KR20110108516A

KR20110108516A - Polyurethane containing cork powder for vibration isolation

Info

Publication number: KR20110108516A
Application number: KR1020100027743A
Authority: KR
Inventors: 박정근
Original assignee: 주식회사 이알에스
Priority date: 2010-03-29
Filing date: 2010-03-29
Publication date: 2011-10-06

Abstract

The present invention relates to a vibration blocking material that blocks vibrations generated from a machine or facility that causes vibrations from propagating to the surroundings, or blocks the vibrations of the surroundings from propagating to an area inhabited by a machine or a person to be protected. In more detail, it relates to a polyurethane material to which cork powder is added.
The anti-vibration polyurethane of the present invention is obtained by mixing cork powder in a non-foaming polyurethane resin having a glass transition temperature (Tg) of -40 ° C. or lower, and hardening the structure. 2) is uniformly mixed.
The anti-vibration polyurethane of the present invention can realize a vibration-proof device having a low natural frequency because a large deformation occurs even at a small load, high linearity in the load-strain relationship, even if there is a frequency variation of external vibration, the elastic modulus and attenuation rate are almost constant. In addition, the change in elastic modulus with temperature is less than that of rubber.
Therefore, the anti-vibration polyurethane of the present invention is suitable for use as an anti-vibration material for blocking vibration.

Description

Polyurethane Containing Cork Powder for Vibration Isolation

The present invention relates to a vibration blocking material that blocks vibrations generated from a machine or facility that causes vibrations from propagating to the surroundings, or blocks the vibrations of the surroundings from propagating to an area inhabited by a machine or a person to be protected. In more detail, it relates to a polyurethane material to which cork powder is added.

Transportation means such as motor vehicles, fans, pumps, engines, machine tools, and other railway vehicles inevitably cause vibrations during operation. Not only may cause discomfort, damage to life, but also damage the structure of the building, cause malfunction of the precision equipment and control system installed nearby, vibration-sensitive precision measuring equipment, optical equipment, precision processing equipment This can degrade accuracy and, in extreme cases, can cause these machines to fail. In addition, when vibration is transmitted to the building structure, it may cause structure pollution (Structure Borne Noise) to cause noise pollution.

In order to remove the bad effects of the vibration, the vibration is prevented by using a dust-proof means in the machine or facility that causes the vibration or the equipment to be protected from the vibration or the area where people live. It is called. Dust-proofing is made of elastic material such as rubber or synthetic rubber in the form of plate and installed in the path where vibration is propagated to block vibration, or the structure at the top and bottom of elastic body such as metal spring, air spring, rubber, etc. Or a method of supporting a machine or structure that causes vibration by using a vibration isolator made by attaching a bracket that can be coupled to the machine is mainly used.

All of the above dustproof methods are the same in that they support a vibrating object with an elastic body to block the transmission of vibration. In addition, a damper may be used to absorb vibration energy and dissipate it into heat, and a viscoelastic material such as rubber has a damping property in which the material itself converts vibration energy into heat and dissipates it.

As shown in FIG. 1, the movement system for vibration movement is composed of a mass (M), an object for vibration movement, a spring (K), and a damper (C) dissipating vibration energy. It is called three elements.

In the vibration system as described above (in the case of a vibration system for vibration protection, referred to as a "vibration system"), the ratio or the floor vibration of the force (F _t ) transmitted to the floor relative to the excitation force (F) that is a repetitive force causing vibration. in that the amplitude (X ₁₎ transmissibility (TR) the ratio of the vibration amplitude (X ₂₎ of the object with respect to, and is expressed by the following equation.

,

Where M is the mass of the object, K is the spring constant of the spring, C is the damping coefficient of the damper,

ω: excitation frequency (rad / sec), j: imaginary symbol,

The transfer rate equation is used modified as follows.

