JP2017007996A - Manufacturing method of lithium 12-hydroxystearate, lithium 12-hydroxystearate and grease composition containing the lithium 12-hydroxystearate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing lithium 12-hydroxystearate less in contamination of contaminants deteriorating silence of a grease.SOLUTION: The manufacturing method of lithium 12-hydroxystearate is a manufacturing method of lithium 12-hydroxystearate obtained by reacting 12-hydroxystearic acid and excessive amount of lithium hydroxide monohydrate and lithium 12-hydroxystearate as a reaction product is applied to a washing treatment by a solution containing water. In the washing treatment, it is preferable to mix the lithium 12-hydroxystearate and the solution containing water at a ratio of 50:50 to 10:90 for washing. Also the solution containing water is preferably contains a surfactant.SELECTED DRAWING: None

Description

  The present invention relates to lithium 12-hydroxystearate that can be used as a thickener with less impurities and can improve the quietness of grease, a method for producing the same, and grease containing the lithium 12-hydroxystearate Relates to the composition.

  Thickeners used for grease are roughly classified into organic and inorganic types. Typical examples of organic thickeners include urea compounds and metal soaps. Among them, metal soap has been used for a long time, and has a characteristic of expressing unique performance by selecting a metal element, and is a grease thickener widely used worldwide.

  As a metal soap, a lithium metal soap system is excellent in heat resistance, water resistance, and shear stability. In particular, lithium 12-hydroxystearate is used in many greases as a versatile thickener.

  The metal soap production reaction can be roughly divided into a double decomposition method and a direct method. Specifically, the metathesis method is a method for obtaining a target metal soap by exchanging metal elements, for example, as shown in the following reaction formula (i). The direct method is a method in which a fatty acid is directly reacted with a metal (Li) oxide or metal hydroxide, for example, as shown in the following reaction formula (ii).

[Example of reaction of double decomposition method]
RCONa + LiCl → RCOOLi + NaCl (i)
[Example of direct method reaction]
RCOOH + Li (OH) .H ₂ O → RCOOLi + 2H ₂ O
... (ii)

  Lithium soap is generally produced by a direct method in which a fatty acid and lithium hydroxide are reacted. Specifically, when lithium 12-hydroxystearate is produced as a lithium soap, 12-hydroxystearic acid and lithium hydroxide monohydrate are used as raw materials, and these are directly reacted at a temperature near the melting point of the fatty acid. At this time, the fatty acid and lithium hydroxide monohydrate are not equal to each other, but an excessive amount of lithium hydroxide monohydrate is added and reacted. This means that if unreacted fatty acid remains, when the obtained lithium soap is used as a thickener to make a grease, the heat resistance of the grease is lowered and negative effects such as discoloration are exerted. Because it ends up.

  As an application destination of grease, for example, there is a bearing. Bearing grease is required to have excellent quietness in addition to lubricity, and such grease is referred to as silent grease. The quietness as a property of grease is greatly affected by the inclusion of foreign matter. For example, if foreign matter exists on the sliding surface of the bearing, the foreign matter particles are crushed along with the sliding, and abnormal noise is generated at that time, which is a factor that hinders quietness.

  Such foreign matter is expected to occur in the manufacturing process of the thickener component constituting the grease. Even in lithium 12-hydroxystearate that can be used as a versatile thickener, there are few impurities. It is desired to produce.

  Patent Document 1 discloses a manufacturing method that can manufacture lithium soap such as lithium stearate in a short time. However, although described in detail later, in the method disclosed in Patent Document 1 and the conventional method for producing lithium 12-hydroxystearate, impurities (lithium carbonate compound) are contained in the obtained reaction product. Will remain and reduce the quietness of the grease.

JP-A-11-106794

  The present invention has been proposed in view of such circumstances, and is a lithium 12-hydroxystearate that can be used as a thickener constituting the grease, which is a contaminant that impairs the quietness of the grease. It is an object of the present invention to provide a method for producing lithium 12-hydroxystearate with low contamination.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, washing treatment is performed with an aqueous solution containing water on lithium 12-hydroxystearate, which is a reaction product obtained by reacting 12-hydroxystearic acid with an excess amount of lithium hydroxide monohydrate. As a result, it was found that lithium 12-hydroxystearate with less impurities was obtained, and the present invention was completed. That is, the present invention provides the following.

