JP7636749B2 - Manufacturing method of synthetic resin adhesive fiber - Google Patents

Description

The present invention relates to a method for producing synthetic resin-bonded fibers for bonding to synthetic resins having polar groups in the molecule, and in particular to a method for producing synthetic resin-bonded fibers produced by applying a treatment agent for water-based adhesives that contains a blocked polyisocyanate compound to synthetic fibers.

Conventionally, rubber or synthetic resin has been combined with fibrous materials such as cloth or cord to be used as a composite material. In order to ensure the strength of these composite materials, it is required that the synthetic resin and fibrous material are firmly bonded. This is generally achieved by applying an adhesive to the fibrous material or by carrying out various adhesive surface treatments such as RFL treatment (see, for example, Patent Document 1). In addition, an organic solvent is generally used as the solvent when forming the adhesive layer.

Patent Document 1 describes a method for manufacturing rubber reinforcing fibers in which a pretreatment liquid containing polyepoxide compounds, blocked polyisocyanates, and rubber latex as main components is applied to the fibers, which are then treated with low-temperature plasma to which a resin containing resorcinol, formalin, and latex as main components is applied. This makes it possible to manufacture rubber reinforcing fibers with high adhesive strength to rubber.

JP 2006-219782 A

In the method for producing rubber reinforcing fibers described in Patent Document 1, the fibers are immersed in a pretreatment liquid and then heat-treated at 240°C. In other words, the fibers are heated to a temperature equal to or higher than the dissociation temperature of the blocking agent of the blocked polyisocyanate. As a result, the blocking agent of the blocked polyisocyanate is dissociated, and the isocyanate groups are regenerated, which react to produce a thermoset product. In other words, the flexibility of the rubber reinforcing fibers is reduced, making them difficult to bend. As a result, the fibers are difficult to handle.
In addition, organic solvents are often used in forming the adhesive layer, which requires the installation of explosion-proof equipment and waste liquid treatment specific to organic solvents, resulting in a large workload.

The object of the present invention is to provide a method for producing synthetic resin adhesive fibers that can produce synthetic fibers that are flexible and have improved adhesive strength, and that can reduce the burden on the worker.

The method for producing a fiber for use with a synthetic resin bond of the present invention includes a treatment-agent application step of applying a treatment agent for an aqueous adhesive containing a blocked polyisocyanate compound to a synthetic fiber, a thermal drying step of thermally drying the synthetic fiber to which the treatment agent has been applied, and a plasma treatment step of irradiating the synthetic fiber with plasma before and after the treatment-agent application step. In the thermal drying step, the synthetic fiber is heated to a temperature lower than the dissociation temperature of the blocking agent of the blocked polyisocyanate compound.

According to this, since the temperature to which the synthetic fiber is heated in the thermal drying step is lower than the dissociation temperature of the blocking agent, it is possible to evaporate the moisture in the treatment agent while suppressing the hardening of the treatment agent. Therefore, the flexibility of the synthetic fiber is maintained. In addition, since the plasma treatment step is performed before and after the treatment application step, the affinity of the synthetic fiber to the treatment agent (adhesive) is increased, and the adhesive strength when the synthetic fiber is bonded to a synthetic resin is improved. In other words, it is possible to manufacture synthetic fiber that has flexibility and improved adhesive strength. In addition, since the treatment agent is for water-based adhesives, there is no need to install explosion-proof equipment or dispose of waste liquid, which are specific to organic solvents, and it is possible to reduce the burden on the work side.

In the present invention, it is preferable that the treatment agent contains a polyepoxide compound. This makes it possible to use a treatment agent that contains a polyepoxide compound.

In addition, in the present invention, it is preferable that in the treatment agent application step, the total amount of the blocked polyisocyanate compound and the polyepoxide compound applied to the synthetic fiber is in the range of 0.5% by weight or more and 5% by weight or less relative to the weight of the synthetic fiber. As a result, since the total amount of these compounds applied to the synthetic fiber is 0.5% by weight or more, it is possible to suppress a decrease in adhesive strength to the synthetic resin. Furthermore, since the total amount of these compounds applied to the synthetic fiber is 5% by weight or less, it is possible to suppress an increase in manufacturing costs.

