JPS6124410B2 - - Google Patents

Abstract

PURPOSE:To unitl firmly the titled pipes useful for a gas pipe within a short period, by applying a specific adhesive on the outer surface of a joining section of the pipe and the inner surface of the other pipe member with a same dimension of the inner diameter as that of the outer diameter of the former pipe, and melting the adhesive by a high temperature heating metal body to unitl the pipes. CONSTITUTION:The joining end outer surface of the crosslinked polyolefin pipe 1 and/or the joinig end inner surface of the crosslinked polyolefin pipe member 2 with the same dimension of the inner diameter as that of the outer diameter of the crosslinked polyolefin pipe 1 are coated with a polyolefin adhesive 3 which would not be crosslinked by organic peroxides, then projections 41, 42 of the heating metal body 4 is kept at high temperatures are fitted onto the joining end outer surface of the crosslinked polyolefin pipe 1 and the joining end inner surface of the crosslinked polyolefin pipe member 2 thereby they are heated, and while the polyolefin adhesive 3 is still in the melted state, the pipe 1 is inserted into the pipe member 2 to unitl them.

Description

[Detailed description of the invention]

The present invention relates to a novel method for connecting crosslinked polyolefin pipes such as crosslinked polyethylene pipes. Cross-linked polyolefin pipes have superior heat resistance, mechanical strength, pressure strength, and especially resistance to environmental stress cracking compared to pipes made of non-cross-linked polyolefin, so they are used as gas pipes, water pipes, and hot water pipes. It is seen as promising. Conventionally, so-called mechanical joints using metal connecting members have been used to connect cross-linked polyolefin pipes, but mechanical joints have problems such as high cost, so organic peroxide A method has been proposed in which a polyolefin composition blended with a compound is used as an adhesive, the adhesive is placed between pipes to be connected, and the pipes are cross-linked by heating. However, this method has a serious drawback in that crosslinking of the adhesive requires a long time. By the way, the present inventors have found that if polyolefin is used as an adhesive in a specific manner, it is possible to connect crosslinked polyolefin pipes extremely firmly without crosslinking the polyolefin adhesive with an organic peroxide. We discovered an unexpected fact that breaks common sense and completed the present invention. Accordingly, the present invention proposes a novel connection method as set forth in the claims that can firmly connect crosslinked polyolefin pipes in a short time. Since the present invention does not require an adhesive crosslinking process, the connection can be made in a short time.Moreover, as shown in the examples below, in many cases, the connection point is surprisingly able to withstand internal pressure greater than the pipe body. Has strength. 1 to 3 are explanatory diagrams (cross-sectional views) of the method of the present invention, in which 1 is a crosslinked polyolefin pipe, 2 is the same as or slightly larger than the outer diameter of the pipe 1, or is slightly larger than the outer diameter of the pipe 1. A crosslinked polyolefin pipe member having a small inner diameter, 3 a polyolefin adhesive, and 4 a metal heating element maintained at a high temperature.
First, polyolefin adhesive 3 is applied to the end surface of pipe 1 (FIG. 1). Next, a ring-shaped protrusion 41 having an inner diameter equal to or slightly larger than the outer diameter of the pipe 1;
2, using a metal heating element 4 having a cylindrical protrusion 42 having an outer diameter equal to, slightly smaller than, or slightly larger than the inner diameter of the pipe member 2 on the side opposite to the side where the pipe member 2 is present. As shown, the tip of the pipe 1 is inserted into the protrusion 41 and the pipe member 2 is inserted into the protrusion 42 and heated. Finally, the pipe 1 and the pipe member 2 are separated from the metal heating element, and while the polyolefin adhesive 3 on the pipe 1 is in a molten state, the pipe 1 is quickly inserted into the pipe member 2 as shown in Fig. 3. . The connection between the pipe 1 and the pipe member 2 is thus completed. Note that the adhesive 3 may be applied to the inner surface of the pipe member 2 or only to the inner surface. Pipe 1 is a pipe to be connected, and pipe member 2 may be a socket, elbow, cheese, etc. fitting, in which case the other end of pipe member 2 is connected in the same manner as shown in Figures 1 to 3. In this manner, another pipe 1' is connected to the other pipe 1', and thus the pipe 1 and the pipe 1' are connected via the pipe member 2. Further, the pipe member 2 may be a pipe to be connected to the pipe 1. In that case, pipes of different diameters will be connected. When the inner diameter of the pipe member 2 before heating is smaller than the outer diameter of the pipe 1, it is preferable to increase the inner diameter of the pipe member 2 by heating and then insert the pipe 1. In this way, an even stronger connection can be made. When the inner diameter of the ring-shaped protrusion 41 with the metal heating body is the same as the outer diameter of the pipe 1 or is very slightly larger,
By inserting the pipe 1 into the protrusion 41 for heating, most of the adhesive 3 is pushed to the rear of the pipe 1, leaving only a very thin layer of adhesive on the tip surface of the pipe 1. In the present invention, surprising adhesive strength can be obtained even with a thin layer adhesive on the order of microns. It goes without saying that the longer the insertion length of the pipe 1 into the pipe member 2, the greater the connection strength, but in the present invention it is desirable to insert at least a length corresponding to the outer diameter of the pipe 1. . It is preferable that the inner diameter of the pipe member 2 is as close to the outer diameter of the pipe 1 as possible, and especially when inserting the pipe 1 into the pipe member 2 with a small amount of adhesive present on the surface as described above, the pushing force will be reduced. It is more preferable that the inner diameter is such that it requires . The base polyolefins constituting the pipe 1, the pipe member 2, and the adhesive 3 all have the same chemical concept, and are α-olefins such as ethylene, propylene, and butene.
Homopolymers and copolymers of α-olefin, such as 1,4-methylpentene-1, homopolymers and copolymers of α-olefin chemically containing halogen, carboxylic acid or its derivative, or carboxylic acid or its derivative and α-olefin copolymers of
For example, polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, ethylene-propylene copolymer, ethylene-propylene-diene terpolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, etc. Examples include polymers and chlorinated polyethylene. Particularly preferred are the following. (i) Linear polyethylene having a density (g/cm ³ ), ie, ρ, of 0.915 to 0.970 as measured by JIS K 6760, and an MP (°C) that satisfies the following relational expression: MP (°C) = 500× ρ−345 Here, MP (°C) is from “Polymer Analysis Handbook” edited by Kanbara and Fujiwara, section 3.15.1, pages 178 to 183 (1966).
