CN103526335B - A kind of preparation method of fluorine-containing PBT-PBT core-skin composite fiber - Google Patents

Abstract

The invention relates to a preparation method of fluorine-containing PBT-PBT sheath-core composite fiber, which comprises the preparation of fluorine-containing PBT as a skin layer material and the preparation of the skin-core composite fiber. Fluorine-containing PBT is obtained by using tetrafluoroterephthalic acid and 1,4-butanediol as raw materials, adding inhibitors, and performing esterification and polycondensation reactions under appropriate conditions. Then use the fluorine-containing PBT as the sheath and the PBT as the core, and adopt a suitable composite spinning process to prepare the sheath-core composite fiber. The fluorine-containing PBT obtained by the invention has good thermal stability and processability, and the introduction of fluorine atoms improves its water-repellent and oil-repellent properties. The fiber made by composite spinning not only has good mechanical properties of PBT, but also has good stain resistance, and at the same time greatly saves costs, making it suitable for waterproof clothing, dirty work clothes and work clothes in some special industries. There are huge prospects.

Description

A kind of preparation method of fluorine-containing PBT-PBT sheath-core composite fiber

technical field

The invention relates to a preparation method of fluorine-containing PBT-PBT sheath-core composite fiber, which comprises the preparation of fluorine-containing PBT as a skin layer material and the preparation of the skin-core composite fiber. In particular, it relates to a preparation method of a skin-core composite fiber with polytetrafluorobutylene terephthalate as the fluorine-containing PBT material in the skin layer and PBT as the core layer material.

Background technique

With the development and progress of technology and the continuous improvement of people's requirements, the fiber of a single material can no longer meet people's needs very well, and various composite fibers have emerged as the times require. They have properties that cannot be possessed by fibers of a single material at the same time. They have the advantages of multiple fibers and can provide better performance. Among them, the skin-core composite fiber is a good composite fiber. This kind of fiber can not only have some properties of the skin fiber, but also have some properties of the core fiber. A reasonable combination of properties can obtain a skin-core composite fiber with excellent performance. The preparation process is simple, and at the same time, the amount of skin material can be reduced. save costs.

