KR101766095B1

KR101766095B1 - Grease composition for reducing NVH

Info

Publication number: KR101766095B1
Application number: KR1020150179891A
Authority: KR
Inventors: 김재현
Original assignee: 현대자동차주식회사; 기아자동차주식회사
Priority date: 2015-12-16
Filing date: 2015-12-16
Publication date: 2017-08-07
Also published as: KR20170071790A

Abstract

More particularly, the present invention relates to a composition for reducing NVH, and more particularly, to a composition for reducing NVH, and more particularly, to a composition for reducing NVH, Viscosity silicone compound as an antioxidant, and is excellent in noise and vibration reduction effect.

Description

A grease composition for reducing NVH (Grease composition for reducing NVH)

The performance of the NVH is very important as an item to judge the performance of the vehicle because the customer directly perceives it. Cars can cause noise and vibration at various locations. The cause of the NVH is mainly a striking sound caused by the gap between the parts, or a stick slip sound generated when the parts are moved when they are in contact with each other. Generally, in the case of a hit sound, the noise can be reduced by minimizing the gap through the design change. In the case of the stick slip sound, the noise is removed by changing the material or changing the driving environment to weaken the force applied to the relative friction material. However, when the design or the material is changed, various problems such as the influence on the peripheral parts and the cost rise occur. Therefore, the grease is applied to the parts where the parts are in contact with each other.

The grease used to improve the NVH performance of automobiles is generally made of high viscosity base oil to thicken the oil film or to add a fluororesin having excellent friction resistance to reduce grease mixing and stick slip noise simultaneously .

However, since the noise generated in the automobile interior parts is minute, the grease is pushed to the outside of the friction surface when the general grease is applied, thereby contaminating the peripheral parts, thereby deteriorating the appearance quality. In addition, greases commonly used in automobile interior parts use a polyolefin-based synthetic polyolefin (PAO) base oil (see Patent Documents 1 and 2), and the PAO synthetic base oil is not only incompatible with plastic materials There is a disadvantage that the lubrication characteristics are lowered at a low temperature.

Korean Patent Publication No. 10-0135414 Korean Patent Registration No. 10-0513625

Disclosure of the Invention An object of the present invention is to provide a novel grease composition having excellent NVH abatement effect and excellent lubricity irrespective of changes in ambient temperature and having good spreading property so as to prevent the grease from being pushed out of the friction surface.

In order to solve the above problems, the present invention provides a NVH abatement grease composition comprising 82 to 90% by weight of a silicone base oil having a viscosity of 3,000 to 6,000 cSt at 40 DEG C; 7 to 15% by weight of a lithium-based thickener; And 0.8 to 3.5% by weight of a silicone compound having a viscosity at 25 캜 of 0.5 to 10 cSt.

In one preferred embodiment of the present invention, the silicone base oil may be a phenyl silicone oil having a phenyl group bonded to the terminal thereof.

In one preferred embodiment of the present invention, the silicone compound is included as a diffusion preventive agent, and includes octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, heptamethylhexyltrisiloxane, heptamethylethyltrisiloxane, And at least one member selected from the group consisting of methyl octyltrisiloxane, octamethyltrisiloxane and decamethyltetrasiloxane.

In one preferred embodiment of the present invention, 0.5 to 2.0% by weight of a friction reducing agent of polytetrafluoroethylene (PTFE), 0.5 to 2.0% by weight of zinc-based antioxidant, .

In one preferred embodiment of the present invention, the grease composition may have a penetration ranging from 358 to 415 measured according to ASTM D217.

Further, as another aspect of the present invention, a plastic part coated with the above-mentioned grease composition can be characterized.

The inventive grease composition contains a silicone base oil and a lithium-based thickener as basic ingredients, thereby solving the compatibility problem with the plastic component material pointed out in the conventional PAO synthetic base oil and the problem of reducing the lubrication at low temperatures.

In addition, the inventive grease composition has an effect of maximizing the NVH abatement efficacy by controlling the viscosity of the base oil and the content of the thickener.

In addition, the inventive grease composition has the effect of maximizing the compatibility with the plastic part material by incorporating a low-viscosity silicone compound as a diffusion preventive agent.

