阅读说明：本技术 木质素/埃洛石杂化填料及其制备方法和应用 (Lignin/halloysite hybrid filler and preparation method and application thereof ) 是由 孙攀 解希铭 赵青松 唐功庆 刘苹 段海东 于 2019-01-10 设计创作，主要内容包括：本发明涉及橡胶助剂领域,公开了一种木质素/埃洛石杂化填料及其制备方法和应用,包括：(1)将埃洛石纳米管分散于溶解有木质素的溶液I中,形成溶液II；(2)将所述溶液II依次在0.05～0.3MPa的第一压力条件下和0～0.03MPa的第二压力条件下分别保持第一时间和第二时间,所述第一时间为1～500min,所述第二时间为5～400minn；(3)重复进行步骤(2)至少两次；(4)将步骤(3)获得的混合物与功能化合物进行接触反应,所述功能化合物为含反应基团二硫键化合物。本发明获得的木质素/埃洛石杂化填料提高了对橡胶的补强作用。(The invention relates to the field of rubber additives, and discloses a lignin/halloysite hybrid filler and a preparation method and application thereof, wherein the lignin/halloysite hybrid filler comprises the following steps: (1) dispersing halloysite nanotubes in a solution I in which lignin is dissolved to form a solution II; (2) sequentially keeping the solution II under a first pressure condition of 0.05-0.3 MPa and a second pressure condition of 0-0.03 MPa for a first time and a second time respectively, wherein the first time is 1-500 min, and the second time is 5-400 minn; (3) repeating the step (2) at least twice; (4) and (4) carrying out contact reaction on the mixture obtained in the step (3) and a functional compound, wherein the functional compound is a disulfide bond compound containing a reactive group. The lignin/halloysite hybrid filler obtained by the invention improves the reinforcing effect on rubber.)

1. A lignin/halloysite hybrid filler, characterized in that it is prepared by a process comprising the following operations: the method comprises the steps of dispersing halloysite nanotubes in a solution I dissolved with lignin to form a solution II, sequentially keeping the solution II under a first pressure condition and a second pressure condition for 1-500 min and 5-400 min respectively, wherein the first pressure is higher than the second pressure, repeating at least twice circulating operation under the first pressure condition and the second pressure condition, and then carrying out contact reaction on the obtained mixture and a functional compound, wherein the functional compound is a disulfide bond compound containing at least one reaction group selected from chlorine, carboxyl, carboxylate, acryloyl chloride, alkoxy and isocyanate.

2. The filler according to claim 1, wherein each of the first pressure conditions is independently 0.05 to 0.3 MPa; and each of the second pressure conditions is independently 0 to 0.03 MPa;

preferably, each of the first pressure conditions is independently 0.07 to 0.1 MPa; and each of the second pressure conditions is independently 0 to 0.02 MPa.

3. A method of making a lignin/halloysite hybrid filler, the method comprising:

(1) dispersing halloysite nanotubes in a solution I in which lignin is dissolved to form a solution II;

(2) sequentially keeping the solution II under a first pressure condition of 0.05-0.3 MPa and a second pressure condition of 0-0.03 MPa for a first time and a second time respectively, wherein the first time is 1-500 min, and the second time is 5-400 min;

(3) repeating the step (2) at least twice;

(4) and (3) carrying out contact reaction on the mixture obtained in the step (3) and a functional compound, wherein the functional compound is a disulfide bond compound containing at least one reaction group selected from chlorine, carboxyl, carboxylate, acryloyl chloride, alkoxy and isocyanate.

4. The method according to claim 3, wherein in the step (1), the concentration of the lignin in the solution I is 10-150 g/L;

preferably, in the step (1), the weight ratio of the halloysite nanotubes to the lignin is 1: 5 to 10: 1.

5. the method according to claim 3, wherein, in step (1), the solvent in the solution I is selected from at least one of acetone, petroleum ether, n-hexane, diethyl ether, dichloromethane, n-pentane, tetrahydrofuran, ethyl acetate, acetonitrile, butanone, methanol, anhydrous ethanol, dioxane, isopropanol and glacial acetic acid;

preferably, in step (1), the halloysite nanotubes are dispersed in the solution I under ultrasonic conditions.