Polyester is currently one of the most widely used synthetic polymers. As early as the 1940s, polyethylene terephthalate (PET) was synthesized and found to have excellent properties. It is widely used in textile, packaging, medical and health, automobile, electronic appliances, safety protection, environmental protection and other fields. Polybutylene terephthalate (PBT) is a crystalline linear saturated polyester, which has the characteristics of high temperature resistance, humidity resistance, good electrical insulation performance, oil resistance, chemical corrosion resistance, and fast molding. Some of its application examples in the industry have shown its irreplaceable superiority in some aspects, and now it has become the next-generation polyamide (PA), polycarbonate (PC), polyoxymethylene (POM) and modified polyphenylene The fifth largest general-purpose engineering plastic after ether (MPPO), it is widely used in the automobile industry, electronic and electrical industry, food and medical equipment, packaging materials, environmental engineering, communication equipment, sports and leisure equipment, etc. With the continuous deepening of research on the structure and performance of PBT, not only have different grades and types of engineering plastics been developed, such as high-impact, heat-resistant, flame-retardant, etc., but also make its application in synthetic fibers more and more valued. PBT fiber has excellent elasticity, soft hand feeling, easy dyeing, and has the advantages of polyester, nylon and spandex. With the progress of society and the improvement of people's living standards, the demand for the differentiation and functionalization of polyester fibers is getting higher and higher. Therefore, the modification of polyester has become particularly important. The purpose of polyester modification is not only to optimize the performance of ordinary polyester, but also to endow new polyester with differentiated functional characteristics through modification means. For example: antistatic, flame retardant, moisture wicking, antifouling and deodorant, etc. At present, the main new varieties of polyester are: antistatic polyester, high-strength wear-resistant polyester, cotton-like supersoft polyester, superhydrophobic polyester, antifouling polyester, etc. At present, by introducing fluorine atoms into polymers, the surface properties of materials, such as hydrophobicity, oil repellency and anti-fouling properties, etc. are improved, and various functions are endowed to polyester materials. Because fluoropolymers usually have low surface energy, low coefficient of friction and non-adhesion, dust and dirt are difficult to adhere to, etc., so fluoropolymers have good anti-fouling and abrasion resistance. The current fluorine-containing polymers are mainly fluoroolefin polymers (for example: polytetrafluoroethylene, polyvinylidene fluoride, perfluoroethylene propylene copolymer, ethylene-tetrafluoroethylene copolymer, etc.); Research on fluoropolyethers and fluoropolyesters is relatively lagging behind. Many scholars have conducted research on fluorine-containing compound-modified polyester, and achieved certain results. At present, polyesters are modified by fluorine-containing compounds mainly by adding fluorine-containing end-capping agents, or by adding fluorine-containing diols, fluorine-containing dibasic acids and other fluorine-containing compounds as the third monomer to modify polyester. In Chinese patent CN101139434A, the addition of fluorine-containing end-capping agent is adopted. Dimethyl isophthalate and butanediol are transesterified, and fluorine-containing end-capping agent N-hydroxyethyl perfluorooctylamide is added to prepare a fluorine-containing end-capping agent. Polyester material with low weight and good stain resistance. Hu Juan (Hu Juan. Molecular design and performance research of fluorine-containing polyester and photoresist waveguide materials [D]. Master's thesis, Jilin: Jilin University, 2007.) Using the principle of molecular design, by adding fluorine-containing diols In the way of copolymerization, terephthaloyl chloride, hexafluorobisphenol A and fluorine-containing octanediol are terpolymerized to form a new type of polyester with high fluorine content. The polyester has excellent properties and is applied to optical waveguide materials. However, the application of these fluorine-containing polyesters to textiles and packaging materials has certain limitations. The main problem is that the prior art fluorine-containing polyesters have low molecular weight and cannot meet the requirements of spinning and film formation; At present, the existing technology mainly uses fluorine-containing finishing methods to endow fabrics with waterproof and anti-fouling functions, but the biggest disadvantage of this method is that it is difficult to solve the problems of timeliness, durability and wear resistance, and it is time-consuming and labor-intensive.

Therefore, the development of new fluorine-containing polyester sheath-core composite fibers for the modification of superhydrophobic, hydrophobic, oil-repellent, and antifouling properties of textile and packaging materials will have important theoretical significance and application value. It has great prospects in the manufacture of waterproof clothing, dirt-resistant work clothes and work clothes in some special industries.

Contents of the invention

The purpose of the present invention is to provide a method for preparing fluorine-containing PBT-PBT sheath-core composite fibers, including the preparation of fluorine-containing PBT as a skin layer material and the preparation of sheath-core composite fibers. Among them, fluorine-containing PBT refers to polytetrafluorobutylene terephthalate. The fluorine-containing PBT described in the present invention introduces fluorine atoms into the main chain of the polymer, and the prepared fluorine-containing PBT chips can be directly used for spinning, which can endow the fluorine-containing PBT fibers with permanent water and oil repellency, and solve the problem of The traditional PBT fiber hydrophobic and oil-repellent modification is time-consuming and labor-intensive. At the same time, the composite spinning method is used to prepare the skin-core composite fiber with fluorine-containing PBT as the skin material and PBT as the core material, which not only endows the skin-core composite fiber with good hydrophobic and oil-repellent properties, but also greatly saves the cost.

A preparation method of fluorine-containing PBT-PBT sheath-core composite fiber of the present invention, the material of the skin layer is PBT containing fluorine, and the material of the core layer is PBT; the PBT containing fluorine is polytetrafluorobutylene terephthalate, and The general structural formula is

Where n=70-150; the ratio of the cross-sectional area of the skin layer to the core layer of the fluorine-containing PBT-PBT sheath-core composite fiber is 2-5:5.