Accordingly, the grease composition of the present invention can be applied to a noise area generated in an automobile interior part, and can be applied particularly to an automobile interior part of plastic or rubber material.

Fig. 1 is a graph comparing the durability characteristics of individual products produced according to the viscosity change of the silicone base oil.
FIG. 2 is a graph comparing the durability characteristics of individual products produced according to the content of the lithium-based thickener.

The present invention relates to a grease composition for NVH reduction, which includes a silicone base oil, a lithium-based thickener, a silicone compound having a low viscosity, and conventional additives.

Specifically, the grease composition of the present invention may contain, in place of the PAO synthetic oil, a silicone base oil having a viscosity (40 ° C.) adjusted to 3,000 to 6,000 cSt, while minimizing the content of a lithium based thickener and having a viscosity (25 ° C.) cSt contains low-viscosity silicone compound as an essential component.

Each component constituting the grease composition according to the present invention will be described in detail as follows.

1) Base oil

The grease composition of the present invention comprises a silicon base oil as a base oil. The silicone base oil has a form in which a methyl group or a phenyl group is bonded to the end of silicon by reacting a reactive silane compound. This silicone base oil maintains lubrication characteristics in a relatively wide temperature range (-40 to + 205 ° C), has a low viscosity change due to a change in temperature, and does not lose its fluidity even at low temperature due to its low freezing point. Particularly, the phenyl-based silicone base oil to which the phenyl group is bonded has a characteristic of excellent heat resistance.

In the present invention, as the base oil, a silicone base oil having a viscosity at 40 ° C of 3,000 to 6,000 cSt is used. If the viscosity of the base oil is less than 3,000 cSt, it is easily evaporated because it is applied to the parts. It is difficult to maintain the lubricating property of the grease for a long time. If the viscosity of the base oil is higher than 6,000 cSt, the grease can not easily harden.

The silicone base oil may be contained in the range of 82 to 90% by weight in the inventive grease composition. If the content of the silicone base oil contained in the composition of the present invention is less than 82% by weight, the inherent advantage of the silicone base oil can not be expected at all. On the other hand, if the content exceeds 90% by weight, the diffusion property is increased and absorbed by the bumper rubber There may be a problem that the grease is pushed out of the part.

2) thickener

The grease composition of the present invention comprises a lithium-based thickener as a thickener. The lithium-based thickener is prepared by reacting lithium hydroxide (LiOH) with a fatty acid compound. The fatty acid compound used in the production of the lithium-based thickener is an acid compound containing an aliphatic hydrocarbon group having 6 to 20 carbon atoms, and may include, for example, stearic acid.

The lithium-based thickener may be contained in the range of 7 to 15% by weight in the inventive grease composition. The grease composition of the present invention, as compared to conventional grease compositions, is characterized in that the content of the thickener relative to the base oil content is controlled to be low, for the purpose of controlling the penetration of the grease composition.

It is preferred that the grease composition of the present invention maintains the penetration measured in accordance with ASTM D217 in the range of 358 to 415. If the content of the lithium-based thickener is less than 7% by weight, the lead of the grease may be too high to cause contamination of the surroundings due to application to the parts, and the content of the lithium-based thickener may exceed 15% If the grease is too low to be applied to the parts, the grease will become bloated during operation and the desired lubrication effect can not be expected.

3) Diffusion inhibitor

The inventive grease composition comprises a low viscosity silicone compound as a diffusion inhibitor. Silicone base oils have a low surface tension compared to other base oils and are well dispersed on the surface of plastic or rubber parts. If the grease is applied to the parts and easily diffused, the grease may adversely affect the durability of the parts due to the loss of the grease as well as the poor appearance due to contamination of peripheral parts.

The silicone compound may be a low viscosity silicone compound having a viscosity (25 DEG C) of 0.5 to 10 cSt. The silicone compound is a low viscosity compound having 2 to 7 silicon atoms (Si) in a linear or cyclic hydrocarbon chain, and the hydrocarbon chain may be an alkyl group or an alkoxy group having 1 to 10 carbon atoms. The silicone compound having a low viscosity is specifically exemplified by octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, heptamethylhexyltrisiloxane, heptamethylethyltrisiloxane, heptamethyloctyltrisiloxane, octamethyl tri Siloxane, decamethyltetrasiloxane, or a mixture of at least one selected from these.

