阅读说明：本技术 磷氮协效阻燃聚乙烯醇纤维的制备方法 (Preparation method of phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber ) 是由 张再兴 舒友 李智超 欧阳跃军 乔志勇 王杰 林红卫 胡扬剑 于 2019-11-25 设计创作，主要内容包括：本发明实施例提供一种磷氮协效阻燃聚乙烯醇纤维的制备方法,通过添加富含活性基团的无卤(含磷)阻燃剂与含氮交联剂共混纺丝,或阻燃剂与含氮交联剂、以及辅助阻燃剂共混纺丝,阻燃剂分子、交联剂分子在纺丝成型后进行热处理与热定型过程中形成交联结构,交联结构穿插于聚乙烯醇分子链间形成网络互穿交联结构,获得高效、耐久的阻燃效果,从而获得磷氮协效阻燃聚乙烯醇纤维；所制备的阻燃聚乙烯醇纤维具备无卤、低毒、对环境友好的特征,可用于衣料、防护服、室内装饰材料以及交通运输用装饰材料等的阻燃与安全防护。(The embodiment of the invention provides a preparation method of a phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber, which comprises the steps of adding a halogen-free (phosphorus-containing) flame retardant rich in active groups and a nitrogen-containing cross-linking agent for blending spinning, or adding the flame retardant, the nitrogen-containing cross-linking agent and an auxiliary flame retardant for blending spinning, wherein flame retardant molecules and cross-linking agent molecules form a cross-linking structure in the processes of heat treatment and heat setting after spinning forming, and the cross-linking structure is inserted among polyvinyl alcohol molecular chains to form a network interpenetrating cross-linking structure, so that a high-efficiency and durable flame-retardant effect is obtained, and the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber; the prepared flame-retardant polyvinyl alcohol fiber has the characteristics of no halogen, low toxicity and environmental friendliness, and can be used for flame retardance and safety protection of clothing materials, protective clothing, interior decoration materials, transportation decoration materials and the like.)

1. The preparation method of the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber is characterized by comprising the following steps of:

dissolving polyvinyl alcohol, and then blending with a phosphorus-containing flame retardant and a nitrogen-containing crosslinking agent to obtain a blending solution;

defoaming, filtering and metering the blended solution, feeding the blended solution into a spinning assembly through a filter, extruding the blended solution into a coagulating bath through a spinneret plate, and carrying out coagulation forming to obtain nascent fibers;

sequentially carrying out wet heat stretching, dry heat stretching and heat setting on the nascent fiber to form a network interpenetrating cross-linked structure fiber;

and then acetalization, washing and drying are carried out to obtain the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber.

2. The method of claim 1, wherein the crosslinking agent has the general structural formula NH ₂-R-NH ₂；

The cross-linking agent is selected from diamine or polyamine, preferably thiourea, guanidine and its derivatives, melamine, ethylenediamine, hexamethylenediamine, decamethylenediamine.

3. The production method according to claim 1, wherein the flame retardant is tetrakis hydroxymethyl phosphonium chloride or tetrakis hydroxymethyl phosphonium sulfate;

the alcoholysis degree of the polyvinyl alcohol is more than 99%, and the average polymerization degree is 1700.

4. The method of claim 1, further comprising the steps of:

adding an auxiliary flame retardant in the blending process; the auxiliary flame retardant is selected from antimony trioxide.

5. The preparation method according to claim 1, wherein the blending process comprises the following steps:

dissolving the dried polyvinyl alcohol in hot water at 93-98 ℃ to obtain a polyvinyl alcohol aqueous solution;

adding a flame retardant with a pH value of 6.5-8.5 into the polyvinyl alcohol aqueous solution in proportion, and stirring and mixing for 0.5-2 hours to obtain a mixed aqueous solution of polyvinyl alcohol;

and adding the water solution of the cross-linking agent into the mixed water solution of the polyvinyl alcohol, and stirring and mixing for 0.5-2 h to obtain the blending solution.

6. The preparation method according to claim 5, wherein the temperature of the blending solution is controlled to be 85-95 ℃, and the pH value is 6.5-7.5;

the weight percentages of the polyvinyl alcohol, the flame retardant and the cross-linking agent are respectively 72-86%, 12-20% and 2-8%;

the defoaming step adopts negative pressure or vacuum defoaming, and the negative pressure is 70-0.5 kPa;

and in the filtering step, two stainless steel filter screens are adopted, and the aperture of each stainless steel filter screen is 60-50 microns and 40-30 microns.

