A lubricating oil friction reducer and preparation method thereof

Abstract

The present disclosure provides a lubricating oil friction reducer and a preparation method thereof, and relates to the field of lubricating oil additives. The preparation method of the lubricating oil friction reducer comprises: adding methyl oleate, glycerol and a catalyst into a reactor for ester exchange reaction; after reduced pressure distillation, removing the catalyst to obtain the lubricating oil friction reducer. The lubricating oil friction reducer comprises the following components by mass: 90 to 100 parts of monooleyl glycerol and 0 to 10 parts of polyoleyl glycerol. The lubricating oil friction reducer of the present disclosure is added to the engine oil to improve the friction performance of the engine oil, enhance the oil film capacity, reduce the friction factor, improve the lubrication performance, and reduce the friction loss by reducing the friction of the boundary and mixed lubrication, thereby improving the fuel economy of the internal combustion engine oil.

Description

Technical Field

[0001] The present invention relates to the field of lubricating oil additives, and in particular to a lubricating oil friction reducer and a preparation method thereof. Background Art

[0002] The main way to improve the fuel economy of internal combustion engines is to appropriately reduce the viscosity of oil products and reduce the friction loss between machine parts. The friction state of different parts of internal combustion engines is different. The energy consumption under boundary lubrication is an important aspect of friction energy consumption. Adding friction modifiers (referred to as friction reducers) is the most effective way to reduce boundary friction energy consumption. It improves fuel efficiency by reducing the friction of boundary and mixed lubrication. Friction reducers are a type of substance that can form an adsorption film or reaction film on the friction surface, thereby reducing the friction factor, improving lubrication performance, and having the ability to enhance oil film.

[0003] Since acid ester type friction reducers contain strong polar esteroxy groups in their molecules, they can form a dense metal film on the metal surface and have very excellent friction reducing properties. At the same time, since ester type friction reducers have extremely low acid values, they are beneficial in reducing corrosion to engine-related components and are the most promising type of friction reducers.

[0004] Oleic acid glyceride is one of the most widely used ashless friction reducers in internal combustion engine oil. It is a type of substance that can form an adsorption film or reaction film on the friction surface, thereby reducing the friction factor, improving lubrication performance and enhancing the oil film. Oleic acid glyceride has two hydroxyl groups and one ester group, which can be firmly adsorbed on the metal surface. In addition, the long-chain hydrocarbon group of oleic acid can extend into the oil to form a dense adsorption layer, thereby effectively reducing the friction between metal parts.

[0005] Foreign countries started research on acid ester friction reducers early, and CRODA, ExxonMobil and other companies have mature products. Currently, the oleic acid glyceride product produced by CRODA is available on the market under the code name Cithrol TM GMO, the company has a number of patents in the field of ester oils. Among them, patent US 14463118 introduces a method for preparing lubricating oil ester base oil through esterification and vacuum deacidification. Patent US15031898 prepares ester oil through esterification, acid addition to remove catalyst, steam deodorization, filtration and other steps. The preparation process and operation are relatively complicated.

[0006] CN113698294A discloses a method for preparing olein by reactive azeotropic distillation. However, the glycerol conversion rate achieved by the inventive process can only reach about 90.5% during the reaction, and a large amount of solvent and dehydrating agent are used in the reaction, so the process is relatively lengthy.

[0007] CN110511795A discloses a novel process for preparing oleic acid glyceride, an ester diesel antiwear agent. The process is relatively complicated, the product color is dark, the amount of catalyst used is large (15% to 50% by mass), and a large amount of solvent is used to produce a large amount of waste water, resulting in high production costs. Summary of the invention

[0008] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a lubricating oil friction reducer with a simple preparation process and good friction reducing performance and a preparation method thereof.

[0009] In order to achieve the above objectives, the present disclosure adopts the following technical solutions:

[0010] The present disclosure provides a method for preparing a lubricating oil friction reducer, comprising:

[0011] adding methyl oleate, glycerol and a catalyst into a reactor to carry out an ester exchange reaction;

[0012] After distillation under reduced pressure, the catalyst is removed to obtain a lubricating oil friction reducer.

[0013] In one embodiment, the catalyst is a solid base catalyst.

[0014] In one embodiment, the solid base catalyst is a mixture of KOH and Al2O3.

[0015] In one embodiment, the mass ratio of KOH to Al2O3 is (1-2):10.

[0016] In one embodiment, the catalyst is used in an amount of 0.1% to 5% of the total mass of the reactants.

[0017] In one embodiment, the molar ratio of the glycerol to the methyl oleate is (1.0:1) to (1.6:1).

