JP2000096073A - Lubricating oil for inner surface of copper pipe and production of copper pipe using the same lubricating oil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject lubricating oil capable of manifesting excellent lubricity and remarkably reducing residual oils after carrying out an annealing treatment by including a hydrocarbon-based polymer having an average molecular weight within a specific range and a specified structure. SOLUTION: This lubricating oil comprises an unhydrogenated hydrocarbon- based polymer which is a copolymer, represented by the formula, having 500-2,000 average molecular weight, consisting essentially of isobutylene and partially reacting n-butene therewith. A copper pipe with a reduced residual oil on the inner surface of the pipe can be obtained by coating the inner surface of the copper pipe with the lubricating oil, carrying out diameter reducing working, then replacing the atmosphere in the pipe of the copper pipe with hydrogen gas (preferably >=99.99% purity) or a mixed hydrogen gas (preferably a mixed gas containing the hydrogen gas of >=99.99% purity in a volume of 20% expressed in terms of volume ratio with a nonoxidizing gas) and performing an annealing treatment in a nonoxidizing atmosphere or a reducing atmosphere. The resultant copper pipe is useful as a copper pipe for air conditioners and freezing or refrigerating equipment and a copper pipe for heat transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper pipe used for manufacturing a copper pipe, particularly a copper pipe for an air conditioner, a refrigerator / refrigerator, a heat transfer pipe, etc. TECHNICAL FIELD The present invention relates to a copper pipe inner surface lubricating oil in which the generation of residual oil is reduced, and a method for manufacturing a copper pipe using the lubricating oil.

[0002]

2. Description of the Related Art Copper pipes used in air conditioners, refrigeration / refrigeration equipments, etc. are subjected to diameter reduction processing using lubricating oil and formed into predetermined dimensions. Annealing treatment for tempering is performed in the form of a level wound coil that has been aligned and wound.

[0003] In this case, in order to prevent oxidation of the inner surface of the tube, annealing is generally performed after replacing the inside of the tube with a non-oxidizing gas such as nitrogen gas, but lubricating oil adhering to the inner surface of the copper tube after processing. Is vaporized and thermally decomposed in the annealing process, it is unavoidable that it remains as oil on the inner surface of the copper pipe after annealing, and if there is a large amount of residual oil, poor joining is likely to occur in brazing joining performed during assembly of equipment, In addition, there is a problem caused by a decrease in the compatibility between the alternative refrigerant and the residual oil, such as a decrease in the performance of the alternative refrigerant used due to the restriction on the use of specific fluorocarbons and a blockage due to a precipitate in an ultrafine copper tube. Countermeasures are being studied to reduce emissions.

For example, a method of cleaning the inner surface of a processed copper tube with a solvent, a method of annealing a copper tube in a vacuum (Japanese Patent Laid-Open No. 1-28-28)
No. 7258), however, these methods have many problems in terms of equipment and cost, and a feed coil is connected to a long copper tube coil so that the long copper tube coil turns the heating zone of the annealing furnace. While feeding the feed coil until it passes, an inert gas is supplied into the long coil through the feed coil, oil in the pipe vaporized by heating is discharged outside the pipe by gas supply, and after the long coil passes through the heating zone. Method of cutting feed coil (Japanese Patent Laid-Open No. 6-170348)
No., a gas supply device is connected to a coil heated in an annealing furnace, and a step of discharging oil evaporated by heating at the time of annealing to the outside of the pipe by gas purging, and then transporting the coil to a cooling chamber is performed for each coil. Repeating method (Japanese Unexamined Patent Publication No.
No. 3) has been proposed, but these methods also have the disadvantage that productivity is reduced, equipment costs are increased, and manufacturing costs are increased.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems in the reduction of residual oil after annealing in a copper tube manufacturing process, and in particular, can reduce the generation of residual oil. The first object of the present invention is to provide a copper pipe having excellent lubricity and capable of greatly reducing residual oil after annealing treatment. It is to provide an internal lubricating oil. A second object of the present invention is to provide a method for manufacturing a copper pipe, which can be carried out by using the lubricating oil with existing equipment configuration without substantially changing a conventional process. It is in.

[0006]

According to a first aspect of the present invention, there is provided a copper pipe inner surface lubricating oil according to the present invention, which is a hydrocarbon polymer having an average molecular weight of 500 to 2,000 as shown in the following (a). It is characterized by consisting of a compound. (A) An unhydrogenated hydrocarbon polymer compound represented by the following general formula (Chemical Formula 3), which is a copolymer mainly composed of isobutylene and partially reacted with n-butene.