6. The method according to any one of claims 3 to 5, wherein, in the step (2), the first pressure condition is 0.07 to 0.1 MPa;

preferably, the second pressure condition is 0-0.02 MPa.

7. The method according to any one of claims 3 to 6, wherein in step (2), the first time is 5 to 200min, and the second time is 15 to 150 min;

preferably, in the step (2), the first time is 15-90 min, and the second time is 30-60 min.

8. The method according to any one of claims 3 to 7, wherein in step (3), the first time and the second time when step (2) is repeated are the same as or different from the first time and the second time in step (2), respectively, the first time in step (3) is 1 to 500min, respectively, and the second time in step (3) is 5 to 400min, respectively;

preferably, the first time in the step (3) is 5-200 min respectively and the second time in the step (3) is 15-150 min respectively and independently;

preferably, the first time in step (3) is 15-90 min independently, and the second time in step (3) is 30-60 min independently.

9. The method according to any one of claims 3 to 7, wherein in step (4), the conditions of the contact reaction comprise: the reaction temperature is 30-80 ℃, and the reaction time is 1-48 h;

preferably, in the step (4), the weight ratio of the dosage of the functional compound to the dosage of the halloysite nanotube is (0.05-0.8): 1.

10. the method according to any one of claims 3 to 7, wherein, in step (4), the functional compound is at least one of disulfide dichloride, bis- (γ -triethoxysilylpropyl) tetrasulfide, bis- (γ -triethoxysilylpropyl) disulfide, and dithio diacid;

preferably, the dithiodiacid is selected from at least one of dithiodipropionic acid, dithiodibutanoic acid and cystine.

11. The method of claim 3, wherein the method further comprises: after the step (4), filtering, washing and drying the solid product obtained after the contact reaction in sequence.

12. The method of claim 3, wherein the method comprises:

(1) dispersing halloysite nanotubes in a solution I in which lignin is dissolved to form a solution II;

(2) sequentially keeping the solution II under a first pressure condition of 0.05-0.3 MPa and a second pressure condition of 0-0.03 MPa for a first time and a second time respectively, wherein the first time is 1-500 min, and the second time is 5-400 min;

(3) repeating the step (2) at least twice;

(4) carrying out contact reaction on the mixture obtained in the step (3) and a functional compound in the presence of a protective gas, wherein the functional compound is a disulfide bond compound containing at least one reaction group selected from chlorine, carboxyl, carboxylate, acryloyl chloride, alkoxy and isocyanate;

(5) and sequentially filtering, washing and drying the solid product obtained after the contact reaction.

13. A lignin/halloysite hybrid filler prepared by the method of any one of claims 3-12.

14. Use of a lignin/halloysite hybrid filler according to any one of claims 1-2 and 13 as a reinforcing agent for rubber.

15. The use according to claim 14, wherein the rubber is at least one of nitrile rubber, styrene butadiene rubber, natural rubber and butadiene rubber.

Technical Field

The invention relates to the field of rubber additives, in particular to a lignin/halloysite hybrid filler, a method for preparing the lignin/halloysite hybrid filler, the lignin/halloysite hybrid filler prepared by the method and application thereof.

Background

The lignin is a byproduct in the paper industry, can be used as a rubber filler to realize high filling in rubber, and achieves the effects of reducing the rubber consumption and controlling the cost.

The lignin molecule contains active groups such as aromatic group, phenolic hydroxyl group, alcoholic hydroxyl group, carbonyl group, methoxyl group, carboxyl group, conjugated double bond, etc., and can be used as dispersant of inorganic filler. Meanwhile, the lignin contains a large number of hindered phenol structures, has certain capturing capacity on free radicals, and can effectively improve the thermo-oxidative aging resistance of the rubber.

Halloysite Nanotubes (HNTs) are a natural nanotube-like material, with Al in the inner lumen of the tube₂O₃SiO on the outer surface₂And the two ends of the tube are provided with hydroxyl groups, and the tube can be used as a reinforcing agent of rubber materials. Due to the higher length-diameter ratio, the addition part of the halloysite nanotube used as the filler for preparing the composite material is far lower than that of the granular filler. Meanwhile, the functional auxiliary agent is loaded in the halloysite nanotube, and the slow release effect of the functional auxiliary agent is utilized to ensure that the functional auxiliary agent has a wide application prospect when being used as a functional filler for a rubber composite material.

