Research on the application of water-based flame retardant coating glue in fabrics

At present, the research, development and application of water-based fire-resistant PU coating adhesives are in a period of steady progress. If safety and environmental protection, fire prevention and smoke suppression, application performance, and cost processes can be better optimized, water-based fire-resistant PU coatings will be better in the future. The application prospects of glue in the field of fabrics will be broader. In the field of fabric products, especially in the field of industrial or household fabric products such as various construction tents, curtains, sofas, seat cloths, carpets, tablecloths, etc., most manufacturers favor using fire-resistant PU coating glue for back PU coating.

1·Performance evaluation of water-based fireproof PU coating glue

The performance evaluation of water-based fireproof PU coating glue includes physical and chemical properties and application performance evaluation. Physical and chemical properties generally test viscosity, solid content, pH value (1% aqueous solution), appearance, PU coating glue stability, etc. The application performance mainly evaluates the fabric after PU coating, including hand feel, fastness, color difference, strength, hydrostatic pressure resistance, and fire resistance. The most important thing is fire resistance, which are introduced below[1]:

(1) Horizontal combustion evaluation criteria

Generally, it is measured according to FZ/T01028-1993 “Determination of Combustion Performance of Cloth Fabrics: Horizontal Method” or JISL1091-1999 “Test on Combustion Performance of Fabrics: A3 Method”, and the carpet is back-coated with bromine antimony type fireproof PU coating glue. , can meet the requirements. However, carpets are usually required to be wear-resistant and abrasion-resistant, and fireproof adhesives are required to be able to withstand millions to tens of millions of frictions without losing the fireproofing effect. Those with high safety and environmental protection requirements require that bromine antimony particles cannot enter the air of the house, or they do not want to use bromine antimony. Tie with fire retardant glue. This puts forward new requirements for the development of environmentally friendly and durable fire retardant agents and fire retardant adhesives.

(2) Vertical combustion evaluation criteria

There are many standards and methods for vertical burning method testing. For example, according to GB/T5455-1997 “Vertical Method for Testing the Combustion Performance of Fabric Products”, five samples of PU coated fabrics are tested in the warp (longitudinal) and weft (transverse) directions. The average afterburning time, smoldering time and damage length. At present, many fire-resistant PU coated fabrics can meet the requirements of damage length ≤ 15cm, smoldering time ≤ 5s, and afterburning time ≤ 5s. Even according to the American standard ASTM D6413 vertical burning test and the Japanese standard JIS1091-1992 “Test method for combustion performance of fiber products” 》 or the corresponding test methods in BSEN ISO6941, you can generally get satisfactory results recognized by customers. Judged by GB17591-2006 “Fireproof Woven Fabrics” or GB50222-1995 (revised in 2001) “Fire Protection Code for Building Interior Decoration Design”, many bromine antimony type fireproof PU coated decorative fabrics or protective clothing fabrics can reach B1 level, and some Bromine antimony type PU coated fire-resistant clothing can also meet the requirements of GB8965-2009 “Protective Work Clothing Fire Protection” with damage length ≤ 150mm, afterburning time ≤ 5s, and fire protection time ≤ 5s. Even after cleaning 50 times, it can also meet the requirements of fireproof welding clothing. Class C standard. Since most fire-resistant clothing requires cleaning, cleaning must be carried out in accordance with standards, such as GB/T17596-1998eqvISO10528:1995 “Commercial Cleaning Procedures for Fabrics before Fabric Burning Tests”.

At present, fire-resistant PU coatings that are subject to the vertical test method generally consider cleaning requirements, but the number of times of washing resistance varies greatly. For the vertical combustion method, there are also tests for the flame spread performance of the sample. For example, methods such as GB/T5456-1997 “Framing Properties of Fabrics in Vertical Direction – Determination of Flame Spread Performance of Samples”, BSEN ISO6941-2004 “Fabric Fabrics. Combustion Properties. Determination of Vertical Flame Spread of Samples”. There are also test methods for testing the ignitability, such as GB/T8746-2001 “Determination of the ignitability of vertical specimens of burning properties of fabrics”. Fire-resistant PU coated fabrics on the market are tested according to these methods, and there are many products that can meet the test. Customer requirements.