According to the method for producing synthetic resin-bonded fibers of the present invention, the temperature to which the synthetic fibers are heated in the thermal drying step is lower than the dissociation temperature of the blocking agent, so that it is possible to evaporate the water in the treatment agent while suppressing hardening of the treatment agent. This maintains the flexibility of the synthetic fibers. Furthermore, by carrying out the plasma treatment step before and after the treatment application step, the affinity of the synthetic fibers to the treatment agent (adhesive) is increased, and the adhesive strength when the synthetic fibers are bonded to the synthetic resin is improved. In other words, it is possible to produce synthetic fibers that are flexible and have improved adhesive strength. Furthermore, because the treatment agent is for water-based adhesives, it is possible to reduce the burden on solvent-compatible equipment and work.

1A to 1C are diagrams illustrating manufacturing steps of a method for manufacturing a synthetic resin bonding fiber according to a first embodiment of the present invention. 1 is a schematic configuration diagram of a manufacturing facility for carrying out a method for manufacturing a synthetic resin bonding fiber according to a first embodiment of the present invention. FIG. 5A to 5C are diagrams showing the manufacturing steps of a method for manufacturing a synthetic resin bonding fiber according to a second embodiment of the present invention. FIG. 4 is a schematic diagram of a manufacturing facility for carrying out a method for manufacturing a synthetic resin bonding fiber according to a second embodiment of the present invention. 10A to 10C are diagrams showing the manufacturing steps of a method for manufacturing a synthetic resin bonding fiber according to a third embodiment of the present invention. FIG. 11 is a schematic diagram of a manufacturing facility for carrying out a method for manufacturing a synthetic resin bonding fiber according to a third embodiment of the present invention. FIG. 13 is a diagram showing a situation when measuring the flexibility of a yarn. FIG. 1A is a diagram showing a state when a thread is adhered to a synthetic resin sheet, and FIG. 1B is a diagram showing a state when the adhesive strength of the thread to the synthetic resin sheet is measured.

The method for producing synthetic resin adhesive fibers according to the first embodiment of the present invention will be described below with reference to Figures 1 and 2.

The fibers used in the manufacturing method of this embodiment are not particularly limited as long as they are synthetic fibers, and are preferably fibers obtained by known spinning and drawing methods, such as semi-aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, aliphatic polyesters such as polylactic acid, polybutylene succinate, and polyethylene adipate, fully aromatic polyesters such as copolymers of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, aliphatic polyamides such as nylon 6, nylon 66, and nylon 12, semi-aromatic polyamides such as nylon 6T and nylon MXD6, fully aromatic polyamides such as polyparaphenylene terephthalamide, and fibers made of fiber-forming thermoplastic polymers such as polyolefins such as polyethylene and polypropylene, polyvinyl alcohol, and polyvinylidene fluoride, fibers containing heterocycles such as polyparaphenylene benzobisoxazole, acrylic and acrylic fibers, polyurethane fibers, and cellulosic fibers such as rayon, lyocell, and acetate.

In addition, there are no particular restrictions on the fiber fineness, number of filaments, cross-sectional shape, etc., and it can be applied to various forms such as thread, string, nonwoven fabric, woven fabric, knitted fabric, etc.

