JPH036106B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thread guide for guiding threads such as natural fibers and synthetic fibers. Conventionally, a large number of thread guides for guiding yarn have been used in devices used in spinning processes and processing processes thereof. Many of these thread guides are made of alumina ceramic. However, alumina ceramic is sintered with sintering aids such as silica and magnesia, and alumina crystal particles with a crystal grain size of 20μ or more are mixed with a large amount of glassy material due to impurities contained in the sintering aid and aluminum oxide. It has a liquid-phase bonded crystal structure, and when a thread runs in contact with such an alumina ceramic thread guide at high speed,
Only the soft glassy layer, which is the bonding layer, is selectively worn away, weakening the bonds between the alumina crystal particles and causing the alumina crystal particles to fall off, resulting in a 20μ layer on the surface in contact with the yarn.
The above recesses are formed. If the thread continues to run in contact with the thread guide in which this recess is formed, changes in the frictional force on the contact surface of the thread or edge phenomenon may cause fuzzing on the thread surface or breakage of the thread due to seizure. There were inconveniences such as spoiling the appearance of the thread. In particular, the above disadvantages tend to occur particularly in yarns having so-called irregular cross-sections, such as hexagonal or elliptical cross-sections other than circular ones. Therefore, conventional thread guides made of alumina ceramic are not the best, and there has been a need for thread guides that do not damage the threads and have good sliding properties. The present invention was developed in view of the above circumstances, and
Even when used for a long period of time, the thread does not become fluffy or break.
Moreover, it is an object of the present invention to provide a thread guide which generates extremely little amount of so-called white powder caused by scraping off the outer surface of the thread. The thread guide of the present invention is characterized by being constructed of a sintered body mainly composed of silicon nitride which has a relatively low thermal conductivity and high hardness (hereinafter referred to as a silicon nitride sintered body). . According to the present invention, the thread guide is based on a completely new idea that deviates from the conventional established concept. In other words, the crystal grain size is small at 0.5 to 2μ, the average pore size of the pores present in the sintered body is small at 1μ, and the hardness (Rockwell) is about 87.
As described above, it is extremely hard and has high abrasion resistance, so the amount of wear when the thread runs in contact with it is extremely small, so there is almost no shedding of crystal particles due to wear, and therefore, the amount of wear is extremely small. Since the number of edges formed around the opening after falling off is small, the extent to which the outer surface of the running yarn is scraped off is also small. Furthermore, since there is no change in the frictional force that accompanies the running of the thread, there is almost no occurrence of thread fuzz or thread breakage. Moreover, the thermal conductivity of the silicon nitride sintered body constituting the thread guide of the present invention is 0.02 [cal/cm・sec・℃], which is 1 compared to about 0.06 to 0.08 [cal/cm・sec・℃] of alumina ceramic. /
It is small, about 3 to 1/4 of the size. The present invention is based on the assumption that the physical properties of the silicon nitride sintered body described above make it suitable as a constituent material for threaded guides. Thread guides of the same shape were fabricated using titanium-based alumina ceramics and silicon carbide sintered bodies. Thereafter, the amount of self-powder produced, which is a particularly important factor as a thread guide, was measured, and the results were as follows. In this experiment, the same undrawn polyester yarn with a thickness of 150 denier and an irregular cross section was used, and the yarn was installed in a device with an average running speed of 950 m/min, and each thread guide that occurred during a 3-week period was The figure shows the total amount of white powder generated. From this measurement result, the thermal conductivity of the alumina ceramic (Al ₂ O ₃ -B) used in the construction of conventional thread guides was 0.02 [cal/cm・sec・℃] for the generation of 40g. ]'s silicon nitride thread guide generates 2g of white powder, while a titanium-based (titanium oxide sintered body) thread guide with the same 0.013 [cal/cm・sec・℃] generates 1.5g of white powder, it has extremely good characteristics. It was found that it has. However, as is clear from the physical property comparison table shown in Table 1, the titanium-based thread guide that showed the lowest amount of white powder generation was compared to other alumina ceramics (Al ₂ O ₃ -B) and silicon nitride sintered bodies. The hardness of the guide member is extremely low compared to other guide members, and in mounting tests, although the amount of white powder generated was small, as the thread ran in contact with the guide member, it wore out to the extent that deep notches were carved in the contact area. It was inappropriate. Next, thread guides with the same shape were manufactured using the four types of materials listed in Table 1, and on the other hand,
950m of 260 denier undrawn polyester yarn
The contact running was carried out for 5 hours at a speed of 50 min, and the weight of the white powder generated during this was measured, and the results were as shown in the graph in the figure.