However, according to the GB20286-2006 combustion performance requirements and labeling of fireproof products and components in public places, fabrics using water-based fireproof PU coatings are difficult to pass the fireproof level 1 (fabric) standard. Often the bromine antimony type fire retardant PU coating cannot meet the requirements of smoke density level (SDR) ≤ 15; smoke toxicity level ≥ ZA2 level, while the halogen-free environmentally friendly fire retardant PU coating cannot meet the requirements of LOI ≥ 32.0 (%), and more It is difficult to meet standards such as fire protection level 1 (fabric resistant to washing 30 times). According to GB8624-2006 “Combustion Performance Classification of Building Materials and Products”, instruments such as cone calorimeters are used to test the total heat release and FIGRA (combustion growth rate index), as well as smoke production and smoke toxicity. Currently, water-based fire protection There is little data on PU coated fabrics in this regard and the results are not very satisfactory (the Public Safety Industry Standard of the People’s Republic of China GA504-2004 Fireproof Decorative Fabrics still uses fire toxicity smoke and heat release rate evaluation). Since most water-based fireproof PU coated fabrics are exported, many manufacturers simply ignore the existence of GB20286-2006 and GB8624-2006, or complain and resist. In fact, additive companies should bear the responsibility for research.

(3) Evaluation criteria for 45° tilt method

This test method stipulates that the sample is placed at a 45° tilt, the combustion source ignites the sample on the upper or lower surface below the sample, and the time required for the sample to burn upward for a certain distance is measured, or the time after the sample is burned is measured. The afterburning and fire prevention time, flame spread speed, damage length, damage area or the number of times the sample needs to be exposed to the flame to burn to a certain distance from the lower end of the sample. The main ones include GB/T14645-1993 “Determination of burning performance of fabrics in 45° direction, damage area and number of flame catches”, GB/T14644-1993 “Determination of burning rate of fabrics in 45° direction”, JISL1091-1999 “Combustion of fabrics Performance Test》,16CRFpart1610��Test Methods for Flammability of Clothing Fabrics》etc. There are not many PU coated products for workwear recognized by customers through such standards.

(4)CPAI-84 standard

The full name of “CPAI-84” is ASpecification for Flame-resistant Materials Used in Camping Tentage. It is a standard for fire-resistant materials used in civilian tents. It was established and published by the International Industrial Fabrics Association in 1980. The CPAI-84 standard is a particularly important standard in the field of fireproof PU coating. Because fireproof cotton tents are basically treated with PU coating and the dosage is particularly large, the industry must pay enough attention to this.

CPAI-84 stipulates the vertical burning method for wall and roof materials. The maximum damaged length of a single sample and the maximum damaged length are shown in Table 1. This strict definition of fabric unit quality actually eliminates Increase the possibility of fire protection by sizing more.

CPAI-84 stipulates that for bottom materials, the methylamine sheet combustion method is adopted, requiring that the damaged length of any test sample cannot exceed 72mm. In addition, all kinds of cotton tent materials must go through Leaching (water immersion) and Accelerated Weathering (aging). Water immersion is to immerse the sample in a constant-temperature circulating water washing tank for 72 hours. Water temperature: 15.5~21℃; PH value: 6~8; water volume: for fabrics, no less than 2L water per 0.1m2 sample. Test if there is no circulating water, the water in the tank should be changed at least 6 times within 72 hours. There are still many fireproof PU coated construction tents that can withstand water immersion. However, there are not many products that can withstand aging tests such as Method 5804 of Fed-std191 (carbon arc lamp) or AATCCMethod169 (xenon lamp) or ASTMD4329 (Fluorescent UV and Condensation Method). In fact, the difficulty and bottleneck in the application expansion of water-based fireproof PU coatings in the field of cotton tents lies in water immersion, aging and hydrostatic pressure resistance.

