JP2766028B2 - Hose for refrigerant gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of the Invention The present invention is mainly used for devices such as refrigerators and coolers, and applies external bending stress to piping in which refrigerant gas, for example, ammonia or chlorofluorocarbon gas passes. The present invention also relates to a hose having a gas barrier property that can be used even in a portion where minute vibrations are constantly applied.

B. Prior Art Devices such as refrigerators and coolers are configured with a closed loop that compresses and circulates refrigerant, and is a facility composed of many pipes. Once the refrigerant in the loop is charged, it is required that the refrigerant be normally unsupplied for 2 to 5 years or more.
Therefore, metal pipes, particularly copper-based pipes having good workability, are used. However, in these devices, external bending stress is applied due to vibration from the compressor and, in the case of a cooler mounted on the vehicle, external vibration, etc., and cracks and pinholes occur in the copper piping portion where the vibration is repeated. And the refrigerant scatters.

Conventionally, a rubber hose using a rubber material such as NBR and EPDM has been used for a part of a pipe, but since the gas barrier property of the refrigerant is not always good, it has been unavoidably used.

Also, recently, the depletion of the ozone layer in the stratosphere due to chlorofluorocarbon gas has become a problem, and it has become necessary to switch from chlorofluorocarbon-12 to chlorofluorocarbon-22. In this case, the gas barrier property of Freon-22 of the rubber hose is several tens of times worse than Freon-12, so that the rubber hose cannot handle it.

Therefore, it has been proposed that a plastic having gas barrier properties, such as polyamide and ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH), be compounded inside a rubber hose, but in any case, it can be used for the following reasons. There was nothing. That is, polyamide has some but not sufficient refrigerant gas barrier properties. Meanwhile, EV
Although OH has a very effective refrigerant gas barrier property,
Deformation and uneven thickness of the EVOH layer in high-temperature, high-humidity atmosphere during molding, especially during vulcanization of rubber, resulting in poor connection joints at both ends of the hose and gas leakage due to this, or in the presence of external bending stress However, there has been a problem in reliability as a refrigerant gas barrier hose due to cracks, pinholes, and the like generated in portions that are constantly subjected to vibration.

JP-A-58-197040 discloses a hose having an EVOH layer as an intermediate layer, a nylon layer as an inner layer, and a polyester-based elastomer layer as an outer layer. Cracks and pinholes are likely to occur in the EVOH / nylon layer because there is almost no adhesion between the layer and the polyester elastomer layer. For example, even if an adhesive resin layer was inserted between the EVOH layer and the polyester elastomer layer to impart adhesiveness, good adhesive resin could not be found, and good results were not always obtained.

JP-A-59-70565 discloses a hose in which an EVOH layer is used as an intermediate layer and a polyesteramide layer is provided in the inner and outer layers. Maybe because of low adhesion to layer
There is a problem that a pinhole is generated in the EVOH layer.

JP-A-2-35291 discloses that the EVOH layer is an intermediate layer,
A hose for a refrigerant gas is described in which an 11-nylon or 12-nylon layer is provided on one of the inner and outer layers and a nylon layer such as 11-nylon, 12-nylon, or 6-nylon is provided on the other layer. However, as shown in Comparative Examples 4 and 5 described below, there is a problem that cracks are generated due to long-time vibration.

C. Problems to be Solved by the Invention The present invention relates to a refrigerant gas pipe used for an apparatus such as a refrigerator and a cooler, and does not generate pinholes, cracks, etc. even if the pipe constantly receives external stress. An object of the present invention is to provide a plastic hose having good gas barrier properties against refrigerant gas.

D. Means for Solving the Problems The present inventor has developed a composite of a single layer pipe of EVOH and a rubber layer including a reinforcing braided layer on the outside of the pipe, which has the best gas barrier property against refrigerant gas, especially Freon-22. A pipe was prepared and used as an automotive cooler hose in a part where bending stress was applied, and a practical test was conducted. As a result, in the case of a multi-layer rubber hose using only EVOH, unevenness in thickness, uneven wall thickness and pipe eccentricity occur in the EVOH layer due to the effects of high temperature and high humidity atmosphere in the vulcanization process, and shrinkage stress of the outer rubber, and both ends of the hose Poor connection of the metal connector to be mounted on the device, gas leakage easily occurs. In addition, when the EVOH composite hose was used for a long period of time, a small crack was generated in a portion having a small radius of curvature and in the vicinity of a joint between the metal pipe and the pipe, and a phenomenon that gas barrier properties deteriorated was recognized.

