LUBRICANT FOR COMPRESSION TYPE REFRIGERATING MACHINES

Abstract

The present invention is a lubricating oil for compression-type refrigerators using a difluoromethane (R32) refrigerant. The lubricating oil for compression-type refrigerators contains a first polyvinyl ether compound that is a polymer having a structural unit of a specific structure and has a carbon/oxygen molar ratio of from 3.0 to less than 4.0.

Claims

1. A lubricating oil for compression-type refrigerators using a difluoromethane (R32) refrigerant, the lubricating oil for compression-type refrigerators containing a first polyvinyl ether compound that is a polymer having a structural unit represented by the general formula (I-1) and has a carbon/oxygen molar ratio of from 3.0 to less than 4.0: ##STR00013## [in the formula, R.sup.1, R.sup.2 and R.sup.3 each represent a hydrogen atom or a hydrocarbon group having from 1 to 8 carbon atoms, and these may be the same or different; R.sup.4 represents a hydrocarbon group having from 1 to 20 carbon atoms; R.sup.1 to R.sup.4 may be the same or different in each structural unit.]

2-11. (canceled)

Description

EXAMPLES

[0180] The present invention will be next described in more detail by way of examples but is not restricted to these examples in any way. Examples and Comparative Example with respect to the first aspect of the present invention are Example 1-1 to Example 1-3, and Comparative Example 1-1; and Examples and Comparative Examples with respect to the second aspect of the present invention are Example 2-1 to Example 2-4, and Comparative Example 2-1 and Comparative Example 2-2.

[0181] With respect to the base oil (polyvinyl ether compound) obtained in each example, the kinematic viscosity (40 C., 100 C.), the viscosity index (VI), the elementary analysis, the methoxy residue content ratio and the polypropylene group content ratio were measured as described below, and the miscibility test for the base oil obtained in each example with R32 is as described below.

(1) Kinematic Viscosity

[0182] The kinematic viscosity at 100 C. and the kinematic viscosity at 40 C. were measured in accordance with JIS K2283 with respect to each oil to be measured.

(2) Viscosity Index (VI)

[0183] The viscosity index Was determined from the above obtained kinematic viscosity in accordance with JIS K2283.

(3) Elementary Analysis

[0184] The polyvinyl ether compound produced in each example was subjected to elementary analysis using Perkin Elmer's 2400-CHN to determine the carbon/oxygen molar ratio (C/O molar ratio) thereof.

[0185] In Examples 1-1 to 1.3 and Comparative Example 1-1 relating to the first aspect of the present invention, the carbon/oxygen molar ratio of the polyvinyl ether compound was determined, and in Examples 2-1 to 2-4 and Comparative Examples 2-1 and 2-2 relating to the second aspect of the present invention, the carbon oxygen molar ratio in all the side chains in the polyvinyl ether compound was determined.

(4) Measurement of Specific Group Content in Polyvinyl Ether Compound Produced in Each Example

[0186] In Examples 1-1 to 1-3 and Comparative Example 1-1, the methoxy group content in all the side chains in the polyvinyl ether compound produced in each example was determined.

[0187] In Examples 2-1 to 2-4 and Comparative Examples 2-1 and 2-2, the content of propylene glycol residue, the ethylene glycol residue or the ethoxy group in the polyvinyl ether compound, relative to the total mass of the polyvinyl ether compound, was determined.

[0188] For determining the specific group content, the polyvinyl ether compound produced in each example was analyzed with JEOL's AL400 Model NMR to measure the NMR spectrum thereof, and based on the spectral data, the content was calculated.

(5) Measurement of Two-Layer Separation Temperature

[0189] A sample of the polyvinyl ether compound produced in each example was analyzed for the miscibility with R32 (difluoromethane) refrigerant. Concretely, the method is as follows:

[0190] A predetermined amount of the sample, metered to be 10% by mass or 20% by mass relative to R32, was put in a pressure-resistant glass ampule, and this was connected to a vacuum pipe and an R32 gas pipe. The ampule was vacuum-degasified at room temperature, then cooled with liquid nitrogen, and a predetermined amount of R32 was introduced thereinto. Next, the ampule was sealed up, and gradually cooled from room temperature in a thermostat tank to measure the low-temperature separation temperature at which phase separation starts. Samples having a lower phase-separation temperature are better.