5) BS5852 standard

BS5852 is a relatively complex system that has detailed regulations on the fire resistance testing of furniture and home furnishing materials (with cushions). The fire resistance performance test of household fabrics is divided into three main parts: (1) Water immersion: use 40°C water immersion for 30 minutes according to BS5651 standard; rinse for 2 minutes; hang to dry; (2) Constant temperature and humidity: The dried fabric is allowed to stand for 72 hours in a standard atmosphere with a temperature of (20±2)°C and a relative humidity of (65±5); (3) Fire protection test (taking No. 1 fire source as an example): D The alkane flow rate is 45±2 ml/min, usually producing a flame with a height of 35 mm at room temperature/normal pressure/indoor humidity; burn for 20 seconds; watch the test sample; watch the time all events occur and last. The judgment of passing/failing the BS5852 test is: all flames must be extinguished within 120 seconds after the fire source is removed, and there is no tendency to re-ignite.

For water-based fireproof PU coated fabrics, BS5852 is a particularly strict fire protection standard. The development of water-based fireproof PU coating glue suitable for BS5852 has become a difficult and hot topic in the domestic fabric industry.

(6) Oxygen index method

For fabrics, the limiting oxygen index is tested according to GB/T5454-1997 “Oxygen Index Method for Testing the Combustion Performance of Fabrics”. Many standards require fabric LOI ≥ 32.0 (%), and any value less than 26 (%) is considered fire retardant. low product. In fact, many light and thin PU coated fabrics with a limiting oxygen index of 23.0-26.0 (%) can successfully pass the B1 level of vertical combustion. At present, oxygen index is not commonly used by manufacturers of fire-resistant PU coatings for fabrics. Most of them are used by R&D personnel for formula design and regular research.

(7) Lighter burning

Lighter burning is a simple method commonly used by PU coating factories and fire-resistant fabric buyers. However, due to the great variability in testing, except for a few fire retardant systems with high gas phase fire retardant activity (such as bromide antimony systems), there are only a limited number of water-based fire retardant PU coated fabrics that can be burned by customers’ lighters. In particular, some products that shrink when heated and are effectively fireproof perform well in the vertical burning test. However, under the persistent grilling of the customer’s lighter, the speed of the fabric shrinkage is offset by the moving speed of the lighter. As a result such products cannot be approved. This cannot but be said to be a pity for the fabric fire protection industry.

2·Research and Development Status of Water-based Fireproof PU Coating Glue for Fabrics

The research on water-based fireproof PU coating adhesives for fabrics is very inconsistent with new developments in the field of fire protection. Academic hot topics such as environmentally friendly halogen-free fireproofing, nano-fireproofing, polymerized fireproofing, and expansion fireproofing are rarely introduced into water-based fireproofing PU coatings. Glue is under development. Currently, those engaged in water-based fire-retardant PU coating adhesives for fabrics in China include additive manufacturers and university research institutes that mainly produce fabric emulsions and adhesives, as well as manufacturers that mainly produce fire-retardant agents. Specifically, the current water-based fireproof PU coating glue mainly includes the following categories [1]:

(1) Phosphorus nitrogen type fire retardant glue

Phosphorus-nitrogen fire retardants are relatively popular, including inorganic APP/MPP/MP, etc., and organic phosphorus-nitrogen fire retardants. This type of fireproof PU coating glue has slightly weaker gas-phase fireproofing activity, the fireproof test results are more random, and the fireproof durability needs to be improved. There is a need to introduce and develop synergists and cross-linkers with good performance.

(2) Halogen-free phosphorus-containing organic fireproof adhesive

There are many halogen-free and phosphorus-containing organic fire retardants, such as RDP, BDP, XDP, CU and other products, as well as a large number of various macrocyclic or double spirocyclic phosphides and cyclic phosphates in the experimental synthesis stage. This type of halogen-free, phosphorus-containing organic fire-retardant adhesive has better effects in some fire protection fields and has a strong condensed phase carbonization effect. However, the preparation of fire-retardant adhesive is slightly more difficult, and the water resistance of PU-coated fabrics still needs to be improved.

(3) Bromine antimony type fire retardant glue

Brome antimony type fire retardant adhesive is a mature, cost-effective and widely used product. Instant decabromodionThe use of phenylene ether is restricted, and hexabromocyclododecane is restricted by REACH and Japan. However, the industry quickly launched decabromodiphenylethane, allowing brominated antimony-based products to occupy a large market share. The main problem with brominated antimony-based fire retardant adhesives is environmental protection hazards. For example, heavy metals such as arsenic and lead in antimony trioxide easily exceed standards. At the same time, the fire protection industry has also introduced many synergists to replace antimony trioxide. Bromine antimony type fire retardant glue is effective on light and heavy fabrics in the vertical burning test, but has a great impact on the feel, color and style of light and thin fabrics. For soft chairs and sofa fabrics tested according to the BS5852 standard, the general bromine antimony type fire retardant adhesive is not ideal.