A fluorine-containing PBT-PBT sheath-core composite fiber as described above, the monofilament fineness of the fluorine-containing PBT-PBT sheath-core composite fiber is 1 to 15 dtex; including the preparation method of fluorine-containing PBT and the preparation of the skin-core composite fiber method, the specific steps are:

1. Preparation method of fluorine-containing PBT

It is divided into two steps of esterification reaction and polycondensation reaction; the specific steps are:

Described esterification reaction:

Adopt tetrafluoroterephthalic acid and 1,4-butanediol as raw materials, add inhibitor, the addition amount of described inhibitor is 0.01%～0.05% of the weight of described tetrafluoroterephthalic acid, is made into uniform Esterification reaction is carried out after the slurry; the esterification reaction is pressurized in a nitrogen atmosphere, the pressure is controlled at less than 1KPa of absolute pressure, the temperature is 160-220°C, the time is 2-3 hours, and the distilled amount of esterification water reaches the theoretical level. More than 90% of the value is the end point of the esterification reaction;

Described suppressor is a kind of in magnesium oxide, silicon oxide, calcium oxide, zinc oxide and manganese oxide; Because there is fluorine atom on the benzene ring of dibasic carboxylic acid used, the electronegativity of fluorine atom is big, in esterification The conjugation effect of the fluorine atom in the reaction stage increases the acidity of the dicarboxylic acid, and at the same time increases the activity of the carboxyl group in the dicarboxylic acid, which speeds up the reaction rate, and the increase in the reaction rate is likely to cause side reactions. The follow-up polycondensation reaction has a greater impact, especially the generation of end-capped products of olefins and aldehydes, which restricts the increase in the molecular weight of the product; from the experimental results, if no inhibitor is added, the molecular weight of the synthesized polyester is low, which cannot meet the requirements. Spinning and film-forming requirements; the addition of inhibitors is used to control the speed of the esterification reaction stage, reducing side reactions, increasing the molecular weight of the product, and meeting the spinning requirements.

Usually, in the polyester esterification process, the hydrogen ion ionized by the dicarboxylic acid used is used as a catalyst for the esterification reaction to carry out a self-catalyzed reaction, and the esterification reaction is controlled by adjusting the temperature, pressure and discharge of small molecules. However, the premise of the esterification reaction is that the esterification reaction can only be carried out under a certain reaction temperature and pressure. When the temperature is too low or the pressure is not enough, the esterification reaction cannot proceed or the speed is extremely slow, thereby affecting the subsequent process. If the small molecules in the esterification reaction are not discharged in time, it is easy to cause unnecessary side reactions. During the synthesis process, due to the conjugation effect of fluorine, the fluorine atom increases the acidity of the dicarboxylic acid in the esterification reaction stage, and at the same time increases the activity of the carboxyl group in the dicarboxylic acid, which makes the reaction speed faster and the side reactions increase. Control, and then affect the growth of the molecular weight of the product, so the addition of inhibitors is adjusted by selecting the metal oxide used. The metal oxide can be dissociated in the following two ways:

Here M is a metal ion. If the electronegativity of M is quite large, it has a strong attraction to the electron pairs of oxygen ions, which can weaken the O—H bond and facilitate the reaction dissociation; on the contrary, if the electronegativity of M If the sex is small, then the base center will be formed. M—O—H is similar to amphoteric compounds. When alkaline substances exist, the reaction will proceed in the form of acid ionization; when acidic substances exist, the reaction will proceed in the form of basic ionization. From the reverse reactions of MO ^- and M ⁺ in the acid ionization mode and base ionization mode, it can be seen that M ⁺ acts as an acidic center, and its strength is only directly related to the electronegativity of the metal ion, while the O ion in MO ^- acts as a base The intensity of the center is related to the negative charge density on the oxygen, the greater the negative charge density, the greater the intensity. It can be seen that the negative charge density on oxygen ions is closely related to the electronegativity of metal ions, the smaller the electronegativity of metal ions, the greater the negative charge density. In this way, the acidity and alkalinity of metal oxides are related to the electronegativity of metal ions. The oxides with high electronegativity of metal ions are mainly acidic, while those with low electronegativity are alkaline.

