CN107190515A - The preparation method and application of epoxy radicals POSS/ ammonium polyphosphate compound fire retardants - Google Patents

Abstract

The invention relates to a preparation method and application of epoxy-based POSS/ammonium polyphosphate composite flame retardant. After emulsifying epoxy-based POSS and ammonium polyphosphate, it is mixed with ammonium polyphosphate to make a composite flame-retardant finishing agent, and then the cotton fabric is rolled and baked to be flame-retardant. Finishing can greatly improve the flame retardant properties of cotton fabrics, and make cotton fabrics have certain water repellency and wrinkle resistance. Compared with the prior art, the present invention introduces an epoxy group that can react with cotton fabrics, can carry out crosslinking reaction with cotton fabrics, and solves the problem of combining POSS flame retardants with cotton fabrics. Compared with coating finishing , Higher bonding fastness, more convenient application.

Description

Preparation method and application of epoxy-based POSS/ammonium polyphosphate composite flame retardant

technical field

The invention relates to the field of cotton spinning finishing, in particular to a preparation method and application of an epoxy-based POSS/ammonium polyphosphate composite flame retardant.

Background technique

Cotton fabric is widely used in clothing, decorative materials and other fields due to its wide source, large output, good hygroscopicity, air permeability and easy degradation. It is a very popular textile in the world. The limiting oxygen index LOI of cotton fabric is about 18. It is a flammable material. If it encounters a fire source, it will burn rapidly and cause a fire easily. According to statistics, 50% of the fires that occur every year are caused by the burning of textiles. Therefore, textiles after flame-retardant finishing are widely used in occupational safety, interior decoration, fire-fighting materials and other fields. Years of scientific research and life practice have shown that rational use of flame retardants is one of the effective measures to prevent and reduce fires. Therefore, it is necessary to carry out flame-retardant finishing on cotton fabrics in order to broaden its application fields.

Cage polysilsesquioxane (Polyhedral Oligomerie Silsesquioxane, referred to as POSS) is a kind of oligomeric siloxane with nanoscale cage structure, also known as cubic silane. POSS has a regular structure, small size (1-3nm in diameter), and itself has two parts, organic and inorganic. It is a kind of substance containing RSiO _1.5 structure. Its interior is composed of Si and O. Covered (shell) by organic substituents, namely R, is a three-dimensional new type of organic/inorganic intramolecular hybrid composite material at the molecular level. The special structural characteristics of cage polysilsesquioxane make it both organic materials and The characteristics of inorganic nanomaterials, such as good reactivity, good heat resistance. Cage polysilsesquioxane has a wide range of applications in textiles, such as water and oil repellent finishing of fabrics, anti-wrinkle finishing, flame retardant finishing, etc. However, POSS is insoluble in water and easily soluble in organic solvents such as tetrahydrofuran, toluene, and chloroform. In terms of flame-retardant finishing, it is generally melt-spun finishing or directly using organic matter as a solvent to finish the fabric. Therefore, it is useful for flame-retardant finishing of cotton fabrics. Certainly limited.

The application of POSS as a flame retardant includes: (1) improving the flame retardancy of rubber and resin, such as: Liang et al. have prepared POSS/EP (epoxy) with different POSS contents (0%, 5%, 10%, 15%) Resin) composites, SEM and TGA test results show that: with the increase of POSS content, the flame retardancy of composites increases, mainly due to the introduction of POSS to form a layer of _SiO2 layer on the surface of EP to prevent further decomposition of polymer structure Gao Junchi et al. used cage octaphenylsilsesquioxane (OPS) and EPDM to make new composite materials. The results showed that compared with pure EPDM, OPS composite EPDM had a certain oxygen index. increased, the heat release rate decreased, the thermal stability increased, and the mechanical properties were significantly improved; Liu Lei et al. used ionic octa(tetramethylammonium) cage silsesquioxane (OctaTMA-POSS) as polystyrene (PS) Resin additives are used to prepare POSS/PS composites. A certain amount of POSS can form nanofibers in PS and distribute them in a network shape, which reduces the peak heat release rate, peak CO and _CO2 release rate, and concentration peak of the composite. (2) Improve the flame retardancy of cellulose, such as Shao Qun etc. have successfully prepared POSS/PA66 nanocomposite fibers by melt spinning, and found that when the octaphenyl POSS addition is 1wt%, OP-POSS/PA66 nanocomposites The initial decomposition temperature of the compound increased by about 10°C, but the effect was not obvious by continuing to add octaphenyl POSS; Qing Fengling et al. from Donghua University used tetrahydrofuran as a solvent to treat cotton fabrics with P(POSS-MMA-VBFC). Coating finishing, the results show that the introduction of POSS improves the flame retardancy of cotton.