Therefore, the present inventors have conducted intensive studies, and as a result, it has been found that in the EVOH composite pipe that does not allow a refrigerant to pass through, no abnormality occurs even when vibration is applied in a state where bending stress is applied. Therefore, the above abnormality is presumed to be caused by cracks and pinholes in the portion of the EVOH layer having a non-uniform thickness due to vibration in an environment where bending stress is applied in the presence of a refrigerant. Therefore, the present inventors conducted further intensive studies and found that EVOH
(A) and a polyamide resin (B).
When a composite pipe in which a layer of the composition having a weight ratio of (B) of 95/5 to 30/70 (hereinafter simply referred to as an EVOH layer) is used as an intermediate layer and a polyamide resin layer as an inner and outer layer is used. Surprisingly, there is no uneven thickness of the EVOH layer, poor connection with the metal connector, no gas leakage, and no cracks or pinholes due to vibration in the presence of a refrigerant and under bending stress. Can be manufactured.
The present invention has been completed.

If the polyamide resin layer is provided only on one of the inner and outer layers, the object of the present invention cannot be sufficiently achieved.

Incidentally, a structure in which an EVOH layer and a polyamide layer are laminated is known, for example, JP-A-61-179737, JP-A-57-41924,
Nos. 61-273931, 50-77474. These include food film, bottle stretchability, retort resistance, O ₂
It is an invention for improving gas barrier properties, and not only does the present inventor have no technical idea on the barrier property of refrigerants, for example, ammonia and chlorofluorocarbon gas, but also such deviation in EVOH thickness and metal connector. From the above patents, the technical ideas for preventing cracks and pinholes caused by repeated vibration in the presence of refrigerant and external bending stress, as well as improvement of poor connection and leakage, etc. It is impossible to do it.

Therefore, the hose in which the polyamide is laminated on both sides of the EVOH layer has an uneven thickness of the EVOH, no poor connection with the metal connector, no gas leakage, and has an external bending stress in the presence of the refrigerant gas barrier property and the refrigerant. Under such circumstances, it was unexpectedly found that vibrations did not cause cracks and pinholes.

E. More Detailed Description of the Invention EVOH of the present invention is a saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol%. If the ethylene content is less than 20 mol%, the melt moldability is poor, while if it is more than 60 mol%, the refrigerant gas barrier properties are insufficient. Further, the degree of saponification of the vinyl acetate component is preferably at least 90 mol%, and if it is less than that, the refrigerant gas barrier properties and the thermal stability deteriorate. Further, the EVOH may be copolymerized with butylene, propylene, a vinylsilane-based compound, a vinylpyrrolidone-based compound, or a plasticizer, a heat stabilizer, an ultraviolet absorber, and an antioxidant within a range not to impair the effects of the present invention. , Colorant, filler, etc. can be freely blended.

In addition, blending the polyamide resin (B) with the EVOH (A) not only improves the adhesion to the polyamide resin layer, but also causes unevenness in thickness and uneven thickness of the EVOH layer due to high temperature and high humidity during the rubber vulcanization process. This is preferable because eccentricity is improved, cracks and pinholes are reduced, and flexibility may be imparted. When blending, the mixing weight ratio is EVOH / compounding resin = 95/5 to 30/70, preferably 85/10 to 4
It is 0/60.

As the polyamide resin of the present invention, 6 nylon, 6,
6 nylon, 6,9 nylon, 6/12 nylon (6 nylon resins such as a copolymer of ε-caprolactam and ω-laurolactam, 11 nylon, 12 nylon and their elastomers and aromatic polyamides, and These blends and the like can be used. Particularly, when the molar ratio (CH ₂ / NHCO) of the —CH ₂ — group to the —NHCO— group in the polyamide is 11 or less, the refrigerant gas barrier property and the moldability are deteriorated. It improved, an effect of further reducing Kuratsuku due to vibration in the stress presence, the occurrence of pinholes by a large margin. more preferably CH ₂ /
NHCO = 5-8.

In general, an adhesive or an adhesive resin is not particularly required between the EVOH layer and the polyamide-based resin layer, and it is often preferable to use no adhesive resin in order to prevent cracks and pinholes. However, when it is desired to provide a large adhesive property, the adhesive layer may be freely added within a range not to impair the present invention.

The inner diameter of the hose having the above-mentioned layer structure of the present invention is generally 7 to 20 mmφ, but is not limited thereto. On the other hand, the total thickness of the hose is preferably in the range of 0.2 to 1.5 mm. Thickness
If the thickness is less than 0.2 mm, it becomes difficult to handle when the rubber layer is compounded on the outside later. On the other hand, if it exceeds 1.5 mm, the flexibility of the hose is inferior, and it is difficult to attach the hose to a cooler or the like.

The thickness of the EVOH layer is preferably 10 to 150 μm,
If it is less than 3, the gas barrier property of the refrigerant is insufficient. On the other hand 150μ
If it exceeds, the flexibility becomes poor. The thickness (total thickness) of the polyamide resin layer is 10 to 1350 μm,
800μ is preferred.