  (1) The first invention of the present invention is a process for producing lithium 12-hydroxystearate obtained by reacting 12-hydroxystearic acid with an excess amount of lithium hydroxide monohydrate, wherein the reaction product This is a method for producing lithium 12-hydroxystearate, in which lithium 12-hydroxystearate is washed with an aqueous solution containing water.

  (2) In the second invention of the present invention, in the first invention, the lithium 12-hydroxystearate and the aqueous solution containing water are mixed and washed in a ratio of 50:50 to 10:90. This is a method for producing lithium 12-hydroxystearate.

  (3) The third invention of the present invention is the method for producing lithium 12-hydroxystearate in the first or second invention, wherein the aqueous solution containing water contains a surfactant.

(4) A fourth invention of the present invention is 12-hydroxylithium stearate obtained by reacting 12-hydroxystearic acid and lithium hydroxide monohydrate, which is a reaction product of 12-hydroxy Lithium stearate is lithium 12-hydroxystearate which is obtained by washing with an aqueous solution containing water, and the filtration rate calculated by conducting the following filtration test is 95% or more.
[Filtration test]
A grease is prepared with the base oil and the lithium 12-hydroxystearate, and 1000 g of the grease is heated and dissolved. The dissolved grease is filtered through a SUS 2000 mesh filter with an opening of 11 μm. The filtration rate is calculated from the mass of grease that has passed through the filter with respect to the mass of grease that has passed through.

(5) A fifth invention of the present invention comprises a base oil and a thickener containing lithium 12-hydroxystearate, wherein the lithium 12-hydroxystearate comprises 12-hydroxystearic acid and water. The filtration rate calculated by conducting the following filtration test is obtained by washing lithium 12-hydroxystearate, which is a reaction product obtained by reacting with lithium oxide monohydrate, with an aqueous solution containing water. The grease composition is 95% or more.
[Filtration test]
A grease is prepared with the base oil and the lithium 12-hydroxystearate, and 1000 g of the grease is heated and dissolved. The dissolved grease is filtered through a SUS 2000 mesh filter with an opening of 11 μm. The filtration rate is calculated from the mass of grease that has passed through the filter with respect to the mass of grease that has passed through.

  According to the production method of the present invention, lithium 12-hydroxystearate with less contamination can be produced.

  In addition, the grease composition using the 12-hydroxylithium stearate obtained by the production method according to the present invention as a thickener exhibits excellent quietness, for example, an environment where quietness such as for bearings is required. Can be suitably used as the grease used in the above.

Hereinafter, specific embodiments of the present invention (hereinafter referred to as “present embodiments”) will be described in detail in the following order. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention.
1. Method for Producing Lithium 2-12-hydroxystearate 2. Lithium Lithium 2-hydroxystearate 3. Grease composition Example

<< 1.12-Production Method of Lithium Hydroxystearate >>
The method for producing lithium 12-hydroxystearate according to the present embodiment is a method for producing lithium 12-hydroxystearate that can be effectively used as a thickener constituting the grease composition.

  Specifically, in this production method, 12-hydroxystearic acid is reacted with an excess amount of lithium hydroxide monohydrate, and the reaction product obtained by the reaction is lithium 12-hydroxystearate. Is washed with an aqueous solution containing water.

<1-1. About generation reaction>
Lithium 12-hydroxystearate uses 12-hydroxystearic acid and lithium hydroxide monohydrate as raw materials and directly reacts these compounds at a temperature near the melting point of 12-hydroxystearic acid, which is a fatty acid. Can be obtained.

In the following formula (ii), a general reaction formula when a fatty acid and a metal (Li) hydroxide are reacted by a direct method is shown. Also in the manufacturing method of lithium 12-hydroxystearate, reaction according to this reaction formula occurs to produce lithium 12-hydroxystearate.
RCOOH + Li (OH) .H ₂ O → RCOOLi + 2H ₂ O
(Ii)

  At this time, the raw materials 12-hydroxystearic acid and lithium hydroxide monohydrate do not react with each other in equal amounts, but an excessive amount of lithium hydroxide monohydrate with respect to 12-hydroxystearic acid. To react. Thereby, the residual of fatty acid can be prevented, and when the reaction product lithium 12-hydroxystearate is used as a thickener, it is possible to suppress a decrease in heat resistance and discoloration of the grease.