7. The method according to claim 1, wherein the coagulation bath is an aqueous sodium sulfate solution having a concentration of 380 to 420g.L ^-1The pH value is controlled to be 7-8, and the temperature is controlled to be 40-50 ℃.

8. The production method according to claim 1,

in the wet-heat stretching step, the moisture content of the nascent fiber is controlled to be 5-15%, hot air drying or infrared drying is adopted, the stretching temperature is 60-120 ℃, and the stretching multiple is 0.1-1;

the stretching temperature of the dry heat stretching is 150-190 ℃, the stretching multiple is 1-2, and the stretching time is 2-5 min;

the heat setting temperature is 170-210 ℃, and the heat setting time is 3-10 min.

9. The preparation method according to claim 1, wherein the acetalization step adopts an acetal solution, the acetalization temperature is 65-75 ℃, and the time is 20-40 min;

the acetal solution consists of: formaldehyde 30 +/-2 g.L ^-1230 +/-10 g.L of sulfuric acid ^-170 +/-5 g.L of sodium sulfate ^-1。

10. A phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber, which is obtained by the preparation method of any one of claims 1 to 9.

Technical Field

The invention relates to a preparation method of flame-retardant polyvinyl alcohol fibers, in particular to a preparation method of phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fibers.

Background

With the development of national economy, the fire caused by textiles is more serious, the development of textiles with flame retardant property is urgent in order to guarantee the development of personal safety and economy, various flame retardant fabrics come out one after another, but most of the flame retardant fabrics belong to the fabric after finishing. The flame-retardant fiber is not developed in China and has small yield. At present, the relatively mature methods for preparing the flame-retardant PVA fiber comprise copolymerization flame retardance, blending flame retardance, yarn and fabric after-finishing flame retardance, preparation of flame-retardant fabric by blending non-flame-retardant PVA fiber and other flame-retardant fibers and the like, and the application range is gradually expanded from military use to industrial use, so that the flame-retardant PVA fiber is developed to civil use.

The flame-retardant polyvinyl chloride fiber is the most main product in the copolymerization flame-retardant modified PVA fiber, and the production technology is a polyvinyl alcohol-vinyl chloride graft copolymerization technology and a wet spinning technology, and the production technology is mainly owned by Korea and Xingshan companies in Japan. The polyvinyl alcohol blending flame-retardant modified fiber generally comprises the working procedures of polyvinyl alcohol and flame retardant blending (decabromodiphenyl ether and antimony trioxide or other powdery insoluble flame retardants are added into a spinning stock solution of the polyvinyl alcohol), grinding (the powdery flame retardants can be ground firstly), filtering, wet spinning, washing, drying, hot stretching, acetalization and the like. At present, research reports on halogen-free flame-retardant polyvinyl alcohol fibers at home and abroad are also provided, for example, if tetraethoxysilane, melamine formaldehyde resin, N-hydroxymethyl-3- (dimethoxyphosphono) propionamide, or modified substances thereof, montmorillonite, phosphate powder, dithiopyrophosphate, silicon dioxide compound powder and the like are adopted as flame retardants and added into a PVA spinning solution, the flame-retardant polyvinyl alcohol fibers have good flame-retardant effect, but the defects of high cost, difficult dispersion of the flame retardants, large addition amount and the like exist. In order to solve the problem of high energy consumption in the processing process of the polyvinyl alcohol flame-retardant fiber, a patent that plasticizer plasticized polyvinyl alcohol can be used for melt spinning is newly appeared, solid flame retardants which are difficult to dissolve in water, such as ammonium polyphosphate, melamine cyanurate and the like, are blended with metal hydroxide or graphene oxide and the like in a system, and the flame-retardant polyvinyl alcohol flame-retardant fiber has a certain flame-retardant effect, but can only be used for preparing thicker fiber or non-woven fabric.

The industrial production of polyvinyl alcohol fiber adopts a wet spinning forming technology, many flame retardants with active groups are easy to react in a polyvinyl alcohol aqueous solution, are difficult to graft or cross-link to hydroxyl groups of a polyvinyl alcohol molecular chain, and the activity of the hydroxyl groups of the polyvinyl alcohol is low, so that permanent and efficient flame retardant polyvinyl alcohol fiber is difficult to obtain.

Disclosure of Invention

The invention aims to provide a preparation method of phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fibers, and the prepared phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fibers have high-efficiency and durable flame-retardant effects.