It means the maximum melting temperature (℃) measured by differential thermal analysis using the method shown in ``Asakura Shoten'' (2007). Commercially available products include many linear low-density polyethylenes and linear medium-density polyethylenes. (ii) The following general formula (Here, R ₁ , R ₂ , R ₃ are hydrogen, halogen, carboxyl group, alkyl group, carboxyalkyl group) ethylenically polymerizable ethylenically unsaturated carboxylic acid or its anhydride, such as acrylic acid, An α-olefin polymer containing about 0.001 to 10% by weight of maleic acid, itaconic acid, heimic acid, or anhydride thereof as a copolymer component, a graft component, etc. As the α-olefin, one or more of ethylene, propylene, butene-1,4-pentene-1, etc. can be used. In particular, ethylene-maleic acid copolymers (maleic acid content 0.01-1% by weight), ethylene-acrylic acid copolymers (acrylic acid content 0.01-1% by weight)
% by weight) is preferred. (iii) Copolymers of one or more α-olefins, such as ethylene, propylene, butene-1 or 4-methylpentene-1, and carboxylic acids or derivatives thereof, such as vinyl acetate and ethyl acrylate. In particular, those having a vinyl acetate content of 5 to 30% by weight are preferred. (iv) A copolymer of ethylene and at least one of _C3 to _C10 α-olefins, such as propylene, butene-1, or 4-methylpentene-1, and has a density measured according to JIS K 6760. less than 0.915 g/cm, and the content of _C3 to _C10 α-olefin is about 0.5 to 50% by weight.
Furthermore, about 0.01 to 10% by weight of non-conjugated dienes such as dicyclopentadiene, methyltetrahydroindene, methylene norponene, ethylidenenorbornene, and 1,4 hexadiene, and/or the above-mentioned ethylenically unsaturated carboxylic acids or their anhydrides. Those contained as copolymer components, graft components, etc. are also used. Particularly preferred is an ethylene-propylene-diene copolymer. In the present invention, two or more of the polyolefins described above may be used in combination. Moreover, the polyolefins used for the pipe 1, the pipe member 2, and the adhesive 3 may be of the same type, or may be of different types. Pipe 1 that can be connected in the present invention
And the pipe member 2 is a low crosslinked gel with a gel fraction of 5 to 50%, which is obtained by crosslinking the polyolefin with organic peroxide crosslinking, water crosslinking, electron beam irradiation, or other methods. fraction 50
% or more, for example, 80 to 95%. In addition, when connecting pipes as described later, maintain a low degree of crosslinking of about 5 to 50%, and after the connection work is completed, additional crosslinking is performed to reduce the gel fraction to 50%.
It is preferable to have the above degree of crosslinking. A particularly good connection is also achieved when both the pipe 1 and the pipe member 2, or at least the pipe 1, are made of water-crosslinked polyolefin. The polyolefin adhesive used in the present invention is applied to the outer surface of the pipe 1 and/or the inner surface of the pipe member 2 at room temperature or at a high temperature below the high temperature during pipe connection work. By heating and melting ordinary polyolefin,
The melt may be applied, or a solution prepared by dissolving the polyolefin in a parent solvent may be used.
Examples of parent solvents include benzene, toluene, xylene, diylene, mesitylene, decalin, tetralin, decane, dodecane, tridecane, tetradecane, nonane, hydrocarbons such as olefin oligomers that are liquid at room temperature, anilish, quinoline, N-
Nitrogen-containing hydrocarbons such as methylpyrrolidone, dimethylformamide, and dimethylacetamide, oxygen-containing hydrocarbons such as tetrahydrofuran, formic acid, malonic acid ester, methyl isobutyl ketone, cyclohexanone, diphenyl ether, and 2-ethylhexanol, or dimethyl sulfoxide, Other organic compounds such as hexamethylphofuramide and o-dichlorobenzene. When polyolefin is used as an organic solvent solution, the coating operation can be carried out at room temperature or at a low temperature of 100° C. or less, making the operation easier and uniform coating possible. Immediately before inserting the pipe 1 into the pipe member 2, it is preferable that the residual amount of the organic solvent in the adhesive 3 is small, but some residual amount is acceptable, and in practice, the amount of organic solvent remaining in the adhesive 3 is acceptable. Since most of the organic solvent is vaporized by heating to a high temperature, the use of an organic solvent does not cause any real harm. However, the appropriate amount of the organic solvent to be used is about 10 to 2000 parts per 100 parts (parts by weight) of the polyolefin. In the present invention, it is understood from the above explanation that the effect of crosslinking of polyolefin as an adhesive by organic peroxide is not expected; For example, it is not excluded that organic peroxides may be incorporated in an amount of about 2 parts or less per 100 parts of polyolefin. Furthermore, it is rather preferable that the polyolefin adhesive used in the present invention is water-crosslinkable. After connecting pipes using a water-crosslinkable polyolefin adhesive, even if the polyolefin adhesive is crosslinked with water, the strength of the pipe connection does not decrease, but rather improves the strength of the pipe connection at high temperatures. Thereafter, water cross-linking of the adhesive can be carried out using moisture in the atmosphere or water flowing inside the pipe while operating the pipe, which is advantageous since there is no need to provide a separate water cross-linking step. The polyolefin adhesive used in the present invention may be made water crosslinkable by a known method such as using a silane modifier such as vinyltrimethoxysilane or an organic peroxide and a silanol condensation catalyst such as t-butyl-tin-dilaurate. When the pipe 1 and the pipe member 2 are made of crosslinked polyethylene, a particularly preferred polyolefin as the adhesive is the linear polyethylene described above. Hereinafter, the present invention will be explained in more detail with reference to Examples. Examples 1 to 24 The outer surface of the tip of a crosslinked polyolefin pipe with an inner diameter of 21 mm and an outer diameter of 27 mm made of the materials shown in Table 1 (all parts and % in the table are parts by weight and weight %) and the materials shown in Table 1 Consisting of inner diameter 27mm, outer diameter 34mm, length 7.5
After wiping off the oil and water on the inner surface of the socket of the cm cross-linked polyolefin socket joint with a dry cloth, apply the polyolefin adhesive shown in the table to a length of about 4 cm on the outer surface of the tip of the cross-linked polyolefin pipe for about 1 mm.
The socket part of the socket joint of the cylindrical projection (outside diameter 27 mm, projection length 5 cm) of the iron heating element having the structure shown in Fig. 2, which was maintained at 220°C by electric heating, was then heated on one side. The tips of the pipes coated with the adhesive were each pushed into ring-shaped protrusions (inner diameter 27 mm, protrusion length 5 cm) and held for about 20 seconds. After this, remove the socket joint and pipe from the iron heating element,
Insert approximately 3 cm of the tip of the pipe into the socket joint. The same pipe as above was connected to the other end of the socket joint in the same manner as above. A water pressure test sample was prepared having a 30 cm pipe at both ends with the socket joint in the center, and the internal pressure of the pipe was increased at a rate of 20 kg/cm per minute to destroy the sample.

