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    Home > Chemicals Industry > New Chemical Materials > The presence of flame retardants, so that the paper can finally "wrap" the fire

    The presence of flame retardants, so that the paper can finally "wrap" the fire

    • Last Update: 2022-06-18
    • Source: Internet
    • Author: User
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    As the saying goes, "Paper cannot wrap fire"
    .
    Whether it is paper or paper products, they are basically composed of plant fibers.
    The flammability of plant fibers makes them "swipe at one point" when they encounter sparks, and then lead to fires.
    Therefore, paper products have been used for fire protection for a long time.
    The focus of the work is to prevent objects
    .
    ? There are many ways to solve fire hazards, such as reasonable fire prevention arrangements and regular safety inspections
    .
    However, if you want to be more direct, you can also cure it from the source, that is, make paper products have higher flame retardant properties-so the application of flame retardants in the paper industry has gradually gained attention, such as flue gas filter bags, aerospace Paper, heatable paper lunch boxes, etc.
    are some of the more typical flame-retardant paper products
    .
    ? 1.
    The principle of flame retardant? The reason why paper can be ignited is that there are fibers in the composition of the paper, which contains carbon, hydrogen and oxygen elements.
    When the temperature reaches a certain level, it can chemically react with oxygen in the air.
    At the same time, heat is released, and this process manifests itself as combustion
    .
    ? Therefore, if you want to prevent this process, flame retardants need to achieve at least any of the following: ①Isolate the paper surface and flame to prevent direct contact between paper products and oxygen; ②Reduce or consume oxygen in the combustion environment; ③The added substance is decomposed by heat Absorb a lot of heat energy and reduce the temperature of the combustion zone
    .
    ? Second, the processing method of flame-retardant paper? Which process and technology to use to make the paper-based material flame-retardant depends on the nature and characteristics of the flame-retardant
    .
    The following are several flame retardant processes commonly used in current production
    .
    ? 1.
    Use non-combustible or non-combustible fiber raw materials to produce non-combustible paper or non-combustible paper, such as using asbestos fiber or glass fiber to produce non-combustible paper or non-combustible paper
    .
    However, asbestos fiber or glass fiber has low strength and is harmful to human health, its use is greatly restricted
    .
    2.
    Dipping method The dipping method is suitable for water-soluble flame retardants, that is, the water-soluble flame retardant is mixed into a solution, dipped into the paper, and heated and dried to make flame-retardant paper
    .
    This method requires the paper to have quite high absorbency and wet strength indicators, but the flame retardant paper obtained is poor in water resistance, strong in moisture absorption, and the paper is easy to turn yellow and become hard.