[0007]

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The copper pipe inner surface lubricating oil according to claim 2 of the present invention has an average molecular weight of 500 to 2,000 shown in the following (b).
Characterized by comprising a hydrocarbon polymer compound of (B) A hydrogenated hydrocarbon polymer compound represented by the following general formula (Chemical Formula 4), which is a copolymer mainly composed of isobutylene and partially reacted with n-butene.

[0009]

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The lubricating oil for an inner surface of a copper pipe according to claim 3 of the present invention is a fatty acid ester represented by the following (c):
And at least one of the following alcohols and the following isoparaffins shown in (e):
% (% By weight, hereinafter the same).

(C) a fatty acid ester represented by the following formula:

R ¹ COOR ² (where R ¹ = C _m H _{2m + 1} or R ¹ = C _m H _2m-1 , R ² = C _n H _{2n + 1} )

(D) an alcohol represented by the following formula:

R ¹ OH (where R ¹ = C _m H _{2m + 1} )

(E) Isoparaffin represented by the following formula:

C _m H _{2m + 2}

According to a fourth aspect of the present invention, there is provided a method for manufacturing a copper tube, comprising applying the lubricating oil according to any one of the first to third aspects to the inner surface of the copper tube to reduce the diameter. After that, the atmosphere inside the copper tube is replaced with a hydrogen gas or a hydrogen mixed gas, and annealing is performed in a non-oxidizing atmosphere or a reducing atmosphere.

According to a fifth aspect of the present invention, in the fourth aspect, the hydrogen replacing the atmosphere in the copper tube has a purity of 99.99% or more, and the hydrogen mixed gas is a hydrogen gas having a purity of 99.99% or more. It is a mixed gas with a non-oxidizing gas containing at least 20% by volume.

According to a sixth aspect of the present invention, in the fourth or fifth aspect, the atmosphere in the copper tube is replaced with hydrogen gas or a hydrogen mixed gas, and both ends of the copper tube are sealed. Annealing is performed in a neutral atmosphere.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When a copper pipe is processed, lubricating oil containing a hydrocarbon compound, an ester and the like conventionally used in the processing step is unavoidably left in the pipe, and the subsequent annealing is performed. In the treatment, the components of the lubricating oil are changed into various hydrocarbons and aromatic compounds by thermal decomposition. In a normal annealing atmosphere, i.e., a nitrogen atmosphere, during the annealing treatment, non-volatile compounds are generated by the dehydrogenation (polycondensation) reaction in the thermal decomposition, and these remain unevenly in the copper tube as residual oil.

In the present invention, as a lubricating oil, a hydrocarbon polymer compound which is easily decomposed or a lubricating oil containing a hydrocarbon polymer compound as a main component is used, and a copper pipe is processed with the lubricating oil. Thereafter, the atmosphere in the tube is replaced with hydrogen or a hydrogen-mixed gas, and thereafter, an annealing process is performed in a non-oxidizing atmosphere or a reducing atmosphere to reduce the generation of residual oil on the inner surface of the copper tube. The lubricating oil of the present invention can be applied to a process for reducing the diameter of a copper tube, for example, lubrication of the inner surface of a tube in a drawing process, a rolling process, and other processing methods.

Hydrogen has a function of suppressing the dehydrogenation (polycondensation) reaction in the thermal decomposition of the lubricating oil component and reducing the production of hardly volatile compounds which are components of the residual oil. By replacing the atmosphere in the copper tube with hydrogen or a mixed gas of hydrogen, and then performing an annealing process in a non-oxidizing atmosphere or a reducing atmosphere, oxidation of the inner and outer surfaces of the copper tube due to the annealing process is also prevented. The quality value does not decrease.

The functions and limitations of the hydrocarbon polymer compound, fatty acid ester, alcohol, and isoparaffin serving as the lubricating oil component of the present invention will be described. The hydrocarbon polymer compound has excellent lubricity, It is stable against heat and heat, but has the characteristic that it depolymerizes when heated to a high temperature and does not generate carbon residues. There is a wide range of viscosities.The higher the viscosity, the thicker the oil film of the lubricating oil introduced between the copper pipe and the floating plug during diameter reduction processing and the better the lubricity. Since the amount of lubricating oil remaining in the pipe increases, it is not preferable from the viewpoint of reducing residual oil. In order to impart excellent lubricity and reduce the residual oil of the annealing treatment, the average molecular weight must be 50 or less.
An unhydrogenated or hydrogenated hydrocarbon polymer, which is a copolymer of isobutylene as a main component and partially reacted with n-butene, is suitably used.

