CN103087516A - Preparation method of nylon 6 and natural fiber composite material - Google Patents

Abstract

The invention discloses a preparation method of nylon 6 and natural fiber composite material, comprising the following steps: step 1, pretreating the natural fiber; step 2, placing the pretreated natural fiber in a freeze dryer for 24 hours, Then preheat; step 3, heat up the nylon 6 monomer caprolactam to 80 to 130°C, vacuumize and drain after melting, then add the initiator and vacuumize and drain, and finally add the activator, mix well and then vacuumize and drain to make Obtain the active material; step 4, add the active material to the natural fiber, quickly vacuumize, polymerize at the polymerization temperature for 0.5 to 1.5 hours, and after cooling, the composite material of nylon 6 and natural fiber is obtained. The material adopts the method of reaction processing, which not only makes the dispersion of natural fibers in the resin more uniform, but also helps to improve the interfacial properties of the composite material. The mechanical performance of this material is higher than that of ordinary nylon 6, and it has the advantages of environmental protection, so it can be used in a wide range of fields.

Description

Preparation method of nylon 6 and natural fiber composite material

technical field

The invention belongs to the field of polymer material preparation, and in particular relates to a preparation method of nylon 6 and natural fiber composite material.

Background technique

Composite materials occupy a place in the field of material science with irreplaceable advantages such as high strength and energy saving, but the waste of many composite materials has brought about increasingly serious environmental problems. With the continuous enhancement of people's awareness of environmental protection, the application of renewable, sustainable utilization and degradable biomaterials has attracted much attention and attention. Environmentally friendly materials are especially concerned by scholars. Therefore, the research and development of natural fiber-reinforced composite materials has become a research hotspot in the new century, such as Chinese patents CN102532661A, CN101003667A, and CN102002859A, which disclose polyethylene, polylactic acid, polyurethane and natural fiber respectively. Methods of preparation of composite materials.

As an engineering plastic, nylon 6 (PA6) has excellent mechanical properties, and has the advantages of wear resistance, oil resistance, solvent resistance, self-lubrication, self-extinguishing, corrosion resistance and good processing performance. Therefore, PA6 and natural fiber composites have great application potential. However, the melt processing temperature of nylon 6 is generally between 230 and 250??C, and the performance of natural fibers will be seriously reduced at this temperature. Therefore, this traditional molding method is not suitable for the preparation of natural fibers and nylon 6 composites. OK.

The reaction processing of nylon 6 composite material is based on anionic polymerized nylon 6, which is catalyzed by an alkali metal initiator and an activator at 150??C to 180?C for 0.5 to 1.5h, the conversion rate is as high as 95%, and the molecular At 80,000 to 100,000, the crystallinity can reach more than 45%. Compared with ordinary hydrolyzed nylon 6, anionic polymerized nylon 6 has the characteristics of low polymerization temperature, fast reaction rate, high conversion rate, high strength and elastic modulus. Therefore, if anionic polymerized nylon 6 and natural fibers are used for reaction processing, the adverse effects of high temperature on the properties of natural fibers can be avoided, and high-performance natural fiber composite materials can be obtained.

Unfortunately, so far, research on the reactive processing of natural fibers and nylon 6 has not been reported. It may be because anionic polymerization has extremely harsh requirements on the synthesis environment, and the polymerization is easily inhibited by proton impurities during the reaction process. The main component of natural fiber is cellulose, which is a linear macromolecule formed by connecting many D-glucopyranose anhydrides with ??-1,4 glycosidic bonds. Each base ring in the repeating unit of the cellulose molecule has Contains 3 highly active hydroxyl groups, which are prone to oxidation, esterification, etherification, graft copolymerization and other reactions. Therefore, many physical and chemical reactions will occur during the reaction between natural fibers and anionic polymerized nylon 6, which may hinder the anionic polymerization. Therefore, the traditional anionically polymerized nylon 6 polymerization system cannot be directly used in the reaction processing of natural fiber composites.

Contents of the invention

The purpose of this invention is to provide a kind of preparation method of nylon 6 and natural fiber composite material.

A kind of preparation method of nylon 6 and natural fiber composite material, comprises the steps:

Step one, carry out pretreatment to natural fiber, remove the colloid, grease, PVA, ash impurity contained therein; Sodium hydroxide, sodium dodecylbenzene sulfonate and sodium carbonate are respectively pressed by 3g/L, 3% weight percent Dissolve 2% by weight in deionized water and stir evenly, then add natural fiber at a weight ratio of 1:50, heat up to 90 to 100°C, and process for 3 to 5 hours under stirring;

Step 2. Dry the pretreated natural fiber in a freeze dryer with a temperature of -45°C and a vacuum of 9Pa for 24 hours, and then preheat it at 140 to 180°C and a vacuum of -0.03 to -0.09MPa;

Step 3. Heat up nylon 6 monomer caprolactam to 80-130 ℃, vacuumize and drain for 10 to 20 minutes after melting, then add initiator and vacuumize and drain for 10 to 20 minutes, and finally add activator, mix well and then vacuumize and drain 5 to 20min to prepare the active material;

Step 4: Add the active material prepared in step 3 to the natural fiber, the weight of the natural fiber is 1% to 200% of the weight of the active material; quickly evacuate to -0.03 to -0.09MPa, at a polymerization temperature of 140 to 180 ℃ Next, polymerize for 0.5 to 1.5 hours, and after cooling, a composite material of nylon 6 and natural fibers can be obtained.

