Formaldehyde-free white latex and preparation method thereof

Abstract

The invention discloses formaldehyde-free white latex and a preparation method thereof, and belongs to the technical field of adhesives. The formaldehyde-free white latex is prepared from the following components in parts by weight: 23 to 38 parts of modified polyvinyl acetate emulsion, 8 to 12 parts of composite filler, 20 to 35 parts of vegetable protein, 3 to 7 parts of solubilizer, 0.5 to 1 part of plasticizer, 0.1 to 0.3 part of preservative and 55 to 65 parts of deionized water, wherein the composite filler comprises an inorganic filler and a functional filler in a weight ratio of 1: (0.2-0.8). The excellent comprehensive performance is ensured, meanwhile, formaldehyde-free, environment-friendly and safe effects are achieved, and the current market requirements are met.

Description

Technical Field

[0001] The present application relates to a formaldehyde-free white latex and a preparation method thereof, belonging to the technical field of adhesives. Background Art

[0002] White latex is an important adhesive product. Its main ingredients are polyvinyl acetate, water, and a variety of other additives. It has the advantages of low price, good bonding performance, easy use, and green environmental protection, and is widely used.

[0003] To enhance the performance of adhesive products, white latex is added with formaldehyde-containing additives during the production process. With growing awareness of the hazards of formaldehyde in the government, industry, and consumers, and new standards further restricting formaldehyde emissions from wood-based panels, "formaldehyde-free" wood adhesives are gaining increasing attention in forest product chemical processing and wood-based panel production. The development and utilization of bio-based, green, and environmentally friendly wood adhesives is imperative. Summary of the Invention

[0004] In order to solve the above problems, a formaldehyde-free white latex and a preparation method thereof are provided, which ensure its excellent comprehensive performance while achieving formaldehyde-free, environmental protection and safety, and meeting current market demand.

[0005] The present invention adopts the following technical solutions:

[0006] According to one aspect of the present application, there is provided a formaldehyde-free white latex, comprising the following components in parts by weight: 23-38 parts of modified polyvinyl acetate emulsion, 8-12 parts of composite filler, 20-35 parts of vegetable protein, 3-7 parts of solubilizer, 0.5-1 part of plasticizer, 0.1-0.3 part of preservative, and 55-65 parts of deionized water;

[0007] The composite filler is an inorganic filler and a functional filler in a weight ratio of 1: (0.2-0.8).

[0008] Optionally, the preparation method of the modified polyvinyl acetate emulsion comprises the following steps:

[0009] S1. Dissolve the dibasic unsaturated carboxylic acid in deionized water, stir magnetically at 70-90° C. for 5-15 minutes, and then add potassium hydroxide solution dropwise to obtain a dibasic unsaturated carboxylic acid solution with a neutralization degree of 30-50%;

[0010] S2. Add lignin to deionized water and ultrasonically treat for 20-40 minutes to obtain a lignin dispersion, then add a diunsaturated carboxylic acid solution to the lignin dispersion, wherein the weight ratio of the diunsaturated carboxylic acid to the lignin is (1.5-3):1, and continue stirring. Then, add ammonium persulfate containing 2-5 wt% of lignin, introduce an inert atmosphere, and magnetically stir at 70-90° C. for 3-5 hours. Filter to obtain polydiunsaturated carboxylic acid grafted lignin;

[0011] S3. Blending the polydiunsaturated carboxylic acid grafted lignin with a solid-liquid ratio of (0.3-0.5):1 with the polyvinyl acetate emulsion, and stirring for 10-20 minutes to obtain the modified polyvinyl acetate emulsion.

[0012] Optionally, the dibasic unsaturated carboxylic acid is at least one of methylene succinic acid, maleic acid, fumaric acid and cis-methyl succinic acid.

