JP2006335780A - Flame-retardant resin composition and resin-coated metal pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal pipe having excellent high-temperature oil resistance, flame retardance, especially external damage resistance by forming a resin-coating layer of a two-layer structure on the surface of the metal pipe for carrying a fluid such as a gas. <P>SOLUTION: The resin-coated metal pipe is obtained by forming the resin-coating layer composed of two layers of an inner layer and an outer layer on the outer periphery of the metal pipe. The inner layer is a flame-retardant resin composition prepared by adding 10-50 pts.mass of a metal hydroxide which is a flame retardant to 100 pts.mass of a base resin composed of 70-90 pts.mass of at least one polyolefinic resin selected from an EEA (ethylene-ethyl acrylate copolymer) or an EVA (ethylene-vinyl acetate copolymer) and 10-30 pts.mass of a polypropylenic resin. The outer layer is the polypropylenic resin. Thereby, good characteristics are obtained. Excellent high-temperature oil resistance, moderate flexibility, excellent flame retardance, high external damage resistance, excellent sheath cutting, sheath drawing properties, etc., are provided in the case of especially a gas pipe, etc. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flame retardant resin composition for coating a surface of a metal tube for carrying a gas such as a gas or a fluid such as a liquid as a protective resin, and a resin-coated metal tube.

  Conventionally, in a metal pipe such as a gas pipe, a vinyl chloride resin (PVC) or a polyolefin resin is used as a protective resin coating.

  However, in the case of PVC, there is a problem that toxic gas is discharged in the event of a fire or the like due to chlorine atoms contained in the resin. Of course, there was a problem that toxic gas was discharged even during the incineration of metal pipes due to the disposal of equipment. In addition, since PVC often uses lead-based stabilizers, even when landfilling is performed, there is a risk that lead will be eluted into the ground and cause soil contamination.

  In this regard, polyolefin resin materials do not have chlorine atoms in the resin, so there is no risk of generating toxic gases during a fire or incineration process, but there is a problem of damage when exposed to high-temperature oil. It was.

Therefore, the present applicant pays attention to a polyolefin resin, in particular, a highly flexible ethylene-ethyl acrylate copolymer (EEA) and an ethylene-vinyl acetate copolymer (EVA), and these resin materials are used as a base resin. Appropriate amount of flame retardant magnesium hydroxide or calcium carbonate is added, while high-temperature oil resistance such as gas pipes (oil resistance performance that soaks in 155 ° C cooking oil for 10 seconds and does not cause defects such as cracking and tearing in the sheath) In order to cope with this problem, a base resin added with a thermoplastic cross-linked resin (such as an ionomer or RC resin) has been proposed (Patent Document 1).
JP 2004-137462 A

  However, according to subsequent studies by the present inventors, when a thermoplastic cross-linked resin is added to EEA or EVA, good high-temperature oil resistance is obtained, and moderate flexibility (softness), excellent Excellent results are also obtained in terms of external flame resistance, sheath cutability that allows the sheath to be cut easily and cleanly, and sheath pullability that allows the sheath to be easily pulled out. However, it was found that the damage resistance needs to be improved to be even better. In other words, in the case of a resin-coated metal pipe, for example, a resin-coated gas pipe, when the gas pipe is drawn indoors, it is often rubbed against building materials such as concrete and wood in the facility, so that the covered portion is easily damaged, and more This is because high trauma resistance is required.

  Therefore, the present inventors conceived of providing a resin coating layer consisting of two inner and outer layers on the outer periphery of the metal tube, and the inner layer is composed of 70 to 90 parts by mass of at least one polyolefin resin selected from EEA or EVA. A flame retardant resin composition in which 10 to 50 parts by mass of a metal hydroxide of a flame retardant is added to 100 parts by mass of a base resin consisting of 10 to 30 parts by mass of a polypropylene resin, and the outer layer is made of a polypropylene resin and As a result, it was found that good results were obtained. That is, on the inner layer side, the main component, EEA or EVA, provides good flexibility, sheath cutability, and sheath pullability, while the outer layer side is made of a strong polypropylene resin. Therefore, large damage resistance is ensured.

