Alkali lignin-based PVC stabilizer and preparation method thereof
A PVC stabilizer was prepared by reacting modified alkali lignin with aldehydes, which solved the toxicity and environmental problems of PVC heat stabilizers, improved the thermal stability of PVC, and effectively utilized the lignin in papermaking black liquor.
Patent Information
- Application Number
- CN202512002073.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-29
- Publication Date
- 2026-02-27
AI Technical Summary
Existing PVC heat stabilizers pose high toxicity and environmental risks, and traditional lignin modification methods have failed to effectively improve their compatibility and thermal stability with PVC.
A modified alkali lignin was reacted with highly active aldehydes to form a modified alkali lignin PVC stabilizer, which was then mixed with PVC to prepare an environmentally friendly PVC stabilizer.
It significantly improves the thermal stability of PVC, reduces the use of toxic additives, achieves environmental protection and cost-effectiveness, and expands the utilization value of lignin.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of high polymer materials, in particular to a heat stabilizer for polyvinyl chloride (PVC) and a new PVC material formed after adding the stabilizer, and more particularly to a PVC stabilizer based on modified alkali lignin. The stabilizer is obtained by chemically modifying alkali lignin, can effectively improve the thermal stability of PVC, reduce the use of toxic additives, and is suitable for the PVC plastic processing industry. BACKGROUND
[0002] Polyvinyl chloride (PVC) is a widely used plastic material, but its thermal stability is poor, and it is prone to thermal decomposition during processing, resulting in color change and performance degradation. Traditional heat stabilizers (such as lead salts) can inhibit decomposition, but have the problems of high toxicity, environmental unfriendliness, etc.
[0003] Lignin is a byproduct of papermaking black liquor, which has the advantages of being renewable, biodegradable, non-toxic and low cost, but its natural form has poor compatibility with PVC, and direct application has limited effect. In the prior art, lignin modification methods (such as hydroxymethylation) can improve its activity, but there is no report of using it as a special stabilizer for PVC. The research of Yue Xiaopeng (2011) and Wang Dizhen et al. (2000) shows that lignin has limited application in PVC composites and its performance is unstable. Therefore, it is urgent to develop an efficient and environmentally friendly lignin-based PVC stabilizer and its preparation method. SUMMARY
[0004] The purpose of the present application is to provide a PVC stabilizer based on modified alkali lignin and an optimized PVC material to overcome the high toxicity and environmental risk of existing stabilizers, and at the same time improve the thermal stability of PVC.
[0005] In order to achieve the above purpose, the technical scheme of the present application is as follows: The present application selects a preparation method of a PVC stabilizer based on modified alkali lignin, comprising the following steps: (1) adding an aldehyde substance to a liquid containing lignin or / and alkali lignin and reacting; (2) adding an aldehyde substance to a polyamine solution and reacting; (3) mixing the system obtained in step (2) with the system obtained in step (1) and continuing to react; (4) cooling the system obtained in step (3), adding acid, precipitating solid, separating solid and liquid, rinsing and drying the obtained solid to obtain the modified alkali lignin PVC stabilizer.
[0006] As a preferred technical solution, in step (1), the liquid containing lignin is the liquid obtained by regulating the raw materials of papermaking black liquor or the liquid obtained by dissolving lignin in water, and the liquid containing alkali lignin is the liquid obtained by dissolving papermaking black liquor or the liquid obtained by dissolving alkali lignin in water.
[0007] As a preferred technical solution, in step (1), the pH value of the liquid containing lignin or / and alkali lignin is first adjusted to 7-8, and then aldehydes are added to react.
[0008] As a preferred technical solution, in step (1), the aldehyde is at least one of formaldehyde, acetaldehyde and glyoxal, the weight ratio of the added aldehyde to lignin and / or alkali lignin is 0.5-0.6:1, and the reaction temperature is 60-95℃.
[0009] As a preferred technical solution, in step (2), the aldehyde is at least one of formaldehyde, acetaldehyde and glyoxal, the polyamine is at least one of melamine, urea, polyamino aromatic amine and fatty amine, the weight ratio of the added aldehyde to the polyamine is 1.5-1.6:1, and the reaction temperature is 60-95℃.
[0010] As a preferred technical solution, in step (3), the weight ratio of the mixed polyamine to lignin and / or alkali lignin is 0.3-0.5:1, and the reaction temperature is 60-95℃.
[0011] As a preferred technical solution, in step (4), the pH of the system when the solid product is precipitated is 3-4.
[0012] The present invention also selected the modified alkali lignin PVC stabilizer prepared by the above preparation method.
[0013] The present invention provides an optimized PVC material, the PVC material comprising PVC (polyvinyl chloride) and the modified alkali lignin PVC stabilizer.