On the other hand, lithium hydroxide monohydrate that has not been consumed in the reaction remains in the reaction product obtained by reacting with an excess amount of lithium hydroxide monohydrate. Lithium hydroxide monohydrate remaining in the reaction product changes into a lithium carbonate compound such as lithium carbonate as shown in the following formula (iii) due to the influence of heat and carbon dioxide in the air.
2Li (OH) .H ₂ O + CO ₂ → Li ₂ CO ₃ + 2H ₂ O
(Iii)

  Thus, the lithium carbonate compound produced | generated based on the remaining lithium hydroxide monohydrate exhibits very fine primary particles, and is contained in the reaction product in the state of primary particles or secondary particles. Since the lithium carbonate compound is a stable compound and has a high melting point, for example, it does not decompose or melt in the temperature range applied in the production of grease.

  When the present inventors use lithium 12-hydroxystearate containing such a lithium carbonate compound as a thickener constituting the grease, the lithium carbonate compound becomes a contaminant and makes the grease quiet. The knowledge that it has a big influence was obtained.

  Specifically, a grease using 12-hydroxylithium stearate as a thickener is a mixture of a base oil and lithium 12-hydroxystearate, heated and stirred to reach the melting point of lithium 12-hydroxystearate. It is obtained by cooling at the place. As described above, the lithium carbonate compound contained as a contaminant in lithium 12-hydroxystearate exists as a solid in the vicinity of the melting point of lithium 12-hydroxystearate. Therefore, the lithium carbonate compound remains in the grease and becomes a foreign substance that affects the quietness of the grease.

  For example, there are bearings as the application destination of grease, but there are environments in which bearing grease requires quietness in addition to lubricity. For such a quiet grease, the inclusion of foreign matter is a factor that greatly affects the quietness. Become. Specifically, if foreign matter is mixed in the grease, when the foreign matter comes to exist on the bearing sliding surface, the foreign matter particles are crushed along with the sliding and an abnormal sound is generated. And significantly impair the quietness of the grease. Therefore, when lithium 12-hydroxystearate is used as a thickener constituting the grease, if the compound contains a lithium carbonate compound as a contaminant, the performance of the grease is reduced.

<1-2. About cleaning process>
Therefore, in the method for producing lithium 12-hydroxystearate according to the present embodiment, an aqueous solution containing water is used for lithium 12-hydroxystearate, which is a reaction product obtained by directly reacting raw materials. It is characterized by performing a cleaning process.

  In the formation reaction of lithium 12-hydroxystearate, the lithium carbonate compound obtained by reacting the remaining lithium hydroxide monohydrate with carbon dioxide has the property of being soluble in water, It is difficult to dissolve in other solvents. From this, the lithium carbonate compound can be dissolved and effectively removed by subjecting lithium 12-hydroxystearate, which is a reaction product, to a washing treatment using an aqueous solution containing water.

  Specifically, in the cleaning treatment, it is preferable to use water alone, and it is desirable to use ion-exchanged water or distilled water as the water.

  Although it is possible to use tap water, industrial water, etc. as water, since those water contains calcium ion, iron ion, magnesium ion, etc., these metal sources are 12-hydroxy stearic acid and By reacting, metal soap may be formed and become another foreign substance. In addition, the reaction stochastic ratio collapses, resulting in a reaction with lithium hydroxide monohydrate that has not been subjected to the reaction, resulting in an increase in the lithium carbonate compound, which may impair the cleaning properties.

  Further, the cleaning treatment may be performed using a mixed solvent of water and alcohols (hereinafter simply referred to as “alcohol”). Since alcohol generally has a boiling point lower than that of water, the drying rate after the washing treatment can be increased by using a mixed solvent of water and alcohol.

  When a mixed solvent of water and alcohol is used, the ratio (water: alcohol) is preferably 40:60 to 90:10. When the content ratio of water in the mixed solvent is less than 40% by mass, the efficiency of washing the lithium carbonate compound may be deteriorated. On the other hand, when the content rate of water exceeds 90% by mass, the drying rate is It will not be improved and sufficient drying properties cannot be imparted.

  Further, a cleaning treatment may be performed by adding a surfactant to an aqueous solution containing water. Since lithium 12-hydroxystearate has hydrophobic properties, it is not well-suited with the main component water used in the cleaning treatment, and particularly when the content of 12-hydroxystearic acid in the slurry is high. Become unfamiliar. From this, it is possible to effectively wet and disperse the hydrophobic surface of lithium 12-hydroxystearate by washing with an aqueous solution to which a surfactant is added. The removal efficiency of the salt compound can be increased.