At present, the application of POSS flame retardants in textiles is not only used in the production of chemical fibers by melt spinning, but also in the application of natural fabrics. Generally, organic substances such as tetrahydrofuran are used as solvents to coat and finish fabrics, which is costly and easy to cause pollution to the environment. .

Contents of the invention

The purpose of the present invention is to provide a preparation method and application of an epoxy-based POSS/ammonium polyphosphate composite flame retardant with a high degree of integration with cotton fabrics and a good flame retardant effect in order to overcome the above-mentioned defects in the prior art.

The purpose of the present invention can be achieved through the following technical solutions:

The preparation method of epoxy-based POSS/ammonium polyphosphate composite flame retardant adopts the following steps:

(1) Synthesis of epoxy-based POSS

(1-1) Add dropwise the isopropanol solution of 3-glycidylpropoxytrimethoxysilane to the isopropanol solution of tetramethylammonium hydroxide while stirring;

(1-2) After the dropwise addition, continue to stir at room temperature for 5-8 hours, and remove isopropanol by rotary evaporation;

(1-3) Add toluene to dissolve the intermediate product, reflux at 60-80°C for 5-8 hours, wash the toluene solution with saturated sodium chloride solution until the pH value of the washed toluene solution is 7, add anhydrous sodium sulfate and dry overnight , toluene is removed by rotary evaporation, and the obtained colorless transparent viscous liquid is epoxy-based POSS;

(2) Emulsification of epoxy-based POSS

Glyceryl monostearate and sodium dodecylbenzenesulfonate are used as compound emulsifiers to emulsify epoxy-based POSS;

(3) Preparation of epoxy-based POSS/APP composite flame retardant finishing agent

Mix uniformly emulsified epoxy-based POSS and ammonium polyphosphate at a mass ratio of 3:1 to 1:2, heat to dissolve at 90°C and stir evenly to make a flame-retardant finishing agent.

The isopropanol solution of tetramethylammonium hydroxide described in step (1) is obtained by preparing isopropanol and tetramethylammonium hydroxide aqueous solution.

The concentration of the tetramethylammonium hydroxide aqueous solution is 3-8wt%, and isopropanol and tetramethylammonium hydroxide aqueous solution are mixed according to 100mL: 5-15g to obtain the isopropanol solution of tetramethylammonium hydroxide.

The isopropanol solution of 3-glycidylpropoxytrimethoxysilane described in step (1) is prepared by mixing isopropanol and 3-glycidylpropoxytrimethoxysilane at 10-30mL: 20-50g get.

Step (2) specifically adopts the following steps:

(2-1) Add sodium dodecylbenzenesulfonate to the epoxy-based POSS, and stir at a high speed above 10000rpm after adding water;

(2-2) Glyceryl monostearate is added, and after adding water, stir at a high speed above 10000 rpm;

(2-3) Control the ultrasonic frequency to 30-40 kHz, and ultrasonically emulsify the mixture to obtain uniformly emulsified epoxy-based POSS.

Preferably, the HLB of glyceryl monostearate is 3.8, and the HLB of said sodium dodecylbenzenesulfonate is 10.64. The mass ratio of glyceryl monostearate to sodium dodecylbenzenesulfonate is 9:8～12:10, and the emulsifier obtained by compounding glyceryl monostearate and sodium dodecylbenzenesulfonate is mixed with cyclic The mass ratio of oxy POSS is 1:8-1:10.

The prepared epoxy-based POSS/ammonium polyphosphate composite flame retardant can be applied to cotton fabrics for flame-retardant finishing, and the following steps are adopted:

(1) After the cotton fabric is ultrasonically cleaned, the cotton fabric is naturally dried;

(2) Cotton fabrics are treated by padding and baking method, and the cotton fabric is treated with epoxy-based POSS/ammonium polyphosphate composite flame retardant, and then pre-baked and baked to complete the process. Flame retardant finishing.

