Pipe fittings and their manufacturing methods

Abstract

To provide a pipe fitting with a high melt mass flow rate value, good formability, and excellent chemical resistance, its manufacturing method, and a piping structure using this pipe fitting.SOLUTION: A pipe fitting 1 has receptacle portions 20a, 20b, and 20c into which a pipe member is inserted, and a channel connecting the plurality of receptacle portions is formed therein. At least the portion in contact with the channel is composed of a resin composition (I). The resin composition (I) contains vinyl cyanide monomer units, diene monomer units, aromatic vinyl monomer units, and methacrylate monomer units. The methacrylic monomer unit content is equal to or lower than 30 mass% as determined by PGC / MS, and the total content of the vinyl cyanide monomer units and methacrylic monomer units is 35 to 80 mass%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pipe joint, a piping structure, and a method for manufacturing a pipe joint.

Background Art

[0002] Conventionally, it is common to prevent condensation around a pipe by covering the pipe made of a steel pipe or a synthetic resin pipe with a heat insulating material such as glass wool. However, in the above conventional method, since an operation of winding or covering a heat insulating material is required separately from the pipe work, the work efficiency is poor, and there are cases where the work cannot be carried out in a narrow work space. Therefore, resin pipe members and pipe joints having a foamed resin layer serving as a heat insulating layer have been proposed. By providing the heat insulating layer, it is possible to prevent condensation without covering with a heat insulating material after pipe construction.

[0003] In Patent Document 1, a pipe joint with a heat insulating layer is proposed, which has a heat insulating layer made of a foamed resin inside a main body portion, and the inner and outer walls of the main body portion surrounding the heat insulating layer and a connecting portion are integrally formed by injection molding. Patent Document 1 describes that a copolymer containing a rubber component excellent in impact resistance, a vinyl cyanide-based monomer unit, and an aromatic vinyl-based monomer unit is kneaded with polymethyl methacrylate, and further a foaming agent is added, and then the resin is injection molded to produce a pipe joint in which the surface of the foamed resin layer is covered with a non-foamed resin layer. As described in Patent Document 1, when an acrylic resin such as polymethyl methacrylate is blended, the pipe joint can be made transparent, and it becomes easier to visually recognize the connection state between the pipe member and the pipe joint.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, further investigation by the inventors revealed that when pipe fittings are manufactured using a resin composition containing polymethyl methacrylate in a copolymer of rubber components, vinyl cyanide monomer units, and aromatic vinyl monomer units, the melt mass flow rate decreases, which can impair moldability. Increasing the temperature makes it easier to ensure the fluidity necessary for molding. However, when injection molding a resin with a foaming agent added to form a non-foamed resin layer on the surface of a foamed resin layer, if the temperature is too high, foaming cannot be controlled, and the surface will not become a non-foamed resin layer.

[0006] Furthermore, since pipe fittings come into contact with various fluids, chemical resistance is required at least in the parts that come into contact with the flow path. The present invention has been made in view of the above circumstances, and aims to provide a pipe fitting with a high melt mass flow rate, good moldability, and excellent chemical resistance, a method for manufacturing the same, and a piping structure using this pipe fitting. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention employs the following configuration. [1] A pipe joint having a plurality of sockets into which a pipe member is inserted, and having a flow path formed inside that connects the plurality of sockets, At least the portion in contact with the flow path is made of resin composition (I), The resin composition (I) comprises a vinyl cyanide monomer unit, a diene monomer unit, an aromatic vinyl monomer unit, and a methacrylic monomer unit. The content of methacrylic monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 30% by mass or less relative to the total resin components of the resin composition (I). A pipe fitting wherein the total content of vinyl cyanide monomer units and methacrylic monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 35 to 80% by mass relative to the total resin components of the resin composition (I). [2] The pipe fitting according to [1], wherein the content of aromatic vinyl monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 30% by mass or less relative to the total resin components of the resin composition (I). [3] The pipe fitting according to [1] or [2], wherein the resin composition (I) contains acrylic rubber. [4] A pipe fitting according to any one of items [1] to [3], wherein the melt mass flow rate of the resin composition (I), measured at a test temperature of 220°C and a test load of 9.8N in accordance with JIS K 7210:1999, is 5 g / 10 min or more. [5] A pipe fitting according to any one of [1] to [4], comprising a surface layer composed of the resin composition (I) and a foamed resin layer covered by the surface layer, wherein the surface layer has a foaming ratio of 1.0 or more and less than 1.1 times, and the foamed resin layer has a foaming ratio of 1.1 times or more. A piping structure comprising a pipe fitting described in any one of items [6][1] to [5], and a pipe member inserted and connected to the socket portion of the pipe fitting. A method for manufacturing a pipe fitting according to any one of items [7][1] to [6], comprising: mixing a foaming agent with the powder or pellets of the resin composition (I) to obtain a foamed resin composition; and injection molding the obtained foamed resin composition. [8] A method for manufacturing a pipe fitting according to [7], wherein the powder or pellets of the resin composition (I) are dried and then mixed with the foaming agent. [Effects of the Invention]

[0008] The pipe fittings and piping structures of the present invention provide pipe fittings and piping structures with excellent chemical resistance. Furthermore, the manufacturing method of the pipe fittings of the present invention uses a resin composition with a high melt mass flow rate and excellent moldability, making manufacturing easy. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a pipe joint according to one embodiment of the present invention. [Figure 2]This is a plan view showing a piping structure related to one embodiment of the present invention. [Modes for carrying out the invention]

[0010] [Structure of pipe fittings] The pipe joint of the present invention has a structure in which a pipe member is inserted into a plurality of sockets, and a flow path is formed inside that connects the plurality of sockets. There is no limit to the number of receiving openings, but two or three are preferable. Figure 1 shows a pipe fitting 1 with three sockets according to one embodiment of the present invention.

