JPH09239844A - Bonding of polymeric material and adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relatively easily bond a polymeric material difficult to bond by an adhesive and difficult to bond by high frequency welding. SOLUTION: Adhesive sheets 4 composed of a thermoplastic resin having 0.5-20wt.% of a carbon fine powder uniformly dispersed therein are interposed between pipes 1, 2 made of a thermoplastic resin to be bonded and a joint 3 and irradiated with microwaves of 0.9-6GHz for a specified time and subsequently radiated.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for adhering a polymer material and an adhesive composition used for the same. More specifically, it is suitable for adhering polymer materials such as polyethylene (PE), polybutene (PB), etc., which are difficult to adhere with adhesives, and further, gas or liquid pipes in an airtight state and a liquidtight state. TECHNICAL FIELD The present invention relates to a method for fusion bonding with high strength, an adhesive composition, an adhesive sheet, and an adhesive pipe joint.

[0002]

2. Description of the Related Art Conventionally, as a method of thermally adhering polyvinyl chloride materials, particularly soft polyvinyl chloride films, films or sheets are stacked and pressed by electrodes, and a megahertz band, particularly short wave or very short wave, is applied between the electrodes. A method of applying a high frequency (for example, 19 MHz, 40 MHz) voltage in a range is known. Since this bonding method enables welding in a short time, it has been industrially widely used as a high-frequency sewing machine and a high-frequency welder since ancient times.

This method is applicable to not only polyvinyl chloride but also other thermoplastic resin materials having a large dielectric constant and dielectric loss tangent. However, materials such as polyethylene (PE) and polybutene (PB) having a low dielectric constant and a low dielectric loss tangent have a low dielectric loss coefficient, so that the temperature does not rise to the extent that welding is possible. Therefore, they cannot be bonded with sufficient strength and airtightness. Moreover, these synthetic resin materials do not have suitable adhesives that can bond in a high strength and airtight state.

Further, for a material having a specific shape such as a sheet-like material, it is possible to press a heat bar heated to a melting temperature or adhere by a method such as ultrasonic welding. It is difficult depending on the form of. That is, the adhesive strength is low when the parts to be joined are hidden, as in the case of pipes fitted in a nesting manner, especially when the materials to be joined cannot be sufficiently pressurized. Moreover, the adhesion device becomes large-scale and cannot be easily used at the work site.

On the other hand, polyethylene and polybutene pipes, which are often used for water pipes and gas pipes, are connected with a mechanical joint means such as a screw after interposing a sealing material. Recently, an electrofusion method has been proposed as a method for melting and adhering such pipes. In this method, a coil-shaped heater is embedded near the inner surface of the pipe-shaped joint, the pipes to be joined are inserted from both sides of the joint, and the heater is energized to heat it with Joule heat generated at that time, The pipes are connected to each other by welding the joint and the pipe.

When a mechanical joint means such as the above-mentioned screw is used, the strength of the joint portion, particularly the strength against vibration such as an earthquake is low, and gas or liquid seal leakage easily occurs. In addition, in the electrofusion method, the coil-shaped heater is embedded in the joint while the joint is made. Therefore, the structure of the joint is complicated, the handling becomes complicated, and the cost per joint is high.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a polymer material such as polyethylene (PE) or polybutene (PB) which is difficult to be bonded with an adhesive and is also difficult to be welded at a high frequency is relatively easily bonded. It is a technical subject to provide a bonding method that can be used. Further, according to the present invention, regardless of the form of the material to be adhered, and even when the part to be joined is hidden, only the part can be partially heat-welded while not affecting other parts as much as possible. It is an object to provide a relatively inexpensive bonding method.

Further, the present invention provides a bonding method, a bonding sheet and a bonding joint pipe which can be simply and easily welded and bonded when a gas or liquid pipe made of polyethylene, polybutene or the like is laid on site. It is a technical issue to provide.