The invention adopts the following technical scheme:

the invention provides a preparation method of a phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber, which comprises the following steps:

dissolving polyvinyl alcohol, and then blending with a phosphorus-containing flame retardant and a nitrogen-containing crosslinking agent to obtain a blending solution;

defoaming, filtering and metering the blended solution, feeding the blended solution into a spinning assembly through a filter, extruding the blended solution into a coagulating bath through a spinneret plate, and carrying out coagulation forming to obtain nascent fibers;

sequentially carrying out wet heat stretching, dry heat stretching and heat setting on the nascent fiber to form a network interpenetrating cross-linked structure fiber;

and then acetalization, washing and drying are carried out to obtain the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber.

Preferably, the structural general formula of the cross-linking agent is NH ₂-R-NH ₂；

The cross-linking agent is selected from diamine or polyamine, preferably thiourea, guanidine and its derivatives, melamine, ethylenediamine, hexamethylenediamine, decamethylenediamine.

Preferably, the flame retardant is tetrakis (hydroxymethyl) phosphonium chloride or tetrakis (hydroxymethyl) phosphonium sulfate;

the alcoholysis degree of the polyvinyl alcohol is more than 99%, and the average polymerization degree is 1700.

Preferably, the method further comprises the following steps:

adding an auxiliary flame retardant in the blending process; the auxiliary flame retardant is selected from antimony trioxide.

Preferably, the blending process specifically comprises the following steps:

dissolving the dried polyvinyl alcohol in hot water at 93-98 ℃ to obtain a polyvinyl alcohol aqueous solution;

adding a flame retardant with a pH value of 6.5-8.5 into the polyvinyl alcohol aqueous solution in proportion, and stirring and mixing for 0.5-2 hours to obtain a mixed aqueous solution of polyvinyl alcohol;

and adding the water solution of the cross-linking agent into the mixed water solution of the polyvinyl alcohol, and stirring and mixing for 0.5-2 h to obtain the blending solution.

Preferably, the temperature of the blending solution is controlled to be 85-95 ℃, and the pH value is 6.5-7.5;

the weight percentages of the polyvinyl alcohol, the flame retardant and the cross-linking agent are respectively 72-86%, 12-20% and 2-8%;

the defoaming step adopts negative pressure or vacuum defoaming, and the negative pressure is 70-0.5 kPa;

and in the filtering step, two stainless steel filter screens are adopted, and the aperture of each stainless steel filter screen is 60-50 microns and 40-30 microns.

Preferably, the coagulating bath is a sodium sulfate aqueous solution, and the concentration of the sodium sulfate aqueous solution is 380-420 g.L ^-1The pH value is controlled to be 7-8, and the temperature is controlled to be 40-50 ℃.

Preferably, in the wet-hot stretching step, the moisture content of the nascent fiber is controlled to be 5-15%, hot air drying or infrared drying is adopted, the stretching temperature is 60-120 ℃, and the stretching multiple is 0.1-1;

the stretching temperature of the dry heat stretching is 150-190 ℃, the stretching multiple is 1-2, and the stretching time is 2-5 min;

the heat setting temperature is 170-210 ℃, and the heat setting time is 3-10 min.

Preferably, the acetalization step adopts an acetal solution, the acetalization temperature is 65-75 ℃, and the time is 20-40 min;

the acetal solution consists of: formaldehyde 30 +/-2 g.L ^-1230 +/-10 g.L of sulfuric acid ^-170 +/-5 g.L of sodium sulfate ^-1。

The invention also provides phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber which is prepared by any preparation method.

The invention has the beneficial effects that:

1. the invention provides a preparation method of phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fibers, and the prepared phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fibers have high-efficiency and durable flame-retardant effects.

2. According to the embodiment of the invention, through adding the halogen-free (phosphorus-containing) flame retardant rich in active groups and the nitrogen-containing cross-linking agent for blending spinning, or adding the flame retardant, the nitrogen-containing cross-linking agent and the auxiliary flame retardant for blending spinning, flame retardant molecules and cross-linking agent molecules form a cross-linking structure in the processes of heat treatment and heat setting after spinning forming, and the cross-linking structure is inserted among polyvinyl alcohol molecular chains to form a network interpenetrating cross-linking structure, so that a high-efficiency and durable flame-retardant effect is obtained, and thus the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber is obtained.

3. The flame-retardant polyvinyl alcohol fiber prepared by the embodiment of the invention has the advantages of good dimensional stability, good hygroscopicity, good dyeability, no melting and dripping when being heated, very low combustion fuming property, less toxic gas generated by decomposition, environmental friendliness and the like.

4. The flame-retardant polyvinyl alcohol fiber prepared by the embodiment of the invention has the characteristics of no halogen, low toxicity and environmental friendliness, and can be used for flame retardance and safety protection of clothing materials, protective clothing, interior decoration materials, decoration materials for transportation and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only examples of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a flow chart of a method for preparing a phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber according to an embodiment of the present invention;

FIG. 2 is an electron micrograph of the interpenetrating cross-linked structure of the network formed in the example of the present invention.