[0013] Optionally, the preparation method of the polyvinyl acetate emulsion comprises the following steps:

[0014] Polyvinyl alcohol with a vinyl acetate content of 1.5-3 wt% and sodium lauryl sulfate with a vinyl acetate content of 1-2 wt% are added to deionized water, stirred at 80-100° C. until completely dissolved, cooled to room temperature, and then vinyl acetate is added and mixed uniformly. Then, an inert gas is introduced, and ammonium persulfate with a vinyl acetate content of 0.3-0.5 wt% is added. The system temperature is raised to 60-70° C. After the reaction is completed, the pH is adjusted to 6-7, and the mixture is filtered to obtain a polyvinyl acetate emulsion.

[0015] Optionally, the inorganic filler is at least one of montmorillonite, kaolin, calcium carbonate and hydroxyapatite;

[0016] The functional filler is at least one of silicon dioxide, cellulose nano whiskers and cellulose nanofibers.

[0017] Optionally, the plant protein is at least one of soy protein, corn protein and wheat protein.

[0018] Optionally, the solubilizer is at least one of silane coupling agent KH550, silane coupling agent KH560 and silane coupling agent KH570.

[0019] Optionally, the plasticizer is at least one of dibutyl phthalate, dioctyl phthalate, dioctyl adipate and acetyl tributyl citrate.

[0020] Optionally, the preservative is at least one of benzisothiazolinone, 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

[0021] According to another aspect of the present application, a method for preparing formaldehyde-free white latex is provided, comprising the following steps:

[0022] (1) Weighing each raw material according to the weight parts of the formaldehyde-free white latex described in any one of the above items;

[0023] (2) 8-12 parts of the composite filler and 3-7 parts of the solubilizer are mixed evenly, 20-35 parts of the plant protein are added, and the mixture is stirred at 40-60° C. for 20-30 minutes to obtain a mixed solution A;

[0024] (3) 23-38 parts of modified polyvinyl acetate emulsion, 0.5-1 parts of plasticizer, 0.1-0.3 parts of preservative, and 55-65 parts of deionized water were mixed at 70-90° C. to obtain a mixed solution B;

[0025] (4) Ultrasonic dispersion of mixed solution A in mixed solution B at an ultrasonic frequency of 25-35 kHz to obtain formaldehyde-free white latex.

[0026] In this application, "room temperature" refers to 20-30°C.

[0027] The beneficial effects of this application include but are not limited to:

[0028] 1. The formaldehyde-free white latex and preparation method thereof of the present application adopt modified polyvinyl acetate emulsion, plant protein, composite filler and environmentally friendly additives. The components work synergistically with each other, have excellent performance, achieve formaldehyde-free, green and environmentally friendly, and meet modern environmental protection requirements; wherein, the modified polyvinyl acetate emulsion and the plant protein complement each other and can effectively enhance the bonding performance of the white latex; the metal ions in the inorganic filler can chelate with the active groups in the plant protein, thereby generating cross-linking in the system, improving the mechanical properties, water resistance and thermal stability of the white latex; the addition of functional fillers can not only improve the compatibility between the inorganic filler and the matrix, but also further enhance the mechanical properties, water resistance and thermal stability of the white latex; the solubilizer ensures the compatibility between the components and the stability of the system, the plasticizer can optimize the flexibility of the film and adapt to the thermal expansion and contraction of the substrate, and the preservative effectively prevents the growth of microorganisms and extends the shelf life of the product.

[0029] 2. The formaldehyde-free white latex of the present application and its preparation method, the lignin contains aromatic / aliphatic hydroxyl functional groups, which can generate active lignin free radicals, thereby initiating in situ free radical polymerization of diunsaturated carboxylic acids, so that polydiunsaturated carboxylic acid chains grow from the lignin. At this time, the introduction of carboxyl groups on the lignin significantly improves its dispersion performance; then a modified polyvinyl acetate emulsion is prepared by a blending method, and the strong hydrogen bond interaction between the carboxyl groups in the polydiunsaturated carboxylic acid grafted lignin and the polar groups (such as -C=O and -OH) in the polyvinyl acetate, this intermolecular hydrogen bonding interaction, enables the formation of a large number of physical cross-linked network structures, which not only enhances the interfacial bonding force between the two phases and significantly improves the bonding strength, but also improves the mechanical properties and water resistance of the composite system. DETAILED DESCRIPTION

[0030] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0031] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. The raw materials or instruments used, if the manufacturers are not specified, are all conventional products that can be purchased commercially.

