basically the same as Example 1, and the reaction temperature and reaction time are consistent with Example 1. The difference is that in solution b, the mass fraction of the mixed hard monomer is 75 parts (65 parts of methyl methacrylate, 7 parts of vinyl acetate and 3 parts of acrylonitrile), and the mass fraction of the soft monomer butyl acrylate is 20 parts.

[0030] Embodiment 5:

[0031] This embodiment is basically the same as Example 1, and the reaction temperature and reaction time are consistent with Example 1. The difference is that in solution b, the mass fraction of the mixed hard monomer is 70 parts (60 parts of methyl methacrylate, 7 parts of vinyl acetate and 3 parts of acrylonitrile), and the mass fraction of the soft monomer butyl acrylate is 25 parts.

[0032] Embodiment 6:

[0033] This embodiment is basically the same as Example 1, and the reaction temperature and reaction time are consistent with Example 1. The difference lies in solution b, the mass fraction of the mixed hard monomer is 65 parts (55 parts of methyl methacrylate, 7 parts of vinyl acetate and 3 parts of acrylonitrile), and the mass fraction of the soft monomer butyl acrylate is 30 parts.

[0034] Comparative Example 1:

[0035] This embodiment is basically the same as Example 1, and the reaction temperature and reaction time are consistent with Example 1. The difference lies in that in solution b, the mass fraction of the hard monomer is 50 parts (50 parts of methyl methacrylate); the mass fraction of the soft monomer butyl acrylate is 45 parts; and the mass fraction of the functional monomer is 5 parts (3 parts of acrylic acid and 2 parts of sodium methacrylate sulfonate).

[0036] Comparative Example 2:

[0037] This embodiment is basically the same as Example 1, and the reaction temperature and reaction time are consistent with Example 1. The difference lies in solution b, the mass fraction of the mixed hard monomer is 50 parts (40 parts of methyl methacrylate, 7 parts of vinyl acetate and 3 parts of acrylonitrile), the mass fraction of the soft monomer butyl acrylate is 45 parts, and the mass fraction of the functional monomer is 5 parts (5 parts of acrylic acid).

[0038] In order to verify the effect of the scheme of the present invention, the emulsion products prepared in Examples 1-4 and Comparative Examples 1-2 were tested for basic properties and applied to paper to test their permeability and paper stiffness improvement rate, paper tensile strength improvement rate, etc., as shown in Table 1: Table 1 Emulsion products prepared in Examples 1-6 and Comparative Examples 1-2 and paper test results after application Solid content / % Emulsion particle size / nm Emulsion stability Paper permeability after gluing / s Improvement rate of paper stiffness after gluing Increase rate of paper tensile strength after gluing Example 1 45.1 ＜180 pass 6 182.3% 175.8% Example 2 45.3 ＜180 pass 6 182.1% 175.4% Example 3 45.2 ＜180 pass 6 181.9% 175.0% Example 4 45.3 ＜180 pass 6 175.2% 162.2% Example 5 45.2 ＜180 pass 6 167.1% 153.8% Example 6 45.0 ＜180 pass 6 159.4% 141.3% Comparative Example 1 45.2 ＜180 pass 6 145.1% 135.2% Comparative Example 2 45.3 ＜180 pass 8 146.6% 135.9% As can be seen from the above table, the acrylic emulsion prepared by the present invention has good permeability to paper, and can significantly improve the stiffness and tensile properties of paper, and also has good emulsion stability. From the comparison results of the embodiments, it can be seen that when the hard monomer contains methyl methacrylate, vinyl acetate and acrylonitrile at the same time, the stiffness of the paper is improved, and when the functional monomer contains acrylic acid and sodium methacrylic acid at the same time, the permeability of the paper is improved. The ratio of the soft and hard monomers in Comparative Example 1 is outside the scope of the present invention, and the hard monomer only contains methyl methacrylate, and its emulsion stiffness and tensile strength are worse. The ratio of the soft and hard monomers in Comparative Example 2 is outside the scope of the present invention, and when the functional monomer is only acrylic acid, its emulsion has a worse penetrant to paper.

