JPH048541B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a polyester fiber structure and a method for producing the same, and particularly to a surface-active polyester fiber structure and a method for producing the same.

(Prior Art) Today, polyester fibers are at their peak as materials for clothing, industrial materials, and the like. It has also been found that they are suitable for special fields such as medical materials, such as artificial blood vessels. The reason for this is that it has excellent mechanical and chemical properties. On the other hand, due to its poor hydrophilicity, it has drawbacks such as lack of hygroscopicity and water absorption, and is easily charged and stained, and research to improve this problem has continued since the invention of polyester fibers.

The reason for the poor hydrophilicity is said to be that the molecular structure constituting the polyester polymer is highly crystalline, which prevents water from entering, and that water is not adsorbed because there is no functional group.

In order to improve these drawbacks, the following methods have been used in the past.

(1) Blending second and third polymer components that disrupt high crystallinity or adding components having functional groups is done at the spinning stage.

(2) Although the principle is completely different from this, it is also possible to make the fiber surface uneven or provide continuous holes in the fiber to make it easier for water to absorb and enter. It is made by a combination of dyeing processes, etc.

(3) As a treatment after the spinning step, it is also possible to graft polymerize a monomer with a functional group to make it hydrophilic.

(4) A hydrophilic agent based on a surfactant or a hydrophilic agent based on a resin component can also be applied.

(Problems to be Solved by the Invention) However, methods (1) and (2) are methods applied at the spinning stage, and cannot be said to be flexible means.

In addition, in method (3), hydrophilic performance cannot be exhibited unless the amount of graft polymerization exceeds a certain amount using only the normal grafting method. In this case, the inherent mechanical properties of polyester are inevitably degraded.

Furthermore, it goes without saying that method (4) is unreasonable in terms of durability.

Therefore, the present invention solves the above problems and provides a method for producing polyester fibers having durable hydrophilicity, antistatic properties, etc. without changing the original properties of polyester, and a method other than spinning. The purpose is to resist the fibrous structures thus produced.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, polyester fibers are immersed in a monomer solution after being treated with a swelling agent or in a monomer solution in the coexistence of a swelling agent,
A graft polymerization reaction is carried out by irradiation with ionizing radiation, then the surface homopolymer is removed by washing with a weak alkaline solution, and etching is carried out by low-temperature plasma discharge treatment to highly expose the graft polymerization, and at the same time chemical modification is performed. A surface-active polyester fiber structure is produced by creating unevenness.

(Function) The polyester fiber in the present invention refers to a fiber made of a polymer whose main structural unit is ethylene terephthalate, and a matting agent, anti-discoloration agent, dye, etc. may be added if necessary.

Moreover, the fiber structure as used in the present invention only needs to be a polyester fiber material, and its form is not restricted. For example, monofilament,
Examples include tow, staple, cotton, thread, fabric (woven and knitted fabrics, non-woven fabrics), etc. If a uniform treatment effect is desired in the present invention, it is most effective to perform the treatment when the constituent single yarns are separated, such as in monofilament, staple, and cotton. When it becomes thread-like, woven, or knitted, the single threads are aggregated, and furthermore, these become intersected, resulting in a loss of uniformity. Generally, polyester fibers are obtained by melt spinning, and the spinning process involves three steps: extrusion from a nozzle, solidification, stretching, and heat setting, but it can be performed after any stage of the process of the present invention. . The treatment of the present invention consists of both graft polymerization treatment and plasma treatment, but the former must always take precedence.

First, the graft polymerization treatment will be explained. Graft polymerization means ``grafting'' and is an attempt to supplement the properties that the main stem lacks by grafting onto the branches. In this case, the polyester fiber is the main fiber, and the branches are polymers produced from monomers. As the word "grafted" means, the main trunk and branches are combined into one whole. In this way, supplementing the properties that the main stem lacks by grafting is useful as a method other than spinning.