  The present invention has been made in view of this point, and basically, a resin coating layer consisting of two inner and outer layers is provided on the outer periphery of the metal tube, one of which is difficult to be coated on the inner layer side. The present invention provides a flammable resin composition, and the other is to provide a resin-coated metal tube in which a resin coating layer comprising two layers of the inner and outer layers is provided on the outer periphery of the metal tube.

  The present invention described in claim 1 includes at least one polyolefin resin 70 to 90 parts by mass selected from ethylene-ethyl acrylate copolymer or ethylene-vinyl acetate copolymer and 10 to 30 parts by mass of polypropylene resin. It exists in the flame-retardant resin composition characterized by adding 10-50 mass parts of metal hydroxides of a flame retardant with respect to 100 mass parts of the resulting base resin.

  The present invention described in claim 2 is characterized in that 0.5 to 3 parts by mass of a lubricant having a surface slipping action is added to the flame retardant resin composition. It is in.

  According to a third aspect of the present invention, a resin coating layer consisting of an inner layer and an outer layer is provided on the outer periphery of a metal tube, and the inner layer is the flame retardant resin composition according to the first or second aspect, and the outer layer. Is a resin-coated metal tube characterized by being a polypropylene resin.

  The present invention according to claim 4 is the resin-coated metal tube according to claim 3, wherein the polypropylene resin has an embrittlement temperature of -30 ° C or lower.

  The present invention according to claim 5 is the resin-coated metal tube according to claim 3 or 4, wherein the metal tube is a flexible metal tube.

  The present invention according to claim 6 is the resin-coated metal tube according to claim 3, 4 or 5, wherein the metal tube is a gas tube.

  According to the flame-retardant resin composition of the present invention, an appropriate amount of a polypropylene resin (10 to 30 parts by mass) having high strength is added to EEA or EVA (70 to 90 parts by mass) which are highly flexible resins. Thus, a flame retardant is added to the base resin having high trauma resistance. Therefore, when a resin coating layer consisting of two inner and outer layers is provided on the outer periphery of the metal tube, an optimum flame retardant for the inner layer is provided. A functional resin composition is obtained.

According to the resin-coated metal tube of the present invention, a resin coating layer consisting of two inner and outer layers is provided on the outer periphery of the metal tube, and the inner layer side is the flame-retardant resin composition according to claim 1. Oil resistance, trauma resistance, desired flame retardancy, moderate flexibility can be obtained, and excellent sheath cut and sheath pull-out properties can be obtained, while the outer layer side is made of a strong polypropylene resin. , Great damage resistance can be obtained. In particular, when the metal pipe is a gas pipe, even if it is rubbed against a building member such as concrete or wood when it is drawn indoors, it can withstand damage due to its high trauma resistance.
In addition, when working on piping, the sheath can be easily cut with a sheath cutter due to excellent sheath cutability, and the covering of the cut portion can also be easily removed by hand due to excellent sheath pullability. it can. That is, it is possible to obtain a gas pipe that is easy to perform terminal construction and intermediate connection work. Of course, since the inner layer side is non-halogen flame retardant, no corrosive gas or dioxin gas is generated during combustion.

  FIG. 1 shows a resin-coated metal tube according to the present invention, which is a normal pipe-shaped tube. In FIG. 1, 1 is a metal tube made of stainless steel or the like, and 2 is a resin coating layer (sheath) made up of inner and outer two layers 2 a and 2 b coated on the outer periphery of the metal tube 1. 2 to 3 show a resin-coated metal tube according to the present invention having flexibility, which is a corrugated tube. 2 to 3, reference numeral 11 denotes a corrugated metal tube made of stainless steel or the like, and 12 denotes a resin coating layer (sheath) made up of inner and outer two layers 12 a and 12 b coated on the outer periphery of the metal tube 11. In the case of this flexible resin-coated metal tube, as shown in FIG. 3, the inner surface is corrugated in a direction (circumferential direction) perpendicular to the corrugated direction of the metal tube 11. A corrugated gap is formed between the resin coating layer 12 and the resin coating layer 12.