,

Where r: frequency ratio (= ω / ω _n ), ω _n : natural frequency (=

),

ζ: decay rate (=

)

The transmission rate is shown in a graph as shown in FIG. 2, but in order to block vibration to a large extent, the transmission rate KR should be low, and the frequency ratio r is

In larger areas, the mass (M) must be large, the spring constant (K) must be low, and the frequency ratio (r)

In the smaller area, it can be seen that the damping ratio ζ should be large. (In practice, since the frequency ratio is larger than 3 in the vibration system and no damper is used, the vibration damper is roughly designed to ignore the influence of the damper. But especially the resonance region (frequency ratio)

In the following), the damping coefficient has a large influence on the transmission rate.)

All materials with elasticity can be used as the elastic body of the vibration isolator. Among them, the metal spring can increase the static deformation and increase the dustproofing efficiency, and the spring constant is always kept linearly and influences the ambient temperature. However, the spring has a problem of causing structure Borne noise due to vibration because the spring is not blocked well by surging phenomenon, and the shape of the vibration isolator is complicated because the spring is difficult to fix. Handling is inconvenient In addition, the metal spring has a problem that the vibration is amplified largely in the resonant region because the transient vibration time is long because there is almost no damping of the material.

Among the elastic materials, rubber (including synthetic rubber) can manufacture dustproof devices in various shapes, and has excellent adhesion with metal, thereby molding dustproof mounts by molding the mounting bracket integrally with rubber. The dustproof device using such a rubber is easy to handle and easy to fix to the dustproof machine and the floor. In addition, rubber has some internal damping characteristics, and no surging occurs, so there is no problem of structural transmission.

However, in the conventional rubber dustproof device, in order to lower the spring constant for high dustproof efficiency, the cross-sectional area of the mount should be small and the height should be high, in which case there is a risk of buckling. Therefore, the rubber mount can not lower the spring constant below a certain limit is limited in dustproof efficiency. In particular, in the case of low frequency vibration, it is impossible to block with a dustproof device using rubber.

In addition, rubber has a constant dustproof effect due to the change in physical properties of the material depending on time and external environment. In addition, the rubber mount is also dependent on the internal damping characteristics of the rubber material, and the damping rate is not so large as 10% or less.It is not as severe as the metal spring, but it is still a problem because of the amplification of vibration during resonance and a long transient response time. .

In addition, the rubber has a low linearity of physical properties, so the spring constant and damping coefficient change greatly according to the magnitude and frequency of the load applied, and also vary greatly depending on the ambient temperature. Therefore, the vibration isolator using rubber has a problem that it is difficult to predict the accurate vibration blocking effect when designing

Recently, in order to improve the problems of the rubber as described above, a foamed rubber in which pores are formed in the rubber using a foaming agent in the process of molding the rubber is used as a dustproof material, and foamed urethane and foamed polyester are typical examples. Such foamed rubber has a much lower elastic modulus than ordinary rubber, which can lower the vibration transmission rate and can block the low frequency vibration to some extent. However, the foamed rubber is worse in the linearity of the physical properties, the water penetrates into the pores, there is a fear of freezing failure when used outdoors in the winter, and there is a problem that the elasticity is lost if a lot of time passes due to the permanent compression.

An air spring is a dustproof device using compressed air packed inside an elastic rubber membrane. The spring constant can be made very low, so the dustproof effect is very high and low frequency vibration such as an earthquake can be blocked. However, the air spring is expensive, it is difficult to maintain and maintain such as to constantly check and replenish the air inside, there is a risk that the mount falls down and the equipment is overturned if damaged by accident.

And, cork board, rubber pad, nonwoven fabric (Felt) and the like is very low vibration isolation efficiency is very high frequency vibration can be used only limited to block the shock vibration. And in the case of low frequency vibration, there is a fear to amplify the vibration rather than by resonance.

As described above, each of the elastic materials used in the conventional vibration isolator has advantages and disadvantages. In particular, rubber has a high elastic modulus, and the spring constant and the damping coefficient are not linear. have. In addition, foam rubber, which improves the problem of rubber, penetrates water into the pores, and there is a problem of permanent compression.

Therefore, there is a need for a new anti-vibration rubber material having a low elastic modulus, maintaining the linearity of the material properties, not allowing water to penetrate, to be used outdoors, and having less permanent compression.

The anti-vibration polyurethane of the present invention is a mixture of cork powder in a non-foaming polyurethane resin having a glass transition temperature (Tg) of -40 ° C. or lower, and its structure is as shown in FIG. 3. ), The cork powder particles 2 are uniformly mixed.

