阅读说明：本技术 一种纸基摩擦材料用碳纤维的改性方法 (Modification method of carbon fiber for paper-based friction material ) 是由 程合丽 张银华 秦亮 李国平 计德林 于 2021-08-24 设计创作，主要内容包括：本发明涉及一种纸基摩擦材料用碳纤维的改性方法,所属纸基摩擦材料制备技术领域,包括如下操作步骤：第一步：碳纤维预处理体系。第二步：碳纤维预处理工艺。第三步：碳纤维的层组装沉积改性体系,将上述碳纤维的悬浮液作为基体进行层沉积改性,层沉积吸附改性采用多层交替沉积的方式,改性剂分为不同阴阳离子强度的聚合物。第四步：碳纤维的层组装沉积改性工艺。重复以上步骤过程,改性3～4次循环后,过滤干燥后得到改性碳纤维。得到的碳纤维即可作为纸基摩擦材料用组份进行添加。具有工艺简单和能耗低的优点。解决增强纤维在纸基摩擦材料制备过程中的分散和结合等技术问题。适合纸基摩擦材料规模化生产过程中对碳纤维进行改性。(The invention relates to a method for modifying carbon fibers for a paper-based friction material, which belongs to the technical field of preparation of the paper-based friction material and comprises the following operation steps: the first step is as follows: a carbon fiber pretreatment system. The second step is that: a carbon fiber pretreatment process. The third step: the carbon fiber layer assembly deposition modification system is characterized in that the suspension of the carbon fiber is used as a matrix to carry out layer deposition modification, the layer deposition adsorption modification adopts a multilayer alternate deposition mode, and the modifier is polymers with different anion and cation strengths. The fourth step: a carbon fiber layer assembling, depositing and modifying process. And repeating the steps, modifying for 3-4 times, and filtering and drying to obtain the modified carbon fiber. The obtained carbon fiber can be used as a component for the paper-based friction material to be added. Has the advantages of simple process and low energy consumption. The technical problems of dispersion, combination and the like of the reinforced fibers in the preparation process of the paper-based friction material are solved. The method is suitable for modifying the carbon fiber in the large-scale production process of the paper-based friction material.)

1. A method for modifying carbon fibers for a paper-based friction material is characterized by comprising the following operation steps:

the first step is as follows: a carbon fiber pretreatment system, which prepares pretreatment liquid containing different surfactants for carbon fiber dispersion according to certain concentration;

the second step is that: the carbon fiber pretreatment process comprises the steps of adding chopped carbon fibers into a pretreatment solution, controlling the concentration of the carbon fibers, and pretreating for a certain time at a certain stirring speed;

the third step: the carbon fiber layer assembly deposition modification system is characterized in that the suspension of the carbon fiber is used as a matrix to carry out layer deposition modification, the layer deposition adsorption modification adopts a multilayer alternate deposition mode, and a modifier is a polymer with different anion and cation strengths;

the modifier is divided into polymers with different anionic and cationic strengths, and the cationic polymer comprises one or more of cationic polyacrylamide, cationic starch and cationic guar gum; the anionic polymer comprises one or more of anionic polyacrylamide, anionic waterborne polyurethane and styrene-acrylic emulsion;

the fourth step: the carbon fiber layer assembly deposition modification process comprises the steps of filtering pretreated and modified carbon fibers to obtain a carbon fiber filter layer, adding the carbon fiber filter layer into a cation deposition modifier system with specific concentration, and modifying at a certain stirring speed; after modification, filtering the fibers to obtain a first layer of deposition-modified carbon fibers; then adding the first layer of modified carbon fiber into an anion deposition modifier system with specific concentration according to the same modification process;

repeating the steps, modifying for 3-4 times, and filtering and drying to obtain modified carbon fibers; the obtained carbon fiber can be used as a component for the paper-based friction material to be added.

2. The method for modifying carbon fibers for paper-based friction materials according to claim 1, characterized in that: the carbon fiber pretreatment system is a surfactant system, and comprises one or a compound of more of sodium dodecyl benzene sulfonate, stearic acid, fatty glyceride of quaternary ammonium compound, sorbitan fatty acid and polysorbate, wherein the concentration of the treatment solution is 0.01-0.03 wt%, and deionized water is adopted for dilution.