However, the halloysite nanotubes have small particle size and are easy to agglomerate in the polymer, and the reinforcing effect is not ideal if the halloysite nanotubes are directly filled in the polymer matrix. Moreover, the performance of single filler reinforced polymers is increasingly unable to meet the industrial requirements for high performance of rubber composites.

In the composite material prepared by directly blending the two fillers with the polymer matrix, the two fillers exist independently in the polymer and generally do not have the synergistic effect of reinforcing the polymer. For example, CN101525447A discloses the use of lignin-modified kaolin as a rubber reinforcing agent. CN105778156A reports that rubber composite filler of two kinds of nano particles is prepared based on thiol chemical reaction, although the prior art can change the surface property of the filler and lead the filler to be dispersed in rubber more uniformly, because of high price of a modifier, complex process and high production cost, the methods are not widely applied, and the rubber composite filler of the prior art has insufficient thermal oxidation aging resistance.

Therefore, the molecular level composite hybridization of the two fillers to prepare the novel reinforcing filler has been a trend in the rubber industry.

The micromolecule anti-aging agent can move among elastomer macromolecule cross-linked networks and is enriched on the surface of the elastomer to generate a 'blooming' phenomenon, so the highest adding part of the anti-aging agent in the elastomer formula is strictly limited. Lignin is often used as a filler and an anti-aging agent, the filling amount of the lignin is often more, and the lignin can partially or completely replace a small molecular anti-aging agent for use. Meanwhile, the requirement on aging-resistant rubber is higher and higher, the research on the supported rubber antioxidant is promoted, and the antioxidant is supported in the nano tube cavity to realize the long-term effect and controllability of thermal-oxidative aging resistance, so that the method has higher application value. The dual advantages of anti-aging and reinforcement realized by loading lignin into the halloysite nanotube cavity are not reported in the prior literature.

Disclosure of Invention

One of the purposes of the invention is to overcome the defects that the single filler is not easy to disperse in the rubber and the effect of reinforcing the rubber is not ideal in the prior art.

The invention also aims to overcome the defect that the composite material prepared by blending more than two fillers and a polymer matrix in the prior art has insufficient thermal-oxidative aging resistance.

In order to achieve the above object, a first aspect of the present invention provides a lignin/halloysite hybrid filler, which is prepared by a method comprising: the method comprises the steps of dispersing halloysite nanotubes in a solution I dissolved with lignin to form a solution II, sequentially keeping the solution II under a first pressure condition and a second pressure condition for 1-500 min and 5-400 min respectively, wherein the first pressure is higher than the second pressure, repeating at least twice circulating operation under the first pressure condition and the second pressure condition, and then carrying out contact reaction on the obtained mixture and a functional compound, wherein the functional compound is a disulfide bond compound containing at least one reaction group selected from chlorine, carboxyl, carboxylate, acryloyl chloride, alkoxy and isocyanate.

In order to achieve the above object, a second aspect of the present invention provides a method of preparing a lignin/halloysite hybrid filler, the method comprising:

(1) dispersing halloysite nanotubes in a solution I in which lignin is dissolved to form a solution II;

(2) sequentially keeping the solution II under a first pressure condition of 0.05-0.3 MPa and a second pressure condition of 0-0.03 MPa for a first time and a second time respectively, wherein the first time is 1-500 min, and the second time is 5-400 min;

(3) repeating the step (2) at least twice;

(4) and (3) carrying out contact reaction on the mixture obtained in the step (3) and a functional compound, wherein the functional compound is a disulfide bond compound containing at least one reaction group selected from chlorine, carboxyl, carboxylate, acryloyl chloride, alkoxy and isocyanate.

A third aspect of the invention provides a lignin/halloysite hybrid filler prepared by the method of the second aspect.