[0018] In one embodiment, the molar ratio of the glycerol to the methyl oleate is (1.2:1) to (1.4:1).

[0019] In one embodiment, the transesterification reaction is carried out under a nitrogen atmosphere at 160-200° C. for 1-6 hours.

[0020] In one embodiment, the reduced pressure distillation is carried out at 60-65° C. for 0.5-1 hour.

[0021] The present disclosure also provides a lubricating oil friction reducer, which is prepared by the method for preparing a lubricating oil friction reducer as described in any one of the above items, and comprises the following components in parts by weight: 90 to 100 parts of monoolein and 0 to 10 parts of polyolein.

[0022] The beneficial effects of the above technical solution provided by the present disclosure include at least:

[0023] The present invention discloses a lubricating oil friction reducer and a preparation method thereof. The lubricating oil friction reducer is prepared by using glycerol, methyl oleate and a catalyst. The preparation process is simple, the reaction is stable, the post-reaction treatment is simple, no solvent is required, and no waste water is generated. The lubricating oil friction reducer prepared adopts a specific addition ratio of monoolein and polyolein, and the obtained product has good friction reduction performance, a lighter appearance color, a lower content of triolein, and can better improve oil solubility during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. By reading the detailed description of the non-limiting embodiments made with reference to the following drawings, other features, purposes and advantages of the present application will become more apparent.

[0025] Figure 1 The infrared spectrum of the product 1 prepared in Example 1 provided in the embodiments of the present disclosure;

[0026] Figure 2 A diagram showing the friction performance test results after adding 150N of base oil to Example 1 provided in the embodiments of the present disclosure;

[0027] Figure 3 A comparison chart of friction performance tests of Example 1 and Comparative Example 4 provided for the embodiments of the present disclosure using SN0W-20 as a reference oil. DETAILED DESCRIPTION

[0028] In order to better understand the present application, the present disclosure is further described below by examples, and it should be understood that these detailed descriptions are only descriptions of exemplary embodiments of the present application, and do not limit the scope of the present application in any way. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0029] The following is a further detailed description of the present disclosure:

[0030] The present disclosure provides a method for preparing a lubricating oil friction reducer, comprising:

[0031] S1, adding methyl oleate, glycerol and a catalyst into a reactor to carry out an ester exchange reaction;

[0032] S2. After reduced pressure distillation, the catalyst is removed to obtain a lubricating oil friction reducer.

[0033] In one embodiment, methyl oleate, glycerol and a catalyst are added to a reactor and stirred to cause an ester exchange reaction. As an example, a four-necked flask can be used as a reactor. The stirring rate can be 300 to 400 rpm.

[0034] In one embodiment, the catalyst is a solid base catalyst. Further, the catalyst used in the method for preparing the lubricating oil friction reducer of the present disclosure is a catalyst used in an ester exchange reaction, which can be a supported metal oxide, an alkaline earth metal oxide, an alkaline earth metal carbonate, and the like.

[0035] In one embodiment, the solid base catalyst is a mixture of KOH and Al2O3, wherein the mass ratio of KOH to Al2O3 in the catalyst is (1-2): 10. KOH / Al2O3 has high catalytic activity and is easy to separate.

[0036] In one embodiment, the amount of the catalyst used is 0.1% to 5% of the total mass of the reactants. Preferably, the amount of the catalyst used is 0.3% to 2% of the total mass of the reactants. After recovery and filtration, the solid base catalyst can be recycled.

[0037] In one embodiment, the molar ratio of the glycerol to the methyl oleate is (1.0:1) to (1.6:1). Preferably, the molar ratio of the glycerol to the methyl oleate is (1.2:1) to (1.4:1). The methyl oleate can be added all at once or in portions.

[0038] In one embodiment, the reaction conditions of the transesterification reaction are 160-200° C. for 1-6 hours under a nitrogen atmosphere, and the transesterification reaction is stopped when no more methanol is distilled out, and the temperature is naturally lowered to 60-65° C. after the reaction is completed.

[0039] In one embodiment, the methyl oleate can be added in portions. For example, the methyl oleate is divided into two portions, and glycerol, a catalyst and one portion of the methyl oleate are first added to a reactor and heated. When the temperature reaches 160-200° C., the remaining portion of the methyl oleate is slowly added to perform an ester exchange reaction.

[0040] In one embodiment, the vacuum distillation is carried out at 60-65° C. for 0.5-1 hour to remove the residual methanol and unreacted products. After the vacuum distillation, the catalyst is removed by filtration, wherein the filter residue is the catalyst and can be reused, and the light yellow, clear and transparent filtrate is the lubricating oil friction reducer, the main component of which is oleic acid glyceride.