[0011] As shown in Figure 1, the pipe fitting 1 of this embodiment is an example of a fitting used for connecting drain pipes (a three-way branched T-shaped pipe joint commonly referred to as a "tees"). The pipe fitting 1 has a first pipe axis O1 and a second pipe axis O2. The two pipe axes O1 and O2 intersect each other at an angle of 90.0° ± 1.1°. The pipe fitting 1 has a tubular main body portion 10 in which a flow path (for example, a drain flow path) is formed inside, and three receiving portions 20a, 20b, and 20c which are integrally formed with the main body portion 10.

[0012] The main body 10 has a foamed resin layer 30 and a non-foamed resin layer 50. Both sides of the foamed resin layer 30 are covered with the non-foamed resin layer 50. That is, the wall of the main body 10 has a three-layer structure with the non-foamed resin layer 50, the foamed resin layer 30, and the non-foamed resin layer 50 positioned from the flow path side. The receiving parts 20a, 20b, and 20c are formed of the non-foamed resin layer 50. That is, the walls of the receiving parts 20a, 20b, and 20c have a single-layer structure formed of the non-foamed resin layer 50. From the viewpoint of enhancing water stoppage performance, it is preferable that the receiving portions 20a, 20b, and 20c are transparent. That is, from the viewpoint of facilitating the confirmation of the connection state between the pipe joint 1 and the pipe member inserted and connected to the receiving portion thereof, the non-foamed resin layer 50 is preferably transparent. Here, "being transparent" means being transparent to such an extent that the inserted pipe and the adhesive applied to the inner surface of the receiving portion can be visually recognized from the outer surface of the receiving portion, and it may be translucent or colored transparent. More specifically, it is preferable that the haze of the receiving portion measured according to JIS K 7136:2000 is 1 or more and 70 or less, and more preferably 1 or more and 60 or less.

[0013] Cylindrical receiving portions 20a and 20b are provided at both ends in the direction of the first pipe axis O1 of the main body portion 10 forming a straight pipe, respectively. A cylindrical receiving portion 20c is provided in the opening 10c formed in the direction of the second pipe axis O2 of the main body portion 10. In the main body portion 10, an injection gate portion 14, which is a position where injection is performed during molding, is provided at a position facing the opening 10c across the first pipe axis O1.

[0014] The inner diameter R of the receiving portion 20a 20a is larger than the inner diameter R of the opening 10a of the main body portion 10 in order to insert and connect a pipe member with a foamed resin layer. Specificially, the ratio R 10a / R 20a / R 10a is preferably more than 1.0 and 2.0 or less, more preferably 1.2 or more and 1.8 or less, and even more preferably 1.4 or more and 1.6 or less. Similarly, the inner diameter R of the receiving portion 20b 20b is larger than the inner diameter R of the opening 10b of the main body portion 10. Specifically, the ratio R 10b / R 20b / R 10b is preferably more than 1 and 2.0 or less, more preferably 1.2 or more and 1.8 or less, and even more preferably 1.4 or more and 1.6 or less. Similarly, the inner diameter R of the receiving portion 20c 20c is larger than the inner diameter R of the opening 10c of the main body portion 10. 10cIt has a larger diameter than . Specifically, ratio R 20c / R 10c However, a value greater than 1 and less than or equal to 2.0 is preferred, a value between 1.2 and 1.8 is more preferred, and a value between 1.4 and 1.6 is even more preferred.

[0015] At the boundary between the receiving portion 20a and the main body portion 10, there is an inner diameter R 20a and inner diameter R 10a A step 12a is formed based on the difference between the two. The step 12a functions as a stopper to prevent the pipe member inserted into the receiving portion 20a from entering. The boundary between the receiving portion 20b and the main body portion 10 has an inner diameter R 20b and inner diameter R 10b A step 12b is formed based on the difference between the two. The step 12b functions as a stopper to prevent the pipe member inserted into the receiving portion 20b from entering. At the boundary between the receiving portion 20c and the main body portion 10, there is an inner diameter R 20c and inner diameter R 10c A step 12c is formed based on the difference between the two. The step 12c functions as a stopper to prevent the pipe member inserted into the receiving portion 20c from entering.

[0016] The step 12a is formed by a peripheral wall 13 located on the periphery of the opening 10a of the main body 10. The peripheral wall 13 is formed around the entire inner circumference of the cylindrical receiving portion 20a and is annular in shape. The step 12b is formed by a peripheral wall 13 located on the periphery of the opening 10b of the main body 10. The peripheral wall 13 is formed around the entire inner circumference of the cylindrical receiving portion 20b and is annular in shape. The step 12c is formed by a peripheral wall 13 located on the periphery of the opening 10c of the main body 10. The peripheral wall 13 is formed around the entire inner circumference of the cylindrical receiving portion 20c and is annular in shape.