A fourth aspect of the invention provides the use of the lignin/halloysite hybrid filler of the third aspect as a reinforcing agent for rubber.

According to the invention, vacuum adsorption of a lignin solution is realized through a halloysite nanotube cavity carrier, so that a supported halloysite nanotube is obtained.

Active groups at two ends of a disulfide bond compound containing reaction groups are utilized to graft lignin onto the surface of the load type halloysite nanotube, hydroxyl on the surface of the halloysite nanotube is consumed, the dispersion of the nanotube and the lignin in a rubber matrix is improved, and the reinforcing effect on rubber is improved.

Meanwhile, a disulfide bond compound containing a reactive group is introduced to form a supported rubber vulcanizing agent taking a hybrid filler as a carrier, so that the traditional rubber vulcanizing agent can be partially replaced, the vulcanizing efficiency is improved, and the appearance of free sulfur and vulcanization reversion is reduced.

The lignin/halloysite hybrid filler has strong interaction with rubber, improves the dispersion between a rubber matrix and the filler, and achieves the effect of improving the mechanical property of the rubber. Meanwhile, the lignin with the anti-aging function is loaded and bonded by sulfur bonds, so that the thermal oxidation aging resistance of the rubber material can be further improved. In addition, the sulfur-containing compound on the covalent bonding enables the nanotube carrier and the lignin to directly generate a crosslinking bond with higher bonding energy with the rubber molecular chain.

The lignin/halloysite hybrid filler provided by the invention is simple and convenient in preparation process, simple in separation process, reusable in solvent, strong in preparation reproducibility, and beneficial to cost reduction and industrial popularization.

The method of the invention also has the following specific advantages:

1. according to the invention, the halloysite nanotube is used for loading lignin, and hydroxyl in the inner cavity of the nanotube and more active groups on the surface of the lignin form hydrogen bond interaction, so that the adsorption capacity of the inner cavity to the lignin is improved, and the long-acting property of the slow release of the lignin serving as an anti-aging agent is ensured.

2. According to the invention, the sulfur-containing bond compound is used for grafting lignin to the halloysite nanotube, and the reaction of the sulfur-containing bond compound and the hydroxyl on the surface of the nanotube reduces the surface energy of the nanotube carrier, reduces the occurrence of agglomeration phenomenon, is beneficial to the dispersion of the hybrid filler in rubber, and is finally beneficial to the cooperative reinforcement of rubber materials. Meanwhile, the disulfide bond compound on the covalent bonding enables the nanotube carrier and the lignin to be directly crosslinked with a rubber molecular chain, and the crosslinking bond is higher than that formed by the traditional insoluble sulfur vulcanizing agent, so that the vulcanized rubber has better aging resistance.

3. According to the invention, lignin is loaded and grafted on the surface of the halloysite nanotube after being dissolved, the contact area between the lignin and the halloysite nanotube is large, and the reaction is sufficient, so that the obtained hybrid filler realizes the effect of combining three agents, namely a rubber reinforcing agent, an anti-aging agent and a vulcanizing agent, which is a function that other single fillers do not have; namely, the introduction of the hybrid filler can reduce the dosage of the reinforcing agent, the anti-aging agent and the vulcanizing agent.

Drawings

FIG. 1 is a scanning electron micrograph of the lignin/halloysite hybrid filler T1 prepared in example 1.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

Unless otherwise specified, the pressures referred to in the present invention are gauge pressures.

As previously mentioned, a first aspect of the invention provides a lignin/halloysite hybrid filler prepared by a process comprising: the method comprises the steps of dispersing halloysite nanotubes in a solution I dissolved with lignin to form a solution II, sequentially keeping the solution II under a first pressure condition and a second pressure condition for 1-500 min and 5-400 min respectively, wherein the first pressure is higher than the second pressure, repeating at least twice circulating operation under the first pressure condition and the second pressure condition, and then carrying out contact reaction on the obtained mixture and a functional compound, wherein the functional compound is a disulfide bond compound containing at least one reaction group selected from chlorine, carboxyl, carboxylate, acryloyl chloride, alkoxy and isocyanate.

Preferably, in the first aspect, each of the first pressure conditions is independently 0.05 to 0.3 MPa; and each of the second pressure conditions is independently 0 to 0.03 MPa.

