JP2000028051A - Tube for water piping of automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the high temperature resistant strength, the fluid transmission resistance, and the fluid degradation resistance by forming a tube consisting of a polyolefin resin with a specified characteristic or an alloy containing the polyolefin resin. SOLUTION: In a tube for the water piping system of an automobile, a resin material to constitute at least one layer thereof is >=4.0 MPa in a yield stress under tension in the atmosphere of 120 deg.C. The resin material can maintain the necessary strength even under a severe high temperature service condition, and it is never fractured. The permeability constant for an LLC (ethylene glycol/ water (50/50 volumetric ratio) mixture solution) in the atmosphere of 90 deg.C is <=4.0 mg.mm/cm2.day, and the LLC permeability resistance to meet the request to no supply of LLC can be demonstrated. Since an alloy material containing a polyolefin resin is used for the resin material, the above-described characteristics are obtained, and the high-temperature degradation resistance against the LLC can be ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based piping tube for automobiles, and more particularly to a resin-based water-based piping tube suitably used as a water-based piping for a radiator for automobiles, a heater for automobiles and the like. In particular, it relates to a long heater piping tube used for an RV vehicle.

[0002]

2. Description of the Related Art Conventionally, as a water-based pipe such as a radiator for an automobile or a heater for an automobile, a pipe in which an internal hose such as EPDM (ethylene propylene diene rubber) is connected to a metal pipe has been used. However, metal pipes have a problem that they are heavy and rust easily. Further, in so-called RV (recreation vehicle) vehicles, which have been increasing in demand recently, the above-mentioned problems have become more remarkable because long pipes to the rear heater core are required.

[0003] Therefore, there is a demand for a lightweight water-based piping tube for automobiles, and as one of the measures, a water-based piping tube made of resin is considered. However, regarding the resin tube, the strength is reduced due to softening at high temperature (actual operating temperature), the resin tube is deteriorated by the internal fluid, and the maintenance is free (no replenishment of the liquid mixture of the internal fluid LLC (Long Life Coolant) and water) From the viewpoint of (1), the reduction of the internal fluid due to the permeation of the internal fluid must be suppressed.

For example, JP-A-57-57737 and JP-A-5-223187 point out that polyethylene and cross-linked polyethylene are suitable for piping used for water heaters and heating. JP-A-61-1406
No. 91 and JP-A-3-24393 also study polyolefins for similar uses.

[0005]

However, the above-mentioned prior art is based on relatively low operating temperature conditions for housing equipment, and can be used as a water pipe for automobiles under extremely severe high temperature operating conditions. Ruptures due to softening. Further, in the above prior art, the deterioration resistance of the tube to LLC, which is the internal fluid of the water system piping tube for automobiles, and the permeation resistance to LLC which becomes apparent in the long piping used in the RV vehicle are completely examined. Not.

On the other hand, in the specifications attached to the applications such as JP-A-8-134319, JP-A-8-157657, and JP-A-8-249786, a composition composed of polypropylene, polyphenylene ether, an inorganic filler and the like is described. An antifreeze-related component for automobiles is disclosed, stating that "the composition has excellent physical properties and antifreeze resistance".

[0007] However, in the above prior art, "parts" are tanks, pump housings, valves, and the like whose use, shape, and function are different from those of the piping tube. Mainly thin physical properties related to the piping tube such as creep resistance and the like, and antifreeze resistance means maintaining such physical properties. No mention is made of a decrease in the amount of liquid due to the permeation of the internal fluid. Therefore, the type and composition ratio of the resin in the compositions disclosed therein are not useful in examining a preferable automotive water-based piping tube.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an automotive water-based piping tube having high temperature strength, fluid permeation resistance and fluid deterioration resistance, which are inherently required for automotive water-based piping tubes. I do.

The inventor of the present application first experimentally investigates the high-temperature strength, fluid permeation resistance, and fluid deterioration resistance required specifically for a water-based piping tube for automobiles, and then, a material composition of the tube meeting the requirements. And completed the present invention.

[0010]

Means for Solving the Problems The structure of the first invention of the present application (the invention of claim 1) for solving the above problems is a piping tube having a single-layer structure or a multilayer structure. A water-based automotive piping tube, at least one of which is composed of a polyolefin-based resin having the following characteristics (a) and (b), or an alloy material containing the polyolefin-based resin. (A) The yield point stress under tension in a 120 ° C. atmosphere is 4.0 MPa or more. (B) Ethylene glycol / water (5
0/50 volume ratio) 4.0 mg
Mm / cm ² · day or less.

(Structure of the Second Invention) The structure of the second invention of the present application (the invention according to claim 2) for solving the above problems is as follows.
A pipe tube having a single-layer structure or a multilayer structure,
At least one layer is a water-based piping tube for an automobile, which is composed of an alloy material having a polyolefin-based resin as a matrix phase and a resin having excellent high-temperature strength as a domain phase.