In the present embodiment, the method for manufacturing the yarn S (fiber for synthetic resin bonding) is carried out in the order of a yarn sending out process, a plasma treatment process, a treatment agent application process, a hot air drying process (thermal drying process), and a yarn winding process, as shown in FIG. 1. The yarn S used in this embodiment is a fiber in which two polyethylene terephthalate fibers (1100 decitex/192 filaments) are twisted together with a twist number of 100 T/M, but may be made of other synthetic fibers. As shown in FIG. 2, the manufacturing equipment 100 for the yarn S in this embodiment has three roller units R1 to R3, a plasma treatment device 20, an oiling roller 30, and a hot air dryer 40. The yarn S is wound around a bobbin 10. The yarn S unwound from the bobbin 10 is passed through the plasma treatment device 20, the oiling roller 30, and the hot air dryer 40 via the three roller units R1 to R3, and then attached to the bobbin 11. After this, the thread S is sent out from the bobbin 10 at a predetermined speed (e.g., 3 m/min), and the processed thread S is passed through the plasma treatment device 20, the oiling roller 30, and the hot air dryer 40 in order, and then wound up on the bobbin 11. In this way, the thread S is produced as a fiber for synthetic resin bonding.

In this embodiment, each of the three roller units R1 to R3 has a drive roller Ra, a driven roller Rb, and a tension roller Rc. The tension roller Rc is disposed between the drive roller Ra and the driven roller Rb, and is configured to apply a predetermined tension to the yarn S. Then, by driving the drive roller Ra of each roller unit R1 to R3, the yarn S is unwound and let out from the bobbin 10 at a predetermined let-out speed (yarn let-out process). Then, the yarn S that has been let out by the yarn let-out process and processed through each process is wound up by the bobbin 11 (yarn winding process).

The plasma treatment device 20 used in the manufacturing method of this embodiment is a known direct atmospheric pressure plasma treatment device capable of irradiating the yarn S with plasma generated by introducing a desired treatment gas into an electric field, but may be a plasma treatment device that performs treatment under reduced pressure or a remote type. In other words, it is sufficient if it is possible to irradiate the yarn S with the desired plasma and perform plasma treatment. As the treatment gas, nitrogen gas, oxygen gas, carbon dioxide gas, helium gas, argon gas, ammonia gas, air, etc., or a mixture of these in a predetermined ratio may be used. By using such a plasma treatment device 20, the yarn S is irradiated with plasma before the treatment agent application process, thereby performing the desired plasma treatment on the yarn S (plasma treatment process). As a result, the yarn S is degreased and the wettability of its surface is improved to become a polar functional state. As a result, the treatment agent (described later) applied to the yarn S is easily penetrated into the fiber filament bundle constituting the yarn S, and the reaction product of the blocked polyisocyanate compound and the polyepoxide compound contained in the treatment agent is easily formed uniformly within the fiber bundle. In other words, the hard resin coating is less likely to form unevenly on the fiber surface, which helps maintain the flexibility of the fiber bundle. In addition, the affinity of the yarn S to the treatment agent is increased, improving the adhesive strength when the yarn S is bonded to a synthetic resin (described later).

In addition, the plasma irradiation section of the plasma treatment device 20 in this embodiment is 0.75 m. Therefore, when the yarn S is fed at 3 m/min, the yarn S is irradiated with plasma for approximately 15 seconds. Note that if the yarn S is fed at a faster speed, the plasma irradiation time becomes shorter, and if the yarn S is fed at a slower speed, the plasma irradiation time becomes longer.

The oiling roller 30 used in the manufacturing method of this embodiment is also a known one, but other application devices such as a metering pump and oiling nozzle application method may be used as long as it is possible to apply the desired amount of treatment agent to the thread S. In addition, the amount of treatment agent applied to the thread S is controlled by appropriately adjusting the oiling roller 30. In this embodiment, the total amount of the blocked polyisocyanate compound and polyepoxide compound contained in the treatment agent applied to the thread S is adjusted to be in the range of 0.5% by weight or more and 5% by weight or less with respect to the weight of the thread S. Since the total amount of these compounds applied to the thread S is 0.5% by weight or more, it is possible to suppress a decrease in the adhesive strength to the thread S. Furthermore, since the total amount of these compounds applied to the thread S is 5% by weight or less, the amount of these compounds used is reduced, and it is possible to suppress an increase in manufacturing costs. The treatment agent is applied to the thread S by such an oiling roller 30, and the blocked polyisocyanate compound and the polyepoxide compound are applied to the thread S (treatment agent application process).