A further solution is: the initiator is caprolactam magnesium bromide, and the addition amount is 0.3 to 2.4 mol% of the nylon 6 monomer caprolactam.

A further solution is: the activator is HDI, TDI, MDI; diphenyl carbonate, dimethyl terephthalate; N-acetyl caprolactam, aminocaprolactam, bisacylated lactam-1,6- One or more of hexamethylenediamine, the addition amount is 0.3 to 2.4mol% of the monomer.

Further scheme is: described natural fiber is wood fiber, hemp fiber, cotton fiber, bamboo fiber, rattan fiber, grass fiber, wheat straw, straw, rice husk, sugarcane fiber, coconut fiber, peanut shell and pure cellulose, One or several types of modified cellulose.

A further solution is: the form of the natural fiber is selected from at least one of nanofibers with a fiber diameter of less than 100 nm, short fibers with a length of 0.2-10 mm, long fibers with a length of 10-50 mm, and continuous fibers.

A further solution is: the continuous fibers are fabric fibers, fiber mats or three-dimensional fibers.

Compared with the prior art, the present invention has the following positive effects:

1. The initiators used in anionic polymerization of nylon 6 are generally highly alkaline and highly active initiators such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, sodium ethoxide, potassium ethoxide, caprolactam sodium salt, caprolactam potassium salt, etc., but they are in When participating in natural fiber reaction processing, it is easy to react with the fiber and be consumed, thereby producing inhibition; and the initiator caprolactam magnesium bromide used in the present invention, because it has low activity and weak alkalinity, can pass through Its own reactive inertia limits the reaction with natural fibers, thereby improving the process of reactive processing of natural fiber composites;

2. The method of reaction processing is used to prepare natural fiber composite materials, and the dispersion effect of fibers in lower viscosity liquids is better, which is conducive to improving the uniformity of the final product;

3. The preparation of natural fiber composite materials by reaction processing can improve the interface performance between the fiber and the matrix, and has the opportunity to form a chemical bond between the surface groups of the natural fiber and the matrix, effectively improving the Comprehensive properties of composite materials;

4. The present invention pre-treats the natural fiber before it is used, which can remove residual colloid, grease, PVA, ash, etc., which will adversely affect the reaction processing impurities, which is conducive to the smooth progress of the reaction processing;

5. The present invention removes water from the pretreated natural fiber through a freeze dryer, because the drying principle of the freeze dryer is to freeze the water-containing substance into a solid state first, and then sublimate the water content from the solid state into a gaseous state. Thereby removing water and preserving substances; water is removed in the form of ice crystals, so most of the free water can be removed. Therefore, the drying effect of the freeze dryer on natural fibers is better than that of heat drying;

6. Generally speaking, there are not many research and development and production of natural fiber composite materials at present. The present invention provides a preparation method of natural fiber composite materials, which can make natural fibers more widely used in the field of polymer materials , improve the utilization level of natural fibers, and at the same time stimulate the development of my country's natural fiber industry.

Detailed ways

The following examples are given to describe the present invention in more detail. It is necessary to point out that the following examples can not be interpreted as limiting the scope of the present invention. Those skilled in the art will make some non-essential aspects of the present invention according to the above-mentioned content of the present invention. Improvements and adjustments still belong to the protection scope of the present invention.

Example 1

Add the caprolactam monomer into the reaction kettle, heat up to 100°C to melt, then vacuumize and drain for 15 minutes, then add the initiator caprolactam magnesium bromide 0.6mol%, vacuumize and drain for 15 minutes, and finally add bis-acylated lactam-1,6 - Hexamethylenediamine 0.6mol%, mix well and then vacuumize for 10min. The active material prepared above was poured into the mold with the ramie fiber fabric, quickly evacuated to -0.05Mpa, polymerized at a polymerization temperature of 160°C for 60min, and the mold was naturally cooled to obtain a composite material product.

Example 2

Add the caprolactam monomer into the reaction kettle, heat up to 120°C to melt, then vacuumize and drain for 15 minutes, then add the initiator caprolactam magnesium bromide 0.6mol% and vacuumize and drain for 15min, finally add TDI 0.6mol%, mix well. The active material prepared above was poured into the mold with the ramie fiber fabric placed, quickly evacuated to -0.05Mpa, polymerized at a polymerization temperature of 165°C for 60min, and the mold was naturally cooled to obtain a composite material product.