  In any of the above metal tubes, the inner layers 2a and 12a of the resin coating layers 2 and 12 are at least one polyolefin selected from ethylene-ethyl acrylate copolymer (EEA) or ethylene-vinyl acetate copolymer (EVA). Flame retardant resin in which 10 to 50 parts by mass of a metal hydroxide of a flame retardant is added to 100 parts by mass of a base resin composed of 70 to 90 parts by mass of a resin and 10 to 30 parts by mass of a polypropylene (PP) resin The inner layers 2b and 12b of the resin coating layers 2 and 12 are made of a polypropylene resin.

  The EEA used in the present invention has an ethyl acrylate content of 5 to 30% by mass and a melt flow rate (MFR, temperature 190 ° C., load 2.2 kg, time 10 minutes) of 0.1 to 5.0. Is preferred. Further, as EVA, it is preferable to use a material having a vinyl acetate content of 5 to 40% by mass and a melt flow rate (MFR, temperature 190 ° C., load 2.2 kg, time 10 minutes) of 0.1 to 5.0. . Furthermore, the polypropylene resin is not particularly limited, and homo PP, random PP, block PP, and the like can be used. This is used by mixing with EEA and EVA, and since EEA and EVA itself have excellent properties such as cold resistance, melt flow rate (MFR, temperature 190 ° C., load 2.2 kg, time 10 minutes) ) Is 0.1 to 5.0, all can be used. For example, as a commercial product, it is desirable to use a polymer obtained by polymerizing an appropriate amount of polyethylene (PE) with respect to block PP (WS234, manufactured by Mitsui Chemicals, Inc.).

  Of these EEA and EVA, at least one of them and a polypropylene resin are mixed to form a base resin. More specifically, 10 to 30 parts by mass of polypropylene resin is mixed with 70 to 90 parts by mass of at least one polyolefin resin selected from EEA and EVA. By mixing this high strength polypropylene resin, the strength of the base resin can be reinforced. Here, the addition amount of the polypropylene-based resin is set to 10 to 30 parts by mass. If the amount is less than 10 parts by mass, the desired damage resistance cannot be obtained, and if it exceeds 30 parts by mass, it becomes too hard. This is because flexibility is lost.

  In other words, since EEA and EVA are resin materials rich in flexibility, the greater the ratio, the greater the flexibility, while the lower the softening temperature, the lower the softening temperature of the entire base resin. This is a factor that decreases the performance. On the other hand, since the polypropylene resin has a high strength and is a hard resin, this addition increases the softening temperature of the entire base resin, and can be expected to improve the heat resistance, particularly the damage resistance. is there.

  The flame retardant added to the base resin is not particularly limited. However, it is preferable to use a metal hydroxide that is a non-halogen flame retardant, such as magnesium hydroxide or aluminum hydroxide, because of its high flame retardant effect. Although this flame retardant may be added as it is, it is preferable to use a material which has been subjected to a surface treatment for improving hydrophobicity in order to reduce aggregation in the polymer and disperse more uniformly. Examples of the surface treatment include silane coupling agents such as polyorganosiloxane, epoxy silane, vinyl silane, amino silane, and mercapto silane, fatty acids such as stearic acid and oleic acid, and titanium coupling agents such as isopropyl isostearoyl titanate. Is mentioned. The addition amount is desirably about 1 to 10% by mass with respect to 100 parts by mass of the base resin.

  The amount of metal hydroxide that is a flame retardant is 10 to 50 parts by mass with respect to 100 parts by mass of the base resin. The reason is that if the amount is less than 10 parts by mass, sufficient flame retardancy of the resin composition cannot be obtained, and conversely if it exceeds 50 parts by mass, the mechanical properties of the resin composition will deteriorate. is there.