Described polycondensation reaction:

Including the low vacuum stage of polycondensation reaction and the high vacuum stage of polycondensation reaction;

In the low-vacuum stage of the polycondensation reaction, a catalyst and a stabilizer are added to the esterification product, and the polycondensation reaction starts under negative pressure. 40-60 minutes;

In the high vacuum stage of the polycondensation reaction, after the low vacuum stage of the polycondensation reaction, the vacuum is continued to reduce the reaction pressure to an absolute pressure of less than 100 Pa, the reaction temperature is controlled at 270-275°C, and the reaction time is 3-4 hours. The polycondensation reaction is based on the power of the stirring motor of the reactor or the reading of the online viscometer to judge the end point of the reaction.

2. Preparation method of fluorine-containing PBT-PBT sheath-core composite fiber

The fluorine-containing PBT is used as the skin layer material, and the PBT is used as the core layer material to carry out sheath-core composite spinning, the spinning temperature is 270-280° C., and the winding speed is controlled at 2700-3200 m/min.

As a preferred technical solution:

According to the method for preparing fluorine-containing PBT-PBT sheath-core composite fibers, the molar ratio of butanediol to tetrafluoroterephthalic acid is 1.4-2.0:1.

A kind of preparation method of fluorine-containing PBT-PBT sheath-core composite fiber as mentioned above, described catalyst is selected from tetrabutyl titanate, tetraisopropyl titanate, tetraethyl titanate, stannous acetate, diacetic acid One of dibutyltin, the amount of the catalyst used is 0.01% to 0.05% of the weight of the tetrafluoroterephthalic acid.

A kind of preparation method of fluorine-containing PBT-PBT sheath-core composite fiber as mentioned above, described stabilizer is selected from a kind of in triphenyl phosphate, trimethyl phosphate and trimethyl phosphite, and stabilizer consumption is 0.01%-0.05% of the weight of the tetrafluoroterephthalic acid.

In the esterification reaction stage of the present invention, the end point of the reaction is determined by the amount of water distilled out actually produced in the esterification reaching more than 90% of the theoretical value. The theoretical value is the distilled amount of water obtained when the chemical reaction equation is completely reacted. Since the esterification reaction itself is a reversible reaction, and the raw materials will remain in the pipeline, and as the reaction progresses, the viscosity of the system will increase, making it difficult to discharge the water produced by the esterification reaction.

In the high vacuum stage of the polycondensation reaction of the present invention, the end point of the reaction is determined by the calculated value of the motor power of the reactor stirrer and the online viscosity reaching the set value. The set values of the motor power of the reactor agitator and the online viscosity calculation value of different devices are not necessarily the same, and the determination of the set values can be obtained by analyzing the polyester chips.

The fluorine-containing PBT obtained in the present invention improves the hydrophobic and oil-repellent properties of the PBT material due to the introduction of fluorine atoms, so the skin-core composite fiber with the fluorine-containing PBT in the present invention as the skin layer and PBT as the core layer not only has good mechanical properties performance, and good permanent oil resistance, and the cost is greatly reduced, so that it has great prospects in the manufacture of waterproof clothing, dirt-resistant work clothes and work clothes in some special industries.

Beneficial effect:

1. The prepared PBT contains fluorine atoms. Due to the strong electronegativity of fluorine, the high C-F bond energy and the shielding effect on the carbon chain, the synthesized copolyester not only further improves the performance of traditional polyester, but also reduces Improve the surface energy of the polyester material, so that the material has a permanent water-repellent, oil-repellent, and oil-resistant properties.

2. During the esterification process of fluorine-containing PBT, the speed of the esterification reaction can be controlled by adding inhibitors to reduce the occurrence of side reactions.