(Structure of Third Invention) The structure of the third invention (the invention according to claim 3) for solving the above-mentioned problem is as follows.
In any one of the first invention and the second invention, the polyolefin-based resin is at least one of polypropylene, cross-linked polypropylene, and polymethylpentene;
A water-based piping tube for automobiles, wherein the resin having excellent high-temperature strength is polyphenylene ether.

(Structure of Fourth Invention) The structure of the fourth invention (the invention described in claim 4) for solving the above-mentioned problem is as follows.
In the second invention, the matrix phase is polypropylene, and the domain phase is polyphenylene ether.
This is an automotive water piping tube.

[0014]

(Operation / Effect of the First Invention) In the water piping system for an automobile of the first invention, at least one layer of the resin material has the above-mentioned characteristic (a).
The required strength can be maintained even under extremely severe high temperature use conditions of water pipes for automobiles, and it does not burst. In addition, since it also has the characteristic (b), it exhibits an LLC permeation resistance that meets the requirement of no replenishment of LLC (ethylene glycol / water (50/50 volume ratio) mixture).

Since a polyolefin resin or an alloy material containing a polyolefin resin is used as the resin material, it is possible to provide the above-mentioned characteristics (a) and (b), and furthermore, it has high temperature degradation resistance to LLC. Is also secured. (Function / Effect of the Second Invention) In the water-based piping tube for a vehicle according to the second invention, the resin material constituting at least one layer is an alloy material of a polyolefin resin and a resin having excellent high-temperature strength, and a polyolefin resin. Resin is part 4
Since it occupies 0 parts by weight or more, the water-based piping tube for automobiles according to the third invention has at least one layer formed of an alloy material having a polyolefin-based resin as a matrix phase and a resin having excellent high-temperature strength as a domain phase. Therefore, the LLC permeation resistance and the LLC deterioration resistance of the polyolefin-based resin and the high-temperature strength of the resin having excellent high-temperature strength are realized in a well-balanced manner.

(Function and Effect of Third Invention) When the polyolefin resin is at least one of polypropylene, cross-linked polypropylene and polymethylpentene, and is blended with polyphenylene ether, the first invention and the second invention can be used.
The effects of the invention are more effectively exhibited.

(Function / Effect of the Fourth Invention) When the resin material constituting at least one layer of the water-based piping tube for an automobile has polypropylene as a matrix phase and polyphenylene ether as a domain phase, the first and second inventions have the following advantages. The effect is particularly effective.

[0018]

Next, embodiments of the first to fourth inventions will be described. In the following, simply "the present invention"
When it says, it refers to 1st invention-4th invention collectively.

[Water-based piping tube for automobiles] The water-based piping tube for automobiles according to the present invention can be used in automobiles with antifreeze, L
It can be used without limitation as a piping tube used for transporting an LC or a similar cooling fluid. Particularly preferred applications include heater hoses for automobile heaters, radiator hoses for automobiles, and the like.

The structure of the water-based piping tube for automobiles of the present invention is particularly limited as long as it has a single-layer structure or a multilayer structure, and at least one of the tubes is made of the resin material of the first invention and the second invention. Not limited. Examples of the multilayer structure include the following. Considering the balance between cost and performance, a multilayer structure in which two or more layers are made of any resin material of the first and second inventions is adopted. The outermost layer of the tube including the layer composed of the resin material of the first invention and the second invention is provided with a soft layer of a thermoplastic elastomer such as olefin, styrene, or vinyl chloride, or a copolymer olefin resin, Improves the resistance to impact fracture caused by spar. An olefin-based thermoplastic elastomer layer is provided on the innermost layer of the tube including the layer made of the resin material of the first invention and the second invention to improve the sealing property of the fastening portion at the end of the tube.

The size and wall thickness of the automotive water-based piping tube of the present invention are appropriately selected depending on the location where the piping is used, but the inner diameter of the tube is about 5 to 50 mm.
More preferably, the wall thickness of the tube wall is about 0.5 to 3.0 mm. If the wall thickness of the tube is less than about 0.5 mm, the pressure resistance and LLC permeability may be insufficient, and the wall thickness may be 3.0 m.
If it exceeds about m, the bending workability of the tube may be deteriorated.

The method for forming the automotive water-based piping tube of the present invention is not limited, but is usually formed by a resin extruder. In addition to the tube being a smooth straight tube, it is a bent tube with one or more bent parts in consideration of ease of assembly to the vehicle, etc., or a bellows tube with one or more bellows shaped parts May be.

[Materials Used in the First Invention] In the first invention, the material constituting at least one layer of the pipe tube having a single-layer structure or a multi-layer structure is a polyolefin resin having the above-mentioned characteristics (a) and (b). Alternatively, an alloy material containing a polyolefin resin may be used.