Now, polyester fiber has a glass transition temperature of 50
The temperature is within the range of ℃~80℃. In order to carry out graft polymerization easily and efficiently, it is preferable to carry out the graft polymerization in a temperature range equal to or higher than this glass transition temperature. Although the temperature for graft polymerization may be simply set within the temperature range, chemicals that swell polyester have the advantage of lowering the glass transition temperature and can be carried out at lower temperatures.
This lower temperature is advantageous in terms of energy consumption, ease of work, etc. However, it goes without saying that the combination of a temperature higher than the glass transition temperature and a swelling agent makes the effects synergistic. Swelling agents include dichloromethane, 1,1-dichloroethane, 1,2-
dichloroethane, 1,2-dichloroethylene,
1,1,2-trichloroethane, trichlorethylene, 1,1,1,2-tetrachloroethane,
1,1,2,2-tetrachloroethane, 1,1,
Chlorinated hydrocarbons such as 2,2-tetrachloroethylene, monochlorobenzene, dichlorobenzene, and trichlorobenzene are preferred. As a monomer, either an unsaturated carboxylic acid, an unsaturated carboxylic acid anhydride, or an unsaturated carboxylic acid amide must be used as a component. For example, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, unsaturated carboxylic anhydrides such as maleic anhydride, itaconic anhydride, unsaturated acids such as acrylamide, methacrylamide, etc. There are carboxylic acid amides, and these are used alone or in combination of two or more. Furthermore, co-graft polymerization with acrylonitrile, vinylpyrrolidone, vinylchloride, etc. may be performed. The effect remains the same regardless of whether the dipping treatment is performed using a swelling agent alone, followed by dipping treatment using a monomer alone, or whether the dipping treatment is performed using a mixed bath of the swelling agent and monomer. Swelling agents may be used after being diluted with water, surfactants, etc., but it is advantageous in terms of application equipment and recovery to process from a bath containing 100% swelling agent. In the treatment with a swelling agent, the degree of swelling can be adjusted by adjusting the immersion temperature and immersion time. This swelling effect varies depending on the state of the crystal structure of the polyester that is the material to be treated. When extruded from a nozzle and solidified, there is only a region with a small amount of crystalline structure, but it easily swells to a large extent, and as it goes through the process, it becomes a region with a large amount of crystalline structure, making swelling difficult and resulting in small swelling. In the present invention, even large swelling does not lead to good results. In order to distribute the graft polymer at high density in the epidermal layer, to put it in an extreme way, only the epidermal layer needs to be swollen. However, such control of swelling is nearly impossible, and the swelling agent, its concentration, dipping temperature, dipping time, etc. are adjusted to approximate this.

Treatment with a swelling agent is 0 when the swelling agent is 100%.
Immersion is performed for 30 seconds to 180 minutes at a temperature range of 80°C to 80°C, and then the swelling agent is removed by normal pressure or vacuum drying at 120°C or lower. Using a higher temperature than this will lead to a reduction in the swollen area due to the heat treatment effect.

When a swelling agent and a monomer are used in a mixed bath, their compatibility must be confirmed. This is because uniform application is difficult unless they are used in a completely compatible state. As long as this compatibility allows, water,
It can be diluted with organic acids, etc. In some cases, chemicals that inhibit homopolymerization (for example, soluble metal salts of copper sulfate and copper chloride) may be added.
The concentration of monomer in this mixed bath depends on the desired amount of graft polymerization, but is adjusted within 10 to 90 volume percent. In the present invention, it is possible to add monomer only from a monomer bath, but in order to obtain a graft polymer that is highly densely distributed in the epidermal layer and has the characteristics shown in the present invention, it is necessary to use the two methods shown above. It is preferable to use either one.

Immersion in a monomer bath or a mixed bath of a swelling agent and a monomer takes a sufficient amount of time while stirring the solution in the bath or agitating the object in order to uniformly apply the monomer. Needless to say, the dipping temperature and dipping time are adjusted in this case as well. If the material has already been treated with a swelling agent, the monomer can easily penetrate into the material, and immersion in the monomer bath can be done for a short time. The proper temperature here is 10℃~80℃
℃ and the time can be set from 5 seconds to 30 minutes.
Immersion in the mixed bath of the swelling agent and monomer is carried out in the same manner as the treatment with the swelling agent described above.

Although the object treated in this manner has absorbed sufficient monomer, it must be ensured that the monomer does not evaporate during the next step of irradiation with ionizing radiation. As a method for this, it is preferable to provide an excessive amount of the above-mentioned processing liquid or to reduce the size of the irradiation reaction chamber. As the ionizing radiation, electron beam irradiation obtained by an industrially widespread accelerator is necessary to achieve the present invention. If other energy sources are used, the grafted material suitable for the purpose of the present invention cannot be obtained due to insufficient energy.

For irradiation, it is preferable to use an electron beam (accelerator) with an energy of 0.1 to 5 MeV in a nitrogen gas atmosphere.
A dose rate of 1.0×10 ⁴ rad/sec to 1.0×10 ⁷ rad/sec is used, and the irradiation dose is preferably 0.1×10 megarad/sec. The monomer solution is completely solidified on the object to be treated by the irradiation, and the grafting reaction is completed.