Example 3

Add the caprolactam monomer into the reaction kettle, heat up to 100°C to melt, then vacuumize and drain for 15 minutes, then add the initiator caprolactam magnesium bromide 0.6mol% and vacuumize and drain for 15 minutes, then add 5% of the dried cellulose powder into the In the solution, stir well to make it evenly dispersed, and finally add 0.6mol% of bisacylated lactam-1,6-hexanediamine, mix well and then vacuumize for 10min. The active material prepared above was poured into a preheated mold, quickly evacuated to -0.096Mpa, polymerized at a polymerization temperature of 160°C for 60 minutes, and the mold was naturally cooled to obtain a composite material product.

Example 4

Add the caprolactam monomer into the reaction kettle, heat up to 100°C to melt, then vacuumize and drain for 15 minutes, then add the initiator caprolactam magnesium bromide 0.6mol% and vacuumize and drain for 15 minutes, then add 5% of the dried ramie chopped fibers Into the solution, stir well to make it evenly dispersed, and finally add 0.6mol% of bisacylated lactam-1,6-hexanediamine, mix well and then vacuumize for 10min. The active material prepared above was poured into a preheated mold, quickly evacuated to -0.096Mpa, polymerized at a polymerization temperature of 160°C for 60 minutes, and the mold was naturally cooled to obtain a composite material product.

Example 5

Add the caprolactam monomer into the reaction kettle, heat up to 100°C to melt, then vacuumize and drain for 15 minutes, then add the initiator caprolactam magnesium bromide 0.6mol%, vacuumize and drain for 15 minutes, and finally add bis-acylated lactam-1,6 - Hexamethylenediamine 0.6mol%, mix well and then vacuumize for 10min. The active material prepared above was introduced into a closed mold with ramie fiber fabric under vacuum conditions, the vacuum degree was -0.05MPa, polymerized at a polymerization temperature of 160°C for 60 minutes, and the mold was naturally cooled to obtain a composite material product. Its performance test indicators are shown in Table 1.

Table 1 Performance test table of natural fiber and nylon 6 in-situ composites

Conversion rate% Fiber content/wt% Crystallinity/% Melting point/??C Flexural modulus/MPa 94.1 37 56 220 3407

Claims (6)

1. the preparation method of a nylon 6 and natural-fiber composite material, is characterized in that comprising the steps:

Step 1, natural fiber is carried out pre-treatment, remove the colloid, grease, PVA, the ash impurities that wherein contain; Sodium hydroxide, Sodium dodecylbenzene sulfonate and sodium carbonate are dissolved in deionized water for stirring by the amount of 3g/L, 3% weight percent and 2% weight percent respectively even, then the weight ratio by 1:50 adds natural fiber, be warmed up to 90 to 100 ℃, under agitation process 3 to 5h;

Step 2, pretreated natural fiber is placed in temperature for-45 C, dry 24h in the freeze drier of vacuum tightness 9Pa, the then preheating to the-0.09MPa 140 to 180 ℃ and vacuum condition-0.03;

Step 3, nylon 6 monomer hexanolactams are warming up to 80 to 130 ℃, vacuumize draining 10 after melting to 20min, then add initiator and vacuumize draining 10 to 20min, add again at last activator, vacuumize again draining 5 after mixing to 20min, make active material;

Step 4, the active material that step 3 is prepared join in natural fiber, and the weight of natural fiber is 1% to 200% of active material weight; Be evacuated to rapidly-0.03 to-0.09MPa, under 140 to 180 ℃ of polymerization temperatures, polymerase 10 .5 to 1.5h, cooling after, namely obtain nylon 6 and natural-fiber composite material.

2. the preparation method of nylon 6 and natural-fiber composite material according to claim 1, it is characterized in that: described initiator is the hexanolactam magnesium bromide, add-on be nylon 6 monomer hexanolactams 0.3 to 2.4mol%.

3. the preparation method of nylon 6 and natural-fiber composite material according to claim 1, it is characterized in that: described activator is HDI, TDI, MDI; Diphenyl carbonate, dimethyl terephthalate (DMT); N-ethanoyl hexanolactam, amino hexanolactam, two acylated lactams-1, one or more in the 6-hexanediamine, add-on be monomer 0.3 to 2.4mol%.

4. the preparation method of the described nylon 6 of arbitrary claim of according to claim 1 to 3 and natural-fiber composite material, it is characterized in that: described natural fiber is one or more in xylon, flaxen fiber, cotton fibre, bamboo fibers, vine fiber ti, straw fiber, wheat straw, straw, rice husk, Caulis Sacchari sinensis fiber, coir, Pericarppium arachidis hypogaeae and pure cellulose, modified-cellulose.

5. the preparation method of nylon 6 and natural-fiber composite material according to claim 4 is characterized in that: the form of described natural fiber is selected from least a less than in the nanofiber of 100nm, staple fibre that length is 0.2～10mm, macrofiber that length is 10 ~ 50mm, continuous fibre of Fibre diameter.

6. the preparation method of nylon 6 and natural-fiber composite material according to claim 5, it is characterized in that: described continuous fibre is fabric fibre, fibrefelt or three-dimensional fiber.