[0009]

According to the bonding method of the present invention, an adhesive layer made of a thermoplastic resin in which an inorganic powder that absorbs microwaves is dispersed between materials made of a polymer material to be bonded. It is characterized in that it is interposed, microwaves are radiated for a predetermined time, and then heat is radiated. At least one of the materials to be bonded is preferably a thermoplastic resin. In that case, it is more preferable that the thermoplastic resin forming the adhesive layer is a thermoplastic resin compatible with the thermoplastic resin forming the material. Further, the adhesive layer can be preheated before irradiation with microwaves.

The frequency of the microwave is preferably in the gigahertz band, particularly 0.9 to 6 GHz. The fine carbon powder is preferably selected from the group consisting of carbon black and crystalline graphite. The carbon black is preferably selected from the group consisting of acetylene black and carbon black having a hollow shell structure.

The bonding method of the present invention can be suitably used when bonding pipes that are fitted together in a nested manner.

The bonding composition used for microwave bonding according to the present invention comprises 99.5 to 80% by weight of a thermoplastic resin and 0.5 to 20% by weight of an inorganic powder uniformly dispersed therein. Has been done. The inorganic powder is preferably carbon fine powder. It is convenient to use such an adhesive composition as an adhesive sheet formed into a sheet, and the sealing action is improved.

The microwave-bonding joint pipe of the present invention comprises a pipe made of a polymer material and an adhesive layer provided on the inner or outer surface thereof, and the adhesive layer is made of an inorganic powder capable of absorbing microwaves. It is characterized by comprising a dispersed thermoplastic resin.

[0014]

[Function] When a microwave is irradiated with an adhesive layer made of a thermoplastic resin in which a predetermined inorganic powder is dispersed between the materials of the polymer material to be adhered and the microwave is irradiated, the microwave is converted into the inorganic powder through the material. Reach Then, the inorganic powder absorbs the microwave and generates heat. Therefore, the heat melts the adhesive layer and bonds the materials together.

The bonding method of the present invention can be suitably applied to a thermoplastic resin having a low dielectric constant and a low dielectric loss tangent, such as polyethylene and polybutene. Such a thermoplastic resin has a low dielectric constant and a low dielectric loss tangent, which makes it difficult to perform high-frequency welding. However, according to the method of the present invention, the above-mentioned adhesive layer and material are welded together, and the strength and airtightness are high. Adhesion with high liquid tightness can be obtained. Further, if a thermoplastic resin layer of the same type as the material is adopted, since the compatibility is high and the melting temperature is the same, it is possible to further integrally bond them.

As the inorganic powder, fine carbon powder,
In particular, carbon black, crystalline graphite, acetylene black, and carbon black having a shell structure are preferably used because they have high microwave absorption.
The content of the powder is preferably 0.5 to 80% by weight, and when it is less than the range, the temperature is hard to rise because the microwave absorption is small, and when it exceeds the range, runaway is likely to occur.

When the bonding method of the present invention is adopted for connecting pipes fitted in a nest, a suitable pressure can be obtained due to expansion of the bonding layer. Therefore, sufficiently high adhesive strength and sealability can be obtained without applying pressure from the outside.

The adhesive composition of the present invention can be suitably used in the above-mentioned adhesion method. As an application method, the adhesive layer can be formed by directly applying it on the surface of the material, but if a sheet-shaped product is used, it is easy to control the thickness and easy to use, and it is easy to store and carry. It is convenient. Furthermore, if a pipe joint consisting of a pipe made of a polymer material and an adhesive layer provided on the inner surface or the outer surface of the pipe is used in advance, the bonding work becomes simple. In that case, the pipe and the adhesive layer can be integrally formed by double-layer extrusion or the like.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the bonding method, the bonding composition, the bonding sheet and the bonding pipe joint of the present invention will be described below with reference to the drawings.

FIG. 1 is a process diagram showing the basic procedure of the bonding method of the present invention. In FIG. 1, reference numerals 1 and 2 are two pipes to be bonded. In this embodiment, it is a polyethylene pipe for gas pipes of the same diameter, which is connected by a joint (socket) 3 made of a polyethylene pipe having a larger diameter.