The fatty acid ester has a function of improving lubricity when added to a hydrocarbon polymer compound. The effect of lubricity improver is as n number of m and the number R ² wherein R ¹ term is greater the better, and the amount of residual oil during annealing is about these small less. In consideration of this, a preferable range of the m number is 11 to 17, and a preferable range of the n number is 1 to 4. The amount of the fatty acid ester added to the hydrocarbon polymer compound is preferably 25% or less,
When the content exceeds 5%, the effect of reducing residual oil after annealing becomes difficult to recognize.

Alcohol has an effect of improving lubricity by being added to a hydrocarbon polymer compound.
The effect of lubricity improver is a good as m number of R ¹ term is greater, the amount of residual oil during annealing becomes smaller as m number is small. Considering this, the number of m is preferably in the range of 10 to 18. Further, the addition amount of the alcohol to the hydrocarbon polymer compound is preferably 10% or less.

Isoparaffin has a function of adjusting the viscosity by adding it to a hydrocarbon polymer compound. The viscosity increases as the m number increases, but the amount of residual oil generated during annealing decreases as the m number decreases. M in consideration of this
The number is in the range of 10 to 30, and the amount of isoparaffin added to the hydrocarbon-based polymer compound is preferably 15% or less.

The above-mentioned hydrocarbon polymer compound can be used alone as a lubricating oil.
Lubricity and viscosity are adjusted by selectively adding one or more of fatty acid esters, alcohols, and isoparaffins. Fatty acid esters, alcohols,
It is preferable that the total amount of isoparaffin added be in the range of 40% or less from the viewpoint of the residual oil reduction effect.

The hydrogen gas for replacing the atmosphere in the copper tube is preferably of high purity, and hydrogen of general industrial use having a purity of 99.99% or more is suitably used. When a mixed gas of hydrogen gas and a non-oxidizing gas such as nitrogen, carbon dioxide, carbon monoxide, helium, and argon is used, hydrogen having a purity of 99.99% or more is preferably 20% or more by volume, and Preferably, when the content is 50% or more, a residual oil reducing effect can be obtained.

In the present invention, in particular, the outer diameter is 9.52 mm.
As described above, in the case of a relatively short coil having a length of several hundred meters, after replacing the inside of the copper tube with a hydrogen mixed gas, the hydrogen mixed gas filled in the tube is hardly volatilized at room temperature, and during the annealing process. It is preferable that both ends of the copper pipe be sealed and subjected to an annealing treatment so that the component in which the lubricating oil is vaporized and its thermal decomposition product are easily volatilized. On the other hand, for example, in the case of a long coil having a length of several thousand meters, even if the copper tube is annealed without sealing both ends thereof, the atmosphere in the tube is easily maintained until the thermal decomposition of the lubricating oil. In addition, it is possible to obtain a sufficient residual oil reduction effect by hydrogen.

In the present invention, the target copper tube is a phosphorus deoxidized copper tube generally used for air conditioners, refrigeration / refrigeration equipment, etc., but a small amount of Fe, Si, Al, Mn, Cr,
The present invention can also be applied to a low alloy copper tube to which other elements are added.

In the case where the atmosphere in the processed copper tube is replaced with a non-oxidizing gas such as nitrogen as in the prior art and the annealing treatment is performed, the lubricating oil adhering to the inner surface of the tube becomes free reaction which is a main reaction in thermal decomposition. The radical chain reaction produces a vaporized decomposition product such as a relatively low molecular weight olefin.
This olefin produces various aromatic compounds (including condensed polycyclic hydrocarbons, the same applies hereinafter) and compounds with relatively high molecular weight such as olefin polymers by secondary reactions such as dehydrogenation. I do. Of these pyrolysis products, many of the aromatic compounds and olefin polymers are hardly volatile, and remain non-uniformly on the inner surface of the copper tube after the annealing treatment to become residual oil components.