The silicone compound may be contained in the range of 0.8 to 3.5% by weight in the composition of the present invention. If the content of the silicone compound contained in the composition of the present invention is less than 0.8% by weight, the effect of preventing diffusion of the grease can not be expected. On the other hand, if the content of the silicone compound exceeds 3.5% by weight, none.

4) Additive

The grease composition of the present invention may further contain usual additives as required. Conventional additives may include at least one kind selected from a friction modifier and an antioxidant, and the content thereof is in the range of 0.1 to 4 wt% in the grease composition. The selection or content of the additive can be suitably adjusted within the range usually applied in the art.

The friction reducing agent may be an organometallic compound selected from an organic molybdenum compound, an organic zinc compound, an organic antimony compound, an organic selenium compound, an organic copper compound, and an organotin compound; A sulfur compound selected from sulfide compounds, polysulfide compounds, thiourea compounds, thiocarbonate compounds and the like; Phosphate compounds such as phosphoric acid esters and phosphorous acid esters; And fluorine-based compounds selected from polytetrafluoroethylene (PTFE) and the like. In the embodiment of the present invention, polytetrafluoroethylene (PTFE) is mainly used as a friction reducing agent. PTFE exhibits excellent friction reduction performance due to its low coefficient of friction, and particularly excellent in friction resistance on a sliding portion. Further, since PTFE is excellent in heat resistance and chemical resistance to plastic or rubber materials, it is useful for manufacturing a grease composition applied to automobile interior parts. The friction modifier may be contained in the range of 0.1 to 2.0% by weight in the composition of the present invention.

The antioxidant may include a monovalent metal such as sodium or potassium, or a salt compound of a divalent metal such as barium, zinc, calcium, or magnesium. The salt compound of the metal may include an organic sulfonic acid salt, an organic carboxylic acid salt, an organic phosphate, and the like. In the examples of the present invention, zinc stearate was mainly used as an antioxidant. The antioxidant may be contained in the range of 0.1 to 2.0% by weight in the inventive grease composition.

The grease composition of the present invention having the above composition and composition ratio is applied to a noise region of a component to exhibit excellent NVH performance, and is particularly excellent in compatibility with a plastic or rubber component.

Accordingly, the grease composition of the present invention can be applied for NVH reduction in automotive interior parts made of plastic or rubber. Particularly, the grease composition of the present invention can be applied to a shock absorber in automobile interior parts. The grease composition of the present invention can be applied to a shock absorber which is damped when a car is hit by a vertical load when passing through a barrier, The stick slip sound generated when the bumper stopper and the strut cap rub against each other can be effectively reduced at the same time.

The present invention will now be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[Example]

Examples 1 to 6 and Comparative Examples 1 to 14. Preparation of a grease composition

A silicone base oil, a lithium-based thickener, a silicone compound, and other additives were compounded in the composition ratios shown in Tables 1 to 3 to prepare a grease composition.

[Ingredients Used]

(1) Silicon base oil: 40 ° C. Phenyl base silicon base oils having different viscosities

(2) Lithium-based thickener: Lithium soap obtained by reacting lithium hydroxide with 12-hydroxystearic acid

(3) Silicone compound: Decamethyltetrasiloxane, DC-200 having a viscosity of 1.0 cSt at 25 ° C, manufactured by Dow Corning

(4) Additive:

① Friction reducing agent: Polytetrafluoroethylene (PTFE), product of SOLVAY

② Antioxidant: Zinc stearate

division Example (% by weight) One 2 3 4 5 6 Silicon base oil Viscosity
(cSt, 40 DEG C) 3000 90 87 82 - - 86 4000 - - - 87 - - 6000 - - - - 87 - Lithium-based thickener 7 10 15 10 10 8.8 Silicon compound 0.8 0.8 0.8 0.8 0.8 3.0 additive PTFE 1.2 1.2 1.2 1.2 1.2 1.2 Zn-sterate 1.0 1.0 1.0 1.0 1.0 1.0

division Comparative Example (% by weight) One 2 3 4 5 6 7 8 9 10
silicon
Base oil

