JPS6368684A - Radiator packing and heat exchanger using the same - Google Patents

Abstract

PURPOSE:To prevent the core plate of a radiator from cracking due to stress corrosion, by using as a radiator packing a molded and vulcanized article of a rubber compsn. contg. ethylene-propylene copolymer rubber, isobutylene- isoprene copolymer, and carbon black. CONSTITUTION:A radiator packing is formed by conducting vulcanization and molding of a rubber compsn. contg. ethylene-propylene copolymer rubber, isobutylene-isoprene copolymer, and carbon black. It is pref. to compound the isobutylene-isoprene copolymer in an amt. of about 10-50pts.wt. based on about 90-50pts.wt. ethylene-propylene copolymer rubber. Further, it is pref. to add the carbon black in such a proportion that a vulcanized rubber molding has a hardness (JIS A) of about 60-80.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radiator packing and a heat exchanger using the same. More specifically, the present invention relates to a gasket used in a heat exchanger in which a core plate is attached to a synthetic resin tank by caulking, such as a gasket for an automobile radiator, and a heat exchanger using the same.

[Conventional technology]

A metal tube through which a heat exchange fluid flows, a brass core plate fixed to the end of the tube, a synthetic resin tank caulked to the core plate, and a compressive deformation between the resin tank and the core plate. mediated by the state,
A heat exchanger, such as an automobile radiator, which is equipped with an elastic sealing member that maintains a seal between the two, has a structure in which an upper tank is hermetically attached to a core portion as shown in FIG.

In this structure, the upper tank 2 is open at one end, and is connected to a tube 8 with a full gate fin.
The tank 2 is completed by covering the end of the core part 1 consisting of the following. Along the entire circumference of the open edge of the tank there is provided a mounting part 10 of approximately square cross section, which has inner and outer working surfaces 11 and 12 with mutually parallel and flat surfaces. and inner and outer side wall surfaces 13, 14 perpendicular to these working surfaces.

A brass core plate 16 is soldered to the end of the core part 1, specifically the tube 7, in the circumferential direction near its upper end.
It is fixed by suitable means such as brazing. The outer periphery of the core plate 16 is shaped into a groove 20 having inner and outer side walls 17,18 and a bottom wall 19.

During assembly, the edge attachment portion 10 of the tank 2 is fitted into the groove portion 20, and at this time, the inner and outer side wall surfaces 13° and 14 of the attachment portion 10 are fitted into the groove portion 20.
are engaged with the inner and outer side walls 17 and 18 of the groove 20, respectively, and between the inner working surface 11 of the mounting portion 10 and the inner surface of the groove bottom wall 19 is an elastic sealing material 21 made of a rubber O-ring. will be installed.

Next, a caulking plate 23 made of iron and having an inverted cross-section and a claw portion 22 at the top edge is engaged with the groove portion 20 of the core plate 16, and the claw portion 22 is attached to the edge attachment portion 10 of the tank 2.
caulk toward the outward working surface 12 of. As a result, the tank edge attachment part 10 compresses and deforms the elastic sealing material 21 with its inner working surface 11, and the groove part 2 of the core plate 16
0 in a tightly sealed manner.

In such a configuration, the cooling water present in the interior A of the tank 2 permeates into the micro space 24 formed from the inner surface of the core plate groove 20, the inner surface of the tank mounting portion 10, and the surface of the elastic sealing material 21. , core plate 1
6, a gap environment occurs. The corrosive components of the heat exchange fluid that has entered the gap 25 are difficult to diffuse, and the passive film (oxide film) on the surface of the brass core plate tries to maintain its passivity. Oxygen in the liquid is consumed, resulting in a difference in oxygen concentration between the liquid in the gap 25 and the liquid in the microspace 24, forming an oxygen concentration battery.

In particular, when used as an automobile radiator, the pH of the liquid in the gap 25 decreases due to the action of the battery, since corrosive components such as amines and ammonia are contained in the engine cooling water that serves as the heat exchange liquid.

The resulting corrosive environment is extremely harsh.

The local cell reaction thus formed is shown as follows.

Fist anode reaction Cu −+ Cu” + 2e− Zn −+ Zn” + 2e− Fist cathode reaction 02+H, 0+2e−→2(OH−) Fist Cu+4NH3+ in the presence of ammonia, +H,O→Cu(NH ，
), “-2(OH-)2Cu (N41. )4” ”
+ H, 0+ 2a-→Cu, 0+2NH4-+2N
H.

[Problem that the invention seeks to solve]

Due to these causes and compression of the elastic sealing material,
In order to prevent stress corrosion cracking from occurring in the core plate portion and shortening the life of the heat exchanger, one of the co-applicants previously proposed that the elastic sealing material should have a square cross-section. It has been disclosed that a vulcanized molded product of ethylene-propylene rubber can be used as the elastic sealing material (Japanese Unexamined Patent Publication No. 58-224, No. 2!1g).