3. The method for modifying carbon fibers for paper-based friction materials according to claim 1, characterized in that: controlling the concentration of the carbon fiber to be 2 wt% -4 wt%, and carrying out pretreatment for 30-60 min at a stirring speed of 60-80 r/min, wherein a spiral propeller blade is adopted for stirring.

4. The method for modifying carbon fibers for paper-based friction materials according to claim 1, characterized in that: the modifier is divided into polymers with different anionic and cationic strengths, and the content of effective components of the cationic polymer and the anionic polymer is kept to be 1: 1 in mass ratio; the concentration of the cationic deposition modifier system is 0.2-0.4 wt%, the stirring speed is 30-50 r/min, and the deposition modification time is 10-15 min; the concentration of the anion deposition modifier system is 0.2-0.4 wt%, the stirring speed is 20-30 r/min, and the deposition modification time is 10-15 min.

5. The method for modifying carbon fibers for paper-based friction materials according to claim 1, characterized in that: after 3-4 times of circulation, filtering by using a filter screen with more than 40 meshes, and drying by using vacuum drying, wherein the drying temperature is 60-70 ℃, the load pressure of the vacuum drying is 0.5-1 Mpa, and the drying time is 10-15 min.

Technical Field

The invention relates to the technical field of preparation of paper-based friction materials, in particular to a modification method of carbon fibers for a paper-based friction material.

Background

Paper-based friction materials are porous wet friction materials and are widely used in wet clutches and brakes of vehicles and construction machines due to their good friction characteristics. The paper-based friction material mainly comprises plant fibers (cotton fibers), reinforcing materials (carbon fibers and aramid fibers), crystalline oxidized mineral substances, antifriction materials (graphite), a binder, a friction performance regulator and the like, and is usually produced by adopting a papermaking mode.

With the increasing demands of the modern vehicle industry on the properties of paper-based friction materials, high-performance fibers, such as carbon fibers, are increasingly used therein. However, the carbon fiber has high surface inertia due to the preparation process and poor mixing dispersibility with the plant fiber, so that the problems of difficult dispersion, poor bonding property and the like exist in the process of adding the carbon fiber into the paper-based friction material, and the carbon fiber is limited to play a more important role in the paper-based friction material.

The carbon fiber is high-strength and high-modulus fiber with carbon content of more than 90 percent as high-performance synthetic fiber, has excellent high-temperature resistance, is mainly prepared by taking acrylic fiber and viscose fiber as raw materials and carrying out high-temperature oxidation and carbonization, and has strong chemical inertia. The Chinese patent of the granted patent No. CN1301286C discloses a carbon fiber reinforced paper-based friction material for a friction plate and a preparation method thereof. Carbon fiber or mixed fiber of carbon fiber and other fiber is taken as reinforced fiber (7-40%), which is sufficient to find the importance of the reinforced fiber in the paper-based friction material. However, the chemical inertness and hydrophobicity of the synthetic fiber in the wet papermaking process limit the exertion of the function of the synthetic fiber, so that the modification of the carbon fiber is imperative. At present, most of carbon fiber is modified in an organic solvent system, for example, a brake band based on modified carbon fiber and a preparation method thereof are disclosed in the patent publication No. CN106349526A Chinese invention patent, wherein the modification of the carbon fiber is carried out in an ethanol system, which is not beneficial to large-scale production.

Disclosure of Invention

The invention mainly solves the defects of difficult dispersion and poor bonding property in the prior art, and provides a method for modifying carbon fiber for a paper-based friction material, which has the advantages of simple process and low energy consumption. The technical problems of dispersion, combination and the like of the reinforced fibers in the preparation process of the paper-based friction material are solved. The method is suitable for modifying the carbon fiber in the large-scale production process of the paper-based friction material.

The technical problem of the invention is mainly solved by the following technical scheme:

a method for modifying carbon fibers for a paper-based friction material comprises the following operation steps:

the first step is as follows: the carbon fiber pretreatment system prepares pretreatment liquid containing different surfactants for carbon fiber dispersion according to certain concentration.

The second step is that: the carbon fiber pretreatment process comprises the steps of adding chopped carbon fibers into a pretreatment solution, controlling the concentration of the carbon fibers, and pretreating for a certain time at a certain stirring speed.

The third step: the carbon fiber layer assembly deposition modification system is characterized in that the suspension of the carbon fiber is used as a matrix to carry out layer deposition modification, the layer deposition adsorption modification adopts a multilayer alternate deposition mode, and the modifier is polymers with different anion and cation strengths.