  In addition to these flame retardants, a flame retardant aid may be added. By adding the flame retardant aid, the amount of the flame retardant added can be reduced to lower the specific gravity of the resin composition and to suppress the deterioration of the mechanical properties. Examples of such flame retardant aids include silicone compounds such as silicone powder and silicone rubber, phosphorus compounds such as tricresyl phosphate, triphenyl phosphate, and ammonium polyphosphate, zinc borate, hydroxytin zinc, and zinc stannate. Such as zinc compounds such as melamine cyanurate, melamine and melam, phosphorus such as phosphazene, nitrogen-containing compounds, red phosphorus, carbon black, maleimide compounds such as N, N'-m-phenylene dimaleimide, etc. Can be mentioned. And the addition amount should just add about 10 mass parts with respect to 100 mass parts of base resin as an upper limit.

  The flame retardant resin composition of the present invention thus obtained may be added with a lubricant having a surface slipping function, if necessary. Examples of the lubricant include stearic acid, stearic acid amide, oleic acid amide, erucic acid amide, silicone oil, polyethylene wax, EVA wax, metal soap, paraffin oil and the like. And the addition amount is good to set it as about 0.5-3 mass parts with respect to 100 mass parts of base resins.

  Furthermore, in the present invention, the flame retardant resin composition includes various kinds of inorganic fillers such as an ultraviolet absorber, an anti-aging agent, a coloring agent, an antistatic agent, an antifungal agent, an antifungal agent, an antifungal agent, and talc. These additives can be added as necessary.

  According to the flame retardant resin composition of the present invention within such a blending range, the properties are well balanced, and appropriate flexibility is obtained along with good heat resistance, trauma resistance, and high temperature oil resistance. Furthermore, a sheath that can easily and cleanly cut the sheath of the sheath, and a sheath that can be easily pulled out even at normal outside air temperature (about 20 ° C) or low temperature (about -5 ° C) Good results are also obtained in pullability.

  The flame-retardant resin composition of the present invention having such a composition is, for example, a well-known extrusion coating on the metal pipes 1 and 11 in FIGS. 1 to 3 as the inner layers 2a and 12a side of the resin coating layers 2 and 12. It is extrusion coated by the method. The inner layers 2 a and 12 a may be formed by forming a tape made of a flame retardant resin composition and winding the tape around the metal tubes 1 and 11. Or the tube which consists of a flame-retardant resin composition is created, this may be covered with the metal pipes 1 and 11, and it may coat | cover by heating. The surface hardness of the resin coating layer thus obtained is adjusted to be 50 or less, more preferably 30 to 50 in Shore D hardness (JIS-6760). By setting it within this range, it is possible to achieve a balance of characteristics that are contradictory to each other between trauma resistance and flexibility.

  On the outer periphery of the inner layers 2a and 12a, as the outer layers 2b and 12b, polypropylene (PP) resin is extrusion coated by, for example, a well-known extrusion coating method. Thereby, the resin-coated metal tube of the present invention is obtained. Since this outer layer is made of a hard, high-strength polypropylene resin to which no flame retardant is added, even greater damage resistance can be obtained. The outer layers 2b and 12b may be covered with a tape made of a polypropylene resin and wrapped around the outer periphery of the inner layer. Alternatively, a tube made of polypropylene resin may be prepared, and this may be covered with the outer periphery of the inner layer of the metal tubes 1 and 11 and coated by heating.

  The polypropylene resin is not particularly limited, and homo PP, random PP, block PP and the like can be used. In particular, since this resin is on the outer layer side, it is desirable to use one having an embrittlement temperature of −30 ° C. or lower. The reason is that when used outdoors, the bent part may be broken. In addition, a small amount of an inorganic filler (filler) can be added to this resin in order to improve surface printability so that a desired display or the like can be printed on the surface as necessary. The surface hardness of the outer layer thus obtained is 70 or less, more preferably 55 to 65 in Shore D hardness (JIS-6760). By setting it as this range, large damage resistance is ensured. For example, as a commercially available product, it is desirable to use a polymer obtained by polymerizing an appropriate amount of polyethylene (PE) with respect to the block PP (WS234, manufactured by Mitsui Chemicals), which is the same as that on the inner layer side.