On the other hand, in the hydrogen atmosphere of the present invention, the lubricating oil produces low molecular weight paraffins and olefins as the main components of thermal decomposition by a free radical chain reaction in thermal decomposition. Both the paraffin and the olefin have a low molecular weight and are easily vaporized. Furthermore, paraffin is less reactive than olefin and less susceptible to a polymerization reaction, and thus is less likely to become a residual oil component due to a secondary reaction. Further, since the hydrogenation reaction proceeds, the dehydrogenation reaction is suppressed, so that the generation of aromatic compounds, especially condensed polycyclic hydrocarbons, is reduced, and the polymerization reaction of olefins is also suppressed. Since the condensed polycyclic hydrocarbon and the olefin polymer are components of the residual oil, their production is suppressed by the hydrogenation reaction. As a result, the residual oil is reduced.

[0033]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. The hydrocarbon polymer compound having the properties shown in Table 1 (P
IB) and fatty acid esters (FAE) (Table 2) added to hydrocarbon-based polymer compounds, alcohols (ALC)
(Table 3) and isoparaffin (ISOP) (Table 4) were prepared.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

Example 1 A phosphorus deoxidized copper tube (JIS H3300 C1220) was
A lubricating oil having the composition shown in Table 5 and a commercially available lubricating oil A (main component: hydrocarbon compound, kinematic viscosity: 538.5 mm ² / s)
(40 ° C.), commercially available lubricating oil B (main component: fatty acid ester, kinematic viscosity: 21.45 mm ² / s, 40 ° C.), and subjected to drawing processing to obtain a pipe outer diameter of 7.00 mm and a wall thickness of 0.10 mm. 32
It was 5 mm in length and 4000 m in length, and was wound up in order to form a level wound coil.

The atmosphere inside these coiled copper tubes was adjusted to 100% hydrogen for general industrial use (purity of 99.99% or more).
Then, an annealing treatment was performed using a roller hearth type annealing furnace for mass production according to the annealing conditions of the soft material in a DX gas atmosphere without sealing both ends of the tube.

After the annealing, in order to investigate the distribution of residual oil in the longitudinal direction of the copper tube, copper tubes for measuring residual oil are sampled at substantially equal intervals from the inlet end to the outlet end of the coil and extracted with an organic solvent. After washing to evaporate the solvent and evaporating the extraction solution, the amount of residual oil remaining in the tube was determined by weight measurement. In addition, the lubricity was evaluated by observing the appearance of the inner surface of the copper tube. Table 6 shows the evaluation criteria for the residual oil amount and lubricity. Regarding the residual oil amount, a good result was obtained in a test on compatibility between the alternative refrigerant and the residual oil, and the residual oil amount was 0.5 mg / m or less (evaluation score: 3 to 5) with good brazing properties. Passed.

[0041]

[Table 5]

[0042]

[Table 6]

Table 5 shows the results of evaluation of the residual oil amount and lubricity of each test material. As can be seen from Table 5, the test materials according to the present invention all had a residual oil amount of 0.5 mg / m or less, and the lubricating oil had good lubricity.

Comparative Example 1 A phosphorous deoxidized copper tube (JIS H3300 C1220) was used.
Drawing processing was performed using a lubricating oil having the composition shown in Table 7, and the pipe outer diameter was 7.00 mm and the wall thickness was 0.325 m, as in Example 1.
m, length 4000 m, and aligned and wound to form a level wound coil. After annealing these coiled copper tubes in the same manner as in Example 1, the residual oil amount and lubricity were evaluated in the same manner as in Example 1. Table 7 shows the results.

[0045]

[Table 7]

As shown in Table 7, the test material No. No. 18 was inferior in lubricity, and test material no. No. 19 cannot achieve reduction of the residual oil, and the average molecular weight of the hydrocarbon polymer compound is 500 to 2
It turns out that the range of 000 is preferable. In addition, when a fatty acid ester, an alcohol, and a lubricating oil to which isoparaffin is added are used, for example, when the addition amount of the fatty acid ester and isoparaffin increases, the lubricating property is improved, but the residual oil reduction effect is inferior, and the addition amount is 2 fatty acid esters
It is recognized that a range of 5% or less, 10% or less of alcohol, 15% or less of isoparaffin, and a total added amount of 40% or less is preferable.

