JPS5857591A - Pipe joint - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Conventionally, so-called mechanical joints using metal connection ladles have been used to connect polyolefin pipes and cross-linked polyolefin pipes. The cost is high. Alternatively, since the pipe and the metal connection ff1s1;l have completely different hardnesses, there are various problems such as the airtightness of the connection part not necessarily being good.

By the way, the present inventors have discovered that the following specific crosslinked polyolefins have much better adhesion and bonding properties to polyolefins and crosslinked polyolefins than ordinary crosslinked polyolefins such as crosslinked polyethylene and crosslinked propylene. In addition, new knowledge was obtained that the material has properties equivalent to those of ordinary cross-linked polyethylene in terms of heat resistance, mechanical strength, and resistance to environmental stress cracking.

The present invention was developed based on the above-mentioned new findings, and its gist is that (b) α-olefin and carboxylic polyolefin modified with ethylenically unsaturated carboxylic acid or its anhydride; It is composed of a crosslinkable substance based on one or more selected from the group consisting of a copolymer with an acid or a derivative thereof, and a copolymer of ta ethylene and an α-olefin of 08 to CIo. This pipe fitting is characterized by:

The above polyolefin (al component) has the following general formula R2 (where a1%a2, FL8 are hydrogen, halo/7'
Ethylenically unsaturated carboxylic acids or anhydrides thereof, such as acrylic acid, maleic acid, and itaconic acid, which have radical polymerizability represented by (carboxyl group, carboxyl group, alkyl group, carboxyl alkyl group).

It is an α-olefin polymer containing about 0.001 to 10% by weight of Himic acid or its anhydride as a copolymer component, a graft component, etc.

As the α-olefin, for example, one or more of ethylene, propylene, butene-1, and pentenato are used.

Particularly preferred are ethylene-maleic acid copolymers (maleic acid content: 0.01 to 1% by weight) and ethylene-acrylic acid copolymers (acrylic acid content: 0.01 to 1% by weight).

The above (b) 1ff1 polyolefin is α-olefin 1. + Toeha is a copolymer of ethylene, phlopyrene, butene and above with carboxylic acid or derivatives thereof, such as vinyl acetate and ethyl acrylate. In particular, it is a copolymer of vinyl acetate content of 5 to 50, self-produced, and ethylene, and the density measured according to JIS K 6760 is 0.91597 cm' or less than 4.
The α-olefin content of ~CIo is 05~soi! 1
It is about fit%. Furthermore, 0.01 to 10% by weight of conjugated dienes such as synchlopentadiene, methyltetrahydroindene, methylenenorbornene, ethylidenenorbornene, and 1.4hexadiene, and/or the above-mentioned ethylenically unsaturated carboxylic acids or their anhydrides. Those contained as copolymer components, graft components, etc. may also be used. Particularly preferred is an ethylene-propylene-diene copolymer.

In the present invention, two or more of the above polyolefins may be used in combination. In addition, polyolefin 1 used in the present invention
If it is less than 500 parts per 00 parts (weight parts, the same applies hereinafter), ordinary polyolefins may be used in combination.

The present invention uses a crosslinkable composition based on the above-mentioned polyolefin, and molds it into a socket, elbow, cheese, or other shape, and if necessary, preliminarily converts the gel fraction to 50% or less of low crosslinking. condition, or brought to a highly cross-linked condition of 50% or more and subjected to pipe connection in the field. In addition, in some cases, it is used for pipe connection without being cross-linked, and the pipe is cross-linked once during or after the pipe connection work. These crosslinked polyolefin pipe caps are produced by, for example, molding and heating crosslinking using a polyolefin composition containing 11a, an organic peroxide known as a crosslinking agent for polyethylene, or crosslinking a water crosslinkable polyolefin composition with water after extrusion molding. Alternatively, a polyolefin composition containing a sensitive substance sensitive to X-rays or ultraviolet rays can be produced by a known method such as crosslinking by irradiating with X-rays or ultraviolet rays after molding. In the invention, any crosslinking method ζ trowel produced can be used.

The pipe fitting of the present invention can be used even when joined to a crosslinked polyolefin or uncrosslinked polyolefin pipe using an adhesive such as a sheet-like or paste-like polyolefin composition containing an organic peroxide crosslinking agent; Even when the above-mentioned pipe and the surface layer are joined by heating and melting without using the pipe, it shows better joining strength than a pipe joint made of a normal crosslinked polyolefin. In particular, when bonding is performed using a crosslinkable polyolefin composition that is liquid, paste, or solid at room temperature and is composed of an organic peroxide crosslinking agent and a polyolefin as an adhesive, extremely excellent bonding strength is exhibited.

The reason why the pipe joint of the present invention exhibits excellent bonding properties is as follows.
(a), (bJ α-olefin, (C) ethylene and/or common polyolefin used together are crosslinked,
exhibiting the properties of a crosslinked product, and (a) ethylenically unsaturated carboxylic acid, (b) carboxylic acid or its derivative, (
It is conceivable that the α-olefin portion of O-0 in c) remains almost uncrosslinked, and this portion exhibits adhesive performance.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 Density 0.95 FΔz, MI 5.09710 min, 7
After injection molding, 2 o.

By heating for 5 minutes at ℃, it meets the Japan Water Works Association standard JWWABz+.
5 (referred to as JWWA under P1) A crosslinked polyolefin joint having the dimensions of the b-shaped socket (nominal diameter 25) shown in Figure 4 was obtained.

