JPH0130018B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved brake material comprising a sheet with excellent frictional properties. Felts made from animal fibers such as wool felt and rabbit hair felt have conventionally been used as sliding brake materials for rotating bodies with relatively low torque that require high precision, stability, and durability.
Felts made from these animal fibers have favorable frictional properties as sliding brake materials under constant temperature and humidity conditions. However, since felt is made from animal fibers, it is highly hygroscopic and its coefficient of friction fluctuates in response to changes in atmospheric humidity. Furthermore, since the thermal properties are sensitive, the coefficient of friction fluctuates in response to temperature fluctuations, making it difficult to perform a stable function as a sliding brake material against changes in the atmosphere. Furthermore, since felt made from animal fibers does not have sufficient abrasion strength, the friction changes over time and repeating friction over a long period of time causes the fibers to tear and generate fiber waste. These fiber debris can contaminate the inside of precision equipment and damage important functional components, and the generated fiber debris may exist at friction interfaces, further changing frictional properties such as the coefficient of friction, resulting in disadvantages that impair originally desirable characteristics. have. In order to improve these drawbacks, the present inventors have already published Utility Model Application No. 56-28727 (Utility Model Application No. 56-28727).
(Refer to Publication No. 141245), but as a result of intensive study to further improve the initial stability and durability stability, and to improve the above-mentioned drawbacks of the conventional sliding brake materials, we have developed a napped sheet. By adhering at least a portion of the single fibers that make up the sheet, and by defining the sheet's apparent density and compressive elastic modulus within a specific range, it has excellent abrasion resistance, is stable against changes in the atmosphere, and has no initial change. It has been possible to find an improved brake material made of a sheet that has less friction, excellent durability and stability, and also has frictional characteristics suitable for a sliding brake material. That is, the present invention mainly consists of synthetic fibers and/or recycled fibers having a single fiber fineness of 1 denier or less, and at least a portion of the single fibers are self-adhesive,
Or in a brake material consisting of a sheet with raised naps adhered by a polymeric binder,
This is an improved brake material characterized in that the sheet has an apparent density of 0.20 to 0.95 g/cm ³ and a compressive elastic modulus of 70% or more. Synthetic fibers include polyester polymers such as polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, copolymers or mixed polymers of these polymers, nylon 6, nylon 66, and nylon 610.
Polyamide polymers consisting of nylon 11, copolymers or mixed polymers of these polymers; polyolefin polymers such as polyethylene and polypropylene; acrylic polymers such as polyacrylonitrile and vinyl halide-acrylonitrile copolymers It is a fiber made up of fusions. Further, if necessary, a material containing a colorant, a modifier, a modifying material, etc. can also be used. The recycled fibers are cellulose fibers such as viscose rayon and copper ammonia rayon, and if necessary, colorants, modifiers, etc. may be added. Among the synthetic fibers, fibers made of linear polyester polymers, linear polyamide polymers, and acrylic polymers are preferable, and fibers made of linear polyester polymers and linear polyamide polymers are more preferable. . The single fiber fineness of the fiber is preferably 1 denier or less. Preferably it is 0.5 denier or less. If the single fiber fineness of the fiber exceeds 1 denier, not only will the contact surface become rough and the friction properties will not be stable, but the fibers on the sheet surface will be hard and will damage the friction surface of the mating material that is being rubbed, resulting in poor friction properties. This is not desirable because it damages the Further, it is preferable that the single fiber fineness of the fiber is 0.001 denier or more because the abrasion strength of the single fiber is reduced and the single fiber on the surface of the sheet does not tear and tear and generate fiber waste. If the single fiber fineness of the fiber is within the range of the present invention, the frictional contact surface will have a suitably dense contact, resulting in not only stable frictional properties but also excellent durable abrasion resistance. These fibers may be of the same fineness or may be a mixture of fibers of different fineness. The fiber having a single filament fineness of 1 denier or less,
For example, fine-grained yarn after forming multicomponent sea-island fibers, mixed spun fibers, special composite fibers, etc. consisting of two or more types of polymers, and removing one component by means such as dissolving and peeling. can be obtained as Furthermore, fibers with a small single filament fineness can also be obtained directly by means such as melt blowing and super draw methods. Furthermore, in the case of linear polyester polymers, the fineness can also be reduced by dissolving the fiber surface in an alkaline solution atmosphere after forming it into a sheet such as a fibrous fabric or a woven or knitted fabric or non-woven fabric. can. The apparent density of the sheet is preferably 0.2 to 0.95 g/cm ³ .
Preferably it is 0.4 to 0.95 g/cm ³ , more preferably 0.5 to 0.95 g/cm ³ . If a sheet with an apparent density of less than 0.2 g/cm ³ is used as a sliding brake material and subjected to continuous friction under pressure for a long time, the sheet structure will become more stable, causing damage to the surface and internal structure of the sheet. changes, the apparent density of the sheet changes accordingly, and the friction coefficient or friction torque changes over time, which is undesirable because stability cannot be expected. Also, the apparent density of the sheet is 0.95g/