  Further, in the present invention, various additives such as an ultraviolet absorber, an anti-aging agent, a coloring agent, an antistatic agent, an antifungal agent, an antifungal agent, an antifungal agent, and an inorganic filler such as talc are added to this polypropylene resin. Can be added as necessary.

  In the present invention, the metal pipe includes a bent pipe and a connecting joint. Furthermore, the shape is not limited to the case of FIGS.

<Examples and comparative examples>
Under the blending conditions shown in Tables 1 to 3, resin-coated metal tubes (Examples 1 to 12) that satisfy the requirements of the present invention, and resin-coated metal tubes that lack the requirements of the present invention (Comparative Examples 1 to 7), Manufactured as a sample. Specifically, a stainless steel (SUS304) flexible pipe having a diameter of 30.8 mm (25A type) as shown in FIG. 2 was prototyped, and this was first coated with an inner layer of the resin composition having the above requirements. . In addition, since the flexible tube is a corrugated tube, the thickness of the thick portion (convex portion) of the inner layer is 0.55 mm, and the thickness of the thin portion (concave portion) is 0.4 mm. Next, the outer layer was coated on the outer periphery of the inner layer. The outer layer has a thickness of 0.2 mm. These inner and outer layers were both formed by extrusion using an extruder.

The EEA used here has an ethyl acrylate content of 15% by mass and a melt flow rate (MFR) of 0.5 g / 10 min. EVA has a vinyl acetate content of 20% by mass and an MFR of 2.5 g / 10 min. The inner layer and outer layer polypropylene (PP) has a melt flow rate (MFR) of 5.0, density = 0.91, breaking strength = 29, elongation at break = 500, hardness (Rockwell) = 85, embrittlement temperature = -30 ° C., volume resistance = 2 × 10 ¹⁷ , stress crack => 1000 (WS234, manufactured by Mitsui Chemicals). The flame retardant magnesium hydroxide is X-22-1894 (manufactured by Shin-Etsu Silicone). The lubricant is erucic acid amide (manufactured by NOF Corporation). The ultraviolet absorber is Tinuvin 111FDL (manufactured by Ciba Specialty Chemicals). The anti-aging agent is Irganox 1010 (manufactured by Ciba Specialty Chemicals).

  Then, for each of these metal tubes, high temperature oil resistance, sheath cut property, sheath pullability (20 ° C. and −5 ° C.), flame retardancy, and trauma resistance were examined by the following methods. These are also shown in Tables 1 to 3. In addition, the numerical value of the compounding material in each table | surface shows a mass part number.

<High temperature oil resistance>
Each metal tube was bent 180 ° along a cylinder with a diameter of 60 mm, and immersed in soybean oil at 155 ° C. for 10 seconds in this state. This was tried 10 times, and the resin coating layer (sheath) with no tearing or cracking was accepted over the entire length, and a part with tearing or cracking was rejected.

<Sheath cut>
Using a commercially available sheet cutter, when the sheath is cut in the circumferential direction by rotating 10 cm from the end of the tube in a circumferential direction, the sheath is divided into two beautifully without being kinked (passed). Those in which the notch of the sheath was insufficiently connected or the cut surface of the sheath was kinked were regarded as defective (failed).

<Sheath pullability>
As described above, a test was conducted in which the sheath cut by the sheet cutter was pulled out manually at an ambient temperature of 20 ° C. and −5 ° C. If it is easy to pull out, it is good (indicated by “Easy” in the table), good if it can be pulled out (indicated by “Yes” in the table), and poor if it is difficult to pull out (“ On the other hand, when the sheath slips too much and easily comes out as much as 30 cm, it is regarded as defective (indicated by “over” in the table). In other words, even if a metal pipe such as a gas is slipped too much, operations such as laying and connection become difficult.

<Flame retardance>
Stand each metal tube vertically, tilt the burner at an angle of 45 °, indirect flame for 5 seconds, then release it if it does not continue to burn for more than 15 seconds, pass, and continue to burn for more than 15 seconds The case was rejected.