[0017] The peripheral wall 13 is solid. The interior of the peripheral wall 13 is composed of a foamed resin layer 30, and the foamed resin layer 30 is covered by a non-foamed resin layer 50. It is preferable that a foamed resin layer 30 is formed around the entire circumference of the peripheral wall 13. When a foamed resin layer 30 is formed around the entire circumference of the peripheral wall 13, the base ends of the receiving portions 20a, 20b, and 20c also have thermal insulation properties, thereby further improving the thermal insulation properties of the pipe joint 1. If the pipe member inserted into the receiving portion 20a, 20b, or 20c is equipped with a foamed resin layer, it is preferable to provide an annular water-sealing member between the end face of the pipe member and the peripheral wall 13. Examples of annular water-sealing members include foamed packing.

[0018] If the foamed resin layer of the pipe member has open-cell structure, it is preferable to provide an annular water-sealing member between the end face of the pipe member and the peripheral wall 13. By providing a water-sealing member, it is possible to prevent drain water from entering the foamed resin layer of the pipe member. If the foamed resin layer of the pipe member has closed cells, it is not necessary to provide a water-sealing member between the end face of the pipe member and the peripheral wall 13. However, if the pipe member is cut at an angle, drain water may accumulate between the end face of the pipe member and the peripheral wall 13, so it is preferable to provide a water-sealing member.

[0019] The socket portion 20a extends from the base end 21a in the direction of the first pipe axis O1. The base end 21a is at the boundary between the socket portion 20a and the main body portion 10. The length of the socket portion 20a from the base end 21a to the open end 22a is L a It is. Length L a d is equal to the length of the receiving portion 20a. The thickness of the receiving portion 20a at the open end 22a is d a Thickness d a This is equal to the thickness of the socket portion 20a. The socket portion 20b extends from the base end 21b in the direction of the first pipe axis O1. The base end 21b is at the boundary between the socket portion 20b and the main body portion 10. The length of the socket portion 20b from the base end 21b to the open end 22b is L b It is. Length L b d is equal to the length of the receiving portion 20b. The thickness of the receiving portion 20b at the open end 22b is d b Thickness d b This is equal to the thickness of the socket portion 20b. The socket portion 20c extends from the base end 21c in the direction of the second pipe axis O2. The base end 21c is at the boundary between the socket portion 20c and the main body portion 10. The length of the socket portion 20c from the base end 21c to the open end 22c is L c It is. Length L c d is equal to the length of the receiving portion 20c. The thickness of the receiving portion 20c at the open end 22c is d c Thickness d c This is equal to the thickness of the socket portion 20c.

[0020] Length L from the base end 21a to the opening end 22a of the receiving portion 20a a And the thickness d of the receiving portion 20a at the opening end 22a. a The ratio to (hereinafter referred to as "L a / d a Also called the "ratio," the ratio is 2.0 or more and 10.0 or less, preferably 2.0 or more and 9.0 or less, more preferably 2.5 or more and 8.0 or less, even more preferably 3.0 or more and 7.0 or less, and particularly preferably 3.5 or more and 6.0 or less. L a / d a If the ratio is above the lower limit value, it is easier to suppress the penetration of the foamed resin layer 30 into the receiving portion 20a, and it is easier to suppress the decrease in strength of the receiving portion 20a. In addition, L a / d a If the ratio is greater than or equal to the lower limit value above, the length L of the receiving portion 20a a Because it is sufficiently long, the adhesive force of the pipe member inserted into the pipe joint 1 is sufficient, and the watertightness can be further enhanced.

[0021] L a / d a If the ratio is less than or equal to the above upper limit, then the thickness d a The thickness is sufficient, making the pipe joint 1 less susceptible to failure due to expansion and contraction fatigue. In addition, L a / d a If the ratio is less than or equal to the above upper limit, the length L a The length is not too long, making it easier for the resin forming the receiving portion 20a to fill to the end of the mold, thus reducing the likelihood of molding defects due to insufficient filling (also called "short"). In other words, L a / d aIf the ratio is below the above upper limit, the formability of the pipe joint 1 can be further improved. L a / d a The ratio can be adjusted by the shape of the molding die. L at the socket portion 20b of the pipe joint 1 b / d b The ratio is L a / d a It is similar to a ratio. L in the socket portion 20c of pipe joint 1 c / d c The ratio is L a / d a It is similar to a ratio.

[0022] The thermal resistance value of the main body 10 is preferably 0.04 K / W or higher, more preferably 0.05 K / W or higher and 0.50 K / W or lower, even more preferably 0.06 K / W or higher and 0.45 K / W or lower, particularly preferably 0.07 K / W or higher and 0.40 K / W or lower, and most preferably 0.08 K / W or higher and 0.35 K / W or lower. If the thermal resistance value of the main body 10 is above the lower limit, the thermal insulation performance of the pipe joint 1 can be further improved. If the thermal resistance value of the main body 10 is below the upper limit, the strength of the main body 10 is sufficient, and in addition, the pipe joint 1 can be made lighter. The thermal conductivity of the main body 10 can be lowered or the thickness (wall thickness) of the main body 10 can be increased by adjusting the composition and type of resin that makes up the pipe fitting 1, as well as the molding conditions of the pipe fitting 1.

[0023] The outer diameter of a typical drain pipe is 30mm to 80mm, and the wall thickness is approximately 5mm to 10mm. The wall thickness of the main body of the pipe fitting 1 used to connect such drain pipes is specified to be between 8mm and 20mm. The thermal resistance of the main body 10 is calculated using the following formula (1) from the thermal conductivity (W / m·K) measured in accordance with JIS A 1412-1:2016 and the thickness (m) of the main body 10 at the point where the thermal conductivity is measured. Thermal resistance (K / W) = Thickness (m) / Thermal conductivity (W / m·K) ... (1)

[0024] The pipe fitting of the present invention is not limited to the pipe fitting 1 described above, but may also be a pipe fitting having other shapes such as an elbow, nipple, or valve socket.