Regarding the characteristic (a), the value is 4.0.
If it is less than this, the pipe tube cannot withstand the pressure during use and bursts, which is not preferable. When the value of the characteristic (b) exceeds 4.0, the amount of the internal fluid, particularly water, permeating the tube wall during use of the piping tube cannot be ignored, and the internal fluid is not replenished ( Contrary to the requirement of “maintenance-free”, it is necessary to replenish the internal fluid.

[Polyolefin Resin] The type of the polyolefin resin used in the present invention is not limited. For example, a homopolymer or copolymer of a monomer having 3 to 20 carbon atoms such as propylene, butene, pentene, hexene, methylpentene, octene, etc. One type of polymer, or a blended material thereof, or an alloy material of these materials and another resin material can be preferably used.
Crosslinked polypropylene or polymethylpentene is preferred.

As the polypropylene, both homopolymers and copolymers can be used, but homopolymers are more preferable in view of high-temperature strength. As the type of the polymer, any of isotactic, syndiotactic and atactic can be used. it can. Polymethylpentene refers to a polymer of 4-methylpentene-1. Examples of the cross-linked polypropylene include those subjected to silane cross-linking, organic peroxide cross-linking, radiation cross-linking, etc., but silane cross-linked polypropylene is preferably used in view of the ease of the cross-linking step.

[Polyolefin Resin and Resin Constituting Alloy Material] In the present invention, the types of the resin constituting the polyolefin resin and the alloy material are not particularly limited in the first invention as long as the functions and effects are not impaired. However, in the second invention, it is a predetermined resin having excellent high-temperature strength.

The above-mentioned "resin having excellent high-temperature strength" is intended to impart the required strength in a high-temperature atmosphere to an alloy material of a polyolefin-based resin.
It has a negative effect on C permeability. Therefore, the composition ratio of the alloy material is preferably such that the polyolefin resin accounts for 40 parts by weight or more. It has also been found that the alloy material preferably has a form in which a polyolefin-based resin is used as a matrix phase and a resin having excellent high-temperature strength is used as a domain phase, as in the second invention. It is more preferable that the polyolefin-based resin accounts for 40 parts by weight or more in the alloy material and this constitutes a matrix phase. The reason is that the alloy material has excellent LLC permeability resistance when the polyolefin-based resin is in the matrix phase, and the strength of the alloy material in a high-temperature atmosphere is improved because the resin having excellent high-temperature strength is in the domain phase. This is because it is considered to be done.

Specific examples of the “resin excellent in high-temperature strength” include polyphenylene ether and nylon resins such as nylon 6 and nylon 12, and the like. From the viewpoint of balance, polyphenylene ether is particularly preferable.

[0030]

Next, an embodiment of the present invention will be described.

(Preparation of Material Test Piece ) A 1 mm thick sheet material having the resin composition shown in Examples 1 to 6 and Comparative Examples 1 to 6 in Table 1 at the end was injection molded, and this was molded. A material test piece was used. In Examples 2 to 4, PP is a matrix phase and PPE is a domain phase. In Comparative Example 6, conversely, PP is a domain phase and PPE is a matrix phase. It was confirmed by observation with a scanning electron microscope.

In Table 1, "Material type" indicating the resin composition is shown.
In the column, “PP” means polypropylene, “PPE”
Represents polyphenylene ether, "PE" represents polyethylene, "PA6" represents nylon 6, "PA12" represents nylon 12, and "PBT" represents polybutylene terephthalate. Then, for example, "PP / PPE 60
The notation “/ 40” indicates that the alloy material is PP and PPE, and the composition ratio of both is 60:40.

( Evaluation of Material Test Piece ) As shown in Table 1, "yield point stress (MPa)", "LLC transmission coefficient (mg.mm/cm@2 .day)" and "LLC resistance" were as follows. The results were evaluated by the method, and the results are shown in Table 1.

1) Yield point stress: A from material test piece
A dumbbell No. 4 of STM D638 was punched out, and this was cut at room temperature and in an atmosphere of 120 ° C. at a speed of 50 mm / mi.
n. , And the yield point stress was measured.

2) LLC transmission coefficient: Ethylene glycol / water (50/5) was placed in a cup having an inner diameter of 66 mm and a depth of 39 mm.
0 volume ratio) 100 cc of the mixed solution is charged, and a material test piece is covered around the opening peripheral portion of the cup through a ring-shaped sealing material of EPDM rubber packing having a thickness of 2 mm so as not to leak liquid. Was fastened to the cup. Next, the cup was placed in an inverted state, left in an atmosphere of 90 ° C., and weighed every 24 hours. Then, from the ratio of the weight loss to the standing time, the L of the unit shown in Table 1 was obtained.
The LC transmission coefficient was calculated.