In such a graft reaction, simultaneous progress of homopolymerization cannot be avoided, and the resulting homopolymer must be dissolved and removed. A weak alkaline solution is used for this. Alkali can be defined as a substance in the form of hydroxide MOH that dissolves in water. In this case, M refers to an alkali metal or ammonium salt, but in a broad sense it also includes sodium carbonate, sodium bicarbonate, ammonium carbonate, sodium phosphate, etc. Here, the purpose of the weakly alkaline solution is to dissolve and remove the above-mentioned homopolymer, and there is no particular limitation as long as the aqueous solution has a concentration that achieves this purpose. As an example, a sodium hydrogen carbonate aqueous solution is used, and the treatment is completed by adjusting a 0.1-1% aqueous solution to a bath ratio of 1:100-200 and performing a treatment at a temperature of 40° C.-80° C. for 1-20 minutes. Next, drying is performed in an atmosphere of 100 to 200°C, and in some cases, heat treatment is simultaneously performed. If the weight is measured here, an increase in weight will be seen compared to the weight before grafting, and this increase corresponds to the graft polymer. The increase due to the polymer is expressed as the grafting rate, which is 0.2 to 15 weight percent, preferably 0.4 to 7 weight percent.

The graft polymer obtained in this way to polyester does not appear on the surface of the polyester, but has the highest density slightly inside the outer skin, called the skin layer, and gradually becomes less dense toward the center. The similar distribution can be confirmed by a combination of alkaline hydrolysis method and coloring method.

A detailed explanation of these is as follows.

When a polyester fiber is cut perpendicular to the fiber axis, a cross section appears. This cross section may be circular or have a specific shape. To make the explanation easier to understand, assume that the cross section is circular. The outer periphery of this cross section, that is, the outer skin, is the part that comes into contact with the outside air, and is the part that comes into contact first during swelling agent treatment or monomer treatment. On the other hand, the center of the cross section is the farthest part from this, and it is the slowest to come into contact with them. From this, it can be assumed that the probability that monomers will be adsorbed and that their graft polymerization will occur is approximately equal for concentric circles on the cross section centered on the center of the cross section. Polyester fibers have a unique property in which the outer skin is uniformly dissolved by alkaline hydrolysis, and can be easily made into thinner fibers while maintaining their original shape. On the other hand, -COOH introduced as a functional group is present in the graft polymer. This is an anionic group, and by utilizing a reaction that quantitatively combines with a cationic dye, the presence and amount of the graft polymer can be measured. Specifically, measurements using cationic dyes are performed using a bath containing 1% by weight of Basic Violet 10 and 0.5cc/L of acetic acid (80%) at a bath ratio of 1:200, 90%.
After color development at ℃ for 20 minutes, washing with 0.5 cc/L aqueous solution of acetic acid (80%) at 60℃ for 10 minutes was repeated twice, followed by washing with water and drying. If this polyester turns violet, it indicates the presence of a graft polymer, and the concentration can be measured with a spectrophotometer and the amount of the graft polymer can be estimated from the correlation with the grafting rate. Based on the data shown in the examples of the present invention, it was confirmed that the distribution is almost U-shaped to V-shaped when shown on a plane cut parallel to the fiber axis of the polyester fiber and passing through the center of the fiber. has been done.

Next, low temperature plasma discharge treatment will be explained.
Low-temperature plasma is one in which a strong electric field is applied to a gas under low pressure to cause a discharge. Here, air, carbon monoxide, carbon dioxide,
Inorganic gases such as oxygen, nitrogen, hydrogen, argon, and helium are used. Among these, three types are often used: air, oxygen, and argon. The discharge treatment is performed by placing the object to be treated in this discharged field. This creates unevenness on the surface (this is called etching). It is known that the size and depth of these irregularities vary depending on the gas used. The size of the unevenness caused by the low-temperature plasma discharge treatment is minute. The method of displaying the size and depth of this unevenness is as follows. In other words, the average plane distance from the concave part to the lowest point of the next adjacent concave part,
Alternatively, it is displayed as both the average planar distance from a convex part to the highest point of the next adjacent convex part, and the average distance, that is, depth, between the highest point of the convex part and the lowest point of the concave part. Then, in order to display how many of these unevennesses exist, a certain number per unit area, that is, a density is displayed. In the present invention, the size and depth of the unevenness are not directly important factors, but are described because they are numerical values obtained as a result, and these are counted from the photograph obtained from the SEM.