[0025] In the pipe fitting of the present invention, at least the portion in contact with the flow path is made of the resin composition (I) described below. In the case of pipe fitting 1, the inner surface of the main body portion 10 and the inner surfaces of the three receiving portions 20a, 20b, and 20c are the portions in contact with the flow path and are made of the resin composition (I). For ease of manufacture, it is preferable that the entire non-foamed resin layer 50 of the pipe joint of the present invention be a surface layer composed of resin composition (I). The monomer composition of the resin composition constituting the foamed resin layer 30 may be the same as or different from that of resin composition (I), but for ease of manufacturing, it is preferable that it be equivalent to that of resin composition (I).

[0026] The surface layer made of resin composition (I) preferably has a foaming ratio of 1.0 or more and less than 1.1 times. That is, it is preferable that there is no foaming or that the foaming ratio is low. This makes it difficult for the fluid in the flow path to penetrate into the interior of the pipe joint material. It is more preferable that the foaming ratio of the surface layer made of resin composition (I) is 1.0 or more and 1.05 or less.

[0027] Furthermore, the foaming ratio of the foamed resin layer 30 covered by the non-foamed resin layer 50, which is the surface layer, is preferably 1.1 times or more, more preferably 1.1 times or more and 5.0 times or less, and even more preferably 1.2 times or more and 3.0 times or less. If the foaming ratio of the foamed resin layer 30 is above a preferred lower limit, an insulating effect is achieved, making it easier to prevent condensation, etc. If the foaming ratio of the foamed resin layer 30 is below a preferred upper limit, the strength can be increased. The expansion ratio is measured in accordance with the method described in JIS K 9798:2006, 6.2(a) or 6.2(b). The expansion ratio can be adjusted depending on the type or amount of resin, the type or amount of foaming agent, and the manufacturing conditions.

[0028] In the foamed resin layer 30, it is preferable that multiple bubbles are formed, the bubble walls are substantially free of pores, and at least some of the multiple bubbles are independent bubbles that are not in communication with each other. A closed-cell ratio of 85% or higher is preferable, and 90% or higher is more preferable. While there is no particular upper limit, it is practically considered to be 99% or less. Within the above numerical range, a low thermal conductivity can be maintained over a long period, resulting in superior thermal insulation. The closed-cell ratio is measured in accordance with JIS K 7138:2006.

[0029] [Resin composition (I)] The resin composition (I) in the present invention comprises vinyl cyanide monomer units, diene monomer units which are rubber components, aromatic vinyl monomer units, and methacrylic monomer units. That is, the resin composition (I) in the present invention is a copolymer containing these monomer units, or a mixture of two or more polymers or copolymers.

[0030] In this specification, "monomer unit" refers to a structural part derived from the monomer compound (monomer) before polymerization. For example, "vinyl cyanide monomer unit" refers to a structural part derived from "vinyl cyanide monomer." The proportion of each monomer unit in the resin composition corresponds to the proportion of that monomer in the monomer mixture used to produce one type of copolymer contained in the resin composition, or the total proportion of that monomer used to produce each of the multiple polymers.

[0031] Examples of vinyl cyanide monomer units include monomer units based on acrylonitrile, methacrylonitrile, and the like. Among these, monomer units based on acrylonitrile are preferred. Examples of aromatic vinyl monomer units include monomer units based on styrene, α-methylstyrene, β-methylstyrene, 4-methylstyrene, β-bromostyrene, etc. Among these, monomer units based on styrene and α-methylstyrene are preferred. Examples of methacrylic monomer units include monomer units based on methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, etc. Among these, monomer units based on methyl methacrylate are preferred.

[0032] Examples of diene monomer units used as rubber components include monomer units based on 1,3-butadiene, isoprene, 1,3-pentadiene, chloroprene, 2-ethylbutadiene, and 2-phenylbutadiene. Among these, monomer units based on 1,3-butadiene, isoprene, 1,3-pentadiene, and 2-phenylbutadiene are preferred.

[0033] In this specification, the content of each monomer unit in the resin composition is the content based on the mass of the corresponding monomer determined by analysis using pyrolysis gas chromatography-mass spectrometry (hereinafter also referred to as "PGC / MS"). The following is an example of measurement conditions using PGC / MS. (Measurement conditions) ·Device Pyrolysis apparatus: PY-2020iD (Frontier Lab Co., Ltd.). Gas chromatograph: GC 2010 (Shimadzu Corporation). Mass spectrometer: GCMS-QP 2010 (Shimadzu Corporation). • Thermal decomposition conditions Pyrolysis temperature: 550℃. Interface temperature: 250℃. • Gas chromatography conditions. Carrier flow rate: 1 ml / min (He). Split ratio: 100:1. Separation column: DB-1 (1.00 μm, 0.25 mmφ × 30 m). Oven temperature: 40°C (3 min) - 320°C (10 min). ·Mass spectrometry conditions Interface temperature: 250℃. Ionization temperature: 220°C. Mass range: 28~700 m / s. Voltage: 1.2kV.

[0034] This section describes a method for calculating the content of each monomer unit in a resin composition using PGC / MS measurement. First, each monomer unit constituting the resin composition is thermally decomposed and separated by thermal gas chromatography to obtain a thermal decomposition pattern (pyrogram) in which the monomers from which each monomer unit originated are recorded as peaks. Next, for each peak in the thermal decomposition pattern, the monomer is identified by the mass spectrum obtained using a mass spectrometer.