[0032] Example 1

[0033] A method for preparing formaldehyde-free white latex comprises the following steps:

[0034] (1) 6.5 parts of montmorillonite, 1.5 parts of cellulose nanowhiskers, and 3 parts of silane coupling agent KH550 were mixed evenly, 20 parts of soy protein were added, and the mixture was stirred at 40°C for 20 minutes to obtain a mixed solution A;

[0035] (2) 23 parts of modified polyvinyl acetate emulsion, 0.5 parts of dibutyl phthalate, 0.1 parts of 5-chloro-2-methyl-4-isothiazoline-3-one and 55 parts of deionized water were mixed at 70° C. to obtain a mixed solution B;

[0036] (3) ultrasonically dispersing the mixed solution A in the mixed solution B at an ultrasonic frequency of 25 kHz to obtain formaldehyde-free white latex;

[0037] The preparation method of the modified polyvinyl acetate emulsion comprises the following steps:

[0038] S1. Dissolve maleic acid in deionized water, stir magnetically at 70°C for 5 minutes, and then add potassium hydroxide solution dropwise to obtain a maleic acid solution with a neutralization degree of 30%;

[0039] S2. Add lignin to deionized water and ultrasonically treat for 20 minutes to obtain a lignin dispersion. Then, add the maleic acid solution to the lignin dispersion at a weight ratio of maleic acid to lignin of 1.5:1. Stir continuously, then add ammonium persulfate containing 2 wt% lignin, introduce nitrogen, and magnetically stir at 70°C for 3 hours. Filter to obtain polymaleic acid-grafted lignin.

[0040] S3, adding polyvinyl alcohol having a vinyl acetate content of 1.5 wt% and sodium lauryl sulfate having a vinyl acetate content of 1 wt% to deionized water, stirring at 80° C. until completely dissolved, cooling to room temperature, adding vinyl acetate, mixing uniformly, then passing nitrogen, adding ammonium persulfate having a vinyl acetate content of 0.3 wt%, and raising the system temperature to 60° C. After completion of the reaction, adjusting the pH to 6, filtering, and obtaining a polyvinyl acetate emulsion;

[0041] S4. Blending the polymaleic acid grafted lignin with the polyvinyl acetate emulsion at a solid-liquid ratio of 0.3:1, and stirring for 10 minutes to obtain the modified polyvinyl acetate emulsion.

[0042] Example 2

[0043] A method for preparing formaldehyde-free white latex comprises the following steps:

[0044] (1) 6.5 parts of calcium carbonate, 3.5 parts of silicon dioxide and 5 parts of silane coupling agent KH560 were mixed evenly, 28 parts of wheat protein were added, and the mixture was stirred at 50°C for 25 minutes to obtain a mixed solution A;

[0045] (2) 30 parts of modified polyvinyl acetate emulsion, 0.8 parts of dioctyl phthalate, 0.2 parts of benzisothiazolinone and 60 parts of deionized water were mixed at 80° C. to obtain a mixed solution B;

[0046] (3) ultrasonically dispersing the mixed solution A in the mixed solution B at an ultrasonic frequency of 30 kHz to obtain formaldehyde-free white latex;

[0047] The preparation method of the modified polyvinyl acetate emulsion comprises the following steps:

[0048] S1. Dissolve methylene succinic acid in deionized water, stir magnetically at 80° C. for 10 minutes, and then add potassium hydroxide solution dropwise to obtain a methylene succinic acid solution with a neutralization degree of 40%;

[0049] S2. Add lignin to deionized water and ultrasonically treat for 30 minutes to obtain a lignin dispersion. Then, add the methylene succinic acid solution to the lignin dispersion at a weight ratio of methylene succinic acid to lignin of 2.2:1. Continue stirring. Then, add ammonium persulfate with a lignin content of 3.5 wt%. Pass nitrogen gas through the mixture. Magnetic stirring is performed at 80° C. for 4 hours. Filter to obtain polymethylene succinic acid-grafted lignin.