In addition to the creation of this unevenness, it is also known that chemical changes occur simultaneously on the surface (this is called chemical modification). This is based on the theory that a new reaction between the atoms of the gas used and the atoms of the object to be treated takes place on the surface under plasma discharge treatment, and that when taken out into the air after plasma discharge treatment, active radicals and oxygen in the air are generated. It is said that a reaction occurs with carbon dioxide and hydrogen, but this has not been definitively proven in the case of the present invention. In any case, these products act like part of the functional group, leading to improved hydrophilicity and adhesiveness that promote adsorption of water molecules. This will be referred to as a chemical modification effect.

The conditions for performing the low temperature plasma discharge treatment of the present invention are as follows:
Frequency: 100KHz~10MHz or 10MHz~
Low frequency discharge plasma of 100MHz, preferably 110KHz, and high frequency discharge plasma of 13.56MHz are good. The processing time is 5 seconds to 1800 seconds at an output of 10 W to 100 KW, a pressure of 2 torr or less, and a gas flow rate of 10 to 300 ml/min. The lower the pressure, the more effective it is because it increases the momentum of the gas atoms, but if you increase the gas flow rate, the pressure will inevitably go to the high pressure side, so if the gas flow exceeds a certain level, the pressure cannot be made to the desired low pressure. It disappears. Specifically, under 0.05 Torr, the gas flow rate is less than 20 ml/min, and under 0.1 Torr, the gas flow rate is 20 ml/min or less.
~100ml/min, 40~200ml/min under 2 torr
That's how it is. As mentioned above, polyester fibers belong to highly crystalline polymers and are not easily etched. However, chemical changes (chemical modifications) can be applied. This is a feature of low-temperature plasma discharge treatment.

The present invention focuses on etching, and it is interpreted that chemical changes (chemical modification) are inevitably imparted as a side effect. Now, if we set 13.56MHz as the frequency and change the output, pressure, gas flow rate, etc., we can of course find the optimal conditions. Among these, the output is important. In order to produce an etching effect, 100 W or more, preferably 300 W or more is required; if it is less than this, unevenness will not occur, or even if it does, it will take a long time.

By the way, polyester fibers are obtained through the processes of fluid extrusion from a nozzle, solidification, stretching, and heat setting. After this process, processes such as twisting and adding bulkiness are added. The fibers obtained in this way have more opportunities to undergo heat treatment later in life, and the properties of the fibers gradually change. In the solidified state of fluid extrusion from the nozzle, it is at a stage where it has just formed a fibrous form, and the crystallinity ratio is low, making it easy to process. However, it is known that stretching increases the crystallinity at once and exhibits the performance of general polyester fibers. From this fact, it is a good idea to perform low-temperature plasma discharge treatment in a state that is easy to process. For this reason, the present invention places importance on producing polyester fibers suited to the purpose. When utilizing the chemical properties of polyester, it is not necessarily necessary to add mechanical properties at the same time.

(Example) Next, examples will be shown.

Apparent Young's modulus 120Kg/ ^mm2 and diameter 40μm (strength
About 2 grams of polyester monofilament (100 g, elongation 40%) was prepared, thoroughly washed in warm water containing a nonionic surfactant, washed with water, dried, and weighed. This value of Young's modulus is very small compared to 1100 Kg/mm ² which is generally said to be the value of polyester fiber.

Below, the following processing was performed.

() Swelling agent 100% bath treatment 1,2-dichloroethane (commercial reagent first grade)
The temperatures are set at 20°C and 40°C, and the object to be treated is immersed in this for 1 hour while stirring. The fibers were then taken out and left at room temperature for a day and night to remove dichloromethane adhering to the surface, and then dried at 80°C for 600 minutes to remove 1,2-dichloroethane adsorbed inside the fibers. Let each sample be a group A sample and a group B sample.

() Monomer bath treatment The A and B group samples obtained in () were immersed in methacrylic acid (commercially available reagent) set at 40°C and stirred for 1 hour.

() Swelling agent/monomer mixed bath treatment A mixed solution of 1,2-dichloroethane (commercially available reagent) and methacrylic acid (commercially available reagent) mixed in a volume ratio of 6:4 was set at 50°C, and the previously coated mixture was placed in it. The treated product was immersed for 2 hours while stirring. This is designated as the C group sample.

() Group A and B samples treated with () and ()
and the Group C samples treated with 1 and 2 were separately transferred onto stainless steel pallets. The pallet is immersed in a treatment solution 5 times the weight of the dough, covered with vinyl film, and the air replaced with nitrogen gas.

() Irradiation was performed using a Van de Graaf electron beam irradiation device at 1.5 MeV, 50 mA, and 0.17 Mrad/sec for a total dose of 6 Mrad.

() Washing was carried out twice at 80°C for 20 minutes with a 10 g/L aqueous solution of sodium hydrogen carbonate.