    .
    ? 3.
    Coating method This method is suitable for insoluble or poorly soluble flame retardants
    .
    The flame retardant powder is uniformly dispersed in a certain binder to make a milky coating, and then the coating is coated on the surface of the paper by a coating method, and the coating type flame retardant paper can be obtained by heating and drying
    .
    In order to achieve a good flame retardant effect, the flame retardant should have a small and uniform particle size
    .
    However, the flame-retardant paper prepared by this method has a general flame-retardant effect
    .
    4.
    Internal addition method This method is suitable for water-insoluble flame retardants.
    The flame retardant is added to the pulp together with other fillers, and then made into paper
    .
    The addition position is more flexible, as long as it can be uniformly dispersed in the slurry
    .
    The advantages of this method are that it is suitable for the production of various papers, the process is simple, and the flame retardant is more evenly distributed in the paper, so the flame retardant function of the paper is more uniform
    .
    The disadvantage is that the loss of flame retardants is more serious, and this problem can be solved by adding suitable retention aids
    .
    ? 3.
    Types and mechanism of flame retardants? There are many types of flame retardants.
    According to the different flame retardant elements they contain, they can be divided into phosphorus series, halogen series, boron series and inorganic elements
    .
    1.
    Phosphorus-based flame retardants Phosphorus-containing compounds of flame retardants for paper.
    In recent years, organic compounds such as phosphates, phosphate derivatives and polyphosphate amides are commonly used
    .
    They will generate volatile phosphorus compounds and phosphoric acid in the burning state, dilute oxygen and combustible gases in the form of gas, and play a diluting effect; at the same time, phosphoric acid will become metaphosphoric acid and polymetaphosphoric acid, forming non-volatile on the burning solid phase The polymer protective film, which plays a flame retardant effect
    .
    2.
    Halogen-based flame retardants Most halogens can be used as flame-retardant elements, but due to factors such as their stability and source, bromine-based and chlorine-based flame retardants are widely used in practical applications
    .
    Halogen flame retardants are decomposed by heat during combustion to produce hydrogen halide.
    Hydrogen halide consumes free radicals produced by polymer degradation, delaying or interrupting the chain reaction of combustion
    .
    At the same time, hydrogen halide, as a kind of flame-resistant gas (density greater than air), can form a high-concentration hydrogen halide barrier on the surface of paper and paper products during combustion to reduce the concentration of flammable gas, isolate the air, and finally achieve the purpose of flame retardancy
    .
    3.
    The flame retardant effect of boron-based flame retardant borate mainly comes from the following aspects: it can form a glassy inorganic intumescent coating; it can promote char formation; it can hinder the escape of volatile combustibles; it can work at high temperatures.
    Dehydration, has the effect of absorbing heat, foaming and diluting combustibles
    .
    At present, due to factors such as stability and price, boron-based flame retardants are mainly inorganic borate and boric acid
    .
    4.
    Nitrogen-based flame retardants Nitrogen-based flame retardants mainly refer to melamine and its derivatives, as well as ammonium phosphate, ammonium chloride, sulfonamide ammonium, and sulfuric acid
    .
    When the nitrogen compound is burned, it will release N2, CO, NH and other gases after being decomposed by heat, blocking the supply of oxygen and achieving the flame retardant effect
    .
    Some nitrogen-based flame retardants can be used alone, and some are the main components of intumescent flame retardants
    .
    These flame retardants are halogen-free, low-toxic, non-corrosive, stable to heat and ultraviolet rays, and have excellent flame retardant effects
    .
    5.
    Compared with the above-mentioned flame retardants, inorganic flame retardants actually have stronger competitiveness and development potential in today with increasing environmental protection requirements.
    In addition to inhibiting fumes and hydrogen chloride generation, inorganic flame retardants have the function of suppressing smoke and hydrogen chloride generation.
    They can also impart non-toxicity and non-corrosive properties to the material, so they are widely used
    .
    In recent years, the flame retardants used in the flame retardancy of paper mainly include aluminum trihydrate, magnesium hydroxide and the like
    .
    ① Aluminum trihydrate Aluminum trihydrate, also known as aluminum hydroxide (ATH), is widely used because of its good stability, low toxicity or non-toxicity, no corrosive gas, long-lasting flame retardant effect, and smoke suppression
    .
    The water vapor released by its separation can also dilute the combustible gas, and also has a cooling effect
    .
    In addition, the aluminum hydroxide filled into the high polymer helps to burn to form a carbonized layer, which covers the surface of the paper product to achieve the purpose of flame retardancy
    .
    At present, the global annual consumption of various flame retardants is estimated to have reached 600,000 tons, of which alumina trihydrate accounts for about 50%
    .
    ② Magnesium hydroxide and aluminum hydroxide is an environmentally friendly green inorganic flame retardant, which has the functions of flame retardant, smoke suppression, acid resistance and filling
    .
    The thermal decomposition temperature of magnesium hydroxide is about 340°C, which is 140°C higher than the currently commonly used inorganic flame retardant aluminum hydroxide, which can make the synthetic materials added with magnesium hydroxide tolerate higher processing temperatures and help accelerate the extrusion speed.
    Shorten the molding time
    .
    In addition, the particle size of magnesium hydroxide is generally fine, and the equipment is less worn, which is beneficial to prolong the service life of processing equipment
    .
    ? At present, the industry believes that the flame retardant and smoke suppression mechanism of magnesium hydroxide is mainly due to the following effects: (1) When heated, it decomposes and releases crystal water and releases a large amount of heat at the same time, thereby inhibiting the temperature rise of polymer materials; ( 2) The stable magnesia produced by decomposition covers the surface of combustibles, which has a certain thermal insulation effect; (3) A large amount of water vapor is generated during decomposition to reduce the concentration of combustibles in the gas phase combustion zone
    .
    However, due to the low flame retardant efficiency of magnesium hydroxide, it generally acts synergistically with other flame retardants, such as aluminum hydroxide, red phosphorus, and borides
    .
    ? Source: Development of flame-retardant fire-resistant paper, Zhou Hui
    .
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