  The surfactant is not particularly limited, and any nonionic, cationic or anionic surfactant may be used. If the surfactant remains after the cleaning treatment, it may affect the heat resistance and water resistance of the grease to be produced. Therefore, it is preferable to use a water-soluble surfactant that can be easily removed by washing with water. Moreover, it does not specifically limit as addition amount of surfactant, It can change suitably according to the density | concentration of 12-hydroxystearic acid contained in the slurry of washing process object.

  In the washing treatment, washing is preferably carried out at a ratio (mixing ratio) of lithium 12-hydroxystearate to water of 50:50 to 10:90. If the ratio of 12-hydroxylithium stearate to water is less than 10% by mass, the amount of water used for washing increases, waste liquid increases, and recovery efficiency deteriorates. Furthermore, problems such as taking time for dehydration may occur. On the other hand, when the ratio of 12-hydroxylithium stearate to water exceeds 50% by mass, the viscosity of the liquid (slurry) becomes high, so that it becomes difficult to flow, resulting in poor cleaning efficiency.

  Although it does not specifically limit as a washing | cleaning method, It can carry out by stirring the slurry of 12-hydroxystearic acid and water using a stirrer etc. The cleaning time may be appropriately adjusted according to the amount of treatment, but it is preferably performed for 1 hour or longer. In addition, the number of washings is preferably repeated at least twice, more preferably three times.

  In the present embodiment, the water used for cleaning is separated after performing the above-described cleaning process. The separation of water is not particularly limited, but can be performed using a solid-liquid separation device such as a centrifugal filter using a filter cloth or a filter press. Moreover, after separating water, it can be dehydrated and dried by a filter with a dryer or a shelf dryer. In the drying process, care should be taken because too high a temperature may cause discoloration.

≪2.12-Hydroxyhydroxystearate≫
Lithium 12-hydroxystearate according to the present embodiment is obtained by reacting 12-hydroxystearic acid as a raw material with lithium hydroxide monohydrate, and reacts lithium 12-hydroxystearate as a reaction product. And washing with an aqueous solution containing water.

  For example, the lithium 12-hydroxystearate has a filtration rate of 95% or more calculated by performing the filtration test shown below.

  Here, as the “filtration test”, first, a base oil and the lithium 12-hydroxystearate are mixed to prepare a grease, and 1000 g of the obtained grease is weighed and heated to 200 to 250 ° C. Dissolve completely. Next, the heat-dissolved grease solution is passed through a SUS 2000 mesh filter having an opening of 11 μm and filtered. And a filtration rate is computed from the mass of the grease which passed the filter with respect to the mass of the grease which passed.

  As described above, lithium 12-hydroxystearate, which is a reaction product obtained by reacting 12-hydroxystearic acid with an excess amount of lithium hydroxide monohydrate, has water remaining unreacted. Lithium oxide monohydrate is present and reacts with carbon dioxide gas such as air to form a lithium carbonate compound. When a grease is prepared using lithium 12-hydroxystearate containing such a lithium carbonate compound as a thickener, the lithium carbonate compound becomes a foreign substance and affects the quietness of the grease.

  And in the grease containing such a lithium carbonate compound as a contaminant, in the above-described filtration test, the lithium carbonate compound is collected on a mesh having an opening of 11 μm, and gradually clogs, thereby reducing the filtration rate. Let

  In contrast, lithium 12-hydroxystearate according to the present embodiment is a reaction product obtained by reacting 12-hydroxystearic acid with lithium hydroxide monohydrate. Is washed with an aqueous solution containing water, so that the lithium carbonate compound as a contaminant is dissolved and removed by the washing treatment. Therefore, by forming a grease using lithium 12-hydroxystearate obtained through this washing treatment as a thickener, a high filtration rate of 95% or more is obtained without causing clogging in the mesh in the filtration test described above. Can be obtained.

  According to such lithium 12-hydroxystearate, when used as a thickener as a constituent of grease, the grease can be improved in quietness, for example, used in an environment where quietness is required. It can be a suitable grease for the bearing.