Comparative Example 2 A copper tube made of the same material as that of Example 1 was used in Example 1 and Comparative Example 1.
Similarly to the above, a lubricating oil having a composition shown in Tables 5 and 7, and a commercially available lubricating oil A (main component: hydrocarbon compound, kinematic viscosity:
538.5 mm ² / s at 40 ° C.), commercially available lubricating oil B (main component: fatty acid ester, kinematic viscosity: 21.45 mm ² / s)
(40.degree. C.), and a coiled copper tube having the same dimensions as in Example 1 was filled with 95% of general industrial nitrogen gas (purity of 99.99% or more) and 95% of general industrial nitrogen gas. Was replaced with a mixed gas of 5% hydrogen gas (purity: 99.99% or more), then annealed under the same conditions as in Example 1, and the residual oil amount and lubricity were evaluated in the same manner as in Example 1.

As a result, the test material using the lubricating oil containing 100% of PIB1 passed the residual oil amount but was inferior in lubricity. Other test materials had good lubricity (evaluation points 4 to 5), but had a large amount of residual oil and a PIB3 of 10
Test material using 0% lubricating oil, PIB3 90%, F
Test material using AE 10% lubricating oil, PIB3 8
Test material using 0%, 20% FAE lubricating oil, PI
The test material using a lubricating oil containing 80% of B3, 10% of FAE and 10% of ALC had an evaluation point of 2, while all other test materials had an evaluation point of 1.

Example 2 A phosphorus deoxidized copper tube (JIS H3300 C1220) was used.
Four of the lubricating oils used in Example 1 (test material no.
The lubricating oil used in 3, 6, 14 and 15) was drawn and the pipe outer diameter was 7.00 mm, the wall thickness was 0.325 mm,
A copper tube having a length of 4000 m was arranged and wound to form a level wound coil. The atmosphere inside these coiled copper tubes is hydrogen gas for general industry (purity of 99.99% or more), and 50% and 20% of this hydrogen gas and the remainder are nitrogen gas for general industry (purity of 99.99% or more). After the replacement with the mixed gas of Example 1, using a roller hearth type annealing furnace for mass production, annealing was performed under the same conditions as in Example 1 without sealing both ends of the tube, and the same method as in Example 1 was used. The residual oil amount was measured according to the following. Table 8 shows the results.

Comparative Example 3 The inside of a coiled copper tube of the same material and the same dimensions as in Example 2, which had been drawn by the same method as in Example 2, was filled with 95% of general industrial nitrogen gas (purity of 99.99% or more). And a 5% mixed gas of hydrogen gas (purity 99.99% or more) for general industry, then annealed under the same conditions as in Example 1,
The residual oil amount was measured according to the same method as in Example 1. Table 8 shows the results.

[0051]

[Table 8]

As shown in Table 8, the residual oil amount of the copper tube treated according to the present invention is reduced as compared with the residual oil amount according to the comparative example. In particular, when the atmosphere in the tube was replaced with only hydrogen gas, the residual oil was reduced to about 1/10 of the residual oil according to the comparative example. Even when the mixture is replaced with a mixed gas having a hydrogen gas concentration of 50%, a high residual oil reduction effect is exhibited. Hydrogen gas concentration is 20
In the replacement with the mixed gas of about%, almost satisfactory results can be obtained, but the residual oil amount may partially increase. Therefore, it is desirable to use a mixed gas having a hydrogen gas concentration of 50% or more if possible. .

Example 3 In Example 2, the dimensions of the processed copper tube were changed to an outer diameter of 9.
52mm, wall thickness 0.30mm, length 4000m,
The inside of the coiled copper tube is filled with hydrogen gas (purity 9) for general industry.
(9.99% or more), annealing was performed under the same conditions as in Example 1, and the residual oil amount was measured according to the same method as in Example 1. As shown in Table 9, the effect of reducing the residual oil amount was as shown in Table 9. Was achieved.

Comparative Example 4 In Comparative Example 3, the dimensions of the processed copper tube were changed to an outer diameter of 9.
It was changed to 52 mm, wall thickness 0.30 mm, and length 4000 m. Further, the copper pipe processed into the above dimensions using the commercial lubricating oils A and B was also subjected to an annealing treatment under the same conditions as in Comparative Example 3, and the residual oil amount was measured. As a result, as shown in Table 9, a large amount of residual oil was observed.

[0055]

[Table 9]

Example 4 Phosphorus-deoxidized copper tube (JIS H3300 C1220) was
Four of the lubricating oils used in Example 2 (test material no.
The lubricating oil used in 3, 6, 14, and 15) was used for processing, and the pipe outer diameter was 9.52 mm, the wall thickness was 0.30 mm, and the length was 8
It was made into a copper pipe having a length of 00 m, and was arranged and wound up to form a level wound shape. After replacing the inside of these coiled copper tubes with hydrogen gas (purity of 99.99% or more) for general industry, both ends of the tubes were sealed, and in a DX gas atmosphere, the same conditions as in Example 1 were used. For an annealing treatment. After the annealing treatment, the residual oil amount was measured in the same manner as in Example 1. As a result, as shown in Table 10, the effect of reducing the residual oil amount was recognized.