More preferably, in the first aspect, each of the first pressure conditions is independently 0.07 to 0.1 MPa; and each of the second pressure conditions is independently 0 to 0.02 MPa.

As previously mentioned, a second aspect of the invention provides a method of preparing a lignin/halloysite hybrid filler, the method comprising:

(1) dispersing halloysite nanotubes in a solution I in which lignin is dissolved to form a solution II;

(2) sequentially keeping the solution II under a first pressure condition of 0.05-0.3 MPa and a second pressure condition of 0-0.03 MPa for a first time and a second time respectively, wherein the first time is 1-500 min, and the second time is 5-400 min;

(3) repeating the step (2) at least twice;

(4) and (3) carrying out contact reaction on the mixture obtained in the step (3) and a functional compound, wherein the functional compound is a disulfide bond compound containing at least one reaction group selected from chlorine, carboxyl, carboxylate, acryloyl chloride, alkoxy and isocyanate.

Preferably, in the step (1), the concentration of the lignin in the solution I is 10-150 g/L.

Preferably, in the step (1), the weight ratio of the halloysite nanotubes to the lignin is 1: 5 to 10: 1.

preferably, in step (1), the solvent in the solution I is at least one selected from the group consisting of acetone, petroleum ether, n-hexane, diethyl ether, dichloromethane, n-pentane, tetrahydrofuran, ethyl acetate, acetonitrile, butanone, methanol, anhydrous ethanol, dioxane, isopropanol, and glacial acetic acid. More preferably, the solvent in the solution I is at least one selected from the group consisting of acetone, petroleum ether, ethyl acetate, n-hexane, acetonitrile, isopropanol and methanol.

According to the present invention, the halloysite nanotubes may be various existing halloysite nanotubes that can be used to improve the mechanical properties of epoxy nanomaterials, and they may be commercially available, for example, from chengtai indigenous clay ltd. The size of the halloysite nanotubes is not particularly limited in the invention as long as the halloysite nanotubes can be well dispersed, and preferably, the outer diameter of the halloysite nanotubes is 40-150nm, the inner diameter is 10-25nm, and the length is 100-2000 nm.

Preferably, in step (1), the halloysite nanotubes are dispersed in the solution I under ultrasonic conditions.

In step (1), the conditions of the ultrasound are not particularly limited, and for example, the conditions of the ultrasound may include: the temperature is 5-40 ℃, the time is 5-180 min, and the frequency is 5-50 Hz.

According to a preferred embodiment, in the step (2), the first pressure condition is 0.07 to 0.1 MPa.

According to another preferred embodiment, in the step (2), the second pressure condition is 0 to 0.02 MPa.

In order to further improve the reinforcing effect of the obtained lignin/halloysite hybrid filler on rubber, preferably, in the step (2), the first time is 5-200 min, and the second time is 15-150 min. More preferably, in the step (2), the first time is 15-90 min, and the second time is 30-60 min.

Preferably, in the step (3), the first time and the second time when the step (2) is repeatedly performed are the same as or different from the first time and the second time in the step (2), the first time in the step (3) is 1 to 500min independently, and the second time in the step (3) is 5 to 400min independently.

Preferably, the first time in step (3) is 5-200 min independently, and the second time in step (3) is 15-150 min independently. More preferably, the first time in step (3) is 15-90 min and the second time in step (3) is 30-60 min.

Step (3) of the present invention is a step of repeating step (2) at least two times, that is, the method of the present invention performs step (2) at least 3 times.

Preferably, in step (4), the contact reaction conditions include: the reaction temperature is 30-80 ℃, and the reaction time is 1-48 h.

Preferably, in the step (4), the weight ratio of the dosage of the functional compound to the dosage of the halloysite nanotube is (0.05-0.8): 1.

preferably, in the step (4), the functional compound is at least one of disulfide dichloride, bis- (γ -triethoxysilylpropyl) tetrasulfide, bis- (γ -triethoxysilylpropyl) disulfide, and dithio diacid. More preferably, the dithiodiacid is dithiodipropionic acid, dithiodibutanoic acid and/or cystine.