[0050] S3, adding polyvinyl alcohol having a vinyl acetate content of 2.3 wt% and sodium lauryl sulfate having a vinyl acetate content of 1.5 wt% to deionized water, stirring at 90° C. until completely dissolved, cooling to room temperature, adding vinyl acetate, mixing uniformly, then passing nitrogen, adding ammonium persulfate having a vinyl acetate content of 0.4 wt%, and raising the system temperature to 65° C. After completion of the reaction, adjusting the pH to 6.5, filtering, and obtaining a polyvinyl acetate emulsion;

[0051] S4. Blending the poly(methylene succinic acid) grafted lignin with a solid-liquid ratio of 0.4:1 with the poly(vinyl acetate) emulsion, and stirring for 15 minutes to obtain the modified poly(vinyl acetate) emulsion.

[0052] Example 3

[0053] A method for preparing formaldehyde-free white latex comprises the following steps:

[0054] (1) 7 parts of kaolin, 5 parts of cellulose nanofibers and 7 parts of silane coupling agent KH570 were mixed evenly, 35 parts of zein were added, and the mixture was stirred at 60°C for 30 minutes to obtain a mixed solution A;

[0055] (2) 38 parts of modified polyvinyl acetate emulsion, 1 part of dioctyl adipate, 0.3 parts of 2-methyl-4-isothiazoline-3-one and 65 parts of deionized water were mixed at 90° C. to obtain a mixed solution B;

[0056] (3) ultrasonically dispersing the mixed solution A in the mixed solution B at an ultrasonic frequency of 35 kHz to obtain formaldehyde-free white latex;

[0057] The preparation method of the modified polyvinyl acetate emulsion comprises the following steps:

[0058] S1. Dissolve cis-methylbutenedioic acid in deionized water, stir magnetically at 90° C. for 15 minutes, and then add potassium hydroxide solution dropwise to obtain a cis-methylbutenedioic acid solution with a neutralization degree of 50%;

[0059] S2. Add lignin to deionized water and ultrasonically treat for 40 minutes to obtain a lignin dispersion, then add the cis-methylbutenedioic acid solution to the lignin dispersion, with the weight ratio of cis-methylbutenedioic acid to lignin being 3:1, continue stirring, then add ammonium persulfate with a lignin content of 5 wt%, introduce nitrogen, magnetically stir at 90° C. for 5 hours, and filter to obtain poly-cis-methylbutenedioic acid-grafted lignin;

[0060] S3. Add polyvinyl alcohol having a vinyl acetate content of 3 wt% and sodium lauryl sulfate having a vinyl acetate content of 2 wt% to deionized water, stir at 100° C. until completely dissolved, cool to room temperature, add vinyl acetate, mix well, then introduce nitrogen, add ammonium persulfate having a vinyl acetate content of 0.5 wt%, and raise the system temperature to 70° C. After completion of the reaction, adjust the pH to 7, filter, and obtain a polyvinyl acetate emulsion;

[0061] S4. Blending polycis-methylbutenedioic acid grafted lignin with a solid-liquid ratio of 0.5:1 with polyvinyl acetate emulsion, and stirring for 20 minutes to obtain modified polyvinyl acetate emulsion.

[0062] Example 4

[0063] The difference from Example 2 is that the preparation method of the modified polyvinyl acetate emulsion comprises the following steps:

[0064] S1. Add polyvinyl alcohol having a vinyl acetate content of 2.3 wt% and sodium lauryl sulfate having a vinyl acetate content of 1.5 wt% to deionized water, stir at 90°C until completely dissolved, cool to room temperature, add vinyl acetate, mix well, then introduce nitrogen, add ammonium persulfate having a vinyl acetate content of 0.4 wt%, and raise the system temperature to 65°C. After completion of the reaction, adjust the pH to 6.5, filter, and obtain a polyvinyl acetate emulsion;

[0065] S2. Blending lignin with a solid-liquid ratio of 0.4:1 with polyvinyl acetate emulsion, and stirring for 15 minutes to obtain modified polyvinyl acetate emulsion.