If it exceeds cm ³ , the hardness of the sheet becomes extremely large, which not only reduces its flexibility and impairs its workability into the desired shape, but also causes the surface condition of the sheet to approximate a mirror surface, as with resin molded plates and metal plates. This is not preferable because favorable friction characteristics cannot be obtained. In other words, the stability of the sheet structure during friction under pressure is what leads to the stability of the friction characteristics, and the scope of the present invention is absolutely necessary to satisfy these requirements. The compression modulus of the sheet is preferably 70% or more. Preferably it is 75%, and even more preferably 80% or more. If the compressive elastic modulus of these sheets is less than 70%, there is a problem that the dynamic friction coefficient or torque value changes over time when friction is continued under a predetermined pressure, making it impossible to exhibit stable friction characteristics, which is preferable. do not have. In other words, in order to stabilize the frictional characteristics of a sheet under pressure and provide durability, one of the important characteristics is how to give the sheet resilience. In order to have excellent restorability,
It is necessary that the compression modulus of the sheet falls within the range of the present invention. The length of the single fibers protruding from the surface of the raised sheet constituting the brake material of the present invention is not particularly limited, but is preferably 0.1 to 5 mm, more preferably 0.2 to 2 mm. Here, the single fibers appearing on the surface of the sheet are single fibers that have a cut surface that can be seen when observing the sheet surface from vertically above. Although these single fibers may be raised at a certain angle to the sheet surface, it is preferable that they lie substantially parallel to the sheet surface from the viewpoint of initial stability and durability stability of frictional properties. Therefore, it is better not to have loop-like fibers on the sheet surface, but even if they are present,
It is preferable that the loop length be short. A raised sheet having the above characteristics can be obtained either by first forming a normal sheet and then carrying out a densification treatment, or by carrying out densification at the same time as forming the sheet. For example, a method in which a fiber web formed from the synthetic fibers and/or regenerated fibers is entangled with each other by a punching process such as needle punching, water jet punching, or air jet punching; It is obtained by a method of laminating and punching, a method of laminating short fibers using a papermaking method, a method of electro-flocking short fibers based on a woven or knitted fabric, etc. At the same time or after that, it is mixed in advance, or Heating self-thermal adhesive fibers such as low melting point synthetic fibers or powder as constituent fibers to bond at least a portion of the single fibers, or using binders such as polyurethane, polyacrylic, polyamide, and polyester. Obtained by impregnating with. In order to obtain the apparent density and compressive modulus specified in the present invention, the amount of binder constituting the sheet, the fineness of the fibers, the density of the fibers, and heating and pressure treatment are adjusted. For example, adjusting the amount of binder impregnated, adjusting the degree of entanglement of fibers by adjusting the degree of punching treatment, adjusting the density of knitted fabric, and heating and pressurizing the sheet in the thickness direction. One or more of these methods may be used in combination. The heating and pressure treatment is preferably carried out using a calender roll, a hot roll, a hot plate, or the like. The brake material of the present invention thus obtained not only has stable friction characteristics against changes in the atmosphere, but also has the advantages of good initial stability and excellent durability. Therefore, the brake material of the present invention is suitable as a high-performance sliding brake material, etc., and is particularly effective in making high-precision audio equipment and video tape players run stably, and provides a homogeneous brake material at a low cost. It has the advantage of being able to Next, preferred specific contents of the present invention will be explained using examples. Although various evaluations are performed in Examples,
The method is as follows. [Appearance density of sheet] Calculate by taking a 100mm square sheet and measuring its weight and thickness. [Sheet compressive elastic modulus] According to the method described in JIS-L1096, a load of 300 g/
Measure in ^cm3 . [Coefficient of Dynamic Friction] A polyacetal resin molded plate is placed horizontally, a 100mm square sheet is placed on top of it, and a 20g/mm sheet is placed on top of it.
Place a load of cm ³ on a polyacetal resin molded plate.
The sheet is run at a speed of 100mm/min. Calculate by measuring the tensile stress at that time. [Torque value] Using a cassette tape player deck type 600 manufactured by Nakamichi Research Institute Co., Ltd., the pressing load of the disc-shaped friction brake for back tension control of the cassette tape was changed by changing the pressing spring.
Use about twice as much as usual. The friction brake disc has an outer diameter of 18.0 mm from the seat and an inner diameter of
It was punched out to a size of 12.0 mm, and attached and fixed to a base with a double-sided adhesive sheet on the back side of the sheet so that the surface of the sheet matched the contact surface of a torque control component made of polyacetal resin and used for measurement.
The friction rotation speed is 65 rpm, and the torque measurement is
Use the TG type torque gauge manufactured by Tohnichi Seisakusho Co., Ltd. [Plane wear] Measured by the Kastom method described in JIS L1096. Example 1 Polyethylene terephthalate (PET) and polystyrene were composite melt-spun and then heated and stretched to obtain a drawn yarn. Next, the fibers were crimped and cut to obtain staple fibers, and then a web was formed by open carding, which was laminated and then needle punched to obtain a nonwoven fabric. Next, the polystyrene was removed by treatment in trichlene, which is a solvent for polystyrene and does not have any effect on polyethylene terephthalate. Subsequently, it was impregnated with polyurethane to obtain a nonwoven fabric comprising polyethylene terephthalate fibers and polyurethane in a weight ratio of 85:15. The single yarn fineness of the polyethylene terephthalate fibers constituting the nonwoven fabric obtained in this way is
It consists of 0.8 denier, 0.14 denier and 0.07 denier, respectively. As a comparative product, polyethylene terephthalate was melt-spun using a conventional method to obtain a drawn yarn having a single filament fineness of 3.0 denier, and a nonwoven fabric impregnated with polyurethane was obtained using the method described above. The nonwoven fabric obtained as above was raised at 180°C.
The sheets were passed between a pair of heated rolls heated to 100° C. to obtain sheets each having a desired apparent density. Furthermore, wool felt was added as a comparison product, and the change in torque value over time was measured. The atmosphere during measurement was 20℃65
%RH. The results are shown in Table 1.