The modifier is divided into polymers with different anionic and cationic strengths, and the cationic polymer comprises one or more of cationic polyacrylamide, cationic starch and cationic guar gum; the anionic polymer comprises one or more of anionic polyacrylamide, anionic waterborne polyurethane and styrene-acrylic emulsion.

The fourth step: the carbon fiber layer assembly deposition modification process comprises the steps of filtering pretreated and modified carbon fibers to obtain a carbon fiber filter layer, adding the carbon fiber filter layer into a cation deposition modifier system with specific concentration, and modifying at a certain stirring speed; after modification, filtering the fibers to obtain a first layer of deposition-modified carbon fibers; and then adding the first layer of modified carbon fiber into an anion deposition modifier system with specific concentration according to the same modification process.

And repeating the steps, modifying for 3-4 times, and filtering and drying to obtain the modified carbon fiber. The obtained carbon fiber can be used as a component for the paper-based friction material to be added.

Preferably, the carbon fiber pretreatment system is a surfactant system, and comprises one or a compound of several of sodium dodecyl benzene sulfonate, stearic acid, fatty glyceride of quaternary ammonium compound, sorbitan fatty acid and polysorbate, the concentration of the treatment solution is 0.01-0.03 wt%, and deionized water is adopted for dilution configuration.

Preferably, the concentration of the carbon fiber is controlled to be 2 wt% -4 wt%, the pretreatment is carried out for 30-60 min at the stirring speed of 60-80 r/min, and a spiral propelling blade is adopted for stirring.

Preferably, the modifier is divided into polymers with different anionic and cationic strengths, and the content of effective components of the cationic polymer and the anionic polymer is kept to be 1: 1 in mass ratio; the concentration of the cationic deposition modifier system is 0.2-0.4 wt%, the stirring speed is 30-50 r/min, and the deposition modification time is 10-15 min. The concentration of the anion deposition modifier system is 0.2-0.4 wt%, the stirring speed is 20-30 r/min, and the deposition modification time is 10-15 min.

Preferably, after 3-4 cycles, filtering by using a filter screen with more than 40 meshes, and drying by using vacuum drying, wherein the drying temperature is 60-70 ℃, the load pressure of the vacuum drying is 0.5-1 Mpa, and the drying time is 10-15 min.

The invention can achieve the following effects:

compared with the prior art, the invention provides the method for modifying the carbon fiber for the paper-based friction material, which has the advantages of simple process and low energy consumption. The technical problems of dispersion, combination and the like of the reinforced fibers in the preparation process of the paper-based friction material are solved. The method is suitable for modifying the carbon fiber in the large-scale production process of the paper-based friction material.

The method obtains the surface activated carbon fiber by means of pretreatment and multilayer adsorption, has simple modification process and low energy consumption, and is suitable for modifying the carbon fiber in the large-scale production process of the paper-based friction material. The pretreatment process mainly adopts specific surface active substances to carry out cleaning treatment on the surface of the carbon fiber in a water environment system; the alternate multi-layer deposition process mainly selects anionic and cationic polymers, realizes alternate adsorption self-assembly on the surface of the carbon fiber under the condition of a water system, and prepares the carbon fiber with excellent hydrophilic performance, which not only has better dispersibility, but also can obviously improve the uniformity of the paper-based friction material; in addition, the method can also endow the carbon fibers with high surface activity, so that the binding force between the carbon fibers and other components in the paper-based friction material is improved, and the material strength is improved.

Firstly, the method for activating the carbon fiber by the wet method normal temperature modification is simple in process, free of side reaction and high in efficiency.

Secondly, the main material used is water-soluble resin or surfactant, which has lower environmental hazard and influence on the product performance.

Finally, according to the preparation method provided by the invention, the carbon fiber is modified by the multilayer charge-opposite polymer, and the modified carbon fiber with stable performance is obtained after modification, so that the carbon fiber with good dispersibility and bonding force and stability can be provided for the preparation of the paper-based friction material.

Detailed Description

The technical scheme of the invention is further specifically described by the following embodiments.

Example 1: a method for modifying carbon fibers for a paper-based friction material comprises the following operation steps:

(1) preparation of carbon fiber pretreatment system

Dispersing sodium dodecyl benzene sulfonate according to the concentration of 0.01 wt% to obtain the carbon fiber pretreatment solution.