Viscosity
(cSt,
40 C) 400 87 1,000 87 2,000 87 3,000 81 78 71 92 8,000 87 16,000 87 20,000 87 Lithium-based thickener 16 19 26 5 10 10 10 10 10 10 Silicon compound 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 additive PTFE 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Zn-sterate 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0

division Comparative Example (% by weight) 11 12 13 14 Silicon base oil Viscosity
(cSt, 40 DEG C) 400 71 3,000 87 81.7 81.0 Lithium-based thickener 26 10.8 12.6 12.3 Silicon compound 0.8 - 3.5 4.5 additive PTFE 1.2 1.2 1.2 1.2 Zn-sterate 1.0 1.0 1.0 1.0

Experimental example. Measurement of physical properties of grease

The properties of the grease compositions prepared in Examples 1 to 6 and Comparative Examples 1 to 14 were measured by the following methods. The results are summarized in Tables 4 to 6 below.

[Measurement of physical properties]

(1) Leading: ASTM D217 (Test Method for Cone Penetration of Lubricating Grease)

(2) Evaluation of single product: The number of durables was measured when initial noise was generated.

(1) Left and right steering: Evaluation was made by implementing a condition in which the steering wheel turns left and right in a vehicle, and evaluated in the landscape (red arrow) direction in the photograph of the single evaluation device. The noise evaluation was carried out under the conditions of a bumper stopper compression amount of 10 mm and a rotation angle of about ± 45 °.

(2) Upward and downward excitation: Evaluation was made in a manner of implementing a condition in which the shock absorber moves up and down when passing through a barrier, and the direction of the up and down (blue arrow) was evaluated in the photograph of the single part evaluation device. Noise evaluation was carried out under the conditions of displacement ± 30 mm, temperature 70 ~ 90 ℃, and frequency 1.0 Hz.

(3) Diffusibility: The grease was coated on the specimen of PP-GF20% used as the strut cap material in the size of 1cm x 1cm, and the degree of spreading was observed at 80 ° C for 72 hours

(4) Contact angle: The contact angle of the grease was measured using the equipment manufactured in KYOWR. The grease was applied with a syringe at a distance of 5 cm from the PP-GF 20% material (strut cap material) perpendicular to the specimen. The fabricated sample was attached to the horizontal position of the measuring camera, and the diffusibility was evaluated by measuring the contact angle after 5 to 10 seconds.

division Example One 2 3 4 5 6 lead 415 392 358 392 392 392 single
evaluation
(time) Upper and Lower 20 million 25 million 20 million 25 million 25 million 25 million Right and left 40 million 50 million 40 million 47 million 43 million 50 million Diffusibility - Good - - - Good Contact angle - 16 - - - 21

According to the results shown in Table 4, the grease compositions prepared in Examples 1 to 6 according to the present invention were able to produce greases having a penetration ranging from 358 to 415 through controlling the viscosity of the base oil and the content of the thickener . As a result of evaluating the single product, it was confirmed that the grease has the NVH reducing effect, and it was confirmed that the spreading property of the grease was good through the spreading degree and the contact angle measurement.

division Comparative Example One 2 3 4 5 6 7 8 9 10 lead 343 322 273 442 392 392 392 392 392 392 single
evaluation
(time) Upper and Lower 11 million 6 million 3 million 2 million 3 million 5 million 7 million 8 million 12 million - Right and left 23 million 7 million 4 only 7 million 5 million 6 million 12 million 10 million - 11 million Diffusibility - - - - - - - - - - Contact angle - - - - - - - - - - Remarks Hardening
phenomenon Hardening
phenomenon Hardening
phenomenon Produce
no High temperature
evaporation High temperature
evaporation High temperature
evaporation Hardening
phenomenon Hardening
phenomenon Hardening
phenomenon

According to the results of Table 5, the comparative examples 1 to 3 were a grease composition containing an excessive amount of a lithium-based thickener and had a low grease lead of less than 358, a bumpiness and an easy hardening phenomenon, Compared with the previous year. Comparative Example 4 was a grease composition containing a small amount of a lithium-based thickener and had a high lead acidity of 442, so that it was impossible to prepare a sample after being applied to a specimen, and the NVH efficacy was remarkably reduced in comparison with the examples.