First, the adhesive sheet 4 is wound around the ends of the two pipes 1 and 2. Then they are inserted into the joint 3 from both sides. As a result, the outer peripheral surfaces of the pipes 1 and 2 to be bonded and the inner peripheral surface of the joint 3 are arranged so as to sandwich the adhesive sheet 4. At this time, loose fitting is still sufficient. As will be described later, the adhesive sheet 4 is a sheet-shaped product obtained by dispersing a carbon fine powder in polyethylene.

Further, as shown in detail in FIG. 2, the joint 3
A shield material or a heat insulating material 5 having a low dielectric loss coefficient is wound around the outer periphery of the metal plate 6 and the metal plate 6 is provided except for the portion to be bonded.
Cover with. The heat insulating material 5 relaxes the microwave applied to the welded portion so that the microwave is applied as uniformly as possible.

In this state, the bonding device 7 is arranged around the joint 3. The bonding device 7 includes a microwave oscillator 8 arranged toward the welded portion, a waveguide 9 extending from the oscillator toward the welded portion, a waveguide 10 extending opposite to the welded portion, and the inside of the waveguide. A microwave reflecting plunger 11 is provided so as to be movable in the axial direction. Then, from the oscillator 8, for example, output 500W
Then, a microwave of 2.45 MHz is generated.

The microwave passes through the waveguide 9 to reach the adhesive portion, and the microwave penetrating to the rear waveguide 10 is reflected by the plunger 11 and enters the welded portion again. Then, the plunger 11 causes interference between the incident microwave and the reflected microwave to adjust the intensity of the microwave absorbed by the welded portion. Further, although multi-mode microwaves can be used, it is preferable to irradiate in a single mode applied in the same cycle from the same direction. The microwave is absorbed by the fusion-bonded portion, and the adhesive sheet 4 rises to a temperature equal to or higher than the melting temperature. During the microwave irradiation, the pipes 1 and 2 may be rotated so that the microwaves are uniformly irradiated.

As a result, the adhesive sheet 4, the surfaces of the first and second pipes 1 and 2 in contact with the adhesive sheet 4, and the inner surface of the joint 3 are melted and expanded. With the pressure due to its expansion,
And the second pipes 1 and 2 and the joint 3 are firmly bonded to each other via the adhesive sheet 4. After that, the temperature is lowered, and after the temperature is lowered, the metal plate 6 and the heat insulating material 5 are removed. If the molten resin comes out from the end of the joint 3, it is removed and the bonding work is completed.

If the joint 3 shown in FIG. 1 is composed of a pipe having a double structure of an inner layer mixed with carbon fine powder, which will be described later, and an ordinary outer layer not containing carbon fine powder, the adhesive sheet 4 is not necessary. (See Figure 3).

A pipe 1 applicable in the above method,
The diameter and the thickness of the joint 2 and the joint 3 are not particularly limited, but those having an inner diameter of 5 to 200 mm and a thickness of 2 to 20 mm are usually applicable. The material is not particularly limited as long as it is a polymer material, but when a thermoplastic resin is used, the pipe itself also melts, so that strong adhesion can be obtained. Moreover, a material having a low dielectric loss coefficient that cannot be directly subjected to high frequency fusion may be used. Therefore, as a material preferably applicable to this method, polyethylene (PE), polybutene (PB), polystyrene (PS), polypropylene (PP), polymethylpentene-1 (PMP), polyamide (nylon resin), polycarbonate (PC) , Polyester resins such as polyethylene terephthalate (PET), polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer (FE
P), tetrafluoroethylene-perfluorovinyl ether copolymer (PFA) and the like.

As the carbon fine powder, fine powder of carbon black, crystalline graphite, acetylene black or the like can be adopted. In particular, Ketjen Black EC and Ketjen Black EC600JD, which are carbon blacks with conductivity and have a fine hollow shell structure, developed by Akzo Co., Ltd. in the Netherlands are preferable because they absorb microwaves well. However, other conductivity-imparting carbons such as acetylene black can also be used. The conductivity-imparting carbon is mixed with an insulating polymer compound such as synthetic resin or rubber to impart conductivity.