[0041] The present disclosure also provides a lubricating oil friction reducer, which is prepared by the method for preparing a lubricating oil friction reducer as described in any one of the above items, and comprises the following components in parts by weight: 90 to 100 parts of monoolein and 0 to 10 parts of polyolein.

[0042] The beneficial effects of the above technical solution provided by the present disclosure include at least:

[0043] The lubricating oil friction reducer and its preparation method disclosed in the present invention optimize the synthesis route, determine the optimal feed ratio and feed sequence of the reaction, use glycerol, methyl oleate and a catalyst to prepare the lubricating oil friction reducer, the preparation process is simple, the reaction is stable, the post-reaction treatment is simple and does not require any solvent, and no waste water is generated. The yield of the lubricating oil friction reducer prepared is as high as 96%, the product appearance color is relatively light, the triolein content in the product is less than 10%, the content is relatively low, and it has excellent friction reduction performance, and the oil solubility can be better improved during use. The acid ester friction reducer synthesized by the preparation method disclosed in the present invention is added to the engine oil, which can improve the friction performance of the engine oil, enhance the oil film capacity, reduce the friction factor, improve the lubrication performance, and reduce the friction loss by reducing the friction of the boundary and mixed lubrication, thereby improving the fuel economy of the internal combustion engine oil.

[0044] Example 1

[0045] Add 50g of propylene glycol, 115g of methyl oleate and 1.65g of solid base catalyst KOH / Al2O3 to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction flask. After fully replacing the air in the flask, continue to maintain the bubbling state of nitrogen. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 180°C, and the methanol generated during the reaction is condensed and collected through the condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. The reaction system is cooled down. When the temperature drops to 60-65°C, it is distilled under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095Mpa. The residual methanol and unreacted products in the reaction system are evaporated under reduced pressure. Then filter the product, and recycle the filtered solid base catalyst. The filtered light yellow liquid is product 1, with a yield of 96.1% and a polyoleylglycerol content of 6.3%.

[0046] Example 2

[0047] Add 50g of propylene glycol, 55g of methyl oleate and 1.65g of solid base catalyst KOH / Al2O3 to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction bottle. After fully replacing the air in the bottle, continue to keep the nitrogen bubbling state. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 180°C, and when the temperature reaches 60g of methyl oleate, slowly add 60g of methyl oleate through a dropping funnel. The methanol generated during the reaction is condensed and collected through a condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. The reaction system is cooled down. When the temperature drops to 60-65°C, it is distilled under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095Mpa. The residual methanol and unreacted products in the reaction system are evaporated under reduced pressure. Then filter the product, and recycle the filtered solid base catalyst. The filtered light yellow liquid is product 2, with a yield of 96.6% and a polyolein content of 4.8%.

[0048] Example 3

[0049] Add 50g of propylene glycol, 150g of methyl oleate and 2g of solid base catalyst KOH / Al2O3 to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction flask. After fully replacing the air in the flask, continue to maintain the bubbling state of nitrogen. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 180°C, and the methanol generated during the reaction is condensed and collected through the condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. The reaction system is cooled down. When the temperature drops to 60-65°C, it is distilled under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095Mpa. The residual methanol and unreacted products in the reaction system are evaporated under reduced pressure. Then filter the product, and recycle the filtered solid base catalyst. The filtered light yellow liquid is product 3, with a yield of 95.3% and a polyoleylglycerol content of 8.5%.

[0050] Example 4

[0051] Add 50g of propylene glycol, 115g of methyl oleate and 3g of solid base catalyst KOH / Al2O3 to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction flask. After fully replacing the air in the flask, continue to maintain the bubbling state of nitrogen. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 180°C, and the methanol generated during the reaction is condensed and collected through the condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. Cool the reaction system. When the temperature drops to 60-65°C, distill under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095Mpa, and evaporate the residual methanol and unreacted products in the reaction system under reduced pressure. Then filter the product, and recycle the filtered solid base catalyst. The filtered light yellow liquid is product 4, with a yield of 95.8% and a polyoleylglycerol content of 5.2%.

[0052] Example 5

[0053] Add 50g of propylene glycol, 115g of methyl oleate and 1.65g of solid base catalyst KOH / Al2O3 to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction flask. After fully replacing the air in the flask, continue to keep the nitrogen bubbling state. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 170°C, and the methanol generated during the reaction is condensed and collected through the condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. Cool the reaction system. When the temperature drops to 60-65°C, distill under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095MPa, and evaporate the residual methanol and unreacted products in the reaction system under reduced pressure. Then filter the product, and recycle the filtered solid base catalyst. The filtered light yellow liquid is product 5, with a yield of 96% and a polyoleylglycerol content of 6.8%.