[Table] According to this, the thermal conductivity is 0.16 [cal/cm・
sec・℃], the largest thread guide made of silicon carbide sintered body is about 700 mg, and the thread guide made of alumina ceramic (Al ₂ O ₃ -B) with 60% alumina content is about 650 mg;
Approximately 200% for those made of alumina ceramic (Al ₂ O ₃ -B), which is 99.0% and has little soft matrix.
mg relatively small. However, the thermal conductivity is 0.02
[cal/cm・sec・℃], 0.013 [cal/cm・sec・℃]
In the thread guides made of small silicon nitride sintered bodies and titanium-based ones, the amount of white powder generated was extremely small at several tens of milligrams. Furthermore, when the surface of the silicon nitride sintered thread guide that the thread ran in contact with was observed under a microscope, the contact area of the thread was generally in a state of wear, and no areas where crystal grains were missing were found. On the other hand, titanium-based threads produced the least amount of white powder, but the parts where the threads came in contact with each other were worn out in the form of thin kerfs. Although it is slightly disadvantageous in that the amount of wear is large compared to other methods, it may be effective in areas where the amount of white powder generated is a particular problem. By the way, the silicon nitride sintered body, which has been found to be extremely advantageous as a thread guide as mentioned above, has features such as high high-temperature strength, excellent thermal shock resistance and abrasion resistance, so it is suitable as a heat-resistant material. Traditionally used in special fields. However, silicon nitride itself is a difficult-to-sinter substance with strong covalent bonds, and therefore, it is important to use a sintering aid in addition to the silicon nitride raw material. The composition of silicon nitride used in the examples of the present invention is as follows. Si ₃ N ₄ = 74.0% FeSi = 6.0% Fe = 1.5% Fe ₂ O ₃ = 11.5% For sintering, a metal oxide such as MgO is added as a sintering aid to a silicon nitride compound having such a composition. Use as raw material. Appropriate amounts of various binders are added to this raw material, molded into the desired thread guide shape, and then _N2
Sintering in a gas atmosphere at a temperature range of 1400-1700℃. The main phase of the obtained sintered body is β-Si ₃ N ₄ , and in addition, unreacted ferri silicon and metal oxides generated by oxidation reactions during the firing process remain as crystals or amorphous. It is a dense, black-gray sintered body. As mentioned above, thread guides made of silicon carbide sintered bodies or alumina ceramic bodies, which have been mainly used in the past, have a crystal structure on the surface that comes in contact with the thread, and the edge portion due to the lack of crystals during use. It is thought that by scraping the surface of the yarn, a relatively large amount of white powder is generated, especially in yarns with irregular cross sections. On the other hand, the thread guide made of the silicon nitride sintered body according to the present invention has very little crystal loss and has lower thermal conductivity than other sintered bodies, so the thread contact area is suitable for the thread to run. It is assumed that the amount of white powder generated becomes extremely small as the temperature rises. Moreover, combined with the small amount of white powder produced, almost no yarn fuzz or yarn breakage was observed.
In addition, silicon nitride is considerably hard with a Rockwell hardness of 87 and has high wear resistance, so it is possible to provide a thread guide with a significantly longer life than conventional products.

[Brief explanation of the drawing]

The figure is a graph showing the measurement results of the thermal conductivity of each material and the amount of white powder generated.

Claims (1)

[Claims] 1. A thread guide characterized by being made of a sintered body whose main component is silicon nitride.