The anti-vibration polyurethane of the present invention can realize a vibration-proof device having a low natural frequency because a large deformation occurs even at a small load, high linearity in the load-strain relationship, even if there is a frequency variation of external vibration, the elastic modulus and attenuation rate are almost constant. In addition, the change in elastic modulus with temperature is less than that of rubber.

Therefore, the anti-vibration polyurethane of the present invention is suitable for use as an anti-vibration material for blocking vibration.

1 is a block diagram of a dustproof system for vibration blocking.
2 is a vibration transmission rate graph according to the change of the frequency ratio and the attenuation rate.
3 is a structural diagram of the anti-vibration polyurethane.
Figure 4 shows the deformation characteristics of the rubber and polyurethane for dustproof.
5 is a load-strain graph of the anti-vibration polyurethane.
6 is a dynamic spring constant-frequency graph of the anti-vibration polyurethane.
7 is a damping rate-frequency graph of the anti-vibration polyurethane.
8 is an elastic modulus-temperature graph of the polyurethane for dustproof.
9 is a graph of water absorption rate-cork content ratio of the anti-vibration polyurethane.

The anti-vibration polyurethane of the present invention is made by incorporating cork powder into a non-foaming polyurethane resin having a glass transition temperature (Tg) of −40 ° C. or lower (hereinafter referred to as “cork urethane”). As shown in the figure, the cork powder particles 2 are uniformly mixed in the polyurethane resin 1.

Polyurethanes come in many varieties, including organic compounds with alcohol groups (-OH) (called "polyols") and organic compounds with isocyanic acid groups (-NCOs) (called "monomers"). A high-molecular compound made by urethane bond (-OCONH-) is a generic term. Polyurethanes having a wide variety of properties can be prepared according to the raw materials used.

Polyurethane of the present invention is used for dustproof, and should have elasticity like rubber at the use temperature (when used outdoors in our country, about -40 ° C to 50 ° C is sufficient).

Plastic materials, including polyurethane, have elasticity, like rubber, above the glass conduction temperature (Tg), since the polyol has a sheath-type bond structure, allowing the bond to rotate freely. If the polyol which is a raw material of polyurethane is selected as a suitable thing, a polyurethane with a glass transition temperature of -40 degrees C or less can be manufactured, and the polyurethane with low glass transition temperature has elasticity like a rubber at normal temperature, and of this invention It can be used as a vibration damping material for the purpose.

Liquid polyurethane resins are commercially available by packing them in cans or drums in a liquid state. Polyurethane resin is one-component and two-component type. One-component type is prepared by mixing all additives and then mixing them into one raw material. The two-component type is separately packaged with additives including a substrate and a curing agent. The two raw materials are mixed before use. In the case of the two-component type, it is troublesome to mix the two raw materials before use, and there is a problem in that the curing speed is partially changed when the mixing is not sufficiently uniform, but the curing speed can be controlled by controlling the amount of the raw material containing the curing agent. There is an advantage.

In the case of the polyurethane of the present invention, there is a process of mixing cork powder with a polyurethane raw material immediately before use, so that a two-component polyurethane is used, and a large amount of hardener is added to cure the cork powder at a high speed so that the cork powder rises to the top. It can prevent the crowd.

Although various additives are added to the polyurethane, the polyurethane foam of the present invention does not add a blowing agent to form pores, and must use a dispersant to prevent the cork powder from rushing to one side by buoyancy or the like.

The anti-vibration polyurethane of the present invention is prepared by incorporating cork powder into a polyurethane raw material at a predetermined ratio, stirring the mixture well, and curing it. The ratio of cork powder is found to be most preferably 1 to 5% of the raw material weight.

If the particle size of the cork powder (defined as the longest in the particles) is too large, water may penetrate into the cork particles exposed to the surface, and in winter, the water penetrates and freezes repeatedly by freezing and melting. It is good to use a small particle size of the cork powder because there is a possibility that the surface cork particles fall off. As for the particle size of the cork powder used for this invention, it is good to use 100 micrometers or less. Cork powder of such a particle size is commercially available.