() After drying at 100°C for 60 minutes using a hot air dryer, the weight was measured, and the graft ratio was calculated for each. A
Group: 4.3% Group B: 4.7% Group C: 4.5%. These samples were colored in the Basic Viret 10 aqueous solution shown above, but the color was so pale that it was difficult to determine that a graft polymer was present on the surface. In addition, these samples were subjected to the same alkaline hydrolysis treatment (sodium carbonate 10 g/L aqueous solution, bath ratio 1:200) as described above.
After 15, 30, 45, and 60 minutes at 100°C, the resulting weight loss was measured and colored with an aqueous solution of Basic Vilet 10. In this coloration, the coloration of all samples was the darkest in the samples treated with alkaline hydrolysis for 15 minutes and 30 minutes, and it was determined that the graft polymer was exposed. That is, when calculating where this location was from the surface based on the weight loss rate at this time, it was found that it was a concentric circle that was 0.15 to 0.2 microns closer to the fiber axis center than the surface.
A schematic diagram of this distribution state is shown in Figure 1. From this, it has been found that in order to expose the polyester graft polymer obtained in the present invention on the surface in contact with the outside air, it is necessary to perform etching to a depth of 0.15 to 2 microns by low-temperature plasma discharge treatment. This is a value of 1 to 2.5% in terms of weight loss rate.

() The frequency of these samples is 13.56MHz, the output is 700W,
Pressure 0.2 torr, oxygen gas flow rate 190ml/
Irradiation treatment was performed for 2 minutes and 4 minutes under conditions of min. When the sample thus obtained was colored with the above-mentioned Basic Violet 10 aqueous solution, a deep color reaction could be seen clearly indicating the exposure of the graft polymer.

() Also, SEM images of these samples were taken from the side of the fiber,
There was no unevenness at the tip, and unevenness was observed on both sides. More than 90% of the particles were between 0.08 and 1.2 microns in size, and about 10% were gigantic particles between 1.8 and 3.0 microns in size. Depth is 0.06 ~
It was 1.0 micron.

() These samples showed good wettability, i.e., they immediately spread even when water droplets were dropped on their surfaces. In addition, the frictional charging voltage was measured using a rotary static tester (Koa Shokai) at a temperature equivalent to 20°C humidity.
Measured after 2 minutes of rubbing with cotton cloth in 40%
It was below 100V.

(XI) Strength and elongation: The strength was 3% lower and the elongation was 4% higher than the untreated sample.

(Effects of the Invention) From the results shown in the examples above, as described in the description of the present invention, a monomer is graft-polymerized to the skin layer of polyester fiber by electron beam irradiation,
Next, by etching and removing the epidermal layer using low-temperature plasma discharge treatment, the graft-polymerized portion is exposed on the epidermis layer, and at the same time, a unique surface-active polyester fiber can be created that creates chemically modified irregularities on the surface. I found out something. In addition, it retains the original polyester performance without deterioration of mechanical properties obtained by the present invention, has hydrophilicity due to the graft polymer arranged at high density on its surface, and has chemically modified minute irregularities added. The resulting so-called surface-active polyester fiber structure can be effectively applied to the medical field, biotechnology field, filter membrane material, etc.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the presence of graft polymers on a cross section cut in the axial direction passing through the fiber axis of a single fiber in the polyester/graft copolymer fiber structure obtained in the present invention. Here, 1... Center of the single fiber, 2... Outer skin surface of the single thread, 3... Graft polymer distribution layer, 4... The highest density layer of the graft polymer, 5... Layer to be removed by etching, 6 ...This is the new outer skin surface after etching.

Claims (1)

[Scope of Claims] 1 Polyester fibers are treated with a swelling agent and then immersed in a monomer solution or immersed in a monomer solution in the coexistence of a swelling agent, irradiated with ionizing radiation to perform a graft polymerization reaction, and then treated with a weak alkali. Surface-active polyester/graft copolymerization, which involves removing the surface homopolymer by solution washing, etching by low-temperature plasma discharge treatment to highly expose the graft polymerization area, and at the same time creating chemically modified irregularities. A method for manufacturing a fiber structure. 2. Polyester fibers are immersed in a monomer solution after treatment with a swelling agent, or immersed in a monomer solution in the coexistence of a swelling agent, irradiated with ionizing radiation to perform a graft polymerization reaction, and then washed with a weak alkaline solution to homogenize the surface. A surface-active polyester fiber structure formed by removing the polymer and etching it by low-temperature plasma discharge treatment to highly expose the graft polymerization, and at the same time creating chemically modified irregularities.