In Comparative Examples 5 to 7, a base oil having a viscosity of 400, 1,000 and 2,000 at 40 DEG C was used as a grease composition containing a base oil, and a base oil having a relatively low viscosity was used and evaporated at a high temperature of 80 DEG C, It was significantly reduced compared to the examples. Comparative Examples 8 to 10 were grease compositions containing a base oil having a viscosity of 8,000, 16,000 and 20,000 at 40 ° C as a base oil, and were observed to have an easy hardening phenomenon, and the NVH efficacy was remarkably reduced as compared with the Examples.

division Comparative Example 11 12 13 14 lead 273 392 392 384 Single item evaluation (times) Upper and Lower 10 million 25 million 25 million 12 million Right and left 20 million - - - Diffusibility - diffusion Good Good Contact angle - 8 21 24 Remarks High temperature
evaporation - - -

According to the results of Table 6, in Comparative Example 11, a grease composition containing a small amount of silicone base oil having a viscosity of 400 at 40 ° C as base oil and containing a lithium-based thickener in an excess amount, The phenomenon of easy evaporation under high temperature conditions was observed, and the NVH efficacy was reduced in comparison with the examples.

In Comparative Example 12, as a diffusion preventive agent, a silicone composition-free grease composition was applied to a specimen and diffused, and the contact angle was also very small.

In Comparative Examples 13 to 14, although the diffusion property including the silicone compound in an excessive amount was good as the diffusion preventive agent, when the content exceeded 3.5 wt%, the grease did not harden or evaporate in the single product. However, Performance has been reduced.

Reference Example 1. Comparison of Noise Reduction Effect According to Viscosity of Silicon Base Oil

This Reference Example 1 is intended to compare the noise reduction effect according to the viscosity of base oil. The durability characteristics of the prepared grease were compared while varying the viscosity (40 ° C) of the phenyl based silicone base oil used as the base oil in the range of 400 to 20,000 cSt in the composition of the same composition and composition as in Example 2 above. The results are shown in Fig.

1 shows that the durability characteristics of the grease changes depending on the viscosity of the base oil, and when the base oil viscosity (40 ° C) is in the range of 3,000 to 6,000 cSt, the left-right steering and the up- have.

Reference Example 2. Comparison of noise reduction effect according to the content of lithium-based thickener

This Reference Example 2 is intended to compare the noise reduction effect with the content of the lithium-based thickener. In the grease composition having the same composition and composition ratios as in Example 2, a part of the base oil was replaced with a lithium thickener, and the durability characteristics of the prepared greases were compared while varying the content of the midrange agent. The results are shown in Fig.

According to Fig. 2, the durability characteristics of the grease changes depending on the content of the lithium-based thickener, and when the content of the lithium-based thickener contained in the whole grease composition is in the range of 7 to 15% by weight, the right- At the same time, it can be confirmed that it is maintained excellent.

Claims

82 to 90% by weight of a silicone base oil having a viscosity of 3,000 to 6,000 cSt at 40 DEG C;
7 to 15% by weight of a lithium-based thickener prepared by reacting lithium hydroxide with a fatty acid compound having an aliphatic hydrocarbon group having 6 to 20 carbon atoms; And
0.8 to 3.5% by weight of a silicone compound having a viscosity at 25 캜 of 0.5 to 10 cSt and containing 2 to 7 silicon atoms in a carbon chain as a diffusion preventive agent; / RTI >
Characterized in that the penetration of the grease measured in accordance with ASTM D217 is in the range of 358 to 415.

The method according to claim 1,
Wherein the silicone base oil is a phenyl-based silicone oil having a phenyl group bonded to the end thereof.

The method according to claim 1,
The silicone compound may be selected from the group consisting of octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, heptamethylhexyltrisiloxane, heptamethyltetrisiloxane, heptamethyloctyltrisiloxane, octamethyltrisiloxane, and decamethyltetra Siloxane, and mixtures thereof.

The method according to claim 1,
Wherein the composition comprises 0.5 to 2.0% by weight of a friction reducing agent of polytetrafluoroethylene (PTFE), 0.5 to 2.0% by weight of zinc-based antioxidant, or both.

delete

A plastic part to which a grease composition of any one of claims 1 to 4 is applied.