[0054] Example 6

[0055] Add 50g of propylene glycol, 140g of methyl oleate and 3g of solid base catalyst KOH / Al2O3 to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction flask. After fully replacing the air in the flask, continue to maintain the bubbling state of nitrogen. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 190°C, and the methanol generated during the reaction is condensed and collected through the condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. Cool the reaction system. When the temperature drops to 60-65°C, distill under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095Mpa, and evaporate the residual methanol and unreacted products in the reaction system under reduced pressure. Then filter the product, and recycle the filtered solid base catalyst. The filtered light yellow liquid is product 6, with a yield of 97.5% and a polyoleylglycerol content of 7.1%.

[0056] Example 7

[0057] In a four-necked flask equipped with a thermometer and a condenser, 50g of propylene glycol, 115g of methyl oleate and 8.25g of a solid base catalyst KOH / Al2O3 are added, wherein the mass of KOH in the catalyst is 1.375g and the mass of Al2O3 is 6.875g. Nitrogen is introduced into the reaction flask, and after fully replacing the air in the flask, the nitrogen bubbling state is continued. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 160°C, and the methanol generated during the reaction is condensed and collected through the condenser. React in this state for about 1h, and stop the reaction when no more methanol flows out. The reaction system is cooled down. When the temperature drops to 60-65°C, it is distilled under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095Mpa, and the residual methanol and unreacted products in the reaction system are evaporated under reduced pressure. The product was then filtered, and the filtered solid base catalyst was recycled. The filtered light yellow liquid was the product 8, with a yield of 98.7% and a polyolein content of 6.8%.

[0058] Comparative Example 1

[0059] Add 20g of glycerol, 190g of methyl oleate and 2.1g of solid base catalyst KOH / Al2O3 to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction flask. After fully replacing the air in the flask, continue to keep the nitrogen bubbling state. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 180°C, and the methanol generated during the reaction is condensed and collected through the condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. Cool the reaction system. When the temperature drops to 60-65°C, distill under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095Mpa, and evaporate the residual methanol and unreacted products in the reaction system under reduced pressure. Then filter the product, and recycle the filtered solid base catalyst. The filtered light yellow liquid is product 7, with a yield of 96.9% and a polyoleylglycerol content of 77.5%.

[0060] Comparative Example 2

[0061] Add 50g of propylene glycol, 80g of methyl oleate and 1.65g of solid base catalyst KOH / Al2O3 to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction bottle. After fully replacing the air in the bottle, continue to keep the nitrogen bubbling state. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 180°C, and when the temperature reaches 60g of methyl oleate, slowly add 60g of methyl oleate through a dropping funnel. The methanol generated during the reaction is condensed and collected through a condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. The reaction system is cooled down. When the temperature drops to 60-65°C, it is distilled under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095MPa, and the residual methanol and unreacted products in the reaction system are evaporated under reduced pressure. Then filter the product, and recycle the filtered solid base catalyst. The filtered light yellow liquid is product 8, with a yield of 95.3% and a polyolein content of 15.6%.

[0062] Comparative Example 3

[0063] Add 50g of propylene glycol, 150g of methyl oleate and 2.5g of catalyst dibutyltin oxide to a four-necked flask equipped with a thermometer and a condenser, and introduce nitrogen into the reaction bottle. After fully replacing the air in the bottle, continue to keep the nitrogen bubbling state. Start heating, start stirring, and the stirring rate is 350 rpm. Gradually heat up to 150°C, and the methanol generated during the reaction is condensed and collected through the condenser. React for about 5h in this state, and stop the reaction when no more methanol flows out. The reaction system is cooled down. When the temperature drops to 60-65°C, it is distilled under reduced pressure for half an hour under a vacuum degree of 0.08MPa-0.095Mpa, and the residual methanol and unreacted products in the reaction system are evaporated under reduced pressure. Then filter the product, and analyze the product, and it is found that almost no reaction occurs, and the polyoleylglycerol content is 0.

[0064] Comparative Example 4

[0065] Commercial olein GMO was used as comparative example 4.

[0066] The product 1 prepared in Example 1 was subjected to infrared analysis, and the analysis results were as follows: Figure 1 As shown, 3444.8cm -1 is the hydroxyl absorption peak, 1740.4cm-1 is the stretching vibration peak of the ester group, and 3008.24cm-1 is the stretching vibration peak of the carbon-carbon double bond.