3) LLC resistance: 4 from material test piece
A 0x6mm strip is punched out and this is a Toyota genuine LLC
(Toyota Motor) / water (50/50 volume ratio) mixture was immersed at 120 ° C. Then, it was taken out after 1000 hours (h) and 2000 hours, and was bent at 180 °. At that time, those with broken strips were marked as x, and those with no break were marked with ○.
Notation as

As can be seen from the results in Table 1, Examples 1 to
In Example 6, the yield point stress, LLC transmission coefficient, and LLC resistance were all satisfactory. In particular, in Examples 2 and 3, the yield point stress and L at high temperature (120 ° C.)
The balance with the LC transmission coefficient was good. Example 4 is further excellent in the balance between the two.

On the other hand, Comparative Examples 3 to 5 using a non-olefin-based material were inferior in LLC transmission coefficient and LLC resistance,
Comparative Examples 1 and 2 using PE or cross-linked PE were at a high temperature (120 °
Comparative Example 6 in which the yield point stress in C) was poor and PPE was in the matrix phase even though the PP / PPE alloy material was used.
Had some problems with the LLC transmission coefficient.

(Preparation of Test Tube ) Using the materials having the resin compositions shown in Examples 1 to 6 and Comparative Examples 1 to 6 in Table 1 at the end, an inner diameter of 12 mm and a thickness of the tube wall of 1 were used.
mm tubes were each extruded and used as test tubes. In Examples 2 to 4 and Comparative Example 6,
The same matrix-domain structure as in the case of the material test piece was confirmed by the same means.

( Evaluation of Test Tube ) As shown in Table 1, "burst pressure (MPa)" and "LLC permeation amount (g / m
.Day)] were evaluated by the following methods, and the results were shown in Table 1.
It was shown to.

1) Burst pressure: A test tube having a length of 300 mm was plugged with a blind plug at one end, filled with water in the test tube, and then subjected to 7 MPa / min with a water pressure pump from the other end.
And the pressure at the time when the test tube was broken was measured. When the measured pressure was at least twice (1.00 MPa) the maximum pressure applied during actual use, it was marked as ○, and when it was less than that, it was marked as x.

2) LLC permeation amount: A blind plug was plugged at one end of a test tube having a length of 300 mm, and the test tube was filled with an ethylene glycol / water (50/50 volume ratio) mixed solution. Blind stopper. Then, after performing a pretreatment of leaving it in a thermostat at 90 ° C. for 24 hours, the test tube was taken out and immediately weighed (W1 gram). Immediately thereafter, the test tube was again left in a constant temperature bath at 90 ° C. for 24 hours, and then the weight (W2 grams) was measured again in the same manner as above. LLC
The transmission amount Q was calculated by the following equation. Note that "L" in the equation
Is the length of the test tube excluding the blind plug (mm)
It is.

Q = 1000 (W 1 −W 2) / L As can be seen from the results in Table 1, Examples 1 to 6 were satisfactory in both burst pressure and LLC permeation amount. In particular, Examples 2 and 3 are high temperature (120 ° C).
And the balance between the burst pressure and the amount of LLC permeation was good. In Example 4, the balance between the two was further improved.
These evaluation values are considered to be values corresponding to the yield point stress shown in the material test pieces according to Examples 1 to 6 made of the same material.

On the other hand, Comparative Examples 3 to 5 using a non-olefin-based material have a large amount of LLC permeation, while Comparative Examples 1 and 2 using PE or crosslinked PE have a burst pressure force at a high temperature (120 ° C.). Low, PPE using PP / PPE alloy material
Comparative Example 6, in which the matrix phase was a matrix phase, had a slightly larger LLC transmission amount.

[0045]

[Table 1]

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroyoshi Mori Komaki City, Aichi Pref.

Claims (4)

[Claims] 1. A piping tube having a single-layer structure or a multilayer structure, at least one of which is made of a polyolefin resin having the following characteristics (a) and (b) or an alloy material containing the polyolefin resin. A water-based piping tube for an automobile characterized by being constituted. (A) The yield point stress under tension in a 120 ° C. atmosphere is 4.0 MPa or more. (B) Ethylene glycol / water (5
0/50 volume ratio) 4.0 mg
Mm / cm ² · day or less. 2. A piping tube having a single-layer structure or a multilayer structure, at least one of which is made of an alloy material having a polyolefin-based resin as a matrix phase and a resin having excellent high-temperature strength as a domain phase. Aqueous piping system for automobiles. 3. The polyolefin resin is at least one of polypropylene, cross-linked polypropylene and polymethylpentene, and the resin having excellent high-temperature strength is polyphenylene ether. 4. A water-based piping tube for an automobile according to any one of 3. 4. The water pipe according to claim 3, wherein the matrix phase is polypropylene, and the domain phase is polyphenylene ether.