(2) Pretreatment process of carbon fiber

The concentration of the carbon fiber pretreatment is 2 wt%, the stirring speed is 60 r/min, and the pretreatment time is 30 min.

(3) Preparation of layer-assembled deposition modification system of carbon fiber

Cationic polyacrylamide and cationic starch are selected, and the anionic polymer comprises anionic polyacrylamide.

(4) Layer assembly deposition modification process of carbon fiber

The concentration of the cationic deposition modifier system is 0.2 wt%, the stirring speed is 30 r/min, and the deposition modification time is 10 min. The concentration of the anion deposition modifier system is 0.2 wt%, the stirring speed is 20 r/min, and the deposition modification time is 10 min.

(5) Vacuum drying is adopted, the drying temperature is 60 ℃, the load pressure of the vacuum drying is 0.5Mpa, and the drying time is 10 min.

(6) And preparing the paper-based friction material by using the obtained modified carbon fiber through a wet process, and performing performance detection.

Example 2: a method for modifying carbon fibers for a paper-based friction material comprises the following operation steps:

(1) pretreatment system preparation of carbon fibers

Stearic acid was dispersed at a concentration of 0.02 wt% to obtain a carbon fiber pretreatment solution.

(2) Pretreatment process of carbon fiber

The concentration of the carbon fiber pretreatment is 3 wt%, the stirring speed is 70 r/min, and the pretreatment time is 40 min.

(3) Preparation of layer-assembled deposition modification system of carbon fiber

Selecting cationic starch as a cationic modified polymer; anionic waterborne polyurethane is selected as the anionic modifier.

(4) Layer assembly deposition modification process of carbon fiber

The concentration of the cationic deposition modifier system is 0.3 wt%, the stirring speed is 40 r/min, and the deposition modification time is 12 min. The concentration of the anion deposition modifier system is 0.3 wt%, the stirring speed is 25 r/min, and the deposition modification time is 12 min.

(5) Vacuum drying is adopted, the drying temperature is 65 ℃, the load pressure of the vacuum drying is 0.7Mpa, and the drying time is 12 min.

(6) And preparing the paper-based friction material by using the obtained modified carbon fiber through a wet process, and performing performance detection.

Example 3: a method for modifying carbon fibers for a paper-based friction material comprises the following operation steps:

(1) pretreatment system preparation of carbon fibers

Stearic acid was dispersed at a concentration of 0.03 wt% to obtain a carbon fiber pretreatment solution.

(2) Pretreatment process of carbon fiber

The concentration of the carbon fiber pretreatment is 4 wt%, the stirring speed is 80 r/min, and the pretreatment time is 50 min.

(3) Preparation of layer-assembled deposition modification system of carbon fiber

Selecting cationic guar gum as a cationic modified polymer; styrene-acrylic emulsion is selected as an anion modifier.

(4) Layer assembly deposition modification process of carbon fiber

The concentration of the cationic deposition modifier system is 0.4 wt%, the stirring speed is 50 r/min, and the deposition modification time is 13 min. The concentration of the anion deposition modifier system is 0.4 wt%, the stirring speed is 30 r/min, and the deposition modification time is 13 min.

(5) Vacuum drying is adopted, the drying temperature is 65 ℃, the load pressure of the vacuum drying is 0.7Mpa, and the drying time is 13 min.

(6) And preparing the paper-based friction material by using the obtained modified carbon fiber through a wet process, and performing performance detection.

Example 4: a method for modifying carbon fibers for a paper-based friction material comprises the following operation steps:

(1) pretreatment system preparation of carbon fibers

Stearic acid was dispersed at a concentration of 0.03 wt% to obtain a carbon fiber pretreatment solution.

(2) Pretreatment process of carbon fiber

The concentration of the carbon fiber pretreatment is 4 wt%, the stirring speed is 80 r/min, and the pretreatment time is 60 min.

(3) Preparation of layer-assembled deposition modification system of carbon fiber

Selecting cationic guar gum as a cationic modified polymer; styrene-acrylic emulsion is selected as an anion modifier.

(4) Layer assembly deposition modification process of carbon fiber

The concentration of the cationic deposition modifier system is 0.4 wt%, the stirring speed is 50 r/min, and the deposition modification time is 14 min. The concentration of the anion deposition modifier system is 0.4 wt%, the stirring speed is 30 r/min, and the deposition modification time is 14 min.

(5) Vacuum drying is adopted, the drying temperature is 70 ℃, the load pressure of the vacuum drying is 0.8Mpa, and the drying time is 14 min.