Further, instead of carbon, fine powder of metal oxide such as aluminum oxide, iron oxide, magnesium oxide, etc., which is capable of kneading with resin and which self-heats by absorbing microwaves, is mixed. May be. Further, as a material suitable for being easily kneaded with a resin material by absorbing such microwave and self-heating, a metal-based material such as aluminum powder, copper powder, nickel powder, iron powder, silver powder, tungsten powder, molybdenum powder, etc. In addition to the good conductive powder of, there are non-oxide ceramics such as titanium nitride and titanium carbide, and the bonding method and composition of the present invention include
It is preferably used alone or as a mixture. It is preferable that any of the above-mentioned inorganic substances has a dielectric constant and a dielectric loss tangent that do not significantly change at the melting temperature of the thermoplastic resin, that is, that has little temperature dependence.

It is preferable that the inorganic powder such as carbon fine powder is put into the above-mentioned thermoplastic resin, kneaded so as to be uniformly dispersed, and molded into a sheet by press molding or the like. However, it is also possible to use a pipe coated on the surface in layers. The ratio of the fine carbon powder varies depending on the thickness of the adhesive sheet 4, but is 0.5 to 0.5% of the total.
20% by weight, more preferably about 1 to 10% by weight. If the carbon fine powder exceeds 20% by weight, runners described later tend to occur, and 0.5% by weight
If it is less than this, the temperature does not rise sufficiently. The thickness of the adhesive sheet 4 is preferably about 0.1 to 7 mm, particularly preferably 0.2 to 5 mm in the range of the above-mentioned pipe.

As another mode for pipe welding, FIG.
As shown in FIG. 3, the joint 3 itself may have a double structure of an inner layer (adhesive layer) 3a mixed with carbon fine powder and a normal outer layer (material to be adhered) 3b containing no pipe fine powder. In that case, since it is not necessary to prepare the above-mentioned adhesive sheet 4, the bonding work becomes more efficient. The outer layer may be an adhesive layer containing carbon fine powder.

Such a double-structured joint 3 can be easily manufactured by cutting the pipe extruded by double-layer extrusion using two plastic extruders and subjecting it to some machining. It can also be manufactured by injection molding. In this case, the thickness of the adhesive layer 3a may be the same as that of the adhesive sheet 4 described above. However, it can be made even thinner.

As shown in FIG. 4, the permittivity of carbon fine powder depends on its temperature, and the permittivity tends to increase as the temperature rises. Therefore, if microwaves are radiated too much, the dielectric constant rises as the temperature rises, so to speak, positive feedback is applied, and the so-called runaway
Away). Therefore, it is preferable to prevent the runaway by winding the above-mentioned heat insulating material 8 in order to reduce the strength of the microwave, adjusting the strength of the microwave, or preheating the portion to be bonded in advance. Further, the microwave output and irradiation time are also appropriate according to their thickness and dielectric constant so that the temperatures of the pipes 1, 2, the joint 3 and the adhesive sheet 4 do not become too high and runaway does not occur. It is preferable to control

The microwave irradiation time depends on the dielectric loss rate of the inorganic fine powder used, the mixing ratio of the thermoplastic resin and the fine powder, the thickness of the adhesive layer (adhesive sheet), the ambient temperature, the microwave intensity, etc. Usually, the entire system is designed so that welding is completed within about tens of minutes.

As the heat insulating material 8, a heat resistant material that does not absorb electromagnetic waves is used, and an inorganic material such as quartz or glass fiber is preferably used.

FIG. 5 shows another embodiment of the bonding method of the present invention. In FIG. 5, the material to be bonded is the polybutene sheets 12, 12. In this embodiment, an adhesive sheet 13 containing carbon fine powder containing polybutene as a base material is sandwiched between them and housed in a box body 14 whose inner surface is covered with a reflective material. A microwave oscillator 8 is provided behind the box body 14. Further, in the box body 14, a turntable 15 is provided so that the material is uniformly irradiated with microwaves.