Preferably, said step (4) of the present invention is carried out in the presence of a protective gas, such as nitrogen, argon, etc.

Preferably, the method further comprises: after the step (4), filtering, washing and drying the solid product obtained after the contact reaction in sequence.

Preferably, the lignin is one or more of organic solvent lignin extracted from wood fiber by a solvent method, enzymolysis lignin extracted from ethanol by fermentation and high-boiling alcohol lignin.

According to a preferred embodiment, the method of the invention comprises:

(1) dispersing halloysite nanotubes in a solution I in which lignin is dissolved to form a solution II;

(2) sequentially keeping the solution II under a first pressure condition of 0.05-0.3 MPa and a second pressure condition of 0-0.03 MPa for a first time and a second time respectively, wherein the first time is 1-500 min, and the second time is 5-400 min;

(3) repeating the step (2) at least twice;

(4) carrying out contact reaction on the mixture obtained in the step (3) and a functional compound in the presence of a protective gas, wherein the functional compound is a disulfide bond compound containing at least one reaction group selected from chlorine, carboxyl, carboxylate, acryloyl chloride, alkoxy and isocyanate;

(5) and sequentially filtering, washing and drying the solid product obtained after the contact reaction.

As previously mentioned, a third aspect of the present invention provides a lignin/halloysite hybrid filler produced by the method of the second aspect.

As previously mentioned, a fourth aspect of the invention provides the use of the lignin/halloysite hybrid filler of the first and third aspects as a reinforcing agent for rubber.

Preferably, the rubber is at least one of nitrile rubber, styrene butadiene rubber, natural rubber and butadiene rubber.

The specific application method of the lignin/halloysite hybrid filler as the reinforcing agent of the rubber is not particularly limited, and various application methods conventional in the art can be adopted, such as mixing the lignin/halloysite hybrid filler as the reinforcing agent and other components, and vulcanizing the obtained rubber compound. Several methods of application of the lignin/halloysite hybrid filler of the invention as a reinforcing agent are exemplified in the examples of the invention, and the person skilled in the art should not be understood as a limitation of the invention.

The present invention will be described in detail below by way of examples. In the following examples, various raw materials used unless otherwise specified are commercially available.

And (3) enzymolysis of lignin: produced by Shandong Longli biological science and technology Co., Ltd, the lignin content is more than or equal to 80 percent, the phenolic hydroxyl content is more than or equal to 3.0 percent, and the number average molecular weight is 3850;

halloysite nanotubes: white powder in a harmonization ceramic filling plant at the exit of the Danjiang province of Hubei province has the diameter distribution range of 50-200 nm and the length distribution range of 500-5000 nm;

solution polymerized styrene-butadiene rubber: 2636, a product of Yanshan division of Beijing, petrochemical, China, having a styrene content of 23 wt%, a vinyl content of 63 wt%, an oil content of 27 wt%, and a Mooney viscosity of 60;

l G3250, acrylonitrile content 41.5 wt%, Mooney viscosity 55;

bis- (γ -triethoxysilylpropyl) tetrasulfide and bis- (γ -triethoxysilylpropyl) disulfide: hangzhou Jessica chemical Co., Ltd;

disulfide dichloride: shanghai Aladdin Biotechnology Ltd, molecular weight 135.04;

dithiodipropionic acid and dithiodibutanoic acid: shanghai Michelle chemical technology, Inc., analytically pure;

zinc oxide, stearic acid, an accelerator TBBS (N-tertiary butyl-2-benzothiazole sulfonamide), sulfur and other rubber auxiliaries: purchased from chemical reagents of yinaoka, beijing, chemically pure;

acetone, ethanol, petroleum ether and other chemical reagents are purchased from Beijing chemical reagent factories.

The rubber processing and testing equipment conditions in the following examples and comparative examples are shown in Table 1:

TABLE 1

And (3) testing tensile property: according to the national standard GB/T528-2009, the stretching speed is 500mm/min, and the testing temperature is 23 ℃. The effective portion of the sample had a length of 25mm and a width of 6 mm. For each set of samples, 10 replicates were run and the results averaged.