In the present embodiment, the treatment agent is a treatment water for water-based adhesives in which a blocked polyisocyanate compound and a polyepoxide compound are mixed and dispersed at 1.5% by weight. Since the treatment agent is for water-based adhesives, there is no need to install explosion-proof equipment or dispose of waste liquid, which is specific to organic solvents, and it is possible to reduce the burden on the work side. In addition, the ratio of the blocked polyisocyanate compound and the polyepoxide compound in the treatment agent is arbitrary. The amount of the blocked polyisocyanate compound applied to the fiber depends on the type, but it is usually necessary that the amount applied to the fiber is 0.1 to 5% by weight, preferably 0.2 to 4.5% by weight. If it is less than 0.1% by weight, the adhesive performance with the synthetic resin is insufficient, and the application of the blocked polyisocyanate compound to the fiber is uneven, which often causes adhesion spots with the synthetic resin, and is not preferable. Also, if the application amount exceeds 4.5% by weight, it is not preferable because it leads to an increase in manufacturing costs.

In addition, as the polyisocyanate type in the blocked polyisocyanate compound, aliphatic polyisocyanate-based, alicyclic polyisocyanate-based, aromatic polyisocyanate-based, and araliphatic polyisocyanate-based can be used. In addition, as the blocking agent type in the blocked polyisocyanate compound, lactam-based blocking agents (dissociation temperature 130°C to 200°C), alcohol-based blocking agents (dissociation temperature 150°C to 210°C), oxime-based blocking agents (dissociation temperature 130°C to 190°C), amine-based blocking agents (dissociation temperature 140°C to 220°C), active methylene-based blocking agents (dissociation temperature 80°C to 160°C), pyrazole-based blocking agents (dissociation temperature 110°C to 180°C), phenol-based blocking agents (dissociation temperature 120°C to 180°C), and imidazole-based blocking agents (dissociation temperature 80°C to 150°C) can be used. In the case where a plasma treatment step is performed after the treatment agent is applied to the thread S, the blocking agent of the blocked polyisocyanate compound used in the manufacturing method has a dissociation temperature of 140°C or higher. This is because, when the plasma treatment step is performed after the treatment agent is applied to the thread S, the blocking agent is not dissociated even if the thread S is heated to about 120°C by the plasma treatment. In the case where a treatment agent application step is performed after the plasma treatment step as in this embodiment, the blocking agent of the blocked polyisocyanate compound used may have a dissociation temperature of less than 140°C.

The hot air dryer 40 used in the manufacturing method of this embodiment is also a known one, but other dryers may be used as long as they can heat the thread S at a temperature lower than the dissociation temperature of the blocking agent of the blocked polyisocyanate compound and evaporate the moisture in the treatment agent applied to the thread S. The thread S coated with the treatment agent is passed through such a hot air dryer 40, and the thread S is heated and thermally dried at a temperature lower than the dissociation temperature of the blocking agent of the blocked polyisocyanate compound (hot air drying process: thermal drying process). In this way, since the temperature at which the thread S is heated in the hot air drying process is lower than the dissociation temperature of the blocking agent, it is possible to evaporate the moisture in the treatment agent while suppressing the hardening of the treatment agent. This maintains the flexibility of the thread S.

In addition, the thermal drying section of the hot air dryer 40 in this embodiment is 2 m. Therefore, when the yarn S is fed at 3 m/min, the yarn S is thermally dried for approximately 40 seconds. Note that if the yarn S feed speed is increased, the thermal drying time will be shortened, and if the yarn S feed speed is decreased, the thermal drying time will be lengthened.

According to the above-mentioned manufacturing method of the thread S (fiber for synthetic resin bonding), since the temperature to which the thread S is heated in the hot air drying process is lower than the dissociation temperature of the blocking agent, it is possible to evaporate the moisture in the treatment agent while suppressing the hardening of the treatment agent. This maintains the flexibility of the thread S. Furthermore, since the plasma treatment process is performed before the treatment agent application process, the affinity of the thread S to the treatment agent (adhesive) is increased, and the adhesive strength when the thread S is bonded to the synthetic resin as described below is improved. In other words, it is possible to manufacture a thread S that has flexibility and improved adhesive strength. Furthermore, since the treatment agent is for water-based adhesives, there is no need to install explosion-proof equipment or dispose of waste liquid, which are specific to organic solvents, and it is possible to reduce the burden on the work side.