The above sandwich-shaped material is placed on the turntable 15 and irradiated with microwaves from the oscillator 8 for a predetermined time. In this case, the microwaves are reflected by the reflection plate and become multimode. Since the carbon of the adhesive sheet 13 absorbs microwaves, the temperature of the adhesive sheet 13 rises, and the polybutene sheets 12, 12 can be firmly fused to each other.

In the above-mentioned embodiment, the adhesive sheet is directly adhered to the surface of the material and is interposed between the materials. However, the adhesive sheet may be interposed in other forms such as winding a thin tape. May be. In that case, the temperature rises slowly, and runaway is less likely to occur.

In the above-mentioned embodiment for adhering pipes, the pipe joint of the same diameter has been described, but the pipe joint of the present invention is not limited to this. That is, in the case of pipes for gas and liquid, T is used as a joint.
There are letter-shaped (cheese), L-shaped (elbow), and different diameter joints for joining pipes of different diameters, and the method and pipe joint of the present invention can be applied to these cases. Even in the case of T-shaped connection, L-shaped connection, or connection with different diameter joints, the connection can be made easier by preparing a dedicated joint and using a dedicated microwave welding machine.

[0040]

EXAMPLES Next, the bonding method by microwave irradiation of the present invention will be described with reference to specific examples.

[Example 1] Two polybutene pipes having an inner diameter of 20 mm, a thickness of 3 mm and a length of 70 mm were prepared as materials to be bonded, and an outer diameter of 18 mm and a thickness of 3 were used as joints.
A pipe made of polybutene having a length of 50 mm and a length of 50 mm was prepared. That is, in this embodiment, as shown in FIG. 6, the joint 3 is inserted inside the two pipes 1 and 2 to be connected. Further, in the state where the adhesive sheet 4 is not interposed, there is a gap of about 1 mm on one side between the pipes 1 and 2 and the joint 3.

Bureau B manufactured by Mitsui Petrochemical Industry Co., Ltd.
95% by weight of 5050 (trademark of polybutene) and 5% by weight of Ketjen Black EC sold by Lion Co., Ltd. are sufficiently melt-mixed by a kneader and formed into a sheet having a thickness of 0.2 mm by press molding. To obtain an adhesive sheet 4.

As shown in FIG. 6, an adhesive sheet 4 was wrapped around the joint 3 and inserted into the ends of the two pipes 1 and 2, and a microwave oven RE-1035 (rated by Sharp Corporation) (rated It was placed in the center of a turntable with an output of 500 W and a frequency of 2450 MHz, and was irradiated with microwaves for 1 minute.

[Examples 2 to 3] Microwave irradiation was performed under the same conditions as in Example 1 except that the microwave irradiation time was set to 2 minutes and 1.5 minutes, and the bonding method of Examples 2 to 3 was applied. Carried out.

[Examples 4 to 5] The thickness of the adhesive sheet 4 was 0.5 mm, the microwave irradiation time was 0.45 minutes and 1.00 minutes, and the adhesive sheet 4 was placed upright in the center of the turntable. Under the same conditions as in Example 1, the bonding methods of Examples 4 and 5 were used.

[Comparative Example] An experiment was conducted under the same conditions except that a 0.5 mm thick film made of polybutene containing no Ketjen Black EC was used in place of the adhesive sheet of Example 1.

Table 1 shows the results obtained by observing the conditions of Examples 1 to 5 and the bonding strength and the state of thermal deformation of the pipe joined body obtained thereby.

[Table 1]

As can be seen from Table 1, Examples 1 to 10 using polybutene sheets mixed with Ketjen Black EC
In the case of No. 5, sufficient welding strength was obtained and thermal deformation was small in all cases. However, in the case of the comparative example, the temperature did not rise, and therefore, no welding occurred.