As a result of various studies, the present joint applicants sought a heat exchanger having the above structure without specifying the shape of the elastic sealing material and which would be less likely to cause stress corrosion cracking in the core plate portion. Elastic sealing materials, especially elastic sealing materials used as radiator packing, are
It has been found that this problem can be effectively solved by forming a vulcanized molded product of a propylene copolymer rubber composition.

[Means for Solving the Problems] and [Operation] Accordingly, the present invention relates to a radiator packing, and this radiator packing is made of rubber containing ethylene-propylene copolymer rubber, isobutylene-isoprene copolymer rubber, and carbon black. It is vulcanized and molded from a composition.

The present invention also relates to a heat exchanger using such a radiator packing, which comprises: a metal tube through which a heat exchange fluid flows; a brass-shaped core plate fixed to the end of the tube; A heat exchanger comprising a caulked synthetic resin tank and an elastic seal member interposed in a compressively deformed state between the resin tank and the core plate to maintain a seal between the two, the elastic seal member A vulcanized molded product of the above rubber composition is used as the rubber composition.

Ethylene-propylene-diene copolymer rubber (EPDM) copolymerized with various diene components and isobutylene-
Blends of isoprene copolymer rubber (IIR) are already known, and such blends have a specific mixing ratio, that is, about 1 IIR to about 90 to 50 parts by weight of EPDM.
A product filled with carbon black at a mixing ratio of 0 to 50 parts and vulcanized and molded works effectively as a radiator packing.

Specifically, if the mixing ratio of IIR is lower than this, oxygen permeability will increase, resulting in stress corrosion and cracking of the core plate, and if IIR is used at a mixing ratio higher than this, processing Sexuality begins to deteriorate.

When preparing a rubber composition using a closed system such as an intermix or a kneader, add everything other than the vulcanizing agent all at once.
After kneading for about 7 to 8 minutes, the vulcanizing agent is added and discharged after about 1 minute.If an open roll is used, the blended rubber is wound around the roll and additives other than the vulcanizing agent are mixed. This is done by adding the vulcanizing agent last.

Vulcanization molding of the rubber composition is generally carried out by compression molding at 170° C. for 15 minutes using a vulcanizing agent such as dicumyl peroxide. When used as a radiator packing, if the hardness of the vulcanized molded product is low, the repulsion force will be small and problems will arise in sealing performance, while those with high hardness will have problems in moldability. For this reason, during vulcanization molding, the hardness (JIS A) of the vulcanized molded product must be approximately 60~60.
The blending amount of carbon black is adjusted so that it becomes 80%.

〔Effect of the invention〕

The vulcanized radiator packing can be formed into an O-ring or the like having an arbitrary cross-sectional shape, and does not cause corrosion or cracking of the core plate.

〔Example〕

Next, the present invention will be described in detail with reference to examples.

Example: After kneading a rubber composition with the mixing ratio (parts by weight) shown in the table below, compression molding was performed at 170°C for 15 minutes to form a radiator packing, which was actually mounted on a radiator and various tests were conducted. Ta. The results obtained are shown in the table below.

(Composition ingredients) EPDM: Japan Synthetic Rubber Products JSREP33IIR:
Japanese synthetic rubber product Butyl 365 Lubricant: Paraffin wax Below the margin is present.
0 Good Yes Good 2 5 95
n 3 10 90 n None 4 20
gQ ll 53070# 6406 (III # 75050 # 8 60 40 /7 Defective 97030 # 1080 20 N 11 90 10 7F 12100 0 II II Note) Sealing performance: Seal performance stress when the engine cooling water temperature reaches its maximum temperature Corrosion cracking: In terms of life, when Nα1 is 1, &2 is twice as high, and Nα3 is more than 5 times as high.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a radiator. (Explanation of symbols) 2...Synthetic resin tank 16...Brass core plate 21...Elastic sealing material 25...Gap part

Claims (1)

[Scope of Claims] 1. A radiator packing molded by vulcanization from a rubber composition containing ethylene-propylene copolymer rubber, isobutylene-isoprene copolymer rubber, and carbon black. 2. About 90 to 50 parts by weight of ethylene-propylene copolymer rubber to about 1 part by weight of isobutylene-isoprene copolymer rubber
Claim 1 used in a proportion of 0 to 50 parts by weight
Radiator packing as described in section. 3. The radiator packing according to claim 1, wherein carbon black is used in an amount that provides a vulcanized rubber molded product having a hardness (JIS A) of about 60 to 80. 4. A metal tube through which heat exchange fluid flows, a brass core plate fixed to the end of the tube, a synthetic resin tank caulked to the core plate, and between the resin tank and the core plate. In a heat exchanger equipped with an elastic seal member which is interposed in a compressively deformed state to maintain a seal between the two, the elastic seal member contains ethylene-propylene copolymer rubber, isobutylene-isoprene copolymer rubber, and carbon black. A heat exchanger using a vulcanized molded product of a rubber composition. 5. The heat exchanger according to claim 4, wherein the elastic sealing member is an O-ring used in a compressed deformation state of 8 to 40%.