Preparation Example 1

Preparation of Catalyst

[0191] In a SUS316L autoclave having a volume of 2 L, 6 g of a nickel diatomaceous earth catalyst (trade name N113 manufactured by JGC Catalysts and. Chemicals Ltd.) and 300 g of isooctane were placed. The atmosphere in the autoclave was substituted with nitrogen and then with hydrogen. Then, the hydrogen pressure was adjusted to 3.0 MPaG and the temperature was raised. The autoclave was maintained at 140 C. for 30 minutes and thereafter cooled to room temperature. After the atmosphere in the autoclave was substituted with nitrogen, 10 g of acetaldehyde diethyl acetal were added to the autoclave. The atmosphere in the autoclave was again substituted with nitrogen and then with hydrogen. The hydrogen pressure was adjusted to 3.0 MPaG and the temperature was raised. The autoclave was maintained at 130 C. for 30 minutes and thereafter cooled to room temperature. As a result of the temperature rise, the pressure within the autoclave increased. However, as a result of the reaction of the acetaldehyde diethyl acetal, the hydrogen pressure was found to decrease. When the hydrogen pressure decreased to below 3.0 MPaG, hydrogen was supplied to maintain the hydrogen pressure therewithin at 3.0 MPaG. The autoclave was then cooled to room temperature and the pressure was released. The atmosphere in the autoclave was then substituted with nitrogen. Thereafter the pressure in the autoclave was released.

Example 1-1

[0192] In a 300-cm.sup.3 glass flask equipped with a stirrer, 40 g of toluene, 8.33 g of methanol and 0.1 g of boron trifluoride diethyl ether complex were put. 150 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3/min, and at the time when the ether was supplied in an amount of 22.5 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining ethyl vinyl ether was supplied taking 4 hours. During this, the temperature inside the flask was controlled with a water bath to be 25 C. After the supply, this was further stirred for 5 minutes. The reaction mixture was transferred to a washing tank, and washed once with 200 ml of an aqueous 1 mass % sodium hydroxide solution, and further washed three times with 200 ml of pure water. Using a rotary evaporator, the solvent and the unreacted materials were removed under reduced pressure to give 150 g of a crude product.

[0193] 120 g of the above crude product and 300 g of isooctane were put into the 2-liter SUS-316L-made autoclave with the catalyst prepared in Preparation Example 1 kept put therein. The autoclave was purged with hydrogen, then with the hydrogen pressure therein kept at 3.5 MPa, this was heated up to 140 C. taking 30 minutes while stirring, and further reacted at 140 C. for 3 hours. After the reaction, this was cooled to room temperature and depressurized to normal pressure. Using filter paper, this was filtered. Using a rotary evaporator, the solvent and moisture and the like were removed under reduced pressure.

[0194] The yield of the base oil was 108 g. The C/O molar ratio was 3.9, and the methoxy group content was 10 mol %.

[0195] The obtained base oil was a polymer having a structural unit represented by the general formula (I-1), and was a polyvinyl ether compound of the general formula (I-1) where R.sup.1 to R.sup.3 are hydrogen atoms and R.sup.4 is an ethyl group.

Example 1-2

[0196] In a 300-cm.sup.3 glass flask equipped with a stirrer, 36 g of isooctane, 8.53 g of methanol and 0.1 g of boron trifluoride diethyl ether complex were put. 135 g of ethyl vinyl ether and 15 g of methyl vinyl ether were put into a pressure container, and sealed up. With stirring inside the flask, a mixture of ethyl vinyl ether and methyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3/min, and at the time when the mixture was supplied in an amount of 22 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining vinyl ether mixture was supplied taking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply, this was further stirred for 5 minutes. Next, this was washed and hydrogenated in the same manner as in Example 1-1 to give 110 g of a base oil.

[0197] The C/O molar ratio in the base oil was 3.8, and the methoxy group content was 20 mol %.

[0198] The obtained base oil was a mixture of a polymer having a structural unit represented by the general formula (I-1), which is a polyvinyl ether compound of the general formula (I-1) where R.sup.1 to R.sup.3 are hydrogen atoms and R.sup.4 is a methyl group, and a polymer having a structural unit represented by the general formula (I-1), which is a polyvinyl ether compound of the general formula (I-1) where R.sup.1 to R.sup.3 are hydrogen atoms and R.sup.4 is an ethyl group.