Next, a method for producing synthetic resin adhesive fibers according to a second embodiment of the present invention will be described below with reference to Figures 3 and 4. Note that parts similar to those in the first embodiment are given the same reference numerals and will not be described.

As shown in FIG. 3, the method for manufacturing the yarn S (fiber for synthetic resin bonding) in this embodiment includes a yarn sending out process, a treatment agent application process, a plasma treatment process, a hot air drying process (thermal drying process), and a yarn winding process, in that order. In other words, the manufacturing method of this embodiment only swaps the order of the plasma treatment process and the treatment agent application process from the first embodiment. In other words, the plasma treatment process is performed after the treatment agent application process. Everything else is the same. Also, as shown in FIG. 4, the manufacturing equipment 200 for the yarn S has the same configuration as the manufacturing equipment 100 of the first embodiment, except that the positions of the plasma treatment device 20 and the oiling roller 30 are swapped.

In this manufacturing method of thread S (fiber for synthetic resin bonding), the temperature to which thread S is heated in the hot air drying process is lower than the dissociation temperature of the blocking agent, so that the same effect as in the first embodiment can be obtained. Furthermore, even if the plasma treatment process is performed after the treatment agent application process, the adhesive strength is improved when thread S is bonded to synthetic resin as described below. In other words, it is possible to manufacture thread S that has flexibility and improved adhesive strength. Furthermore, since the treatment agent is for water-based adhesives, there is no need to install explosion-proof equipment or dispose of waste liquid, which are specific to organic solvents, and it is possible to reduce the burden on the work side. Note that the same effect can be obtained for a configuration similar to that of the first embodiment.

Next, a method for manufacturing synthetic resin adhesive fibers according to a third embodiment of the present invention will be described below with reference to Figures 5 and 6. Note that parts similar to those in the first and second embodiments are given the same reference numerals and will not be described.

As shown in FIG. 5, the manufacturing method of the yarn S (fiber for synthetic resin bonding) in this embodiment is the same as the manufacturing method of the first embodiment, except that a plasma treatment process is added between the hot air drying process (thermal drying process) and the yarn winding process. In other words, the plasma treatment process is carried out both before and after the treatment agent application process. Everything else is the same. As shown in FIG. 6, the manufacturing equipment 300 for the yarn S has a plasma treatment device 50 and a roller unit R4 installed next to the roller unit R3 of the manufacturing equipment 100 of the first embodiment. The plasma treatment device 50 has a configuration similar to the plasma treatment device 20 described above. The roller unit R4 also has a configuration similar to the roller units R1 to R3 described above.

In this method of manufacturing thread S (fiber for synthetic resin bonding), the temperature to which thread S is heated in the hot air drying process is lower than the dissociation temperature of the blocking agent, so that the same effect as in the first embodiment can be obtained. In addition, since the plasma treatment process is performed both before and after the treatment agent application process, the adhesive strength is improved when thread S is bonded to synthetic resin as described below, as in the first and second embodiments. In other words, it is possible to manufacture thread S that has flexibility and improved adhesive strength. In addition, since the treatment agent is for water-based adhesives, there is no need to install explosion-proof equipment or dispose of waste liquid, which are specific to organic solvents, and it is possible to reduce the burden on the work side. Note that the same effect can be obtained for configurations similar to those of the first and second embodiments.

The manufacturing method in the third embodiment is a continuous manufacturing method in which a plasma treatment process is carried out following a hot air drying process, but it may also be a two-step manufacturing method in which a yarn winding process is carried out after the hot air drying process, the yarn S that has been treated up to that point is wound onto a bobbin, the wound yarn S is then sent out from the bobbin, the plasma treatment process is carried out, and the yarn S is then wound onto another bobbin.