Reference numerals: 1 represents polyvinyl alcohol; 2 represents a crosslinked structure of the flame retardant and the crosslinking agent.

Detailed Description

The conception, the specific structure, and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below, so that the objects, the features, and the effects of the present invention can be fully understood. It is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and those skilled in the art can obtain other embodiments without inventive effort based on the embodiments of the present invention, and all embodiments are within the protection scope of the present invention.

An embodiment of the invention provides a preparation method of a phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber, which comprises the following steps of S1-S4:

s1, dissolving the dried polyvinyl alcohol (PVA) in hot water, and then blending with the flame retardant and the crosslinking agent to obtain a blending solution;

s2, defoaming and filtering the blended solution to obtain a spinning solution, metering the spinning solution, feeding the spinning solution into a spinning assembly through a candle filter, extruding the spinning solution into a coagulating bath through a spinneret plate, and coagulating and forming to obtain nascent fibers;

s3, sequentially carrying out wet heat stretching, dry heat stretching and heat setting on the nascent fiber, and mutually crosslinking the flame retardant and the crosslinking agent to form a crosslinking structure, wherein the crosslinking structure is inserted into a polyvinyl alcohol molecular chain or crosslinked with polyvinyl alcohol molecules to form a network interpenetrating crosslinking structure, so that the polyvinyl alcohol fiber has a permanent and efficient flame retardant effect.

And S4, acetalizing, washing and drying to obtain the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber. The phosphorus-nitrogen synergistic flame-retardant wet-process polyvinyl alcohol filament fiber is obtained in the embodiment.

Wherein, the washing and drying processes can be carried out after acetalation and under the relaxed state, so as to improve the hot water resistance of the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber.

It can be understood that the invention also provides another embodiment, the network interpenetrating crosslinked structure fiber can be cut before acetalization, and acetalization is carried out, and finally the phosphorus-nitrogen synergistic flame-retardant wet-process polyvinyl alcohol short fiber is obtained.

Optionally, during the blending process, auxiliary flame retardants may also be added, namely: dissolving polyvinyl alcohol in hot water, and then blending with the flame retardant, the cross-linking agent and the auxiliary flame retardant.

In one embodiment, the crosslinking agent is selected from diamine or polyamine, and the structural formula can be NH ₂-R-NH ₂Preferably, thiourea, guanidine and derivatives thereof, melamine, ethylenediamine, hexamethylenediamine and decamethylenediamine are used, and antimony trioxide can be used as the auxiliary flame retardant.

In one particular embodiment, the flame retardant may be tetrakis hydroxymethyl phosphonium chloride or tetrakis hydroxymethyl phosphonium sulfate.

In one particular embodiment, the blending process is required to achieve: the alcoholysis degree of the polyvinyl alcohol is more than 99 percent, and the average polymerization degree is 1700.

Specifically, the blending process comprises the following steps of ① - ③:

①, dissolving the dried polyvinyl alcohol in hot water at 93-98 ℃ to obtain a polyvinyl alcohol aqueous solution;

②, adding a flame retardant with the pH value adjusted to 6.5-8.5 into the polyvinyl alcohol aqueous solution in proportion, and stirring and mixing for 0.5-2 h to obtain a mixed aqueous solution of polyvinyl alcohol;

③ adding the water solution of the cross-linking agent into the mixed water solution of the polyvinyl alcohol, stirring and mixing for 0.5-2 h to obtain a blended solution.

Furthermore, the temperature of the blending solution is controlled to be 85-95 ℃, and the pH value is 6.5-7.5.

Optionally, the PH of the flame retardant in step ② is adjusted to neutral, i.e., PH 7.0 ± 0.2, and the stirring and mixing time of step ② and step ③ are both 1h, the PH of the final blend solution is 7.0 ± 0.2, and the temperature of the blend solution is 90 ± 2 ℃.

In a specific embodiment, the blending solution comprises, by weight, 72-86% of polyvinyl alcohol, 12-20% of a flame retardant and 2-8% of a crosslinking agent.

Preferably, in the blending solution, by weight percentage, the polyvinyl alcohol accounts for 76-86%: 12-18% of flame retardant: 2-6% of a cross-linking agent. In the blending solution, the weight percentage of polyvinyl alcohol and water is 15-20%: 80-85%.

It is understood that the weight percentages of the present examples are calculated on a dry weight basis or on a pure material from which the specific gravity of the water and contained acids has been removed.