In the two-dipping and two-rolling process, the excess rate is controlled at 80-90%, the pre-baking temperature is 75-100° C., and the time is 3-5 minutes, and the baking temperature is 150-170° C., and the time is 3-5 minutes.

At present, the application of POSS flame retardants on textiles is not only used for melt spinning to produce chemical fibers, but the application of POSS flame retardants on natural fabrics is limited to coating finishing. The main reason is that POSS flame retardants can react with natural fibers when they are not successfully introduced. group.

The present invention starts with the selection of raw materials, selects 3-glycidyl propoxytrimethoxysilane with epoxy groups, and synthesizes epoxy group POSS through methods such as dehydration and condensation. The reaction formula is as follows:

POSS with reactive groups (epoxy groups) capable of reacting with cotton fabrics was prepared.

Compared with the prior art, the present invention has the following advantages:

(1) In the prepared POSS, an epoxy group that can react with cotton fabrics is introduced, which can carry out crosslinking reaction with cotton fabrics, and solves the problem of combining POSS flame retardants with cotton fabrics. Compared with coating finishing , Higher bonding fastness, more convenient application.

(2) Emulsify epoxy-based POSS to make it soluble in water, and use water as a solvent, which is not only rich in sources, but also cheap in price and energy-saving and environmentally friendly.

(3) Apply epoxy-based POSS to the flame retardancy of cotton fabrics, and make composite flame-retardant finishing agents from epoxy-based POSS and ammonium polyphosphate to carry out flame-retardant finishing on cotton fabrics. It is found that not only the flame-retardant properties of cotton fabrics are improved , and has wrinkle resistance and water repellency.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

Example 1

Flame Retardant Properties of Cotton Fabrics Without Flame Retardant Treatment

The test results of the flame retardant properties of pure cotton fabrics show that the limiting oxygen index (LOI) of pure cotton fabrics is 15.11, the vertical burning performance results show that the afterburning time is 30.27s, the smoldering time is 10.34s, and the damage length is 30cm.

Example 2

Flame retardant properties of cotton fabrics treated with epoxy-based POSS/APP composite flame retardant finishing agent (3:1)

Preparation of epoxy-based POSS/APP composite flame-retardant finishing agent: After emulsifying an appropriate amount of epoxy-based POSS evenly, add APP according to the mass ratio of epoxy-based POSS and APP to 3:1, heat to dissolve at 90°C and stir evenly to prepare Into a flame retardant finishing agent.

Flame retardant finishing of cotton fabrics: Cotton fabric → double dipping and double rolling (residue rate 90%) → pre-baking (100°C, 3min) → baking (150°C, 3min).

The limiting oxygen index of the cotton fabric after finishing is 34.11, the vertical burning performance is 18.54s afterburning time, smoldering time is 0s, and the damage length is 30cm.

Example 3

Flame-retardant properties of cotton fabrics treated with epoxy-based POSS/APP composite flame-retardant finishing agent (3:2)

Preparation of epoxy-based POSS/APP composite flame-retardant finishing agent: After emulsifying an appropriate amount of epoxy-based POSS evenly, add APP according to the mass ratio of epoxy-based POSS and APP to 3:2, heat to dissolve at 90°C and stir evenly to prepare Into a flame retardant finishing agent.

Flame retardant finishing of cotton fabrics: Cotton fabric → double dipping and double rolling (residue rate 90%) → pre-baking (100°C, 3min) → baking (150°C, 3min).

The limiting oxygen index of the cotton fabric after finishing is 40.56, the vertical burning performance is 0s afterburning time, smoldering burning time is 0s, and the damage length is 5.0cm.

Example 4

Flame-retardant properties of cotton fabrics treated with epoxy-based POSS/APP composite flame-retardant finishing agent (3:3)

Preparation of epoxy-based POSS/APP composite flame-retardant finishing agent: After emulsifying an appropriate amount of epoxy-based POSS evenly, add APP according to the mass ratio of epoxy-based POSS and APP to 3:3, heat to dissolve at 90°C and stir evenly to prepare Into a flame retardant finishing agent.