Example 1-3

[0199] In a 300-cm.sup.3 glass flask equipped with a stirrer, 38 g of toluene, 20.3 g of dimethyl acetal and 0.1 g of boron trifluoride diethyl ether complex were put. 130 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied via a pump taking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply, this was further stirred for 5 minutes. Next, this was washed and hydrogenated in the same manner as in Example 1-1 to give 100 g of a base oil..

[0200] The C/O molar ratio in the base oil was 3.8, and the methoxy group content was 20 mol %.

[0201] The obtained base oil was a polymer having a structural unit represented by the general formula (I-1), and was a polyvinyl ether compound of the general formula (I-1) where R.sup.1 to R.sup.3 are hydrogen atoms and R.sup.4 is an ethyl group.

Comparative Example 1-1

[0202] In a 300-cm.sup.3 glass flask equipped with a stirrer, 24 g of isooctane, 7.67 g of ethanol and 0.1 g of boron trifluoride diethyl ether complex were put. 90 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3min, and at the time when the ether was supplied in an amount of 14 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining vinyl ether was supplied taking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply, this was further stirred for 5 minutes. Next, this was washed and hydrogenated in the same manner as in Example 1-1 to give 75 g of a product.

[0203] The C/O molar ratio of the above product was 4.0, and the methoxy group content was 0 mol %.

[0204] The obtained base oil was a polyvinyl ether compound of the general formula (I-1) where R.sup.1 to R.sup.3 are hydrogen atoms and R.sup.4 is an ethyl group.

[0205] Properties of the base oils obtained in the above Examples 1-1 to 1-3 and Comparative Example 1-1 are shown in Table 1.

TABLE-US-00001 TABLE 1 Kinematic Two-Layer Separation Viscosity (mm.sup.2/s) Temperature ( C.) C/O Outline 40 C. 100 C. VI low-temperature side Molar Ratio Example 1-1 Initiator: with methanol 34.0 5.4 91.7 24.1 3.9 Example 1-2 Initiator: with methanol, copolymerization 27.8 4.7 81.4 37.7 3.8 Example 1-3 Initiator: with dimethyl acetal 30.0 5.0 88.0 35.0 3.8 Comparative Initiator: without methanol 33.3 5.3 90.3 17.1 4.0 Example 1-1

[0206] As known from Table 1, in Comparative Example 1-1 where the C/O molar ratio was 4.0, the two-layer separation temperature was 17.1 C. on the low-temperature side and was high as compared with that in Examples 1-1 to 1-3, and a desired low-temperature miscibility could not be attained.

Example 2-1

[0207] In a 300-cm.sup.3 glass flask equipped with a stirrer, 43 g of toluene, 19.8 g of ethylene glycol monomethyl ether and 0.1 g of boron trifluoride diethyl ether complex were put. 150 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3/min, and at the time when the ether was supplied in an amount of 22 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining vinyl ether was supplied taking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply, this was further stirred for 5 minutes. The reaction mixture was transferred to a washing tank, and washed once with 200 ml of an aqueous 1 mass % sodium hydroxide solution, and further washed three times with 200 ml of pure water. Using a rotary evaporator, the solvent and the unreacted materials were removed under reduced pressure to give 150 g of a crude product.

[0208] 120 g of the crude product and 300 g of isooctane were put into the 2-liter SUS-316L-made autoclave with the catalyst prepared in Preparation Example 2-1 kept put therein. The autoclave was purged with hydrogen, then with the hydrogen pressure therein kept at 3.5 MPa, this was heated up to 140 C. taking 30 minutes while stirring, and further reacted at 140 C. the 3 hours. After the reaction, this was cooled to room temperature and depressurized to normal pressure. Using filter paper, this was filtered. Using a rotary evaporator, the solvent and moisture and the like were removed under reduced pressure. The yield of the base oil was 108 g. The C/O molar ratio in all the side chains in the polymer was 1.89, and the estimated value of the molecular weight of the polymer, as based on the theoretical structural formula of the base oil estimated from the charge-in quantity of the source materials, was 564. The ethylene glycol residue content in the base oil was 13.3% by mass.