In one embodiment, the defoaming step adopts negative pressure or vacuum defoaming, and the negative pressure is selected from 70-0.5 kPa;

in one embodiment, the filtering step employs two stainless steel filter screens, and the aperture of each stainless steel filter screen is 60-50 μm and 40-30 μm. Preferably, the pore diameters of the two stainless steel filter screens are 50 μm and 40 μm respectively.

In one embodiment, the coagulating bath is an aqueous sodium sulfate solution, and the concentration of the aqueous sodium sulfate solution is 380-420 g.L ^-1Sodium hydroxide aqueous solution can be added to control the pH value to be 7-8 and the temperature to be 40-50 ℃.

In one embodiment, in the wet-hot stretching step, the moisture content of the nascent fiber is controlled to be 5-15%, hot air drying or infrared drying is adopted, the stretching temperature is 60-120 ℃, and the stretching ratio is 0.1-1;

the stretching temperature of dry heat stretching is 150-190 ℃, the stretching multiple is 1-2, and the stretching time is 2-5 min;

the heat setting temperature is 170-210 ℃, the heat setting time is 3-10 min, and the heat setting is carried out under low tension.

Preferably, the wet-heat stretching temperature is 90-110 ℃, and the stretching multiple is 0.5 +/-0.1; the stretching temperature of dry heat stretching is 170-180 ℃, the stretching multiple is 1.5-2, and the stretching time is 4-5 min; the heat setting temperature is 190-200 ℃, and the heat setting time is 5-8 min.

After the solidified and formed polyvinyl alcohol nascent fiber is subjected to wet-heat stretching, dry-heat stretching and heat setting processes, a cross-linking structure shown as a formula I is formed, namely, a flame retardant and a cross-linking agent react in the wet-heat stretching, dry-heat stretching and heat setting processes (the reaction principle is shown as a formula II), and the cross-linking structure shown as the formula I is formed gradually; the cross-linking structure is inserted among polyvinyl alcohol molecular chains or is cross-linked with polyvinyl alcohol molecules to form a network interpenetrating cross-linking structure, so that the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber has a permanent and efficient flame-retardant effect. An electron microscope image of the interpenetrating cross-linked structure of the network is shown in fig. 2, wherein the network is a cross-linked structure and the solid part is polyvinyl alcohol.

A cross-linked structure formed by the flame retardant of the formula (I) and the cross-linking agent

Wherein, R can be C ═ NH, C ═ S, C-C straight-chain alkyl and C-N heterocycle.

Reaction principle of flame retardant of formula (II) and crosslinking agent

Wherein, R can be C ═ NH, C ═ S, C-C straight-chain alkyl and C-N heterocycle.

In one embodiment, the acetalization step uses an acetal solution, the acetalization temperature is 65-75 ℃, and the acetalization time is 20-40 min; preferably, the acetalization temperature is 70 ℃ and the time is 30 min.

The acetal solution consisted of: formaldehyde 30 +/-2 g.L ^-1230 +/-10 g.L of sulfuric acid ^-170 +/-5 g.L of sodium sulfate ^-1

According to the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber prepared by the method disclosed by the embodiment of the invention, through test tests, the linear density of the fiber is 1.56-22.22 dtex, the breaking strength is 2.0-7.7 cN.dtex-1, the elongation at break is 10-50%, and the Limiting Oxygen Index (LOI) is 29.2-34.1%; preferably, the linear density can reach 1.56-6.67 dtex, the breaking strength is 3.0-6.0 cN.dtex-1, the elongation at break is 10-30%, and the Limiting Oxygen Index (LOI) is 30-34.1%, so that the requirements of flame retardance and protection in the textile field are completely met; moreover, the prepared phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber has the advantages of good dimensional stability (the softening point in water is more than 110 ℃), good hygroscopicity, good dyeability (reactive dyes, disperse dyes and the like can be dyed), no melting and dripping when being heated, very low combustion fuming property (the maximum smoke density is 50-60%, the smoke density grade is 20-30%), less toxic gas generated by decomposition, environmental friendliness and the like.

Therefore, the phosphorus-nitrogen synergistic flame-retardant polyvinyl alcohol fiber obtained in the embodiment of the invention can be used for a plurality of purposes in the aspects of clothing, protective clothing, interior decoration materials, transportation decoration materials and the like. For example, protective clothing for use in fire fighting, military, and the like; the product is applied to decorative materials such as curtains, carpets, covering cloth, bedding and the like; especially can be used in the clothes of women and children, the plush toys of children and the like, and can provide better safety guarantee for women and children.

The following are specific examples.