Flame retardant finishing of cotton fabrics: Cotton fabric → double dipping and double rolling (residue rate 90%) → pre-baking (100°C, 3min) → baking (150°C, 3min).

The limiting oxygen index of the cotton fabric after finishing is 40.15, the vertical combustion performance is 1s afterburning time, smoldering time is 0s, and the damage length is 10cm.

Example 5

Flame-retardant properties of cotton fabrics treated with epoxy-based POSS/APP composite flame-retardant finishing agent (3:2)

Preparation of epoxy-based POSS/APP composite flame-retardant finishing agent: After emulsifying an appropriate amount of epoxy-based POSS evenly, add APP according to the mass ratio of epoxy-based POSS and APP to 3:2, heat to dissolve at 90°C and stir evenly to prepare Into a flame retardant finishing agent.

Flame retardant finishing of cotton fabrics: Cotton fabrics→two dipping and two padding (residue rate 90%)→pre-baking (100°C, 3min)→baking (150°C, 3min)→washing at room temperature five times.

The limiting oxygen index of the cotton fabric after finishing is 38.5040.56, the vertical burning performance is 0s afterburning time, smoldering burning time is 0s, and the damage length is 6.8cm.

Example 6

Flame-retardant properties of cotton fabrics treated with epoxy-based POSS/APP composite flame-retardant finishing agent (3:2)

Preparation of epoxy-based POSS/APP composite flame-retardant finishing agent: 15% epoxy-based POSS flame-retardant finishing agent, 10% APP flame-retardant finishing agent, 15% epoxy-based POSS and 10% APP composite flame-retardant finishing agent.

Flame retardant finishing of cotton fabrics: Cotton fabric → double dipping and double rolling (residue rate 90%) → pre-baking (100°C, 3min) → baking (150°C, 3min).

After flame-retardant finishing, the water repellency of cotton fabrics was tested by static contact angle: the contact angles of pure cotton fabrics and epoxy-based POSS and APP-treated cotton fabrics were all 0°, and the contact angles of epoxy-based POSS/APP-treated cotton fabrics were 0°. It is 130.9°, which has certain water repellency.

Example 7

The preparation method of epoxy-based POSS/ammonium polyphosphate composite flame retardant adopts the following steps:

(1) Synthesis of epoxy-based POSS

(1-1) While stirring, add dropwise the isopropanol solution of 3-glycidylpropoxytrimethoxysilane to the isopropanol solution of tetramethylammonium hydroxide, wherein the tetramethylammonium hydroxide The isopropanol solution adopts isopropanol and a concentration of 3wt% tetramethylammonium hydroxide aqueous solution to obtain by 100mL: 5g preparation, and the isopropanol solution of the 3-glycidyl propoxytrimethoxysilane added dropwise is obtained by isopropanol Alcohol and 3-glycidylpropoxytrimethoxysilane are prepared by mixing 10mL: 20g;

(1-2) After the dropwise addition, continue stirring for 5 h at room temperature, and remove isopropanol by rotary evaporation;

(1-3) Add toluene to dissolve the intermediate product, reflux at 60°C for 8 hours, wash the toluene solution with saturated sodium chloride solution until the pH value of the washed toluene solution is 7, add anhydrous sodium sulfate to dry overnight, and remove by rotary evaporation Toluene, the colorless transparent viscous liquid that obtains, is epoxy-based POSS;

(2) Emulsification of epoxy-based POSS

Using glyceryl monostearate and sodium dodecylbenzenesulfonate as a compound emulsifier to emulsify epoxy-based POSS, the following steps are specifically adopted:

(2-1) Add sodium dodecylbenzenesulfonate of HLB=10.64 to the epoxy-based POSS, and stir at a high speed above 10000rpm after adding water;

(2-2) Add glyceryl monostearate with HLB=3.8, add water and stir at a high speed above 10000rpm, the mass ratio of glyceryl monostearate to sodium dodecylbenzenesulfonate is 9:8, The mass ratio of the emulsifier obtained by compounding glyceryl monostearate and sodium dodecylbenzenesulfonate to epoxy group POSS is 1:8;

(2-3) Control the ultrasonic frequency to be 30kHz, and ultrasonically emulsify the mixture to obtain evenly emulsified epoxy-based POSS;

(3) Preparation of epoxy-based POSS/APP composite flame retardant finishing agent

Mix uniformly emulsified epoxy-based POSS and ammonium polyphosphate at a mass ratio of 3:1, heat to dissolve at 90°C and stir evenly to make a flame-retardant finishing agent.

