CN100349970C - Preparation method of regenerated cellulose / nanometer SiO2 fire-retardant composite material - Google Patents

Abstract

The invention relates to a preparation method of regenerated cellulose/nano- _SiO2 flame-retardant composite material. A certain quality of nano- _SiO2 or a mixture of nano- _SiO2 and sodium silicate is added to the viscose solution and heated at 10-50°C. , fully stirred to get the viscose- _SiO2 dispersion, then add the viscose- _SiO2 dispersion into the coagulation acid bath made of sulfuric acid, sodium sulfate, zinc sulfate and water, and coagulate at 10-100°C. The regenerated cellulose/nanometer SiO ₂ flame retardant composite material is obtained, which can be made into flame retardant viscose fiber, film, etc. according to different forming methods. The prepared regenerated cellulose nanocomposite material has the advantages of high heat resistance and high flame retardancy.

Description

Preparation method of regenerated cellulose/nanometer SiO2 flame retardant composite material

Technical field:

The invention relates to a preparation method of a regenerated cellulose composite material, in particular to a preparation method of a flame-retardant composite material composed of regenerated cellulose and nano silicon dioxide (SiO ₂ ).

Background technique:

Regenerated cellulose can be used to make fiber (commonly known as viscose fiber, rayon), plastic, film, film, etc. It is widely used in civil, industrial, medical, national defense and scientific research. The resource of cellulose is unlimited, making full use of this abundant resource to develop the regenerated cellulose industry has long-term and important significance, and meets the requirements of sustainable development in today's society. Regenerated cellulose is as environmentally friendly as natural cellulose, and its waste can be degraded naturally.

Regenerated cellulose fiber (viscose fiber, artificial cotton) has a history of more than 100 years of development. Its appearance ended the history of human clothing completely relying on nature, and became a good substitute for cotton, which greatly reduced the burden on the human body. The contradiction between dressing and eating for land enables people to solve the problem of dressing through chemical means. Although the production of cellulose fibers by the viscose method has the problem of environmental pollution, it will still be the main production method of regenerated cellulose fibers in the foreseeable decades. The cuproammonia solution method is only used in very few enterprises, and NMMO (N- Methylmorpholine-N-oxide) green solvent method to produce Lycell (lyocell, Tencel) fiber technology is still difficult to adopt on a large scale, and my country is only at the level of pilot production. Therefore, the production of modified and functionalized regenerated cellulose fibers by the viscose method still has great practical significance. Nano SiO ₂ is an amorphous white powder. It is a non-toxic, odorless and non-polluting inorganic non-metallic material. Its particle size is small, its specific surface area is large, and there are unsaturated residual bonds and hydroxyl groups in different bonding states on the surface. It can be widely used in electronic packaging materials, polymer composite materials, plastics, coatings, rubber, pigments, ceramics, adhesives, glass fiber reinforced plastics, drug carriers, cosmetics and antibacterial materials and other fields. Nano-SiO ₂ has been well applied in many aspects. The addition of SiO ₂ in regenerated cellulose can reach 40%. On the one hand, it can improve the heat resistance and flame retardancy of cellulose materials. On the other hand, high The added amount of _SiO2 can replace part of the cellulose, and also reduce the environmental pollution caused in the viscose production process. The production of regenerated cellulose packaging material (cellophane) is the same as that of viscose.

The regenerated cellulose fiber will only be carbonized when it is burned in a fire, so it can be used as clothing fabrics such as army combat uniforms, firefighting clothing, bedding, clothing for the elderly, children, and patients, etc., to make up for the shortage of thermoplastic fibers. Existing research hotspots on the flame retardant modification of regenerated cellulose fibers are the use of phosphonate flame retardants and polysilicic acid flame retardants, such as Exolit flame retardants and flame retardant viscose fibers from Clarian and Kemira's Visil fiber, etc., which meet the requirements of non-halogenation, low toxicity, and smoke suppression of flame retardants. Phosphonate flame retardants are generally difficult to prepare, and there are environmental problems in their raw materials and production process. Phosphonate flame retardants are generally added to viscose fibers. After the flame retardant viscose fibers are discarded, the flame retardants contained in the fibers are easy to slowly seep out. The red tide phenomenon in the ocean is caused by excessive phosphide and eutrophication of seawater. Therefore, the inorganicization of flame retardants will be the development direction of all flame retardant materials.

Visil fiber is a very good inorganic flame-retardant viscose fiber. Sodium silicate is used as a flame retardant. Although the addition amount is relatively high, it has little effect on the strength of the fiber. Sodium silicate decomposes and polymerizes into polysilicic acid in the coagulation bath. Because polysilicic acid is not resistant to alkali washing, the flame-retardant viscose fiber must be treated with sodium aluminate to improve its alkali resistance. In addition, the oligomers of silicic acid are soluble in the coagulation bath, and at the pH value of the existing spinning coagulation bath, the polymerization rate of silicic acid is the slowest, so the flame retardant is easy to enter the coagulation bath, and the coagulation bath Zinc sulphate gelled, causing clogging of the filter unit, which was also a problem with Visil fibers.