3. The resulting fluorine-containing PBT chips can be directly spun.

4. The obtained fluorine-containing PBT has good thermal stability and processability.

5. The skin-core composite fiber made of fluorine-containing PBT as the skin material and PBT as the core material has good mechanical properties and permanent oil resistance, and compared with fibers prepared by using fluorine-containing PBT alone, the cost is greatly reduced , so it has better application value.

detailed description

The present invention will be further described below in combination with specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

A fluorine-containing PBT-PBT sheath-core composite fiber of the present invention, the material of the skin layer is PBT containing fluorine, and the material of the core layer is PBT; the PBT containing fluorine is polytetrafluorobutylene terephthalate, and its general structure is for

Wherein n=70～150.

According to the above-mentioned fluorine-containing PBT-PBT sheath-core composite fiber, the ratio of the cross-sectional area of the skin layer to the core layer of the fluorine-containing PBT-PBT sheath-core composite fiber is 2-5:5.

A fluorine-containing PBT-PBT sheath-core composite fiber as described above, wherein the monofilament fineness of the fluorine-containing PBT-PBT sheath-core composite fiber is 1-15 dtex.

Example 1

1. The preparation method of fluorine-containing PBT polyester is divided into two steps of esterification reaction and polycondensation reaction. The specific steps are:

Described esterification reaction:

Use 1,4-butanediol and tetrafluoroterephthalic acid with a molar ratio of 1.4:1 as raw materials, and add 0.01% magnesium oxide based on the weight of tetrafluoroterephthalic acid at the same time, make a uniform slurry and carry out esterification reaction ; The esterification reaction is carried out in a nitrogen atmosphere, the pressure is controlled below 1KPa, the temperature is controlled at 220°C, and the esterification water distillate reaches 90% of the theoretical value, which is the end point of the esterification reaction.

Described polycondensation reaction:

Including low vacuum stage of polycondensation reaction and high vacuum stage of polycondensation reaction:

In the low-vacuum stage of the polycondensation reaction, 0.01% of the weight of tetrafluoroterephthalic acid is added to the esterified product. The catalyst tetrabutyl titanate and the stabilizer triphenyl phosphate of 0.01% of the weight of tetrafluoroterephthalic acid are added, The polycondensation reaction starts under the condition of negative pressure, said negative pressure means that the absolute pressure is less than 500 Pa, the temperature is controlled at 265° C., and the reaction time is 60 minutes.

In the high vacuum stage of the polycondensation reaction, after the low vacuum stage of the polycondensation reaction, the vacuum is continued to reduce the reaction pressure to an absolute pressure of less than 100 Pa, the reaction temperature is controlled at 270° C., and the reaction time is 4 hours. The polycondensation reaction is based on the power of the stirring motor of the reactor or the reading of the online viscometer to judge the end point of the reaction. When the viscosity of the polymer reaches the desired value, the material is discharged, and after casting, cooling and pelletizing, the fluorine-containing PBT polyester chips are obtained.

2. Preparation of skin-core composite fiber: use the fluorine-containing PBT as the skin layer material, PBT as the core layer material, and carry out skin-core composite spinning, the ratio of the cross-sectional area of the skin layer and the core layer is 2:5, and the spinning temperature The temperature is 270°C, the winding speed is controlled at 2700m/min, and the monofilament fineness of the obtained fluorine-containing PBT-PBT sheath-core composite fiber is 1dtex.

Example 2

1. The preparation method of fluorine-containing PBT polyester is divided into two steps of esterification reaction and polycondensation reaction. The specific steps are:

Described esterification reaction:

Use 1,4-butanediol and tetrafluoroterephthalic acid with a molar ratio of 1.6:1 as raw materials, and add 0.02% silicon oxide based on the weight of tetrafluoroterephthalic acid at the same time, make a uniform slurry and carry out esterification reaction ; The esterification reaction is carried out in a nitrogen atmosphere, the pressure is controlled below 900Pa, the temperature is controlled at 200°C, and the esterification water distillate reaches 90% of the theoretical value, which is the end point of the esterification reaction.