In addition, in the third embodiment and its modified example, the plasma treatment is performed after the hot air drying process, but the plasma treatment process may be performed between the treatment agent application process and the hot air drying process. This also provides the same effects as described above.

Next, a description will be given below of Examples 1 to 11 and Comparative Examples 1 to 4. Table 1 shows the yarn delivery speed, the amount of treatment agent applied, the timing and treatment gas of the plasma treatment, the temperature and time of the heat drying treatment, the flexibility after these treatments, and the adhesive strength of Examples 1 to 11 and Comparative Examples 1 to 4.

The yarn used in Examples 1 to 11 and Comparative Examples 1 to 4 is a fiber made by twisting two polyethylene terephthalate fibers (1100 decitex/192 filaments) at a twist rate of 100 T/M, similar to the yarn S described above. The treatment agents used in Examples 1 to 11 and Comparative Examples 1 to 3 are all similar to the treatment agents described above (treatment water for water-based adhesives in which a blocked polyisocyanate compound and a polyepoxide compound are mixed and dispersed at 1.5% by weight each). The blocked polyisocyanate compound used was ε-caprolactam blocked diphenylmethane diisocyanate (product name "DM30") manufactured by Meisei Chemical Industry Co., Ltd. The dissociation temperature of this blocking agent is about 180°C. The polyepoxide compound used was sorbitol polyglycidyl ether (product name "Denacol EX-614B") manufactured by Nagase ChemteX Corporation. The treatment agent used in Comparative Example 4 was a treatment agent in which a blocked polyisocyanate compound and a polyepoxide compound were each dissolved in an organic solvent, N-methylpyrrolidone, at a concentration of 1.5% by weight. As shown in Table 1, the yarn delivery speeds of Examples 1 to 10 and Comparative Examples 1 to 4 were all 3 m/min, and the yarn delivery speed of Example 11 was 9 m/min. The amount of treatment agent applied, i.e., the total amount of the two compounds contained in the treatment agent applied to the yarn, was 1% by weight relative to the weight of the yarn in Examples 1 to 4, 7 to 10, and Comparative Examples 1 and 4, 2% by weight relative to the weight of the yarn in Example 5 and Comparative Examples 2 and 3, and 0.5% by weight relative to the weight of the yarn in Example 11.

Also, as shown in Table 1, in Examples 1, 3, 4, 5 and Comparative Example 2, the plasma treatment process is performed only before the application of the treatment agent. In other words, the timing of the plasma treatment process in Examples 1, 3, 4, 5 and Comparative Example 2 is the same as the timing of the plasma treatment process in the manufacturing method of the first embodiment described above. In Example 2, the plasma treatment process is performed only after the application of the treatment agent. In other words, the timing of the plasma treatment process in Example 2 is the same as the timing of the plasma treatment process in the manufacturing method of the second embodiment described above. In Examples 6 to 11, the plasma treatment process is performed both before and after the application of the treatment agent. In other words, the timing of the plasma treatment process in Examples 6 to 11 is the same as the timing of the plasma treatment process in the manufacturing method of the third embodiment described above. Note that the plasma treatment process is not performed in Comparative Examples 1, 3, and 4. The treatment gas used is only nitrogen gas in Examples 1, 2, 5, 6, and 11, only oxygen gas in Example 3, and only carbon dioxide gas in Example 4. In Examples 7 and 8, oxygen gas and nitrogen gas are used as the processing gas, in Example 9, carbon dioxide gas and nitrogen gas are used as the processing gas, and in Example 10, air and nitrogen gas are used as the processing gas. In addition, the plasma processing time in Examples 1 to 10 and Comparative Example 2 is about 15 seconds per process. In Example 11, the plasma processing time is about 5 seconds per process.