To sum up, there are generally disadvantages in the prior art that the preparation process is complicated, difficult, and pollutes the environment.

Invention content:

The purpose of the present invention is to overcome the shortcomings of the prior art, aiming to provide a simple, easy-to-operate, and less environmental pollution preparation method for regenerated cellulose composite materials. Evenly distributing nano-SiO ₂ in the regenerated cellulose matrix can reduce the amount of SiO ₂ added and reduce the impact on the physical and mechanical properties of cellulose. On the other hand, nano-SiO ₂ with high flame retardant activity can solve the problem The contradiction between flame retardancy and physical and mechanical properties of materials. The prepared material has the outstanding advantages of high heat resistance and high flame retardancy.

In order to realize the foregoing invention object, regenerated cellulose/nanometer _SiO provided by the present inventionThe preparation method of flame-retardant composite material is as follows:

The first step, preparation of viscose- _SiO2 dispersion

Nano- _SiO2 or nano- _SiO2 and sodium silicate are added to the viscose aqueous solution consisting of 6-9% by mass of α-cellulose and 5-6% by mass _of sodium hydroxide. The addition amount is 1-50% of the mass of α-cellulose in viscose, the addition amount of sodium silicate is measured by the contained _SiO2 , at 10-50°C, fully stirred for 0.5-2 hours, and mixed to obtain viscose-SiO ₂ dispersion, and then at 18 ° C, the viscose-SiO ₂ dispersion was subjected to vacuum defoaming treatment to remove the gas contained in the dispersion.

The optimum amount of _SiO2 added is 15-30% of the mass of α-cellulose in the viscose.

Due to different preparation methods and techniques, the hydroxyl content of nano-SiO ₂ varies greatly. As the nano-SiO ₂ used in this preparation method, its hydroxyl content is less than 15%.

It is also possible to firstly modify the surface of nano-SiO ₂ to improve the dispersion and stability of nano-SiO ₂ , and the organic modifier used may be PEG (polyethylene glycol) or hydroxyl silicone oil or R-SiX ₃ . Among them, R in R-SiX ₃ is amino, hydrocarbyl, methacrylate, X is methoxy, ethoxy or halogen; the organic modifier used is methyltrimethoxysilane, N-βaminoethyl - One or both of γ-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysiloxane, the addition amount is 0.5-15% of the mass of nano- _SiO2 , the best is 2-5 %.

Sodium silicate can be used to replace part of the nano-SiO ₂ when added to the viscose, the modulus of sodium silicate is 1-3.7, and sodium silicate with a modulus of 1 contains zero water (Na ₂ SiO ₃ ), pentahydrate ( Na ₂ SiO ₃ ·5H ₂ O) or nonaqueous (Na ₂ SiO ₃ ·9H ₂ O) sodium silicate, using solid sodium silicate or sodium silicate aqueous solution.

The second step, preparation of regenerated cellulose/nano- _SiO2 composites

Add the viscose-SiO ₂ dispersion into the coagulation acid bath composed of 50-150 g/L sulfuric acid, 0-350 g/L sodium sulfate, 0-11 g/L zinc sulfate and water, at 10-100 Coagulate at ℃ for 0.1-60 seconds, viscose reacts with sulfuric acid in the coagulation bath to generate regenerated cellulose, and obtain regenerated cellulose/nano- _SiO2 composite material or spin the viscose- _SiO2 dispersion into the coagulation bath to form filaments, After washing with water and alkali, the regenerated cellulose/nano- _SiO2 composite fiber is obtained, that is, the flame-retardant viscose fiber. According to different forming methods, nanocomposites are made into fibers, films and other forms.

The best composition of the coagulation bath is sulfuric acid 100-130 g/L, sodium sulfate 270-340 g/L, zinc sulfate 0-11 g/L and water. The best acid bath temperature is 30-50°C, and the best coagulation time is 0.5 to 10 seconds.

The method of the invention has simple process and is easy to operate; the regenerated cellulose/nanometer _SiO2 flame-retardant composite material prepared by the preparation method can achieve better heat-resistant and flame-resistant effects. Part of the cellulose is replaced by SiO ₂ , which reduces the environmental pollution caused in the viscose production process.

Detailed ways:

Embodiment 1: 12.5 grams of hydroxyl content is 10% SiO ₂ , join 500 grams of α-cellulose content and be 8.35% (mass), sodium hydroxide content is in the viscose solution of 5.8% (mass), at 18 ℃, fully stirred for 1 hour, mixed to obtain the viscose-SiO ₂ dispersion, and then at 18 ℃, the viscose-SiO ₂ dispersion was subjected to vacuum defoaming treatment for 8 hours to remove the gas contained in the dispersion. Take a little dispersion liquid and paint it into a uniform film, put the film into a coagulation bath composed of sulfuric acid content of 100 g/l, sodium sulfate 270 g/l, zinc sulfate 11 g/l and water, and solidify at 50°C 10 seconds, and finally a regenerated cellulose/nano-SiO ₂ composite membrane with a SiO ₂ content of 30% was obtained.