  In addition, in the grease produced using lithium 12-hydroxystearate as a thickener, for example, there is a foreign substance measuring method described in JIS K 2220 as a method for examining the amount of the lithium carbonate compound that is a foreign substance. In this method, a template of a prescribed size is filled with grease in a clean environment, and the number is measured by the size (particle size) of impurities using a microscope.

  More specifically, this foreign matter measurement method uses a metal plate having a predetermined shape and dimensions as a template, and inserts a notch with a width of about 10 mm and a length of about 20 mm into the template, and fills the notch with the prepared grease. It is sandwiched between cover glasses, and the foreign particles are divided into four parts of 10-25 μm, 25-75 μm, 75-125 μm, 125 μm or more by a microscope at a magnification of about 100 times, and the number of particles by particle size is measured is there. Thus, by counting the number of particles for each particle size, the amount of foreign matter that affects the quietness of the grease can be quantified.

≪3. Grease composition >>
<3-1. About grease composition>
The grease composition according to the present embodiment contains at least a base oil and lithium 12-hydroxystearate as a thickener.

  In this grease composition, lithium 12-hydroxystearate used as a thickener is a reaction product obtained by reacting 12-hydroxystearic acid and lithium hydroxide monohydrate, as described above. -A lithium hydroxystearate that is washed with an aqueous solution containing water is used.

[Base oil]
Base oil (base oil) is the main component of grease, and constitutes bale grease (base grease) together with a thickener. The base oil is not particularly limited, and those conventionally used in general can be used. Examples thereof include mineral oil, synthetic hydrocarbon oil, ether oil, ester oil, polyalkylene glycol oil, and silicone oil. Among them, it is preferable to use a synthetic hydrocarbon oil or an ester oil from the viewpoint of improving quietness. These base oils can be used alone or in combination of two or more.

  The content of the base oil in the grease composition is not particularly limited, and can be determined in consideration of the blending ratio with the thickener constituting the base grease. Specifically, for example, it can be contained in a ratio of about 49.0 to 98.0% by mass in the total composition of the grease.

  The blending ratio of the base oil and the thickener in the grease is not particularly limited, and can be arbitrarily determined in order to obtain a desired grease hardness. For example, the base oil ratio can be reduced to increase the grease hardness, while the base oil ratio can be increased to increase the grease hardness.

[Thickener]
The thickener is a material necessary for retaining the oil, and constitutes the base grease together with the base oil. In the grease composition according to the present embodiment, lithium 12-hydroxystearate is used as the thickener. Lithium 12-hydroxystearate is particularly excellent in heat resistance, water resistance and shear stability.

  And in the grease composition which concerns on this Embodiment, it is a reaction product obtained by making 12-hydroxy stearic acid and lithium hydroxide monohydrate which are raw materials react as 12-hydroxy lithium stearate. -A lithium hydroxystearate that is washed with an aqueous solution containing water is used.

  As described above, the contamination of the lithium 12-hydroxystearate obtained by the reaction is suppressed. Specifically, it is lithium 12-hydroxystearate in which the lithium carbonate compound generated in the process of the reaction is effectively removed and impurities are reduced. By using such lithium 12-hydroxystearate as a thickener, the quietness of the grease can be enhanced.

  The content of the thickener in the grease composition is not particularly limited, and can be determined in consideration of the blending ratio with the base oil constituting the base grease. Specifically, for example, it is preferably contained at a ratio of 1.0 to 25.0 mass% in the total composition of the grease. When the content of the thickener is less than 1.0% by mass, the thickening effect is small and it is difficult to form a grease. On the other hand, if the content exceeds 25.0% by mass, the obtained composition becomes too hard, and the desired effect of grease may not be obtained.

  In the grease composition, other compounds may be used in combination as a thickener. Specific examples include other lithium soaps, soap-based compounds such as calcium soaps and aluminum soaps. Non-soap compounds such as urea, sodium terephthalate, fluororesin, organic bentonite, and silica gel can also be used.

[Other additives]
In the grease composition, various additives generally used in grease can be blended in addition to the components described above. Specific examples of the additive include an antioxidant, a solid lubricant, a friction modifier, an antioxidant, a viscosity index improver, a pour point curing agent, and a corrosion inhibitor. From the viewpoint of improving the quietness of the grease, it is not preferable to use a solid lubricant that may impair the quietness as a foreign matter.