Described polycondensation reaction:

Including low vacuum stage of polycondensation reaction and high vacuum stage of polycondensation reaction:

In the low-vacuum stage of the polycondensation reaction, 0.02% of the weight of tetrafluoroterephthalic acid is added to the esterification product. The catalyst tetraisopropyl titanate and the stabilizer triphenyl phosphate of 0.02% of the weight of tetrafluoroterephthalic acid are added. , the polycondensation reaction starts under the condition of negative pressure, said negative pressure means that the absolute pressure is less than 400Pa, the temperature is controlled at 260°C, and the reaction time is 60 minutes.

In the high vacuum stage of the polycondensation reaction, after the low vacuum stage of the polycondensation reaction, the vacuum is continued to reduce the reaction pressure to an absolute pressure of less than 80 Pa, the reaction temperature is controlled at 270° C., and the reaction time is 4 hours. The polycondensation reaction is based on the power of the stirring motor of the reactor or the reading of the online viscometer to judge the end point of the reaction. When the viscosity of the polymer reaches the desired value, the material is discharged, and after casting, cooling and pelletizing, the fluorine-containing PBT polyester chips are obtained.

2. Preparation of skin-core composite fiber: use the fluorine-containing PBT as the skin layer material, PBT as the core layer material, and carry out skin-core composite spinning, the ratio of the cross-sectional area of the skin layer and the core layer is 4:5, and the spinning temperature The temperature is 274°C, the winding speed is controlled at 3200m/min, and the monofilament fineness of the obtained fluorine-containing PBT-PBT sheath-core composite fiber is 15dtex.

Example 3

1. The preparation method of fluorine-containing PBT polyester is divided into two steps of esterification reaction and polycondensation reaction. The specific steps are:

Described esterification reaction:

Use 1,4-butanediol and tetrafluoroterephthalic acid with a molar ratio of 1.8:1 as raw materials, and add 0.03% calcium oxide based on the weight of tetrafluoroterephthalic acid at the same time, make a uniform slurry and carry out esterification reaction ; The esterification reaction is carried out in a nitrogen atmosphere, the pressure is controlled below 800Pa, the temperature is controlled at 180°C, and the esterification water distillate reaches 90% of the theoretical value, which is the end point of the esterification reaction.

Described polycondensation reaction:

Including low vacuum stage of polycondensation reaction and high vacuum stage of polycondensation reaction:

In the low-vacuum stage of the polycondensation reaction, 0.03% of the catalyst tetraethyl titanate and 0.03% of the weight of the tetrafluoroterephthalic acid are added to the esterification product, and the stabilizer trimethyl phosphate is added, The polycondensation reaction is started under the condition of negative pressure, said negative pressure means that the absolute pressure is less than 300 Pa, the temperature is controlled at 265° C., and the reaction time is 50 minutes.

In the high vacuum stage of the polycondensation reaction, after the low vacuum stage of the polycondensation reaction, the vacuum was continued to reduce the reaction pressure to an absolute pressure of less than 60 Pa, the reaction temperature was controlled at 275° C., and the reaction time was 3.5 hours. The polycondensation reaction is based on the power of the stirring motor of the reactor or the reading of the online viscometer to judge the end point of the reaction. When the viscosity of the polymer reaches the desired value, the material is discharged, and after casting, cooling and pelletizing, the fluorine-containing PBT polyester chips are obtained.

2. Preparation of skin-core composite fiber: use the fluorine-containing PBT as the skin layer material, PBT as the core layer material, and carry out skin-core composite spinning, the ratio of the cross-sectional area of the skin layer and the core layer is 3:5, and the spinning temperature The temperature is 279°C, the winding speed is controlled at 2900m/min, and the monofilament fineness of the obtained fluorine-containing PBT-PBT sheath-core composite fiber is 10dtex.