[0035] Here, since the depolymerization rate by thermal decomposition (the rate at which a polymer decomposes into monomers) differs depending on the type of monomer unit, the peak area (Z) of each monomer unit is obtained by dividing the area of ​​each peak (X) in the pyrogram by the depolymerization rate (Y) of each monomer unit by thermal decomposition. The depolymerization rates (Y) of each monomer unit are as follows: monomer unit based on acrylonitrile, which is a vinyl cyanide monomer unit: 0.15; monomer unit based on diene monomer units: 0.10; monomer unit based on styrene, which is an aromatic vinyl monomer unit: 1.0. Furthermore, the depolymerization rate of monomer units based on methyl methacrylate, which is a methacrylic monomer unit, is 1.0 if it exists as a resin such as polymethyl methacrylate before thermal decomposition. Furthermore, the depolymerization rate of monomer units based on acrylic acid ester, which is an acrylic rubber, is 1.0 if it exists as an acrylic acid ester copolymer resin before thermal decomposition.

[0036] Then, the ratio (Z / T) of the peak areas (Z) of each component in the thermal decomposition pattern to the sum (T) is defined as the monomer content (mass%) in the resin composition. In other words, the content of each monomer unit in the total resin component in the present invention is the ratio of the mass of each monomer to the total mass of all monomers constituting the resin composition.

[0037] The content of methacrylic monomer units in the total resin components of resin composition (I) is 30% by mass or less, preferably 0.1 to 30% by mass, more preferably 0.5 to 28% by mass, and even more preferably 0.5 to 22% by mass. By having a methacrylic monomer unit content of 30% by mass or less, a resin composition with a high melt mass flow rate and good moldability can be obtained. By having a methacrylic monomer unit content above a preferred lower limit, transparency can be easily achieved.

[0038] The total content of vinyl cyanide monomer units and methacrylic monomer units in the total resin components of resin composition (I) is 35 to 80% by mass, preferably 40 to 80% by mass, more preferably 45 to 80% by mass, and even more preferably 45 to 75% by mass. Chemical resistance is obtained when the total content of vinyl cyanide monomer units and methacrylic monomer units is 35% by mass or more. When the total content of vinyl cyanide monomer units and methacrylic monomer units is 80% by mass or less, a resin composition with a high melt mass flow rate and good moldability can be obtained.

[0039] The content of vinyl cyanide monomer units in the total resin components of resin composition (I) is preferably 5 to 70% by mass, more preferably 30 to 70% by mass, even more preferably 40 to 70% by mass, and particularly preferably 50 to 70% by mass. Having a vinyl cyanide monomer content above a preferred lower limit makes it easier to obtain good chemical resistance. Having a vinyl cyanide monomer content below a preferred upper limit makes it easier to obtain good impact resistance.

[0040] The content of diene monomer units in the total resin components of resin composition (I) is preferably 5 to 40% by mass, more preferably 15 to 35% by mass, and even more preferably 30 to 35% by mass. Having a diene monomer content above a preferred lower limit makes it easier to obtain good impact resistance. Having a diene monomer content below a preferred upper limit makes it easier to obtain good chemical resistance.

[0041] The resin composition (I) preferably contains acrylic rubber. Examples of acrylic rubber include acrylic acid esters such as methyl acrylate, ethyl acrylate, and butyl acrylate, which may be included in the resin composition (I) as copolymers with vinyl cyanide monomer units, diene monomer units, or tacryl monomer units. The acrylic rubber content in the total resin components of resin composition (I) is preferably 0.1 to 5% by mass, more preferably 0.3 to 3% by mass, and even more preferably 0.5 to 1% by mass. When the acrylic rubber content is above a preferred lower limit, the affinity with other monomer units is increased, making it easier to ensure chemical resistance even with a higher content of diene monomer units, which are rubber components. When the acrylic rubber content is below a preferred upper limit, good moldability is easily obtained.

[0042] The content of aromatic vinyl monomer units in the total resin components of resin composition (I) is preferably 5 to 30% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 13% by mass. When the content of aromatic vinyl monomer units is above a preferred lower limit, it is easier to achieve a higher melt mass flow rate and improve moldability. When the content of aromatic vinyl monomer units is below a preferred upper limit, it is easier to obtain better chemical resistance.

[0043] The resin composition (I) may contain other monomer units other than vinyl cyanide monomer units, diene monomer units, aromatic vinyl monomer units, and methacrylic monomer units, to the extent that it does not impair the effects of the present invention. Other monomeric units include N-phenylmaleimide and glycidyl methacrylate. The content of other monomer units in the total resin components of resin composition (I) is preferably less than 5% by mass, and more preferably less than 1% by mass. In other words, the total content of vinyl cyanide monomer units, diene monomer units, aromatic vinyl monomer units, and methacrylic monomer units in the resin composition (I) is preferably 95% by mass or more, and more preferably 99% by mass or more.

[0044] The resin composition (I) may contain components other than monomer units, i.e., components other than resin components, to the extent that they do not impair the effects of the present invention.

[0045] According to JIS K 7210:1999, the melt mass flow rate (hereinafter also referred to as "MFR") of resin composition (I), measured at a test temperature of 220°C and a test load of 9.8 N (test load of 10 kg), is preferably 5 g / 10 min or more, preferably 5 g / 10 min to 90 g / 10 min, more preferably 10 g / 10 min to 80 g / 10 min, even more preferably 15 g / 10 min to 70 g / 10 min, and particularly preferably 20 g / 10 min to 60 g / 10 min.