[0209] The obtained base oil was a polymer having a structure represented by the general formula (I-2), which is a polyvinyl ether compound of the general formula (I-2) where R.sup.1 to R.sup.3 in the alkylene glycol unit are hydrogen atoms, R.sup.a is a methyl group, R.sup.b is an ethylene group and m is 1, and where R.sup.1 to R.sup.3 in the vinyl ether unit are hydrogen atoms and R.sup.5 is an ethyl group.

Example 2-2

[0210] In a 300-cm.sup.3 glass flask equipped with a stirrer, 48 g of toluene, 42.7 g of triethylene glycol monomethyl ether and 0.1 g of boron trifluoride diethyl ether complex were put. 150 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3/min, and at the time when the ether was supplied in an amount of 22 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining vinyl ether was supplied taking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply, this was further stirred for 5 minutes. Next, this was washed and hydrogenated in the same manner as in Example 2-1 to give 150 g of a base oil.

[0211] The C/O molar ratio in all the side chains in the polymer of the base oil was 1.91, and the estimated value of the molecular weight of the polymer, as based on the theoretical structural formula of the base oil estimated from the charge-in quantity of the source materials, was 696. The triethylene glycol residue content in the base oil was 23.4% by mass.

[0212] The obtained base oil was a polymer having a structure represented by the general formula (I-2), which is a polyvinyl ether compound of the general formula (I-2) where R.sup.1 to R.sup.3 in the alkylene glycol unit are hydrogen atoms, R.sup.a is a methyl group, R.sup.b is an ethylene group and m is 3, and where R.sup.1 to R.sup.3 in the vinyl ether unit are hydrogen atoms and R.sup.5 is an ethyl group.

Example 2-3

[0213] In a 300-cm.sup.3 glass flask equipped with a stirrer, 37 g of toluene, 46.2 g of polyethylene glycol (PEG200) and 0.2 g of boron trifluoride diethyl ether complex were put. 100 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3/min, and at the time when the ether was supplied in an amount of 40 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining vinyl ether was supplied taking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply, this was further stirred for 5 minutes. Next, this was washed and hydrogenated in the same manner as in Example 2-1 to give 70 g of a base oil.

[0214] The C/O molar ratio in all the side chains in the polymer of the base oil was 2.18, and the estimated value of the molecular weight of the polymer, as based on the theoretical structural formula of the base oil estimated from the charge-in quantity of the source materials, was 796, The polyethylene glycol residue content in the base oil was 25.8% by mass.

[0215] The obtained base oil was a polymer having a structure represented by the general formula (1-2), which is a polyvinyl ether compound of the general formula (I-2) where R.sup.1 to R.sup.3 in the alkylene glycol unit are hydrogen atoms, R.sup.a is a methyl group, R.sup.b is an ethylene group and m is 4, and where R.sup.1 to R.sup.3 in the vinyl ether unit are hydrogen atoms and R.sup.5 is an ethyl group.

Example 2-4

[0216] In a 300-cm.sup.3 glass flask equipped with a stirrer, 54 g of isooctane, 65.2 g of polypropylene glycol monomethyl ether (mean polymerization number: 3) and 0.1 g of boron trifluoride diethyl ether complex were put. 150 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3/min, and at the time when the ether was supplied in an amount of 40 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining vinyl ether was supplied talking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply, this was further stirred for 5 minutes. Next, this was washed and hydrogenated in the same manner as in Example 2-1 to give 150 g of a base oil.

[0217] The C/O molar ratio in all the side chains in the polymer of the base oil was 2.20, and the estimated value of the molecular weight of the polymer, as based on the theoretical structural formula of the base oil estimated from the charge-in quantity of the source materials, was 594. The polypropylene glycol residue content in the base oil was 34.5% by mass.

[0218] The obtained base oil was a polymer having a structure represented by the general formula (I-2), which is a polyvinyl ether compound of the general formula (I-2) where R.sup.1 to R.sup.3 in the alkylene glycol unit are hydrogen atoms, R.sup.a is a methyl group, R.sup.b is a propylene group and m is 3, and where R.sup.1 to R.sup.3 in the vinyl ether unit are hydrogen atoms and R.sup.5 is an ethyl group.

Comparative Example 2-1

[0219] In a 300-cm.sup.3 glass flask equipped with a stirrer, 74 g of isooctane, 146 g of polypropylene glycol monomethyl ether (mean polymerization number: 7) and 0.1 g of boron trifluoride diethyl ether complex were put. 150 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3/min, and at the time when the ether was supplied in an amount of 40 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining vinyl ether was supplied taking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply; this was further stirred for 5 minutes. Next, this was washed and hydrogenated in the same manner as in Example 2-1 to give 160 g of a base oil.