Example 4

1. The preparation method of fluorine-containing PBT polyester is divided into two steps of esterification reaction and polycondensation reaction. The specific steps are:

Described esterification reaction:

Use 1,4-butanediol and tetrafluoroterephthalic acid with a molar ratio of 1.9:1 as raw materials, and add 0.04% zinc oxide based on the weight of tetrafluoroterephthalic acid at the same time, make a uniform slurry and carry out esterification reaction ; The esterification reaction is carried out in a nitrogen atmosphere, the pressure is controlled below 700Pa, the temperature is controlled at 170°C, and the esterification water distillate reaches 90% of the theoretical value, which is the end point of the esterification reaction.

Described polycondensation reaction:

Including low vacuum stage of polycondensation reaction and high vacuum stage of polycondensation reaction:

In the low vacuum stage of the polycondensation reaction, add 0.04% of the catalyst stannous acetate of tetrafluoroterephthalic acid weight and 0.04% of the stabilizer trimethyl phosphate of tetrafluoroterephthalic acid weight in the esterification product, The polycondensation reaction starts under the condition of pressure, the said negative pressure means that the absolute pressure is less than 300Pa, the temperature is controlled at 270°C, and the reaction time is 40 minutes.

In the high vacuum stage of the polycondensation reaction, after the low vacuum stage of the polycondensation reaction, the vacuum is continued to reduce the reaction pressure to an absolute pressure of less than 60 Pa, the reaction temperature is controlled at 275° C., and the reaction time is 3 hours. The polycondensation reaction is based on the power of the stirring motor of the reactor or the reading of the online viscometer to judge the end point of the reaction. When the viscosity of the polymer reaches the desired value, the material is discharged, and after casting, cooling and pelletizing, the fluorine-containing PBT polyester chips are obtained.

2. Preparation of skin-core composite fiber: use the fluorine-containing PBT as the skin layer material, PBT as the core layer material, and carry out skin-core composite spinning, the ratio of the cross-sectional area of the skin layer and the core layer is 5:5, and the spinning temperature The temperature is 275°C, the winding speed is controlled at 2800m/min, and the monofilament fineness of the obtained fluorine-containing PBT-PBT sheath-core composite fiber is 5dtex.

Example 5

1. The preparation method of fluorine-containing PBT polyester is divided into two steps of esterification reaction and polycondensation reaction. The specific steps are:

Described esterification reaction:

Use 1,4-butanediol and tetrafluoroterephthalic acid with a molar ratio of 2.0:1 as raw materials, and add 0.05% manganese oxide by weight of tetrafluoroterephthalic acid at the same time, make a uniform slurry and carry out esterification reaction ; The esterification reaction is carried out in a nitrogen atmosphere, the pressure is controlled below 600Pa, the temperature is controlled at 160°C, and the esterification water distillate reaches 90% of the theoretical value, which is the end point of the esterification reaction.

Described polycondensation reaction:

Including low vacuum stage of polycondensation reaction and high vacuum stage of polycondensation reaction:

In the low-vacuum stage of the polycondensation reaction, add 0.05% of the catalyst dibutyltin diacetate and 0.05% of the tetrafluoroterephthalic acid weight in the esterification product. Stabilizer trimethyl phosphite, The polycondensation reaction starts under the condition of negative pressure, said negative pressure means that the absolute pressure is less than 300 Pa, the temperature is controlled at 265° C., and the reaction time is 40 minutes.

In the high vacuum stage of the polycondensation reaction, after the low vacuum stage of the polycondensation reaction, the vacuum is continued to reduce the reaction pressure to an absolute pressure of less than 50 Pa, the reaction temperature is controlled at 275° C., and the reaction time is 3 hours. The polycondensation reaction is based on the power of the stirring motor of the reactor or the reading of the online viscometer to judge the end point of the reaction. When the viscosity of the polymer reaches the desired value, the material is discharged, and after casting, cooling and pelletizing, the fluorine-containing PBT polyester chips are obtained.