[0039] The preparation method of the modified acrylic ester emulsion of the invention is simple and easy to operate. The obtained product can improve the permeability of the emulsion to paper and improve the stiffness of paper. Meanwhile, green production is realized, which is safe and environmentally friendly and has a great market prospect.

[0040] The above is only an implementation method of the invention, and does not limit the scope of patent protection. Those skilled in the art can make non-substantial changes or substitutions based on the invention, which still fall within the scope of patent protection.

Claims

1. An anionic modified acrylic emulsion for paper, characterized in that: It includes hard monomers, soft monomers, functional monomers, surfactants, initiators, residual free radical treatment agents, pH regulators and water; the contents of the above components are as follows: hard monomers account for 65 wt%~80 wt% of the total monomers, soft monomers account for 15 wt%~30 wt% of the total monomers, functional monomers account for 1 wt%~15 wt% of the total monomers, surfactants account for 1 wt%~3 wt% of the total emulsion, initiators account for 0~3 wt% of the total emulsion, residual free radical treatment agents account for 0~3 wt% of the total monomers, pH regulators account for 0%~6 wt% of the total emulsion, and the solid content is 30wt%~50wt%.

2. The anionic modified acrylic emulsion for paper according to claim 1, characterized in that: The hard monomer is selected from one or more of methyl methacrylate, vinyl acetate, acrylonitrile, styrene, ethyl methacrylate, isobutyl methacrylate, methyl acrylate and acrylamide.

3. The anionic modified acrylic emulsion for paper according to claim 1, characterized in that: The soft monomer is selected from one or more of butyl acrylate, ethyl acrylate and isooctyl acrylate.

4. The anionic modified acrylic emulsion for paper according to claim 1, characterized in that: The functional monomer is selected from one or more of acrylic acid, methacrylic acid, sodium methacrylic acid sulfonate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and glycidyl methacrylate.

5. The anionic modified acrylic emulsion for paper according to claim 1, characterized in that: The surfactant is one or more of sodium lauryl sulfate, ammonium lauryl sulfate, and fatty alcohol polyoxyethylene ether.

6. The anionic modified acrylic emulsion for paper according to claim 1, characterized in that: The initiator is one or more of ammonium persulfate, potassium persulfate, and sodium bisulfite.

7. The anionic modified acrylic emulsion for paper according to claim 1, characterized in that: The residual free radical treatment agent is a thiol compound.

8. The anionic modified acrylic emulsion for paper according to claim 7, characterized in that: The residual free radical treatment agent is 2-mercaptoethanol or dodecyl mercaptan.

9. The anionic modified acrylic emulsion for paper according to claim 1, characterized in that: The pH regulator is one or more of sodium hydroxide, triethylamine, triethanolamine and ammonia water.

10. A method for preparing the anionic modified acrylic emulsion for paper according to any one of claims 1 to 9, characterized in that The steps include: Step (1) mixing the initiator and water according to a ratio and fully dissolving them to obtain a solution a; Step (2) stirring and mixing the hard monomer, the soft monomer and the functional monomer to obtain a mixed monomer solution b; Step (3) pure water, surfactant and pH adjuster are stirred and mixed according to the proportion, and after they are fully dissolved, solution b is slowly added under strong stirring to obtain pre-emulsion c; Step (4) Add 1 / 5 of the pre-emulsion c into a four-necked flask, start stirring, add 1 / 3 of the initiator aqueous solution a when the temperature is 50-65°C, maintain the temperature at 60-65°C until blue light appears, and continue the reaction for 20-50 minutes to prepare the seed emulsion d; Step (5) Based on the seed emulsion d, the temperature is raised to 65°C-70°C, and the remaining pre-emulsion c and the initiator aqueous solution a are added continuously in two ways at the same time, and the addition time is controlled within 2-4 hours; After the step (6) is completed, the temperature is kept at 65°C to 70°C for 1-2 hours, and then the initiator is added and the temperature is kept at 65°C to 70°C for another 1-2 hours; In step (7), a residual monomer treatment agent is added to remove free radicals, the mixture is stirred at 65°C to 70°C for 30-40 minutes, the mixture is cooled to 40-50°C and filtered, and a pH adjuster is added to the filtrate to adjust the pH of the emulsion to 8-9, thereby obtaining an anionic modified acrylic emulsion.

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