[0067] Comparative Example 4 was used to compare the friction performance and oil solubility with Example 1.

[0068] The tribological properties of Example 1 and Comparative Example 4 were investigated using an MTM (Mini-Traction Machine) micro-traction tester. The MTM test conditions were a load of 36 N, a sliding-rolling ratio (SRR) of 50%, and a temperature of 120°C.

[0069] The base oil is 150N produced by Formosa Plastics, and the product disclosed in the present invention is added at a ratio of 0.3%. The friction performance of the base oil before and after the friction reducer is added is evaluated on an MTM test machine. The experimental results are as follows: Figure 2 shown.

[0070] In order to investigate the friction performance of lubricating oil friction reducer in engine oil, SN0W-20 was selected as reference oil, and oleic acid glyceride synthesized in Example 1 and comparative example 4 were added at an addition amount of 0.5% to prepare the evaluation oil, which was evaluated on the MTM test machine. The experimental results are shown in FIG. Figure 3 shown.

[0071] At the same time, different additive amounts were used to conduct oil solubility experiments. The base oil was Formosa Plastics' 150N. It was found that the additive amount of Comparative Example 4 was less than 0.50%, and the additive amount of Example 1 was 1.5%. The experimental results are shown in the following table.

[0072]

[0073]

[0074] It can be seen from Table 1 that the lubricating oil friction reducer prepared according to the preparation method disclosed in the present invention has good oil solubility and good friction reducing property.

[0075] from Figure 2 It can be seen that the addition of olein reduces the friction coefficient of the base oil 150N, indicating that olein has good friction reduction performance. However, as the speed increases, the friction state transitions from boundary lubrication and mixed lubrication to fluid lubrication, and the reduction in the friction factor gradually decreases.

[0076] from Figure 3 It can be seen that the olein synthesized in Comparative Example 4 and Example 1 were added to the SN0W-20 oil respectively, which significantly reduced the friction coefficient of the moving contact parts in the boundary lubrication and mixed lubrication regions, thereby improving the lubrication performance. This shows that olein has good friction reduction performance, and the synthesized olein GMO is better than the friction reduction performance of Comparative Example 4.

[0077] As can be seen from the above embodiments, the preparation method of the acid ester friction reducer provided by the present disclosure is simple in process, the post-treatment is not complicated and no waste water is generated. The present disclosure mainly optimizes the synthesis route, determines the optimal feed ratio and feed sequence of the reaction, so that the obtained oleic acid glyceride product has a light yellow liquid appearance, the polyoleic acid glyceride content in the product is low, less than 10%, and the yield is high at more than 96%. The performance of the product is greatly improved, and the experimental results show that the product has a light color appearance, good oil solubility, and excellent friction reduction performance.

[0078] The above description only describes the specific implementation methods of the present disclosure. Various examples do not limit the essential content of the present disclosure. After reading the description, ordinary technicians in the relevant technical field can modify or deform the specific implementation methods described above without departing from the essence and scope of the present disclosure.

Claims

1. A method for preparing a lubricating oil friction reducer, characterized in that: include: adding methyl oleate, glycerol and a catalyst into a reactor to carry out an ester exchange reaction; After distillation under reduced pressure, the catalyst is removed to obtain a lubricating oil friction reducer; The catalyst is a solid base catalyst; The solid base catalyst is a mixture of KOH and Al2O3; The molar ratio of the glycerol to the methyl oleate is (1.0:1) to (1.6:1); The lubricating oil friction reducer comprises the following components in parts by weight: 90 to 100 parts of monoolein and 0 to 10 parts of polyolein.

2. The method for preparing the lubricating oil friction reducer according to claim 1, characterized in that: The mass ratio of the KOH to the Al2O3 is (1-2):

10.

3. The method for preparing the lubricating oil friction reducer according to claim 1, characterized in that: The usage amount of the catalyst is 0.1% to 5% of the total mass of the reactants.

4. The method for preparing the lubricating oil friction reducer according to claim 1, characterized in that: The molar ratio of the glycerol to the methyl oleate is (1.2:1) to (1.4:1).

5. The method for preparing the lubricating oil friction reducer according to claim 1, characterized in that: The reaction conditions of the transesterification reaction are nitrogen atmosphere, 160-200° C., and 1-6 hours.

6. The method for preparing the lubricating oil friction reducer according to claim 1, characterized in that: The conditions of the reduced pressure distillation are reduced pressure distillation at 60-65° C. for 0.5-1 hour.

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