2. Preparation of skin-core composite fiber: use the fluorine-containing PBT as the skin layer material and PBT as the core layer material to carry out skin-core composite spinning. The ratio of the cross-sectional area of the skin layer to the core layer is 1:2, and the spinning temperature is The temperature is 280°C, the winding speed is controlled at 3100m/min, and the monofilament fineness of the obtained fluorine-containing PBT-PBT sheath-core composite fiber is 3dtex.

Claims (4)

1. a preparation method of fluorine-containing PBT-PBT sheath-core composite fiber is characterized in that: the cortex material of said fluorine-containing PBT-PBT sheath-core composite fiber is fluorine-containing PBT, and the core layer material is PBT; PBT is polytetrafluorobutylene terephthalate, its general structure is Wherein n=70～150; the ratio of the cross-sectional area of the skin layer and the core layer of the fluorine-containing PBT-PBT sheath-core composite fiber is 2～5:5; The monofilament fineness of the fluorine-containing PBT-PBT skin-core composite fiber is 1-15 dtex; the preparation method of the fluorine-containing PBT-PBT skin-core composite fiber includes the preparation method of fluorine-containing PBT and the preparation method of the skin-core composite fiber , the specific steps are: 1) The preparation method of the fluorine-containing PBT is divided into two steps of esterification reaction and polycondensation reaction; Described esterification reaction: Using tetrafluoroterephthalic acid and 1,4-butanediol as raw materials, adding an inhibitor, the addition of the inhibitor is 0.01% to 0.05% of the weight of the tetrafluoroterephthalic acid; it is made into a homogeneous slurry The esterification reaction is carried out after feeding to obtain the esterification product; the esterification reaction is carried out in a nitrogen atmosphere, the pressure is controlled at less than 1KPa of absolute pressure, the temperature is 160-220°C, the time is 2-3 hours, and the distilled amount of esterification water reaches the theoretical level. More than 90% of the value is the end point of the esterification reaction; The inhibitor is one of magnesium oxide, silicon oxide, calcium oxide, zinc oxide and manganese oxide; Described polycondensation reaction: Including low vacuum stage of polycondensation reaction and high vacuum stage of polycondensation reaction: In the low-vacuum stage of the polycondensation reaction, a catalyst and a stabilizer are added to the esterification product, and the polycondensation reaction starts under negative pressure. 40-60 minutes; In the high vacuum stage of the polycondensation reaction, after the low vacuum stage of the polycondensation reaction, the vacuum is continued to reduce the reaction pressure to an absolute pressure of less than 100Pa, the reaction temperature is controlled at 270-275°C, and the reaction time is 3-4 hours; Prepare fluorine-containing PBT; 2) The preparation method of the skin-core composite fiber is as follows: the fluorine-containing PBT is used as the skin layer material, and the PBT is used as the core layer material to perform skin-core composite spinning, the spinning temperature is 270-280 ° C, and the winding speed is controlled at 2700～3200m/min. 2. the preparation method of a kind of fluorine-containing PBT-PBT sheath-core composite fiber according to claim 1 is characterized in that, the mol ratio of described 1,4-butanediol and tetrafluoroterephthalic acid is 1.4 ~2.0:1. 3. the preparation method of a kind of fluorine-containing PBT-PBT sheath-core composite fiber according to claim 1 is characterized in that, described catalyst is selected from tetrabutyl titanate, tetraisopropyl titanate, tetraisopropyl titanate One of ethyl ester, stannous acetate, and dibutyltin diacetate, and the amount of the catalyst is 0.01% to 0.05% of the weight of the tetrafluoroterephthalic acid. 4. the preparation method of a kind of fluorine-containing PBT-PBT sheath-core composite fiber according to claim 1 is characterized in that, described stabilizer is selected from triphenyl phosphate, trimethyl phosphate and trimethyl phosphite One of them, the amount of the stabilizer is 0.01%-0.05% of the weight of the tetrafluoroterephthalic acid.