(4) Halogen-phosphorus fireproof glue

Using halogenated phosphate as the main fire retardant and adding various synergists and fire retardants, water-based fire retardant PU coating glue can also be prepared. Generally, the fabrics made from this type of fire-retardant adhesive have a soft feel, small color difference, are slightly sticky, and are easy to migrate.

(5) Intrinsic fireproof glue

Water-based fireproof polymer PU/PA is directly synthesized through fireproof monomers and raw materials. This type of fire-retardant adhesive is durable fire-retardant and has a lot of room for growth in the future.

(6) Inorganic fireproof adhesive

Inorganic hydroxides (MH/ATH/LDH), zinc borate, borax, zinc oxide, silica, etc. can be used as fire retardants, but appropriate and efficient synergists must be added. In some special applications, Can play a fire protection role. Inorganic fire retardants are non-toxic, environmentally friendly and low-priced, but are usually used as auxiliary components of other fire retardants, and there is huge room for growth in the future.

(7) Mixed fireproof glue (with various fireproof elements)

In response to increasingly stringent and detailed fire protection standards, it is now popular to combine gas phase and condensed phase fire protection mechanisms, and various fire protection ingredients are blended into the same product. At present, what this type of products urgently needs is theoretical guidance and intellectual support from the academic community. At present, many fireproof adhesives are developed mainly for fireproofing. The color, feel, fastness, hydrostatic pressure resistance and strength of the fabric are more or less affected.

1. Basic raw materials for water-based fireproof PU coating glue

The main raw materials for preparing water-based fireproof PU coating glue are water-based adhesives and fire retardants. Commonly used water-based adhesives are water-based polyacrylate (water-based PA) and water-based polyurethane (water-based PU).

Water-based PA products are not expensive, have less yellowing, and are generally obtained by emulsion polymerization. Since external emulsifiers are often used, the compatibility and stability with fire retardants are relatively good when non-ionic surfactants and ammonia are added. The film-forming temperature, softness, hardness, fastness, gloss, and cross-linking degree of water-based PA can be flexibly adjusted through various basic monomers and functional monomers. However, after film-forming, water-based PA is hot, sticky, cold, and brittle. The industry still needs to pay attention to issues such as excessive formaldehyde and insufficient film feel or fastness of cross-linked products and continue its efforts.

Due to the unique soft segment and hard segment structure of the polymer, water-based PU has particularly good comprehensive mechanical properties in the field of PU coating, including good fastness, hand feel, film feel, water resistance, wash resistance, and shear resistance. Water-based PU using aromatic isocyanate (such as TDI/MDI) as raw material has good wear resistance, cold resistance, elasticity, toughness and fastness after film formation. The disadvantage is that it is easy to yellow. Water-based PU is mostly anionic products. It often achieves good self-emulsification function through the introduction of hydrophilic chain extender DMPA and neutralizing agent triethylamine. It has good mechanical stability, but is resistant to electrolytes, especially cationic fire retardants or additives. The ability is very poor. Even if a large amount of non-ionic emulsifier is added, it is still easy to break emulsification, slag or agglomerate.

Others, there are other water-based polymers that can also be used as adhesives for fire-retardant adhesives, such as PVC emulsion, water-based epoxy resin emulsion, silicone-acrylic emulsion, vinegar-acrylic emulsion, styrene-acrylic emulsion, chloropropylene emulsion, PUA emulsion (The latter five can be regarded as modified products of water-based PA emulsion). In addition, there are water-based intrinsically fire-resistant PA prepared with halogenated acrylate as monomer, water-based intrinsically fire-resistant PU prepared with phosphorus-containing polyol or halogen-containing polyol or phosphorus-containing isocyanate or halogenated isocyanate as monomer, and water-based halogenated PU. Special adhesives such as epoxy resin. Among them, Chuanhua Co., Ltd. has done a lot of work in the development of water-based intrinsically fire-resistant PU/PA. When applied to fabric PU coatings, its durability and washability are greatly improved, and the PU coating is transparent and has a filmy feel. It has good fastness and integrity, and also has high resistance to hydrostatic pressure. However, the price of fire-retardant monomers is relatively high and can only be used in a few high value-added fabrics [1].