[0046] If the MFR of the resin composition (I) is above the lower limit, it is easier to fill the mold to the ends when manufacturing the pipe fitting 1, and molding defects due to insufficient filling, which are particularly likely to occur at the socket portion, are less likely to occur. In other words, if the MFR of the pipe fitting 1 is above the lower limit, the moldability of the pipe fitting 1 can be further improved. If the MFR of the pipe fitting 1 is below the upper limit, the molecular weight is not too low, and it has excellent strength and chemical resistance.

[0047] Preferred embodiments of the resin composition (I) include, for example, the following: A: A resin composition obtained by mixing a copolymer obtained by polymerizing methyl methacrylate onto ABS resin with acrylic rubber made of acrylic acid ester or acrylic rubber made of a copolymer of acrylic acid ester and methyl methacrylate. (i) A resin composition obtained by mixing ABS resin with acrylic rubber made of a copolymer of styrene and methyl methacrylate and an acrylic acid ester, or acrylic rubber made of a copolymer of an acrylic acid ester and methyl methacrylate. U: A resin composition obtained by mixing ABS resin, methyl methacrylate, and acrylic rubber made of an acrylic acid ester, or acrylic rubber made of a copolymer of an acrylic acid ester and methyl methacrylate. E: A resin composition obtained by mixing polymethyl methacrylate with a copolymer of acrylonitrile, butadiene, styrene, and an acrylic acid ester. The above-mentioned ABS resin may be a resin composition obtained by physically mixing an acrylonitrile-styrene-methyl methacrylate copolymer with polybutadiene, a resin obtained by grafting methyl methacrylate, styrene, and acrylonitrile onto polybutadiene, or a resin obtained by emulsion polymerization of the four monomers that make up acrylonitrile, butadiene, methyl methacrylate, and styrene.

[0048] [Method of manufacturing pipe fittings] The method for manufacturing a pipe fitting according to the present invention involves mixing a foaming agent with powder or pellets of resin composition (I) to obtain a foamed resin composition, and then injection molding the obtained foamed resin composition. The inside of the molded product obtained by this method becomes a foamed resin layer due to heating during injection molding, but the surface layer becomes a so-called skin layer with a low foaming ratio, i.e., a non-foamed resin layer.

[0049] It is preferable to pre-dry the powder or pellets of resin composition (I) and then mix in the foaming agent. By drying the material before mixing in the foaming agent, the generation of unintended air bubbles inside and on the surface of the joint due to moisture evaporated in the molding machine can be suppressed, thereby preventing a decrease in the transparency of the socket and a decrease in the strength of the main body. Drying methods include using a hot air dryer such as a hopper dryer or a box-type drying oven. The temperature for hot air drying is preferably 60-90°C, and the drying time is preferably 2-6 hours.

[0050] Either a volatile foaming agent or a decomposing foaming agent may be used as the foaming agent. Examples of volatile blowing agents include aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, ethers, and ketones. Examples of aliphatic hydrocarbons include propane, butane (n-butane, isobutane), and pentane (n-pentane, isopentane, etc.), while examples of alicyclic hydrocarbons include cyclopentane and cyclohexane. Examples of halogenated hydrocarbons include one or more halogenated hydrocarbons such as trichlorofluoromethane, trichlorotrifluoroethane, tetrafluoroethane, chlorodifluoroethane, and difluoroethane. Examples of ethers include dimethyl ether and diethyl ether, and examples of ketones include acetone and methyl ethyl ketone.

[0051] Examples of decomposition-type blowing agents include inorganic blowing agents such as sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium nitrite, azide compounds, and sodium boride, and organic blowing agents such as azodicarbonamide, barium azodicarboxylate, and dinitrosopentamethylenetetramine. In addition, gases such as carbon dioxide, nitrogen, and air may be used as blowing agents. From the viewpoint of superior foaming performance, decomposing foaming agents are preferred, and among them, sodium bicarbonate and azodicarbonamide are more preferred. These may be used individually, or two or more may be used in combination. The amount of foaming agent added is preferably 0.1 parts by mass or more and 8 parts by mass or less, more preferably 1 part by mass or more and 5 parts by mass or less, and even more preferably 1 part by mass or more and 3 parts by mass or less, per 100 parts by mass of resin composition (I).

[0052] In injection molding, the temperature of the foamed resin composition immediately before injection into the mold (molding temperature) is preferably 200°C to 280°C, and more preferably 220°C to 260°C. When the molding temperature is within the above numerical range, the foamed resin composition is sufficiently melted, and good fluidity of the foamed resin composition is obtained. Furthermore, if the foamed resin composition contains acrylic resin, the transparency of the pipe fitting 1 can be increased by having the molding temperature above the lower limit. The molding time in the mold is preferably between 1 minute and 10 minutes. If the molding time in the mold is above the lower limit, the foamed resin composition can be sufficiently cured. If the molding time in the mold is below the upper limit, the productivity of the pipe fitting 1 can be easily improved.