[Examples 6 to 7] A polyethylene pipe of 70 mm in length manufactured by Kubota Corporation (inner diameter: 30 mm, thickness: 3.9).
mm), the inner surface of one polyethylene pipe is machined to a depth of 2.1 mm and a length of 30 mm, and the outer surface of the other polyethylene pipe is also machined to a depth of 2.1 mm and a length of 30 mm. , The trimmed parts are fitted together. A sheet obtained by kneading polyethylene with 5% by weight of Ketjenblack was used as an adhesive sheet.

Next, as shown in FIG. 7, the adhesive sheet 4 was sandwiched between the fitting portions 21 and 22 of these two polyethylene pipes 1 and 2, and microwave irradiation was performed to perform welding. Table 2 shows the results.

[0051]

[Table 2] From Table 2, it can be seen that also in the cases of Examples 6 to 7, the adhesive strength is sufficient and thermal deformation does not occur.

[0052]

According to the bonding method of the present invention, since the inorganic powder in the bonding layer absorbs microwaves to raise the temperature, it is difficult to bond the materials with an adhesive and to prevent the high frequency welding. Welding can be performed. Further, since the microwave penetrates the polymer material and is absorbed by the inorganic powder, it is possible to weld only the necessary portion without excessively melting the material. It is also possible to bond parts that are difficult to heat from the outside.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a bonding method of the present invention.

FIG. 2 is an enlarged view showing main steps of the bonding method of FIG.

FIG. 3 is a cross-sectional view showing an embodiment of the pipe joint of the present invention.

FIG. 4 is a conceptual diagram schematically showing the tendency of the temperature dependence of the dielectric loss coefficient in the carbon fine powder according to the present invention.

FIG. 5 is a schematic view showing another embodiment of the bonding method of the present invention.

FIG. 6 is a perspective view showing a pipe connection structure used in an example of the bonding method of the present invention.

FIG. 7 is a perspective view showing a pipe connection structure used in another embodiment of the bonding method of the present invention.

[Explanation of symbols]

 1 Pipe 2 Pipe 3 Joint 4 Adhesive Sheet 5 Heat Insulating Material 7 Adhesive Device 8 Oscillator 9 Waveguide 10 Waveguide

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Claims (14)

[Claims] 1. An adhesive layer made of a thermoplastic resin in which an inorganic powder that absorbs microwaves is dispersed is interposed between raw materials made of a polymer material to be adhered, and microwaves are irradiated for a predetermined time. Then, the method of adhering polymer material, which radiates heat. 2. The bonding method according to claim 1, wherein at least one of the materials to be bonded is made of a thermoplastic resin. 3. The thermoplastic resin forming the adhesive layer,
The bonding method according to claim 2, wherein the thermoplastic resin is compatible with the thermoplastic resin that constitutes the material. 4. The bonding method according to claim 2, wherein the thermoplastic resin forming the material is selected from the group consisting of polyethylene and polybutene. 5. The bonding method according to claim 1, wherein the inorganic powder is fine carbon powder. 6. The bonding method according to claim 5, wherein the carbon fine powder is selected from the group consisting of carbon black and crystalline graphite. 7. The bonding method according to claim 6, wherein the carbon black is selected from the group consisting of acetylene black and carbon black having a hollow shell structure. 8. The microwave has a frequency of 0.9 to 6
The bonding method according to claim 7, which is GHz. 9. A thermoplastic resin of 99.5 to 80% by weight,
Inorganic fine powder 0.5 to 2 uniformly dispersed therein
A bonding composition used for microwave bonding, which comprises 0% by weight. 10. The adhesive composition according to claim 11, wherein the inorganic powder is fine carbon powder. 11. An adhesive sheet obtained by molding the adhesive composition according to claim 9 or 10 into a sheet shape. 12. A pipe for microwave bonding, comprising a pipe made of a polymer material and an adhesive layer provided on an inner surface or an outer surface thereof, the adhesive layer being made of a thermoplastic resin in which an inorganic powder is dispersed. Fitting. 13. The pipe joint of claim 12, wherein the thermoplastic resin is selected from the group consisting of polyethylene and polybutene. 14. The pipe joint according to claim 12, wherein the inorganic powder is fine carbon powder.