In the field of fabrics, especially in the field of industrial or household fabrics such as various cotton tents, curtains, sofas, seat cloths, carpets, tablecloths, etc., most manufacturers use fireproof PU coating glue for back PU coating. favor. At present, the research, development and application of water-based fireproof PU coating adhesives are in a period of steady progress. If safety and environmental protection, fire prevention and smoke suppression, application performance, and cost processes can be better optimized, water-based fireproof PU coating adhesives will be used on fabrics in the future. The application prospects in the field will be broader [1].

3·Basic raw materials for water-based fireproof PU coating glue

Water-based PA products are not expensive, have little yellowing, and are generally obtained by emulsion polymerization. Because external emulsifiers are often used, the compatibility and stability with fire retardants are relatively good when non-ionic surfactants and ammonia are added. Film-forming temperature, softness, hardness, fastness, etc. of water-based PAThe degree of finish and cross-linking can be flexibly formulated through various basic monomers and functional monomers. However, there are problems such as hot stickiness and cold brittleness after film formation of water-based PA, excessive formaldehyde in the cross-linked product, and insufficient film feel or fastness. , the industry still needs to pay attention and continue its efforts.

In the field of fabric PU coating, common fire retardants are still common decabromodiphenyl ether, decabromodiphenyl ethane, antimony trioxide, hexabromocyclododecane, chlorophosphate (such as V6 /TCPP/TDCP/TCEP), halogen-free phosphates (BDP/RDP/DMPP/CP/CU), ammonium polyphosphate (APP), melamine pyrophosphate (MPP), melamine cyanurate (MCA), melamine, Hydroxymethylmelamine resin, inorganic hydroxides [magnesium hydroxide (MH), aluminum hydroxide (ATH), layered double hydroxide (LDH)], inorganic fillers and synergists (such as zinc borate, talc, Silica, zinc oxide, zeolite, etc.), organic silicon, reactive fire retardant additives, fire retardant cross-linking agents, transition metal complexes, etc. 1-6].

With increasingly severe environmental pressure, increasingly strict European and American requirements, and severe reliance on exports, the field of fabric PU coatings still uses restricted decabromodiphenyl ether (RoHS banned), hexabromocyclododecane (REACH restricted) used), TCEP (restricted by REACH), antimony trioxide (heavy metals can easily exceed the standard), CP (N-hydroxymethyl-3-(dimethoxyphosphono)propionamide, formaldehyde can easily exceed the standard), environmentally friendly, halogen-free and fireproof Efficient APP/CU/RDP/BDP/DMPP and other water-resistant and washable properties are not ideal [2-4].

IV. Preparation and application process of water-based fireproof PU coating glue

The preparation of water-based fireproof PU coating glue usually involves adding a certain amount of water, water-based adhesive, surfactant, fire retardant, functional additives (for fabrics), leveling agent, feel regulator, and additives. Plasticizer, smoothing agent, fastness promoter, stabilizer, wetting agent, titanium dioxide, synergist and other components are added to the mixing kettle in a certain order, stirred and dispersed evenly at a certain speed, and then circulated through the colloid mill. Grind, add defoamer and thickener to prepare water-based fireproof PU coating glue.

The application of water-based fireproof PU coating glue generally uses a scraper PU coating. After fixing the cloth, according to the gap size (or knife edge distance), knife head type, blade thickness, cloth feeding speed, slurry solid content, slurry viscosity, etc., a reasonable process is controlled to achieve complete, uniform, efficient and specific fire prevention. coating. In the Jiangsu and Zhejiang markets, most use blade PU coatings, but few use roller coating or spraying processes. During the PU coating process, it is generally baked at 150-180℃, and the baking time ranges from 40-90 seconds. Different types of fabrics and fabrics with different weights per square meter need to be tested to determine the sizing amount and fire resistance. Whether the fabric is water-blocking or rolled-finished will have a great impact on the sizing amount of the PU coating, as well as fire resistance and hydrostatic pressure resistance. It will also affect the feel, fastness and surface effect of the fabric, which requires detailed testing by upstream and downstream manufacturers. Determine the process.