The prepared epoxy-based POSS/ammonium polyphosphate composite flame retardant can be applied to cotton fabrics for flame-retardant finishing, and the following steps are adopted:

(1) After the cotton fabric is ultrasonically cleaned, the cotton fabric is naturally dried;

(2) Cotton fabric is processed by padding and baking method, and the process of two dipping and two rolling is adopted, and the excess rate is controlled at 80%, and the cotton fabric is treated with epoxy-based POSS/ammonium polyphosphate composite flame retardant, and then After pre-baking and baking, the pre-baking temperature is 75°C for 5 minutes, and the baking temperature is 150°C for 5 minutes to complete the flame retardant finishing.

Example 8

The preparation method of epoxy-based POSS/ammonium polyphosphate composite flame retardant adopts the following steps:

(1) Synthesis of epoxy-based POSS

(1-1) While stirring, add dropwise the isopropanol solution of 3-glycidylpropoxytrimethoxysilane to the isopropanol solution of tetramethylammonium hydroxide, wherein the tetramethylammonium hydroxide The isopropanol solution adopts isopropanol and a concentration of 8wt% tetramethylammonium hydroxide aqueous solution to obtain by 100mL: 15g preparation, and the isopropanol solution of the 3-glycidyl propoxytrimethoxysilane added dropwise is obtained by isopropanol Alcohol and 3-glycidylpropoxytrimethoxysilane are prepared by mixing 30mL: 50g;

(1-2) After the dropwise addition, continue to stir for 8 hours at room temperature, and remove isopropanol by rotary evaporation;

(1-3) Add toluene to dissolve the intermediate product, reflux at 80°C for 5 hours, wash the toluene solution with saturated sodium chloride solution until the pH value of the washed toluene solution is 7, add anhydrous sodium sulfate to dry overnight, and remove by rotary evaporation Toluene, the colorless transparent viscous liquid that obtains, is epoxy-based POSS;

(2) Emulsification of epoxy-based POSS

Using glyceryl monostearate and sodium dodecylbenzenesulfonate as a compound emulsifier to emulsify epoxy-based POSS, the following steps are specifically adopted:

(2-1) Add sodium dodecylbenzenesulfonate of HLB=10.64 to the epoxy-based POSS, and stir at a high speed above 10000rpm after adding water;

(2-2) Add glyceryl monostearate with HLB=3.8, add water and stir evenly at a high speed above 10000rpm, the mass ratio of glyceryl monostearate to sodium dodecylbenzenesulfonate is 12:10, The mass ratio of the emulsifier obtained by compounding glyceryl monostearate and sodium dodecylbenzenesulfonate to epoxy group POSS is 1:10;

(2-3) Control the ultrasonic frequency to be 40kHz, and ultrasonically emulsify the mixture to obtain evenly emulsified epoxy-based POSS;

(3) Preparation of epoxy-based POSS/APP composite flame retardant finishing agent

The prepared epoxy-based POSS/ammonium polyphosphate composite flame retardant can be applied to cotton fabrics for flame-retardant finishing, and the following steps are adopted:

(1) After the cotton fabric is ultrasonically cleaned, the cotton fabric is naturally dried;

(2) Cotton fabric is processed by padding and baking method, and the process of two dipping and two rolling is adopted, and the excess rate is controlled at 90%, and the cotton fabric is treated with epoxy-based POSS/ammonium polyphosphate composite flame retardant, and then After pre-baking and baking, the pre-baking temperature is 100°C for 53 minutes, and the baking temperature is 170°C for 3 minutes to complete the flame retardant finishing.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (10)

1. the preparation method of epoxy radicals POSS/ ammonium polyphosphate compound fire retardants, it is characterised in that this method uses following steps：

(1) epoxy radicals POSS synthesis

(1-1) under agitation, 3- glycidoxypropyl front threes is added dropwise into the aqueous isopropanol of TMAH The aqueous isopropanol of TMOS；