Comparative Example 5 Phosphorus-deoxidized copper tube (JIS H3300 C1220) was used.
Four of the lubricating oils used in Example 2 (test material no.
The lubricating oils used in 3, 6, 14 and 15) and commercial lubricating oils A and B were processed and the pipe outer diameter was 9.52 m.
m, a copper tube having a wall thickness of 0.30 mm and a length of 800 m, which were aligned and wound to form a level wound. The inside of these coiled copper tubes was filled with nitrogen gas (purity 99.
95% and hydrogen for general industrial use (purity 9
After replacing with a mixed gas of 5% (9.99% or more), both ends of the tube were sealed, and an annealing treatment was performed in a DX gas atmosphere under the same conditions as in Example 1. After the annealing treatment, the residual oil amount was measured in the same manner as in Example 1. As a result, as shown in Table 10, a large amount of residual oil was observed.

[0058]

[Table 10]

[0059]

According to the present invention, there is provided a copper tube inner surface lubricating oil which has excellent lubricity and can greatly reduce residual oil after annealing. In addition, by using the lubricating oil, a hydrogen gas supply device is installed, and hydrogen gas is introduced instead of the conventional non-oxidizing gas introduction process. With little change, it is possible to manufacture a copper pipe having a low residual oil inside the pipe.
This pipe with low residual oil inside is used for air conditioners, refrigeration and refrigeration equipment,
It can be suitably used as a copper tube for heat transfer. Documents describing chemical formulas, etc.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) // C10N 40:30 (72) Inventor Akira Matsushita 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Money (72) Inventor Toru Tamai 5-11-3, Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal F-term (reference) 4H104 BA02C BA07A BB03C BB22C BB03C BB22C CA04A EA03A LA20 PA33 PA50 QA12

Claims (6)

[Claims] An average molecular weight of 500 shown in the following (a):
An internal lubricating oil for copper pipes, comprising a hydrocarbon polymer compound of up to 2000. (A) An unhydrogenated hydrocarbon polymer compound represented by the following general formula (Chemical Formula 1), which is a copolymer mainly composed of isobutylene and partially reacted with n-butene: 2. An average molecular weight of 500 shown in (b) below:
An internal lubricating oil for copper pipes, comprising a hydrocarbon polymer compound of up to 2000. (B) A hydrogenated hydrocarbon polymer compound represented by the following general formula (Chemical Formula 2), which is a copolymer mainly composed of isobutylene and partially reacted with n-butene: 3. A fatty acid ester represented by the following (c):
Claims characterized in that one or more of the alcohols shown in (d) below and the isoparaffins shown in (e) below are contained in a total amount of 40% (% by weight, the same applies hereinafter) or less. Item 4. The copper tube inner surface lubricating oil according to Item 1 or 2. (C) a fatty acid ester R ¹ COOR ² represented by the following formula (where R ¹ = C _m H _{2m + 1} or R ¹ = C
_m H _2m-1 , R ² = C _n H _{2n + 1} ) (d) Alcohol R ¹ OH represented by the following formula (where R ¹ = C _m H _{2m + 1} ) (e) Represented isoparaffin C _m H _{2m + 2} 4. After the lubricating oil according to any one of claims 1 to 3 is applied to the inner surface of the copper tube to reduce the diameter, the atmosphere in the copper tube is replaced with hydrogen gas or a hydrogen mixed gas. And performing an annealing treatment in a non-oxidizing atmosphere or a reducing atmosphere. 5. The hydrogen replacing the atmosphere in the copper tube has a purity of 99.99% or more, and the hydrogen mixed gas has a purity of 99.99%.
The method for producing a copper tube according to claim 4, wherein the mixed gas is a mixed gas with a non-oxidizing gas containing at least 20% by volume of hydrogen gas of 9.99% or more. 6. The method according to claim 1, wherein the atmosphere inside the copper tube is replaced with a hydrogen gas or a hydrogen mixed gas, and both ends of the copper tube are sealed, followed by annealing in a non-oxidizing atmosphere or a reducing atmosphere. The method for producing a copper tube according to claim 4.