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【table】 [Brief explanation of the drawing]

1 to 3 are explanatory views of the method of the present invention, in which 1 is a crosslinked polyolefin pipe, 2 is a crosslinked polyolefin pipe member, 3 is a polyolefin adhesive, and 4 is a metal heating body.

Claims (1)

[Scope of Claims] 1. Organic peroxide crosslinking essentially on the outer surface of the connecting end of a crosslinked polyolefin pipe and/or on the inner surface of the connecting end of a crosslinked polyolefin pipe member having an inner diameter approximately the same as the outer diameter of the crosslinked polyolefin pipe. A non-polymerized polyolefin adhesive is applied, and then at least the outer surface of the connecting end of the crosslinked polyolefin pipe and the inner surface of the connecting end of the crosslinked polyolefin pipe member are brought into contact with a metal heating body kept at a high temperature and heated to form the polyolefin adhesive. A method for connecting a crosslinked polyolefin pipe, comprising inserting the crosslinked polyolefin pipe into a crosslinked polyolefin member while the agent is in a molten state. 2. The connection method according to claim 1, wherein the polyolefin adhesive is an organic solvent solution of polyolefin adhesive. 3. The connection method according to claim 1 or 2, wherein the crosslinked polyolefin pipe is a water crosslinked polyethylene pipe, the crosslinked polyolefin pipe member is a crosslinked polyethylene pipe member, and the polyolefin adhesive is a solution of polyethylene in an organic solvent. 4. The connection method according to claim 3, wherein the polyolefin adhesive is a solution of linear polyethylene in an organic solvent. 5. The connection method according to claims 1 to 4, wherein the polyolefin adhesive is water-crosslinkable.