[0053] The pipe fitting according to the present invention may be manufactured by a manufacturing method other than the one described above. For example, a foaming agent may be mixed with the powder or pellets of resin composition (I) to obtain a foaming resin composition, and the obtained foaming agent resin composition may be extruded. In the case of extrusion molding, the foamable resin composition is heated and melted, injected into a mold from an extruder, and heated at a desired temperature for a desired time to foam and mold the foamable resin composition. After cooling at a desired temperature for a desired time, a pipe fitting having a predetermined foaming ratio is obtained by cutting it to a predetermined length. The inside of the molded product obtained by this method becomes a foamed resin layer due to heating during extrusion molding, but the surface layer becomes a so-called skin layer with a low foaming ratio, i.e., a non-foamed resin layer. In the case of extrusion molding, for the same reasons as in injection molding, it is preferable to dry the powder or pellets of resin composition (I) beforehand and then mix in the foaming agent.

[0054] The pipe fitting according to the present invention may be manufactured by multilayer molding in which a layer of resin composition containing a foaming agent is sandwiched between layers of a pair of resin compositions (I) that do not contain a foaming agent. Alternatively, it may be manufactured by multilayer molding in which a layer of resin composition containing a foaming agent is laminated on one side (opposite the flow path) of a layer made of resin composition (I) that does not contain a foaming agent. In these multilayer moldings, the resin composition containing the foaming agent may be a foamed resin composition obtained by mixing the foaming agent with resin composition (I), or it may be a foamed resin composition obtained by mixing the foaming agent with a resin composition different from resin composition (I). Alternatively, it may be manufactured using only a resin composition (I) that does not contain a foaming agent.

[0055] [Piping structure] The piping structure of the present invention comprises a pipe joint of the present invention and a pipe member inserted and connected to the socket portion of the pipe joint. A piping structure according to an embodiment of the present invention will be described based on the drawings. As shown in Figure 2, the piping structure 100 comprises a pipe joint 1 and three pipe members 201, 202, and 203. The pipe member is not particularly limited and can be any pipe member that can be connected to the pipe joint of the present invention. The pipe member may be a steel pipe or a synthetic resin pipe. From the viewpoint of excellent heat insulation, a synthetic resin pipe is preferred as the pipe member, and a synthetic resin pipe having a foamed layer is more preferred. The foamed layer may be a continuous cell where the bubbles are in communication with each other, or a closed cell where the bubbles are not in communication with each other.

[0056] In this embodiment, pipe member 201 is inserted into and connected to the socket portion 20a of pipe joint 1 along the direction of the first pipe axis O1. Pipe member 202 is inserted into and connected to the socket portion 20b of pipe joint 1 along the direction of the first pipe axis O1. Pipe member 203 is inserted into and connected to the socket portion 20c of pipe joint 1 along the direction of the second pipe axis O2. Outer diameter R of pipe member 201 201 The inner diameter R of the receiving portion 20a 20a It is slightly smaller than that. Note that the inner diameter R of the receiving portion 20a referred to here. 20a This refers to the inner diameter of the receiving end of the receiving portion 20a, and the ratio R 201 / R 20a A value of 0.986 to 0.997 is preferable. Outer diameter R of pipe member 202 202 The inner diameter R of the receiving portion 20b 20b It is slightly smaller than that. Note that the inner diameter R of the receiving portion 20b referred to here. 20bThis refers to the inner diameter of the receiving end of the receiving portion 20b, and the ratio R 202 / R 20b A value of 0.986 to 0.997 is preferable. Outer diameter R of pipe member 203 203 The inner diameter R of the receiving portion 20c 20c It is slightly smaller than that. Note that the inner diameter R of the receiving portion 20c referred to here. 20c This refers to the inner diameter of the receiving end of the receiving portion 20c, and the ratio R 203 / R 20c A value of 0.986 to 0.997 is preferable.

[0057] The piping structure 100 functions as a connection point for the piping used to drain the drain. In addition, the piping structure 100 functions as a branch point for the piping used to drain the drain.

[0058] [Manufacturing method for piping structures] The method for manufacturing the piping structure is not particularly limited, and the piping structure of the present invention can be obtained by inserting a pipe member into the socket portion of the pipe joint of the present invention and connecting them. The method for connecting the pipe joint and the pipe member is not particularly limited, and they may be connected using an adhesive, or they may be connected without using an adhesive by installing a water-sealing member such as a rubber gasket between the inner surface of the socket portion of the pipe joint and the outer surface of the pipe member.

[0059] In the piping structure 100 of this embodiment, the pipe fitting 1 and the pipe members 201, 202, and 203 are connected using adhesive. By connecting the pipe fitting and the pipe members using adhesive, the watertightness and strength of the piping structure can be further enhanced. The adhesive used to connect pipe fittings and pipe members is not particularly limited, and known adhesives such as instant adhesives and hot melt adhesives can be used.

[0060] The piping structure of this embodiment, equipped with the pipe fittings of this embodiment, offers excellent heat insulation. In addition, the piping structure of this embodiment is superior in strength because it is equipped with the pipe fittings of this embodiment. Furthermore, the piping structure of this embodiment, equipped with the pipe fittings of this embodiment, offers excellent watertightness. [Examples]

[0061] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1-3, 5, and 7 are for reference only. The raw materials and evaluation methods used in each example and comparative example are as follows.