At present, the development and application of water-based fireproof PU coating adhesives emphasize performance over environmental protection, American standards over European standards, results over process, fire prevention over smoke suppression, short-term over long-term effects, immediate over long-term, The short-sighted behavior of emphasizing cost over quality and formula over mechanism has led some manufacturers to even return to the path of solvent-based fire-retardant adhesives. The progress of water-based fire-retardant adhesives still needs to bear a heavy burden [1]. 5. Research progress of water-based fireproof PU coating glue for fabrics. For the development of water-based fireproof PU coating glue for fabrics, the author believes that the following aspects are worthy of efforts and expectations [1-4]:

(1) The synthesis research and industrialization process of various new environmentally friendly halogen-free macromolecular fire retardants are accelerating, and water-based fire retardant PU coating adhesives are ushering in more high-efficiency special materials.

(2) The synthesis and application of trace synergists continue. Domestic scholars have done a lot of research in this area [5,6]. If a mechanism breakthrough and industrialization are successful in the future, it will also be of great benefit to the research and development of water-based fireproof PU coatings.

(3) Fireproof PU coatingThe anti-ultraviolet and anti-aging properties of fabrics have been greatly improved. For the civilian tent market (CPAI84 standard) and curtain market, it is necessary to develop anti-UV and anti-aging water-based fireproof PU coating glue.

(4) Environmentally friendly intumescent fire retardant agents are applied in fabric PU coatings. There is still room for improvement in the fire retardant effect of environmentally friendly intumescent fire retardant agents on fabrics. What is needed in the future is for fire retardant agent manufacturers to continue to make breakthroughs in the polymerization and coating modification of fire retardant agents, so that the hydrophilicity of the fire retardant agent can be reduced and the adhesive can be The binding force is improved, and PU coating developers need to synthesize and modify suitable high molecular weight adhesives and cross-linking agents to improve the water resistance and washability of environmentally friendly intumescent fireproof PU coated fabrics

(5) Explore water-based fireproof PU coating glue suitable for mattresses. The U.S. mattress fireproof market has a particularly large capacity. In order to accumulate or make breakthroughs in this area in the future, the evaluation and testing system needs to be established first, and exchanges and cooperation must be strengthened in the research and development of fireproof PU coatings.

(6) Substitute and upgrade brominated antimony products to achieve environmental protection. Through upstream and downstream efforts, we will gradually realize the replacement of decabromodiphenyl ether with decabromodiphenyl ethane and the replacement of toxic heavy metal antimony powder with high-purity environmentally friendly antimony trioxide, achieving the basic environmental protection of products

(7) Research on the fire protection development of fabrics for soft chairs, seats and sofas, and pass the BS5852 standard to open up the European and American markets.

(8) Establish a suitable fireproof PU coating product system and database for blended chemical fiber fabrics. Blended chemical fiber fabrics such as polyester-cotton fabrics are generally considered to be more difficult to fireproof. In fact, this is not necessarily the case. For example, in the BS5852 test, the cotton support effect of heavy polyester-cotton fabrics blocks fabric droplets and breaks large holes, which is conducive to passing the test. Relevant product libraries and databases need to be built quickly.

(9) New fire-proof technology, modified finishing and dyeing and finishing processes introduce fabric PU coating to innovate fire-proof PU coating technology. For example, borrowing from the dye industry, a process similar to dye-dyed fibers is designed to bind the fire retardant directly to the crystalline areas of the fiber or adhesive.

5·Conclusion

Water-based fireproof PU coating glue has been well applied in the field of fabrics, but there are still many areas with huge potential. If the upstream and downstream fire protection industry, academia and research circles work together to target different fabrics, different testing methods and evaluation standards, it is expected to develop a wide variety of environmentally friendly water-based fire-retardant PU coating products in the future.

AAADFWGREGTR

Extendedreading:https://www.alltextile.cn/product/product-4-124.html