[0066] Example 5

[0067] The difference from Example 2 is that methylene succinic acid is replaced by acrylic acid.

[0068] Comparative Example 1

[0069] A method for preparing formaldehyde-free white latex comprises the following steps:

[0070] (1) 6.5 parts of calcium carbonate, 3.5 parts of silicon dioxide and 5 parts of silane coupling agent KH560 were mixed evenly, 28 parts of wheat protein were added, and the mixture was stirred at 50°C for 25 minutes to obtain a mixed solution A;

[0071] (2) 30 parts of polyvinyl acetate emulsion, 0.8 parts of dioctyl phthalate, 0.2 parts of benzisothiazolinone and 60 parts of deionized water were mixed at 80° C. to obtain a mixed solution B;

[0072] (3) ultrasonically dispersing the mixed solution A in the mixed solution B at an ultrasonic frequency of 30 kHz to obtain formaldehyde-free white latex;

[0073] The preparation method of polyvinyl acetate emulsion comprises the following steps:

[0074] Polyvinyl alcohol with a vinyl acetate content of 2.3 wt% and sodium lauryl sulfate with a vinyl acetate content of 1.5 wt% were added to deionized water, stirred at 90° C. until completely dissolved, cooled to room temperature, and then vinyl acetate was added and mixed uniformly. Then, nitrogen was introduced, and ammonium persulfate with a vinyl acetate content of 0.4 wt% was added. The system temperature was raised to 65° C. After the reaction was completed, the pH was adjusted to 6.5, and the mixture was filtered to obtain a polyvinyl acetate emulsion.

[0075] Comparative Example 2

[0076] The difference from Example 2 is that no silicon dioxide is added.

[0077] Comparative Example 3

[0078] The difference from Example 2 is that no wheat protein is added.

[0079] Test example

[0080] The performance test of the formaldehyde-free white latex prepared in the above examples 1-5 and comparative examples 1-3 was carried out, wherein:

[0081] Free formaldehyde content test: GB / T 14074-2017 standard was used to measure the free formaldehyde content in the white latex of Examples 1-5 and Comparative Examples 1-3. The national standard value was ≤0.3.

[0082] Viscosity test: The white latex of Examples 1-5 and Comparative Examples 1-3 was placed in a beaker, and then placed in a constant temperature water bath at 25°C. The rotor was screwed into the connecting rod of the rotational viscometer and incorporated into the sample. The rotational viscometer was started at a speed of 10 r / min to perform the viscosity test.

[0083] Adhesive strength test: Two 30mm×30mm plywood specimens were used, and the white latex of Examples 1-5 and Comparative Examples 1-3 were evenly applied (100g / cm2 ), then press at 1Mpa for 24 hours, and then place at normal pressure for 48 hours, use a material mechanics testing machine to stretch the plate until the adhesive layer is damaged, record the maximum failure load, and the bonding strength of the white latex can be obtained;

[0084] Water resistance test: Two 30mm x 30mm plywood boards were glued together using the white glue of Examples 1-5 and Comparative Examples 1-3, respectively. After 24 hours, the two boards were firmly bonded together. The boards were then placed in boiling water. The time it took for the glue layer to crack and the boards to separate was used as an indicator of water resistance.

[0085] The results are shown in Table 1 below.

[0086] Table 1

[0087]

[0088]

[0089] It can be seen from the results in Table 1 that the formaldehyde-free white latex of the present application is green and environmentally friendly, reducing pollution to the environment; at the same time, the white latex of the present application has excellent performance in indicators such as bonding strength and water resistance, and has superior comprehensive performance, which can meet current market demand.

[0090] The foregoing is merely an embodiment of the present application, and the scope of protection of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application may have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc. made within the technical ideas and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A formaldehyde-free white latex, characterized in that: The invention comprises the following components in parts by weight: 23-38 parts of modified polyvinyl acetate emulsion, 8-12 parts of composite filler, 20-35 parts of vegetable protein, 3-7 parts of solubilizer, 0.5-1 part of plasticizer, 0.1-0.3 part of preservative, and 55-65 parts of deionized water; The composite filler is an inorganic filler and a functional filler in a weight ratio of 1: (0.2-0.8).