The method for producing the multilayer hose of the present invention is not particularly limited, but coextrusion hose molding, extrusion lamination hose molding, coextrusion lamination hose molding, and the like are used.

The multi-layer hose of the present invention is an outer, inner,
Alternatively, a rubber layer or the like is used in combination with both the inner and outer layers.
In particular, the total thickness of the EVOH layer and the polyamide resin layer is 0.5 mm
For the following hoses, a composite with a rubber layer is preferred.
As the rubber layer, a configuration in which the rubber layer is composited with a multilayer rubber layer including a reinforcing braid layer or the like is preferable. As the rubber, either natural rubber or synthetic rubber can be used. Further, the thickness of the rubber layer is from 500 μm to 10,000 μm, preferably from 1000 μm to 5000 μm.

When a rubber layer is laminated on the multilayer hose of the present invention, the multilayer hose is provided on the inner layer, the outer layer, or the intermediate layer of the rubber hose, but when the multilayer hose is used as the inner layer, contact between the end of the multilayer hose and the connection fitting is made. It has the feature of minimizing gas permeation in the part. Also, when used as an outer layer, as in the case of the inner layer, not only gas permeation is minimized but also rubber deterioration due to oil, organic solvent, etc., which easily adheres to the outer layer of the hose is suppressed. On the other hand, when used as an intermediate layer, it is more effective in preventing gas leakage due to a break in a hose end at the time of connecting a metal fitting and at the time of use as compared with using an inner layer or an outer layer. However, in this method, gas permeation from a contact portion between the hose and the fitting becomes larger than when an inner layer or an outer layer is used. Therefore, it is preferable that the multi-layer hose is configured so as to be offset to the innermost layer or the outermost layer as much as possible.

On the other hand, the number of EVOH layers may be two or more. In this case, not only generation of pinholes and increase in gas permeability due to vibration are suppressed to a large extent than in the case of a single layer having the same total thickness of the EVOH layer. The deterioration of the rubber due to the gas is greatly suppressed, and the performance as a gas pipe is greatly improved. When the number of EVOH layers is two or more, for example, polyamide / EVOH / EVOH
/ Polyamide, polyamide / EVOH / E polyamide / EVOH / polyamide.

In the present invention, the refrigerant gas is Freon 12 (CCl ₂ F ₂ ),
Freon 22 (CHClF ₂ ), Freon 134A, Freon 115 (CCl ₂ F ₃
+ CClF ₃ ) and the like, but the hose of the present invention is particularly effective against Freon 22.

Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.

F. Examples Example 1 and Comparative Examples 1 to 5 EVOH (melt index: 1.3 g / l) was prepared by using three extruders and a coextruder for three types of three-layer hoses composed of a circular multilayer die.
(0 min, 190 ° C.) to prepare a hose composed of polyamide. At this time, the thickness of each layer is 100 μm for the middle layer (EVOH layer) and 500 μm for the inner and outer layers (polyamide layer).
The inner diameter was 1.1 mm. This hose was further multi-layered with EPDM rubber (outermost layer) having a thickness of 2 mm via an adhesive layer, and then vulcanized. Table 1 shows the brands, layer configurations, refrigerant permeability, etc. of the used EVOH, polyamide, and polyurethane.

Cut these multi-layer hoses to 50 cm, attach a blind lid on one side of the hose, and attach a mouth, a pressure gauge and a pressure gauge on the other side that can introduce Freon-22 gas.
The pipe was bent 180 cm in cm. In this state, the pressure gauge side was fixed, the pressure was increased with 2 kgG of Freon-22 gas, a vibration tester was attached to the blind lid side, a vibration having a frequency of 100 Hz and a vibration width of 5 mm was applied, and the change with time of the internal pressure was measured. Table 1 shows the results.

In the table, the permeability indicates cc / m ² · day · atm, and the holding pressure indicates the pressure kg · G in the hose after operation for 2000 hours.

G. Effect of the Invention The multilayer hose of the present invention, in which a polyamide resin layer is laminated on both sides of the EVOH layer, has not only excellent gas barrier properties against a refrigerant, especially Freon-22, but also has a multilayer structure with rubber. Insufficient connection of metal connectors at both ends of the hole due to uneven thickness, uneven thickness, and eccentricity of the EVOH layer generated in the process in the above, almost no occurrence of gas leakage, and repeated vibrations with locally applied bending stress Deterioration of gas barrier properties in the part is hardly recognized.

Claims (2)

(57) [Claims] An ethylene having an ethylene content of 20 to 60 mol%.
Consisting of a vinyl alcohol copolymer (A) and a polyamide resin (B), the weight ratio of (A) / (B) is 95/5 to 30/7
A hose for a refrigerant gas in which a layer of the composition which is 0 is an intermediate layer and a polyamide resin layer is an inner and outer layer. 2. A refrigerant gas hose having a rubber layer on at least one surface of the hose according to claim 1.