(6) And preparing the paper-based friction material by using the obtained modified carbon fiber through a wet process, and performing performance detection.

Example 5: a method for modifying carbon fibers for a paper-based friction material comprises the following operation steps:

(1) pretreatment system preparation of carbon fibers

Stearic acid was dispersed at a concentration of 0.03 wt% to obtain a carbon fiber pretreatment solution.

(2) Pretreatment process of carbon fiber

The concentration of the carbon fiber pretreatment is 4 wt%, the stirring speed is 80 r/min, and the pretreatment time is 60 min.

(3) Preparation of layer-assembled deposition modification system of carbon fiber

Selecting cationic guar gum as a cationic modified polymer; styrene-acrylic emulsion is selected as an anion modifier.

(4) Layer assembly deposition modification process of carbon fiber

The concentration of the cationic deposition modifier system is 0.4 wt%, the stirring speed is 50 r/min, and the deposition modification time is 15 min. The concentration of the anion deposition modifier system is 0.4 wt%, the stirring speed is 30 r/min, and the deposition modification time is 15 min.

(5) Vacuum drying is adopted, the drying temperature is 70 ℃, the load pressure of the vacuum drying is 0.9Mpa, and the drying time is 15 min.

(6) And preparing the paper-based friction material by using the obtained modified carbon fiber through a wet process, and performing performance detection.

Example 6: a method for modifying carbon fibers for a paper-based friction material comprises the following operation steps:

(1) pretreatment system preparation of carbon fibers

Stearic acid was dispersed at a concentration of 0.03 wt% to obtain a carbon fiber pretreatment solution.

(2) Pretreatment process of carbon fiber

The concentration of the carbon fiber pretreatment is 4 wt%, the stirring speed is 80 r/min, and the pretreatment time is 60 min.

(3) Preparation of layer-assembled deposition modification system of carbon fiber

Selecting cationic guar gum as a cationic modified polymer; styrene-acrylic emulsion is selected as an anion modifier.

(4) Layer assembly deposition modification process of carbon fiber

The concentration of the cationic deposition modifier system is 0.4 wt%, the stirring speed is 50 r/min, and the deposition modification time is 15 min. The concentration of the anion deposition modifier system is 0.4 wt%, the stirring speed is 30 r/min, and the deposition modification time is 15 min.

(5) Vacuum drying is adopted, the drying temperature is 70 ℃, the load pressure of the vacuum drying is 0.9Mpa, and the drying time is 15 min.

(6) And preparing the paper-based friction material by using the obtained modified carbon fiber through a wet process, and performing performance detection.

Example 7: a method for modifying carbon fibers for a paper-based friction material comprises the following operation steps:

(1) pretreatment system preparation of carbon fibers

Stearic acid was dispersed at a concentration of 0.03 wt% to obtain a carbon fiber pretreatment solution.

(2) Pretreatment process of carbon fiber

The concentration of the carbon fiber pretreatment is 4 wt%, the stirring speed is 80 r/min, and the pretreatment time is 60 min.

(3) Preparation of layer-assembled deposition modification system of carbon fiber

Selecting cationic guar gum as a cationic modified polymer; styrene-acrylic emulsion is selected as an anion modifier.

(4) Layer assembly deposition modification process of carbon fiber

The concentration of the cationic deposition modifier system is 0.4 wt%, the stirring speed is 50 r/min, and the deposition modification time is 15 min. The concentration of the anion deposition modifier system is 0.4 wt%, the stirring speed is 30 r/min, and the deposition modification time is 15 min.

(5) Vacuum drying is adopted, the drying temperature is 70 ℃, the load pressure of the vacuum drying is 1.0Mpa, and the drying time is 15 min.

(6) And preparing the paper-based friction material by using the obtained modified carbon fiber through a wet process, and performing performance detection.

TABLE 1 paper-based Friction Material Properties

In conclusion, the method for modifying the carbon fiber for the paper-based friction material has the advantages of simple process and low energy consumption. The technical problems of dispersion, combination and the like of the reinforced fibers in the preparation process of the paper-based friction material are solved. The method is suitable for modifying the carbon fiber in the large-scale production process of the paper-based friction material.

The above description is only an embodiment of the present invention, but the structural features of the present invention are not limited thereto, and any changes or modifications within the scope of the present invention by those skilled in the art are covered by the present invention.