[0014] As a preferred technical solution, the modified alkali lignin PVC stabilizer has a mass fraction of 0.1%-5% in the material.
[0015] The beneficial effects of this invention are: This invention innovatively selects alkali lignin and highly active aldehydes as the main raw materials. After reacting to obtain modified alkali lignin, it is then mixed with PVC for processing to obtain a modified alkali lignin PVC stabilizer.
[0016] This modified alkali lignin PVC stabilizer has low production costs and is environmentally friendly. It can completely replace toxic stabilizers (such as lead salts). When added to PVC materials, the thermal stability of PVC is significantly improved, resulting in excellent performance.
[0017] This invention can also utilize lignin (alkali lignin) in papermaking black liquor as a raw material, which not only effectively treats papermaking black liquor but also makes rational use of lignin, successfully turning waste into treasure and has broad market prospects. Attached Figure Description
[0018] Figure 1 Image of modified alkali lignin PVC stabilizer; Figure 2 Infrared spectral analysis of modified alkali lignin PVC stabilizer; Figure 3 Scanning electron microscope image of PVC after the addition of modified alkali lignin PVC stabilizer; Figure 4 The image shows the finished product of PVC molding after adding modified alkali lignin PVC stabilizer; Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings.
[0020] This invention uses highly active aldehydes and polyamines as the main raw materials. First, lignin (alkali lignin) is grafted and activated with aldehydes, while polyamines undergo condensation reaction under the action of aldehydes. Then, the two are mixed and reacted to obtain a modified alkali lignin.
[0021] Lignin is a biopolymer with a three-dimensional network structure formed by three phenylpropane units linked together by ether bonds and carbon-carbon bonds. It contains abundant aromatic ring structures, aliphatic and aromatic hydroxyl groups, and quinone groups and other active groups.
[0022] The structures of the three phenylpropane units of lignin are shown below:
[0023] Taking the guaiac propane unit as an example, its grafting activation reaction with aldehydes (such as formaldehyde) is as follows:
[0024] Polyamines (taking melamine as an example) can also undergo condensation polymerization under the action of aldehydes (taking formaldehyde as an example) to form polyamine-aldehyde polymers:
[0025] After mixing the first two, the polyamine aldehyde polymer can be grafted onto the activated lignin units:
[0026] The present invention will be described in detail below with reference to the embodiments, but the present invention is not limited thereto.
[0027] Example 1: Preparation of modified alkali lignin PVC stabilizer (1) Dissolve alkali lignin (powder obtained by drying papermaking black liquor, which contains alkali lignin such as sodium lignin phenolate and potassium lignin phenolate) in water at a weight ratio of 1:1.57, stir evenly, adjust its pH to 9, add formaldehyde at a weight ratio of alkali lignin to formaldehyde of 1:0.52, and stir the reaction at 88℃ for 3 hours. (2) Disperse melamine and water at a mass ratio of 1:0.4, and add formaldehyde dropwise to the melamine dispersion at a weight ratio of 1:1.52. Stir the reaction until the system is homogeneous (not exceeding 30 minutes) and the reaction temperature is 90℃. (3) Pour the homogeneous system obtained after the reaction in step (2) into the system obtained after the reaction in step (1) and mix. The weight ratio of melamine to alkali lignin after mixing is 0.4:1. Continue stirring and reacting for 3 hours at a reaction temperature of 90℃. (4) Add acid to the system obtained in step (3) to adjust the pH to 2, and after sedimentation, separate the solid and liquid. After rinsing and drying the obtained solid, the modified alkali lignin PVC stabilizer is obtained.
[0028] Example 2: Application Test of Stabilizer in PVC The thermal stability of PVC was tested according to the Congo Red method in GB / T 2917.1-2002: 100g of PVC was added to modified alkali lignin PVC stabilizer (0.1%-2% by mass), mixed, and placed in a test tube. The mixture was then heated in an oil bath at 180℃, and the thermal stability time was recorded. The test results of thermal stability are shown in the table below.
[0029] Results: The stability time was 8-10 minutes with 0.1% added and 24-25 minutes with 2% added, a significant improvement compared to pure PVC (7-8 minutes). When the addition exceeded 2%, the Congo red test paper was bleached, and no color change could be observed.
[0030] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. An optimized PVC material and its preparation method, characterized in that: The PVC material includes PVC and the modified alkali lignin PVC stabilizer obtained by the block copolymer preparation method described in Chinese patent document CN 113563553 A.
2. The PVC material according to claim 9, characterized in that: The modified alkali lignin PVC stabilizer has a mass fraction of 0.1%-5% in the optimized material.