<Trauma resistance>
With respect to each metal tube, a pull-out test was performed using an apparatus (a narrow passage test apparatus) as shown in FIG. In this apparatus, three control panels each having a thickness of 12 mm and a hole with an inner diameter of 36 mm were installed at an interval of 450 mm, and the sample was pulled through a metal tube.
At this time, if the outer diameter of the metal tube is larger than the inner diameter of 36 mm of the hole of the device, the gap between the two becomes smaller, so that the outer periphery of the metal tube is easily caught. This time, in order to confirm the further improved damage resistance, the outer diameter of the metal tube is 30.8 mm (25A type) and the gap with the hole with an inner diameter of 36 mm is small, as described above, under more severe conditions. Tested. The height of the second panel hole is 150 mm higher than the left and right panel holes in the vertical direction (the amount of eccentricity is 150 mm). The length of the metal tube was 3 m, the drawing speed was 1 m / sec, and three tests were performed per sample. And by this drawing, it was set as the pass if there was no damage, a crack, and a tear in a sheath, and it was set as the failure if there was a damage, a crack, and a tear.

  From Tables 1 and 2 above, in the metal pipe (Examples 1 to 12) provided with a resin coating having a two-layer structure that satisfies the conditions of the present invention, high-temperature oil resistance, sheath cut property, sheath pull-out property, flame retardancy, It turns out that there is no problem in all of the trauma resistance.

On the other hand, it can be seen from Table 3 that there is a problem in any of the metal pipes (Comparative Examples 1 to 7) provided with a resin coating having a two-layer structure that lacks the requirements of the present invention.
That is, it can be seen that Comparative Examples 1-2 and 5-6 are problematic because the conditions for the base resin are lacking. In particular, in the case of Comparative Example 5, it can be seen that when the PP is too much (40 parts by mass), the sheath contracts at low temperatures, so that the sheath drawability (−5 ° C.) is greatly deteriorated. In Comparative Example 3, it is understood that the flame retardancy is rejected when the flame retardant magnesium hydroxide is low (5 parts by mass). On the contrary, Comparative Example 4 is a case where the amount of magnesium hydroxide as a flame retardant is large (60 parts by mass). In the case of the comparative example 7, since there is too much addition amount of a lubricant (3.5 mass parts), it turns out that there exists a problem because sheath drawability (20 degreeC) becomes large too much.

It is the longitudinal cross-sectional view which showed an example of the resin-coated metal tube which concerns on this invention. It is the vertical side view which showed the other example of the resin-coated metal pipe which concerns on this invention. It is the II sectional view taken on the line longitudinal axis of FIG. It is a schematic explanatory drawing of the apparatus (narrow place through-pipe test apparatus) for determining damage resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Metal pipe, 2 ... Resin coating layer, 2a ... Inner layer, 2b ... Outer layer, 11 ... Metal pipe, 12 ... Resin coating layer, 12a ... Inner layer, 12b ..Outer layer

Claims (6)

With respect to 100 parts by mass of a base resin consisting of 70 to 90 parts by mass of a polyolefin resin and 10 to 30 parts by mass of a polypropylene resin selected from an ethylene-ethyl acrylate copolymer or an ethylene-vinyl acetate copolymer A flame retardant resin composition comprising 10 to 50 parts by mass of a metal hydroxide of a flame retardant. The flame retardant resin composition according to claim 1, wherein 0.5 to 3 parts by mass of a lubricant having a surface lubricity effect is added to the flame retardant resin composition. A resin coating layer comprising two layers of an inner layer and an outer layer is provided on the outer periphery of the metal tube, the inner layer is the flame retardant resin composition according to claim 1 or 2, and the outer layer is a polypropylene resin. Resin-coated metal tube The resin-coated metal tube according to claim 3, wherein the polypropylene resin has an embrittlement temperature of -30 ° C or lower. 5. The resin-coated metal tube according to claim 3, wherein the metal tube is a flexible metal tube. 6. The resin-coated metal pipe according to claim 3, 4 or 5, wherein the metal pipe is a gas pipe.

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