<3-2. About manufacturing method of grease composition>
The grease composition according to the present embodiment is a grease using lithium 12-hydroxystearate as a thickener as described above, and such a grease is not particularly limited. Can do.

  Specifically, the base oil and lithium 12-hydroxystearate as a thickener are mixed in a copper kettle and stirred while being heated to about 150 to 300 ° C. and dissolved. Moreover, when adding another additive, an additive is added and it stirs further. Thereafter, the melt is transferred to an aluminum bat or the like and naturally cooled. Thereby, grease can be obtained.

  Stirring can be performed using, for example, a well-known stirring / dispersing apparatus such as a universal stirrer, a homogenizer, and a colloid mill.

<< 4. Examples >>
EXAMPLES Hereinafter, although the Example of this invention is shown and demonstrated in detail, this invention is not limited to a following example at all.

(1) Preparation of 12-hydroxy lithium stearate as a thickener A 12-hydroxy lithium stearate (S-7000H, manufactured by Sakai Chemical Co., Ltd.) was used as a thickener.

  The prepared 12-hydroxylithium 12-hydroxystearate, 1180 g of ion-exchanged water, and 20 g of nonionic surfactant were weighed and mixed to form a slurry. Next, the obtained slurry was stirred for 2 hours at 500 rpm by a three-one motor. The stirred slurry was put into a centrifugal filter and dehydrated. Thereafter, 500 g of ion-exchanged water was added and stirred again for 1 hour. By carrying out such an operation three times in total, washing treatment for lithium 12-hydroxystearate was performed.

  After the washing treatment, it was dried for 12 hours using a shelf dryer. Lithium 12-hydroxystearate after drying was used as a thickener (660 g).

(2) Preparation of grease Next, a grease containing the prepared lithium 12-hydroxystearate as a thickener was prepared.

  Specifically, a polyol ester oil (Synative ES 2939, manufactured by BASF) that does not contain impurities is used as a base oil, and 850 g of this base oil and 150 g of lithium 12-hydroxystearate as a thickener are weighed. And mixed and heated to 210 ° C. and stirred. Thereafter, the solution was transferred to an aluminum vat and quenched to obtain a grease.

  Grease using 12-hydroxystearic acid prepared by washing with water (washing) as described above as a thickener is referred to as “Grease of Example 1”, and 12-hydroxystearic acid is used without washing with water. The grease using as a thickener was designated as “Grease of Comparative Example 1”. Table 1 below shows the grease compositions of Example 1 and Comparative Example 1, including the presence or absence of the cleaning treatment.

(3) Evaluation of produced grease [Filtration test using filter (2000 mesh)]
Under an environment where no contamination occurs, 1000 g of each of the greases of Example 1 and Comparative Example 1 were weighed and heated to 210 ° C. to completely dissolve them. Using a SUS 2000 mesh (opening 11 μm) filter, a solution of grease obtained by dissolving in this filter was passed through and a filtration test was conducted. The filter was carried out while securing an effective mesh diameter of 5 cm by pressing with a fluorine rubber packing having a diameter of 5 cm.

  In this filtration test, when a foreign substance of 11 μm or more is present, it is collected between the collection meshes because it is larger than the mesh opening. As the collection of foreign matter by the mesh proceeds, the mesh becomes clogged and the solution cannot be filtered gradually. Therefore, as a foreign substance presence evaluation index, based on this filtration test, the “filtration rate” was calculated from the mass of grease that passed through the filter with respect to the charged amount (mass of passed grease).

[Observation of filter]
After performing a filtration test using a SUS 2000 mesh filter as described above, the filter was recovered, and the grease component adhering to the mesh was dissolved and washed with methanol. And each of 2000 mesh in a filter was observed with the scanning electron microscope (SEM). In the SEM observation, the field of view was fixed at a magnification of 250 times, the foreign matter occupation area in the observation visual field was calculated, and the collection rate of foreign matters by the filter was calculated. In addition, the range which can be seen by the field of view with a magnification of 250 times by SEM was a range of 335 μm in length × 506 μm in width, and the area was 0.18 mm ² . The observation point was the central part of the place where the filtration treatment was performed.

[Grease evaluation]
In order to confirm the change in grease performance depending on the presence or absence of washing treatment for lithium 12-hydroxystearate, the characteristics of the thickener were evaluated.