[0220] The C/O molar ratio in all the side chains in the polymer of the base oil was 2.46, and the estimated value of the molecular weight of the polymer, as based on the theoretical structural formula of the base oil estimated from the charge-in quantity of the source materials, was 826. The polypropylene glycol residue content in the base oil was 52.9% by mass.

[0221] The obtained base oil was a polymer having a structure represented by the general formula (I-2), which is a polyvinyl ether compound of the general formula (I-2) where R.sup.1 to R.sup.3 in the alkylene glycol unit are hydrogen atoms, R.sup.a is a methyl group, R.sup.b is a propylene group and m is 7, and where R.sup.1 to R.sup.3 in the vinyl ether unit are hydrogen atoms and R.sup.5 is an ethyl group. Comparative Example 2-2

[0222] In a 300-cm.sup.3 glass flask equipped with a stirrer, 62 g of isooctane, 97.5 g of polypropylene glycol monomethyl ether (mean polymerization number: 7) and 0.1 g of boron trifluoride diethyl ether complex were put. 150 g of ethyl vinyl ether was put in an Erlenmeyer flask. With stirring inside the flask, ethyl vinyl ether was supplied thereinto via a pump at 5 cm.sup.3/min, and at the time when the ether was supplied in an amount of 27 g, the pump was once stopped. Temperature increase inside the flask owing to the reaction was confirmed, and then the pump was re-started, and the remaining vinyl ether was supplied taking 4 hours. During this, the temperature was so controlled with a water bath that the temperature inside the flask could be 25 C. After the supply, this was further stirred for 5 minutes. Next, this was washed and hydrogenated in the same manner as in Example 2-1 to give 180 g of a base oil.

[0223] The C/O molar ratio in all the side chains in the polymer of the base oil was 2.43, and the estimated value of the molecular weight of the polymer, as based on the theoretical structural formula of the base oil estimated from the charge-in quantity of the source materials, was 1041. The polypropylene glycol residue content in the base oil was 42.0% by mass.

[0224] The obtained base oil was a polymer having a structure represented by the general formula (I-2), which is a polyvinyl ether compound of the general formula (I-2) where R.sup.1 to R.sup.3 in the alkylene glycol unit are hydrogen atoms, R.sup.a is a methyl group, R.sup.b is a propylene group and m is 7, and where R.sup.1 to R.sup.3 in the vinyl ether unit are hydrogen atoms and R.sup.5 is an ethyl group.

[0225] Properties of the base oils obtained in the above Examples 21 to 2-4 and Comparative Examples 2-1 and 2-2 are shown in Table 2.

TABLE-US-00002 TABLE 2 Kinematic Two-Layer Separation Content of Specific Viscosity (mm.sup.2/s) Temperature ( C.) C/O Molecular Weight Group in Polymer Number 40 C. 100 C. VI low-temperature side Molar Ratio Calculated Value (mass %) Example 2-1 21.5 4.2 97.9 33.6 1.89 564 13.3 Example 2-2 18.7 4.1 123.2 <50 1.91 696 23.4 Example 2-3 17.1 4.2 157.8 28.7 2.18 796 25.8 Example 2-4 29.2 5.4 124.0 30.1 2.20 594 34.5 Comparative 38.2 7.3 161.0 (separated) 2.46 826 52.9 Example 2-1 Comparative 67.8 10.5 142.8 (separated) 2.43 1042 42.0 Example 2-2

[0226] As known from Table 2, in Comparative Examples in which the C/O molar ratio in all the side chains in the polymer was not less than 2.40, the two-layer separation temperature was high on the low-temperature side as compared with that in Examples 2-1 to 2-4, and a desired low-temperature miscibility could not be attained.

INDUSTRIAL APPLICABILITY

[0227] The lubricating oil for compression-type refrigerators of the first and second aspects of the present invention can use R32 refrigerant having a low global warming coefficient, and therefore contributes toward prevention of global warming. Further, the lubricating oil for compression-type refrigerators of the second aspect of the present, invention has a low viscosity and a high viscosity index, and therefore improves the energy efficiency in refrigerators.