2. The formaldehyde-free white latex according to claim 1, characterized in that The preparation method of the modified polyvinyl acetate emulsion comprises the following steps: S1. Dissolve the dibasic unsaturated carboxylic acid in deionized water, stir magnetically at 70-90° C. for 5-15 minutes, and then add potassium hydroxide solution dropwise to obtain a dibasic unsaturated carboxylic acid solution with a neutralization degree of 30-50%; S2. Add lignin to deionized water and ultrasonically treat for 20-40 minutes to obtain a lignin dispersion, then add a diunsaturated carboxylic acid solution to the lignin dispersion, wherein the weight ratio of the diunsaturated carboxylic acid to the lignin is (1.5-3):1, and continue stirring. Then, add ammonium persulfate containing 2-5 wt% of lignin, introduce an inert atmosphere, and magnetically stir at 70-90° C. for 3-5 hours. Filter to obtain polydiunsaturated carboxylic acid grafted lignin; S3. Blending the polydiunsaturated carboxylic acid grafted lignin with a solid-liquid ratio of (0.3-0.5):1 with the polyvinyl acetate emulsion, and stirring for 10-20 minutes to obtain the modified polyvinyl acetate emulsion.

3. The formaldehyde-free white latex according to claim 2, characterized in that The dibasic unsaturated carboxylic acid is at least one of methylene succinic acid, maleic acid, fumaric acid and cis-methyl succinic acid.

4. The formaldehyde-free white latex according to claim 2, characterized in that The preparation method of the polyvinyl acetate emulsion comprises the following steps: Polyvinyl alcohol with a vinyl acetate content of 1.5-3 wt% and sodium lauryl sulfate with a vinyl acetate content of 1-2 wt% are added to deionized water, stirred at 80-100° C. until completely dissolved, cooled to room temperature, and then vinyl acetate is added and mixed uniformly. Then, an inert gas is introduced, and ammonium persulfate with a vinyl acetate content of 0.3-0.5 wt% is added. The system temperature is raised to 60-70° C. After the reaction is completed, the pH is adjusted to 6-7, and the mixture is filtered to obtain a polyvinyl acetate emulsion.

5. The formaldehyde-free white latex according to claim 1, characterized in that The inorganic filler is at least one of montmorillonite, kaolin, calcium carbonate and hydroxyapatite; The functional filler is at least one of silicon dioxide, cellulose nano whiskers and cellulose nanofibers.

6. The formaldehyde-free white latex according to claim 1, characterized in that The plant protein is at least one of soy protein, corn protein and wheat protein.

7. The formaldehyde-free white latex according to claim 1, characterized in that: The solubilizer is at least one of silane coupling agent KH550, silane coupling agent KH560 and silane coupling agent KH570.

8. The formaldehyde-free white latex according to claim 1, characterized in that: The plasticizer is at least one of dibutyl phthalate, dioctyl phthalate, dioctyl adipate and acetyl tributyl citrate.

9. The formaldehyde-free white latex according to claim 1, characterized in that: The preservative is at least one of benzisothiazolinone, 5-chloro-2-methyl-4-isothiazolin-3-one and 2-methyl-4-isothiazolin-3-one.

10. A method for preparing formaldehyde-free white latex, characterized in that: The following steps are involved: (1) Weighing the raw materials according to the weight proportions of the formaldehyde-free white latex according to any one of claims 1 to 9; (2) 8-12 parts of the composite filler and 3-7 parts of the solubilizer are mixed evenly, 20-35 parts of the plant protein are added, and the mixture is stirred at 40-60° C. for 20-30 minutes to obtain a mixed solution A; (3) 23-38 parts of modified polyvinyl acetate emulsion, 0.5-1 parts of plasticizer, 0.1-0.3 parts of preservative, and 55-65 parts of deionized water were mixed at 70-90° C. to obtain a mixed solution B; (4) Ultrasonic dispersion of mixed solution A in mixed solution B at an ultrasonic frequency of 25-35 kHz to obtain formaldehyde-free white latex.

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