As shown in Table 1, the temperature of the thermal drying treatment is 120°C for Examples 1 to 11 and Comparative Example 1, and 210°C for Comparative Examples 2 to 4. The time of the thermal drying treatment is 40 seconds for Examples 1 to 10 and Comparative Examples 1 to 4, and 13 seconds for Example 11.

The results of measuring the flexibility and adhesive strength of the yarns of Examples 1 to 11 and Comparative Examples 1 to 4, which were produced by processing under these conditions, are also shown in Table 1. The flexibility of the yarns will be explained below with reference to Figure 7.

First, each of the threads S1 manufactured by processing under the conditions of each of Examples 1 to 11 and Comparative Examples 1 to 4 is fixed to the fixed plate 70. The fixed plate 70 is an acrylic resin plate with a width of 10 mm, a length of 1200 mm, and a thickness of 2 mm. The length of the thread S1 is 40 mm. Then, as shown in FIG. 7, one end of the thread S1 is attached to the surface at the center of the lower end of the fixed plate, and the other end of the thread S1 is attached to the back surface at the center of the lower end of the fixed plate. The attachment length at this time is 10 mm for both ends. In other words, the 20 mm thread S1 is in a U-shaped state hanging down from the fixed plate 70. In this state, the thread S1 is left to stand for 24 hours at room temperature of 23° C. and humidity of 65% RH. After this, the thread S1 is lowered together with the fixed plate 70 at a speed of 1.5 mm/s, and the thread S1 is brought into contact with the upper surface 80 of the load cell. The descent of the fixed plate 70 is stopped 2 seconds after the thread S1 comes into contact with the upper surface 80 of the load cell. That is, the yarn S1 is brought into contact with the upper surface 80 of the load cell, and then the fixed plate 70 is lowered 3 mm and stopped. The repulsive force (N) of the yarn S1 at this time is measured by the load cell. This measurement is performed five times for one yarn S1, and the average value is evaluated as the flexibility. As a result, the repulsive force was 0.03 N for Examples 1 to 11 and Comparative Example 1, 0.20 N for Comparative Example 2, 0.21 N for Comparative Example 3, and 0.19 N for Comparative Example 4. Untreated yarns that have not been treated are not hardened in the first place, so they are easy to bend and flexible, and are easy to handle. When the flexibility of this untreated yarn is evaluated in the same manner, it was 0.03 N. As a result, for Examples 1 to 11 and Comparative Example 1, the flexibility is good, similar to that of untreated yarns, and the treated yarns can be easily used in the production line. On the other hand, for Comparative Examples 2 to 4, the repulsive force is six times or more than that of the untreated one, and the flexibility is significantly reduced. This shows that the yarn maintains its flexibility by being heated and thermally dried at a temperature below the dissociation temperature of the blocking agent of the blocked polyisocyanate compound during the thermal drying process.

Next, the adhesive strength of the thread will be described below with reference to FIG. 8. First, the manufactured multiple threads S1 are attached to a synthetic resin sheet 90 as shown in FIG. 8(a). That is, the multiple threads S1 are arranged at equal intervals while being spaced apart from each other along the width direction of the synthetic resin sheet 90. The synthetic resin sheet 90 is a thermoplastic polyurethane sheet having a width of 100 mm, a length of 200 mm, and a thickness of 2 mm. Then, the multiple threads S1 are attached to the synthetic resin sheet by heat pressing. The conditions of the heat pressing at this time are a temperature of 160° C., a pressure of 18 kg/cm ² , and a pressing time of 5 minutes. Then, the heat-pressed synthetic resin sheet 90 is cooled. Then, in this state, it is left to stand for 24 hours at room temperature of 23° C. and a humidity of 65% RH. This is performed for each of the threads S1 manufactured by processing under the conditions of each of Examples 1 to 11 and Comparative Examples 1 to 4.