After (1-2) completion of dropwise addition, continue to stir 5~8h at ambient temperature, rotary evaporation removes isopropanol；

(1-3) adds toluene dissolving intermediate product, and 60~80 DEG C of 5~8h of back flow reaction wash toluene with saturated nacl aqueous solution Solution, until the pH value of the toluene solution after washing is 7, adds anhydrous sodium sulfate drying and stays overnight, rotary evaporation removes toluene, obtains The water white transparency arrived glues shape liquid, as epoxy radicals POSS；

(2) epoxy radicals POSS emulsification

Using glycerin monostearate and neopelex as composite emulsifier emulsified epoxy base POSS；

(3) epoxy radicals POSS/APP composite flame-proofs finishing agent is prepared

It is 3 in mass ratio with APP that uniform epoxy radicals POSS, which will be emulsified,:1~1:2 mixing, 90 DEG C dissolve by heating and stir Uniformly, antiflaming finishing agent is made.

2. the preparation method of epoxy radicals POSS/ ammonium polyphosphate compound fire retardants according to claim 1, it is characterised in that The aqueous isopropanol of TMAH described in step (1) is prepared using isopropanol with tetramethylammonium hydroxide aqueous solution Obtain.

3. the preparation method of epoxy radicals POSS/ ammonium polyphosphate compound fire retardants according to claim 2, it is characterised in that The concentration of described tetramethylammonium hydroxide aqueous solution is 3-8wt%, and isopropanol is pressed with tetramethylammonium hydroxide aqueous solution 100mL：5-15g mixed preparings obtain the aqueous isopropanol of TMAH.

4. the preparation method of epoxy radicals POSS/ ammonium polyphosphate compound fire retardants according to claim 1, it is characterised in that The aqueous isopropanol of 3- glycidoxypropyl trimethoxy silanes described in step (1) is by isopropanol and 3- glycidols third Epoxide trimethoxy silane presses 10-30mL：20-50g mixed preparings are obtained.

5. the preparation method of epoxy radicals POSS/ ammonium polyphosphate compound fire retardants according to claim 1, it is characterised in that Step (2) specifically uses following steps：

(2-1) adds neopelex into epoxy radicals POSS, adds water after more than 10000rpm rotating speed high-speed stirreds Uniformly；

(2-2) adds glycerin monostearate, adds water uniform after more than 10000rpm rotating speed high-speed stirreds；

(2-3) controls supersonic frequency to be 30-40kHz, by mixture through ultrasonic emulsification, obtains emulsifying uniform epoxy radicals POSS。

6. the preparation method of epoxy radicals POSS/ ammonium polyphosphate compound fire retardants according to claim 5, it is characterised in that The HLB=3.8 of described glycerin monostearate, the HLB=10.64 of described neopelex.

7. the preparation method of the epoxy radicals POSS/ ammonium polyphosphate compound fire retardants according to claim 5 or 6, its feature exists In described glycerin monostearate and the mass ratio of neopelex are 9:8~12:10, glycerin monostearate The mass ratio that obtained emulsifying agent and epoxy radicals POSS are compounded with neopelex is 1:8~1:10.

8. the epoxy radicals POSS/ ammonium polyphosphate compound fire retardants prepared according to claim 1 are hindered bafta Fire the application arranged.

9. epoxy radicals POSS/ ammonium polyphosphate compound fire retardants according to claim 8 carry out flame-proof treatment to bafta Using, it is characterised in that use following steps：

(1) bafta is dried naturally after ultrasonic wave cleaning bafta；

(2) use pads the method for baking and bafta is handled, the techniques rolled using two leachings two, utilizes the poly- phosphorus of epoxy radicals POSS/ Sour ammonium composite flame-retardant agent handles bafta, and preliminary drying is then passed through again, is baked, flame-proof treatment is completed.

10. epoxy radicals POSS/ ammonium polyphosphate compound fire retardants according to claim 9 carry out flame-proof treatment to bafta Using, it is characterised in that the pick-up control in two two roll process of leaching is in 80-90%, and the temperature of preliminary drying is 75-100 DEG C, time For 3-5min, the temperature baked is 150-170 DEG C, and the time is 3-5min.