Example 2: 6.25 grams of hydroxy content of 10% SiO ₂ and 29.76 grams of _SiO content of 21% sodium silicate (Na ₂ SiO ₃ 9H ₂ O) powder, added to 500 grams of α-cellulose content 8.35% (mass), sodium hydroxide content of 5.8% (mass) viscose solution, at 18 ° C, fully stirred for 1 hour, mixed to obtain viscose-SiO ₂ dispersion, and then at 18 ° C, viscose Glue-SiO ₂ dispersion was subjected to vacuum defoaming treatment for 8 hours to remove the gas contained in the dispersion. Take a little dispersion liquid and paint it into a uniform film, put the film into a coagulation bath composed of sulfuric acid content of 100 g/l, sodium sulfate 270 g/l, zinc sulfate 11 g/l and water, and solidify at 50°C For 10 seconds, a regenerated cellulose/nano-SiO ₂ composite film with a SiO ₂ content of 30% was obtained.

Example 3: Surface modification of _SiO2 with N-βaminoethyl-γ-aminopropyltrimethoxysilane, N-βaminoethyl-γ-aminopropyltrimethoxysilane The dosage is 2% of _SiO2 . Then prepare _{the regenerated cellulose/nanometer SiO 2 composite} film according to the method of Example 1 with a SiO content of 30%.

Embodiment 4: Get the viscose- _SiO2 dispersion liquid that handles in embodiment 1, adopt the known method for preparing viscose fiber to carry out spinning. The coagulation bath is composed of sulfuric acid content of 130 g/l, sodium sulfate of 270 g/l, zinc sulfate of 11 g/l, and reaction temperature of 50°C. Using the conventional production process of viscose fiber, the viscose- _SiO2 dispersion liquid is drawn into the coagulation bath at a speed of 80 m/s to form filaments, and then washed with water and alkali to obtain regenerated cellulose/nano- _SiO2 composite fibers, namely Flame retardant viscose.

Comparative example 1: SiO ₂ with a hydroxyl content of 45% was used instead of SiO ₂ with a hydroxyl content of 10%, and other methods according to Example 1 were used to prepare a regenerated cellulose/nano-SiO ₂ composite film with a SiO ₂ content of 30%.

Comparative example 2: without adding SiO ₂ , the method of Example 1 was used to prepare a pure regenerated cellulose film.

The samples prepared in Example 1-4 and Comparative Example 1-2 were heated at 750°C for 1 hour, and the residual amount of each sample was measured. The residual amount results are shown in the table below, and the samples added with nano-SiO with low hydroxyl content can _all be To achieve a better flame retardant effect, ignite the sample with a fire source, then remove the fire source, and the sample will be extinguished immediately. The nano- _SiO2 with high hydroxyl content may have reacted with NaOH in the viscose to generate a water-soluble salt, which is lost in the coagulation bath, which can be verified from the result of the residual amount. sample number Residue (%) Combustion performance Example 1 25.8 self extinguishing Example 2 22.0 self extinguishing Example 3 26.1 self extinguishing Example 4 25.1 self extinguishing Comparative example 1 9.1 burn completely Comparative example 2 0.17 burn completely

Claims (2)

1, a kind of regenerated cellulose/nanometer SiO ₂The preparation method of flame-proof composite material is characterized in that preparing according to the following steps: the first step, and with nanometer SiO ₂Join and consist of that the alpha-cellulose mass percentage content is 6～9%, the sodium hydroxide mass percentage content is in 5～6% the viscose solution, nanometer SiO ₂Hydroxy radical content be below 15%, SiO ₂Add-on be in the viscose glue alpha-cellulose quality 1～50%, stir down fully at 10～50 ℃, mix obtaining viscose glue-SiO ₂Dispersion liquid is then under 18 ℃, to viscose glue-SiO ₂Dispersion liquid carries out vacuum defoamation to be handled; Second step is with viscose glue-SiO ₂Dispersion liquid joins by solidifying in the acid bath that 50～150 grams per liter sulfuric acid, 270～350 grams per liter sodium sulfate, 11 grams per liter zinc sulfate and water are made into, solidifies under 10～100 ℃ 0.1～60 second, obtains regenerated cellulose/nanometer SiO ₂Condensation material according to different forming modes, is made fiber, film and other form with nano composite material.

2, regenerated cellulose according to claim 1/nanometer SiO ₂The preparation method of flame-proof composite material is characterized in that SiO ₂Add-on be in the viscose glue alpha-cellulose quality 15～30%.