Cork is a structure in which air is trapped between fine resin films. The cork is elastic against a small load, but under a large load, the cork breaks and loses elasticity. However, when the cork is pulverized into small particles in the form of powder and impregnated with polyurethane as in the present invention, most of the load is supported by polyurethane, and the cork is not subjected to excessive load, thereby maintaining elasticity.

Foam urethane has empty pores, so when it is subjected to large loads for a long time, the pores are destroyed and permanent compression deformation occurs. It does not occur Cork urethane thus maintains the same elasticity even for prolonged use.

Since non-foamed polyurethane is incompressible like rubber, and the Poisson's ratio is close to 0.5, as shown in FIG. Is nonlinear in relation to However, the foamed polyurethane and the cork urethane of the present invention, as shown in (b) or (c) of FIG. 4, do not cause lateral expansion because the pores or cork particles of the polyurethane absorb the deformation of the polyurethane, and thus the load and Linearity is relatively well maintained in relation to deformation.

Figure 5 shows the load-displacement diagram of the cork urethane and rubber of the present invention, a large deformation occurs at a constant load, the elastic modulus is low, and the section in which the load and deformation is proportional relationship is wide. Therefore, when the cork urethane of the present invention is used as an anti-vibration elastic body, it can be seen that the vibration can be blocked to a high degree, the low frequency vibration can be blocked, and the spring can be a good linearity.

6 is an experimental diagram of cork urethane and rubber obtained by dynamic spring constant-frequency diagram, it can be seen that the dynamic spring constant is uniform according to the frequency of cork urethane compared to rubber. That is, when cork urethane is used as the anti-vibration material, it can be seen that the spring constant is almost constant even if the frequency of the vibration is changed, and thus the vibration blocking performance (vibration transfer rate) for each vibration frequency can be predicted.

Figure 7 is the damping ratio of the cork urethane and rubber obtained experimentally (frequency diagram)-it can be seen that the attenuation ratio is uniform according to the frequency of cork urethane has a rubber. That is, when cork urethane is used as the anti-vibration material, it can be seen that the attenuation rate is almost constant even if the frequency of the vibration is changed, and thus the vibration blocking performance (vibration transfer rate) for each vibration frequency can be predicted.

8 is an elastic modulus (Young's modulus)-temperature diagram of the cork urethane and rubber obtained experimentally, it can be seen that the change in the elastic modulus of cork urethane is small with temperature changes compared to rubber. Cork urethane can be seen that the higher the content of cork, the more stable the elastic modulus.

9 is a graph of water absorption by cork content, the water absorption amount should be less than 10% by weight compared to dry cork urethane. If the water absorption exceeds this, the static modulus decreases and the dynamic modulus increases, so the modulus predicted by the design is not maintained. Referring to the graph of FIG. 9, the point at which the weight ratio of the water absorbing cork urethane to the weight of the dry cork urethane becomes 1.1 is that the cork content is 5% by weight, and the cork urethane having a cork content of more than 5% is used outdoors. It can be seen that it is inadequate. When the cork content was less than 1%, the cork powder had a slight effect of lowering the elastic modulus of the polyurethane resin. In addition, the water absorption of cork urethane is also affected by the particle size of the cork powder, the smaller the particle size, the lower the water content.

Cork urethane has high linearity in the load-strain relationship, elastic modulus and attenuation rate are almost constant even if frequency fluctuation of external vibration is constant. It can be seen that it is very suitable to be used as a material for the spring.

1: polyurethane resin
2: cork powder particles

Claims

Cork powder is uniformly mixed with a liquid polyurethane raw material and then cured without foaming. Cork powder particles 2 are uniformly mixed and cured in the polyurethane resin 1, and the glass transition temperature of the polyurethane resin is cured. The dustproof polyurethane containing cork powder whose (Tg) is -40 degrees C or less.

The method of claim 1,
The cork powder is a dust-proof polyurethane containing a cork powder, characterized in that the particle size is 100㎛ or less.

The method of claim 1,
The mixing ratio of the cork powder is 1 to 5% of the weight of the raw material resin, cork powder-containing polyurethane for dust.