  Specifically, based on JIS K 2220, the penetration, dropping point, and oil separation degree in the grease were determined. Moreover, in order to confirm the foreign material in grease, the foreign material in each grease of Example 1 and Comparative Example 1 was measured.

  The measurement of contaminants is based on JIS K 2220. A metal plate having a predetermined shape and size is used as a template, and a notch with a width of about 10 mm and a length of about 20 mm is made into the template, and the grease prepared for the incision is used. The sample was filled with a cover glass and measured for each particle size of the contaminant particles using a microscope with a field of view of about 100 times. The particle size was divided into four groups of 10 to 25 μm, 25 to 75 μm, 75 to 125 μm, and 125 μm or more, and the number of particles for each particle size was measured.

(4) Evaluation results Table 2 below shows the results of the tests described above.

  As shown in the results summarized in Table 2, the grease of Example 1 prepared by washing a lithium 12-hydroxystearate and using it as a thickener had a filtration rate in a 2000 mesh filtration test. It was 99.80%, and almost the entire amount could be filtered except for some contamination. Moreover, when the mesh after a filtration test was observed, the foreign material occupation area in a mesh was 0.7% or less, and the solid component was hardly confirmed.

  On the other hand, in the grease of Comparative Example 1 prepared using lithium 12-hydroxystearate not subjected to washing treatment as a thickener, the filtration rate was very low at about 50% in a 2000 mesh filtration test. Moreover, when the state of the mesh after the filtration test was confirmed, the area occupied by foreign matter in the mesh was 7%, and collection of solid components was confirmed. The collected solid component was collected and analyzed by FT-IR (Fourier transform infrared spectroscopy). As a result, it was confirmed that the compound was similar to lithium carbonate.

  Moreover, although the grease of Example 1 and the grease of Comparative Example 1 did not show large differences in the values of the penetration, drop point, and oil separation, the contamination measured by the contamination measurement It was found that the values changed greatly depending on the presence or absence of washing treatment with water. That is, it has been found that by subjecting lithium 12-hydroxystearate to a washing treatment with water, impurities generated in the reaction process are removed, and mixing into grease is suppressed.

  From the above results, it was found that the grease obtained by subjecting lithium 12-hydroxystearate to a washing treatment and containing the treated lithium 12-hydroxystearate as a thickener is a grease with less impurities. . Such a grease is expected to be a grease suitable for use in an environment where quietness performance is greatly improved and quietness is required.

Claims (5)

A process for producing lithium 12-hydroxystearate obtained by reacting 12-hydroxystearic acid with an excess of lithium hydroxide monohydrate,
A method for producing lithium 12-hydroxystearate, wherein a reaction product, lithium 12-hydroxystearate, is washed with an aqueous solution containing water.   The method for producing lithium 12-hydroxystearate according to claim 1, wherein the lithium 12-hydroxystearate and the aqueous solution containing water are mixed and washed at a ratio of 50:50 to 10:90.   The method for producing lithium 12-hydroxystearate according to claim 1 or 2, wherein the aqueous solution containing water contains a surfactant. Lithium 12-hydroxystearate obtained by reacting 12-hydroxystearic acid and lithium hydroxide monohydrate,
Lithium 12-hydroxystearate, obtained by washing the reaction product lithium 12-hydroxystearate with an aqueous solution containing water and having a filtration rate of 95% or more calculated by conducting the following filtration test.
[Filtration test]
A grease is prepared with the base oil and the lithium 12-hydroxystearate, and 1000 g of the grease is heated and dissolved. The dissolved grease is filtered through a SUS 2000 mesh filter with an opening of 11 μm. The filtration rate is calculated from the mass of grease that has passed through the filter with respect to the mass of grease that has passed through. A base oil and a thickener containing lithium 12-hydroxystearate,
The lithium 12-hydroxystearate is
A reaction product obtained by reacting 12-hydroxystearic acid and lithium hydroxide monohydrate is washed with an aqueous solution containing water and subjected to the following filtration test. The grease composition whose filtration rate calculated in this way is 95% or more.
[Filtration test]
A grease is prepared with the base oil and the lithium 12-hydroxystearate, and 1000 g of the grease is heated and dissolved. The dissolved grease is filtered through a SUS 2000 mesh filter with an opening of 11 μm. The filtration rate is calculated from the mass of grease that has passed through the filter with respect to the mass of grease that has passed through.