[Table] In the product of the present invention, a sheet having a desired apparent density could be obtained by using fine-grained polyethylene terephthalate fibers as constituent fibers and by densification. Therefore, in nonwoven fabrics using wool felt and ordinary thick denier polyethylene terephthalate fibers, torque changes occur in a fairly short number of days, but the product of the present invention was able to significantly extend the life of a stable torque value. It can also be seen that there is a significant delay in the generation of wear debris that could contaminate equipment or cause problems. In particular, with wool felt, fine powder of polyacetal, which is the object of friction, accumulates on the wool felt as the wool fibers are torn and fall off due to friction. Although there were no fibers that fell due to tearing, it was observed that polyacetal resin was scraped off and accumulated on the surface of the nonwoven fabric sheet. Example 2 Single yarn fineness produced by the same method as Example 1 was
A nonwoven fabric made of 0.07 denier polyethylene terephthalate fibers with a weight ratio of polyethylene terephthalate fibers and polyurethane of 80:20 was formed, and the appearance of the nonwoven fabric sheet was changed by changing the hot roll temperature and contacting the hot roll for 1 minute. Samples with different densities were made. The nonwoven fabric sheets thus obtained were measured for changes in torque over time, and in particular, the initial changes in torque were compared. The results are shown in Table 2.

【table】

[Table] As shown in Table 2, the densified sheet having the apparent density of the present invention not only stabilizes the friction torque value over a long period of time, but also has a great ability to stabilize the initial friction torque value. I can see that it will work. Furthermore, it was found to be very effective in suppressing variations between samples to an extremely small range. Example 3 A nonwoven fabric sheet made of polyethylene terephthalate fibers with a single fiber fineness of 0.07 denier and polyurethane was made in the same manner as in Example 1, and heated with a heated roll at 175°C by changing the fiber/binder ratio.
A nonwoven fabric sheet was obtained by hot pressing for a minute. Nonwoven fabric sheets obtained in this way had different apparent densities and sheet compressive elastic moduli. Using this nonwoven fabric sheet, we measured the change in torque value over time,
The number of days until the torque value started to fluctuate was determined. The results are shown in Table 3.

[Table] As shown in Table 3, when the fiber/binder ratio is changed and further heat pressing is performed, the compressive elastic modulus of the sheet is Since the friction behavior did not fall within the desired range of the invention, it was observed that the frictional behavior changed over time and deteriorated particularly in the early stages. Example 4 Staple fibers were obtained by crimping and cutting nylon 6 drawn yarn having a single yarn fineness of 0.7 denier and polyethylene terephthalate drawn yarn having a single yarn fineness of 0.7 denier. Next, the opened webs were laminated and needle punched to produce each nonwoven fabric. Next, foamed polyurethane is added as a binder at a ratio of 20 parts by weight to 100 parts by weight of the fibers, and one surface is brushed to increase the thickness.
Single fibers having a cut surface of 1.5 mm were formed on the surface of the nonwoven fabric, which was further passed through a pair of hot press rolls to obtain a nonwoven fabric sheet with a thickness of 1 mm. A commercially available wool felt with a thickness of 1 mm was used as a comparison product. After each sample thus obtained was conditioned in a predetermined atmosphere for 24 hours, the coefficient of dynamic friction with the polyacetal resin plate was measured in the atmosphere. The results are shown in Table 4.

[Table] As seen in Table 4, it can be seen that the change in the coefficient of dynamic friction of the nonwoven fabric obtained according to the present invention due to changes in temperature and humidity is extremely small compared to that of wool felt, and is not easily affected by the atmosphere. Among them, it can be seen that polyesters such as polyethylene terephthalate are excellent, and it can be seen that all the products of the present invention have excellent abrasion resistance. This shows that stable friction characteristics can be maintained over long periods of friction.

Claims (1)

[Claims] 1. A brake consisting of a sheet mainly made of synthetic fibers and/or recycled fibers with a single fiber fineness of 1 denier or less, and at least a portion of the single fibers having raised fibers bonded by self-adhesion or a polymeric binder. An improved brake material, characterized in that the sheet has an apparent density of 0.20 to 0.95 g/cm ³ and a compressive modulus of elasticity of 70% or more.