Next, as shown in FIG. 8(b), one end of two adjacent threads S1 among the multiple threads S1 attached to the synthetic resin sheet 90 is attached to a jig 95. After this, the strength (adhesive strength) is measured when the two threads S1 are peeled off from the synthetic resin sheet 90 by the jig 95 in a U-shape such that the threads S1 are folded back 180 degrees. The measurement method is performed in accordance with JIS K 6854-2:1999 (ISO 8510-2:1990) "Adhesives - Peel Adhesion Strength Test Method - Part 2: 180 Degree Peel". The moving speed of the jig 95 at this time is 50 mm/min, and the moving length is 200 mm. The maximum value obtained by this measurement is the adhesive strength (N). The measurement is performed five times for each example, and the average value is evaluated as the adhesive strength. Also, if the thread S1 (synthetic fiber) itself breaks during measurement, this is indicated as breakage, and the desired adhesive strength of 20N or more, as described below, is deemed to be good. Note that the evaluation standard for adhesive strength is 20N or more, which is the standard between the thread and synthetic resin when used as a fire hose, and it is evaluated as having no practical problems.

In all of Examples 1 to 11, the adhesive strength was 20 N or more or the thread S1 broke. In other words, the adhesive strength was satisfactory and practically acceptable. This is because plasma treatment was performed in all of Examples 1 to 11. It can be seen that the plasma treatment makes it possible to achieve a desired adhesive strength or higher in order to maintain flexibility, even if the heating temperature of the thread S1 in the thermal drying treatment is below the dissociation temperature of the blocking agent of the blocked polyisocyanate compound. On the other hand, in Comparative Example 1, the adhesive strength is low and does not have the desired adhesive strength because no plasma treatment was performed. In Comparative Examples 2 to 4, the heating temperature of the thread S1 in the thermal drying treatment exceeds the dissociation temperature of the blocking agent, so the desired adhesive strength is achieved, but the thread S1 itself is in a hardened state and therefore has no flexibility.

From the above Examples 1 to 11, it can be seen that it is possible to manufacture thread S1 (synthetic fiber) that is flexible and has improved adhesive strength by performing plasma treatment before and/or after the treatment agent application process and by setting the heating temperature of thread S1 in the thermal drying process to less than the dissociation temperature of the blocking agent of the blocked polyisocyanate compound. This makes it possible to reduce the workload.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications are possible within the scope of the claims. For example, the treatment agent used in the manufacturing methods of the first to third embodiments described above contains a blocked polyisocyanate compound and a polyepoxide compound, but may contain a compound other than a polyepoxide compound.

The amount of the compound contained in the treatment agent applied to the synthetic fibers in the treatment agent application process may be less than 0.5% by weight or more than 5% by weight relative to the weight of the synthetic fibers.

In addition, when adhering a synthetic resin to which the treatment agent of the present invention does not sufficiently improve adhesion, it is possible to form a layer of the treatment agent on the surface of the synthetic fiber, and then apply to the surface another adhesive that has good adhesion to both the treatment agent and the synthetic resin. In this case, the treatment agent is used as an intermediate layer between the synthetic fiber and the other adhesive.

10, 11 Bobbin 20 Plasma treatment device 30 Oiling roller 40 Hot air dryer 100, 200, 300 Manufacturing equipment R1 to R4 Roller unit S Yarn

Claims (3)

A treatment agent application step of applying a treatment agent for aqueous adhesives containing a blocked polyisocyanate compound to synthetic fibers;
a thermal drying step of thermally drying the synthetic fiber to which the treatment agent has been applied;
a plasma treatment step of irradiating the synthetic fibers with plasma before and after the treatment application step,
2. The method for producing a synthetic resin-bonded fiber, wherein in the thermal drying step, the synthetic fiber is heated to a temperature lower than a dissociation temperature of a blocking agent of the blocked polyisocyanate compound. The method for producing synthetic resin adhesive fibers according to claim 1, characterized in that the treatment agent contains a polyepoxide compound. The method for producing synthetic resin-bonded fibers according to claim 2, characterized in that in the treatment agent application step, the total amount of the blocked polyisocyanate compound and the polyepoxide compound applied to the synthetic fibers is in the range of 0.5% by weight to 5% by weight based on the weight of the synthetic fibers.

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