Example 2 Density gO, 959 weight cm% MI 1.59/j 0 minutes, vinyl acetate content 10 weight t% ethylene-acetate vinyl copolymer 10 (+6, vinyl trimethoxine 7) 2.5 parts, After injection molding the composition,
It was immersed in hot water at 90° C. for 10 hours to obtain a crosslinked polyolefin pipe fitting having a gel fraction of 74% and having the dimensions of a B-shaped elbow (nominal diameter 25) in Figure 7 attached to J WWA.

Example 3 In place of the ethylene-vinyl acetate copolymer of Example 2, density 0.885'Δi, MI+, 5y/10min, nf'h' included! 1122% ethylene-butene-1
A crosslinked polyolefin pipe fitting having the same dimensions as Example 2 and a gel fraction of 75% was obtained, except that a copolymer was used.

Example 4 50 parts of modified polyethylene used in Example 1, 50 parts of ethylene-vinyl acetate copolymer used in Example 2, DOP
A crosslinked polyolefin pipe fitting having the same dimensions and a gel fraction of 80% was obtained in the same manner as in Example 1 using a composition consisting of 2.0 parts of THMBP and 0.2 parts of THMBP.

Example 5 70 parts of the ethylene-vinegar vinyl copolymer used in Example 2, 30 parts of the ethylene-butene copolymer used in Example 5,
Vinyltrimethoxysilane 2.5 parts, D OP 0.2
2 parts, and di-butyl-tin-diurea-1-0,05
Using the same method as in Example 2, using a composition consisting of
A crosslinked polyolefin pipe fitting with dimensions 5x25) was obtained.

Example 6 50 parts of the ethylene-vinyl acetate copolymer used in Example 2, 50 parts of polyethylene with a density of 0.95 FΔLML 1.6 P/no, 2.5 parts of vinyltrimethoxysilane, D
Run 9'l1 using a composition consisting of 0.22 parts of OP and 0.05 parts of di-butyl-tin-dilaurate.
A crosslinked polyolefin pipe joint with the same method number and dimensions as No. 2 and a gel fraction of 75% was obtained.

Example 7 50 parts of modified polyethylene used in Example 1, 50 parts of ethylene-vinyl acetate co-fi combination used in Example 2, D O
A crosslinked polyolefin pipe fitting having the same dimensions and a gel fraction of 80% was obtained in the same manner as in Example 1 using a composition consisting of 2.0 parts of P and 0.2 parts of T B M HP.

The pipe joint numbers of each example and comparative example were checked, and the following connections were checked.

Joint Connection Method After wiping off the oil and moisture on the outer surface of the socket of a cross-linked polyethylene pipe with an inner diameter of 27mm and an outer diameter of 54I11++1 and the inner surface of the socket of the joint of each example with a dry cloth, wipe the inner surface of the pipe insertion end with a dry cloth. I chamfered it at an angle of about 30 to about the thickness.

Insert the electrically heated connecting jig Kako pipe and the fitting in advance, heat them at about 230°C for 2 minutes, remove them from the connecting jig, and add the separately prepared composition shown in Table 1. After quickly applying the adhesive to the pipe insertion port, #! I inserted the hand tube.

After pressing and fixing the joint without moving it until the surface temperature of the inserted joint reaches approximately 50°C, heat the joint again with a torch lamp to approximately 250°C, and then heat the joint to 230°C.
When the temperature crayon for °C melted, heating was stopped and the mixture was allowed to cool and assimilate.

Subsequently, the remaining side of the joint was joined to the tube in the same manner.

In the case of an adhesive that can be formed into a film in advance, the width should be 18 mm, which is the same as the length of the tube to be inserted, and 1.2 times the outer circumference of the tube.
A rectangular sheet with a length of 128III11 corresponding to this was made, and when the tube was released from the connecting jig heated to about 250° C., the sheet was quickly wrapped around the tube insertion part.

For adhesives that cannot be formed into a film in advance,
Make it into a paste, heat the paste to an upper limit of 130°C to lower its viscosity, and apply it quickly to the heated pipe insertion part with one brush with a coating margin of about 18 degrees. did.

It should be noted that the reason why the bonded portion was once cooled to 50° C. and then heated again was to completely decompose the crosslinking agent in the adhesive composition inserted into the bonded portion.

Test of Joint Connections The following tests were conducted on the pipes joined using the pipe joints obtained by the method described above. The test results are shown in Table 1.

Hydraulic fracture test after heat cycle Cut a pipe of approximately 800 + III + length with the pipe joint in the center, and with an internal pressure of 5 to 9/α applied, the pipe sample including the joint was heated at 80°C. Time heating 2
Cooling at 5° C. for 1 hour was repeated for 5 cycles. After that, the JIS sample including the joint part was heated at 25°C.
A hydraulic rupture test was conducted in accordance with Section 6.8 of K 6774.

Comparative Example 1 Cross-linked polyethylene Pi with an inner diameter of 27 m and an outer diameter of 34 m, Japan Water 11i11A Association Standard JWWA B-116 I.
1 Connection was made using the Zocket B type (metal joint) shown in Figure 4.

The test method is the same as in Example 1.

Test results Hydraulic fracture test M (n=3) after heat cycle Test 3
Among the samples, leakage occurred from the connection in two samples in the first cycle [1] and in the third cycle for one sample.

The gold fitting was further tightened and the heat cycle was continued, but leakage occurred again in the first restart cycle for three samples, and it was not possible to perform the first hydraulic fracture test.

patent application), Dainichi Nippon Electric Cable Co., Ltd. Representative Director Yukio Aoyama

Claims (1)

[Claims] IaI polyolefin modified with ethylenically unsaturated carboxylic acid or its anhydride, (b) α-olenoin and carboxylic acid or its derivative (small combination, 1. A pipe fitting characterized by comprising a crosslinkable substance based on one or more types selected from the group consisting of copolymers with olefins.