[0062] [Example 1] A non-foaming resin composition was obtained by heating and kneading acrylonitrile monomer, styrene monomer, polybutadiene (Asahi Kasei Corporation, Diene 35NF), methyl methacrylate monomer, and butyl acrylate in the presence of a polymerization initiator. At this time, the non-foaming resin composition was kneaded in a ratio such that the content of each monomer unit, as measured by PGC / MS, is as shown in Table 1. This non-foaming resin composition was formed into pellets and dried at 70°C for 2 hours using a known hot air dryer. ADCA (manufactured by Otsuka Chemical Co., Ltd., trade name "AZ-HM", azodicarbonamide) was mixed with the dried pelletized non-foaming resin composition as a foaming agent to obtain a foaming resin composition. A two-layer pipe fitting of the DV type, as shown in Figure 1, was manufactured by injecting a predetermined amount of the obtained non-foaming resin composition into the mold cavity from the injection gate 14 using a first injection molding machine, then injecting the obtained foaming resin composition into the mold cavity from the injection gate 14 using a second injection molding machine, and finally injecting a predetermined amount of the non-foaming resin composition into the mold cavity from the injection gate 14 again using the first injection molding machine. The receiving portion, which is the end of the mold cavity, is made of a solid non-foaming resin layer, with a thickness of 3.0 mm between the inner and outer wall surfaces at the end of the receiving portion and a length of 22 mm. The main body portion, where the foaming resin is covered with the non-foaming resin inside the mold cavity, has a thickness of 10 mm between the inner and outer wall surfaces and a foaming resin layer with a foaming ratio of 1.8 times. The receiving portion has an inner diameter of 48.3 mm.

[0063] The meanings of the abbreviations in Table 1 are shown below. A: monomer content based on acrylonitrile, B: Content of diene rubber components, S: Content of monomer units based on styrene, MMA: monomer unit content based on methyl methacrylate. A+MMA: Total content of monomer units based on acrylonitrile and monomer units based on methyl methacrylate.

[0064] [Example 2] A non-foaming resin composition was obtained in the same manner as in Example 1, except that acrylonitrile monomer, styrene monomer, polybutadiene, methyl methacrylate monomer, and butyl acrylate were kneaded in ratios such that the content of each monomer unit, obtained by PGC / MS measurement, was as shown in Table 1. This non-foaming resin composition was formed into pellets and dried at 60°C for 4 hours using a known hot air dryer. ADCA (manufactured by Otsuka Chemical Co., Ltd., trade name "AZ-HM", azodicarbonamide) was mixed with the dried pelletized non-foaming resin composition as a foaming agent to obtain a foaming resin composition. The obtained foamed resin composition was injected into a gas-filled and pressurized mold cavity at a molding temperature of 240°C, and then the gas in the mold cavity was removed to reduce the pressure and cause foaming. This resulted in the production of a pipe fitting of the DV type shown in Figure 1, in which the socket portion is solid, consisting of a non-foamed resin layer, the thickness between the inner and outer wall surfaces at the end of the socket portion is 3.0 mm, the length of the socket portion is 22 mm, the thickness between the inner and outer wall surfaces of the main body portion is 10 mm, and the foamed resin layer has a foaming ratio of 1.8 times, with a skin layer (non-foamed resin layer) formed on the surface of the socket portion.

[0065] [Examples 3, 5-7, Comparative Examples 1, 2] A pipe fitting with a skin layer (non-foamed resin layer) formed on its surface was manufactured in the same manner as in Example 2, except that acrylonitrile monomer, styrene monomer, polybutadiene, methyl methacrylate monomer, and butyl acrylate were kneaded in ratios such that the content of each monomer unit, obtained by PGC / MS measurement, was as shown in Table 1.

[0066] [Example 4] A two-layer pipe fitting was manufactured in the same manner as in Example 1, except that acrylonitrile monomer, styrene monomer, polybutadiene, methyl methacrylate monomer, and butyl acrylate were kneaded in ratios such that the content of each monomer unit, obtained by PGC / MS measurement, was as shown in Table 1.

[0067] [MFR measurement] The MFR of the pipe fittings manufactured in each example was measured according to JIS K 7210:1999, at a test temperature of 220°C and a test load of 9.8N. The results are shown in Table 1.

[0068] [Evaluation of chemical resistance] Test specimens were obtained by injection molding the non-foaming resin compositions used in the above examples and comparative examples into dumbbell shapes with a length of 200 mm. The obtained test specimens were fixed to a bending jig prepared to apply an expansion and contraction stress of 3 MPa in a room at 23°C, and a 10 mm x 20 mm piece of cotton soaked in 2 mL of polyethylene glycol (Nacalai Tesque #200, average molecular weight 190-210) was placed on the center of the test specimen. Three test specimens were prepared for each example, and one of the three test specimens was left for 36 hours, after which the cotton was removed and visually inspected. The other two test specimens were left for 72 hours, after which the cotton was removed and visually inspected to evaluate their chemical resistance. Chemical resistance was evaluated by checking for cracks in the test specimen according to the evaluation criteria below. The results are shown in Table 1. (Evaluation Criteria) ○: No fracture or cracking occurred even after 72 hours. △: Fracture and cracking occurred after a display period of 1 hour or more but less than 72 hours. ×: Fracture and cracking occurred within 1 hour of placement.

[0069] [Evaluation of moldability] Based on the above examples and comparative examples, 10 pipe fittings were manufactured for each example, and the socket portion of the pipe fittings was visually inspected for any molding defects (mainly short circuits caused by insufficient resin filling to the end of the mold). The moldability was evaluated according to the evaluation criteria below. The results are shown in Table 1. (Evaluation Criteria) ○: No molding defects in any of the 10 pieces. ×: One or more molding defects present.

[0070] [Table 1]

[0071] As shown in Table 1, the pipe fittings in each embodiment had a sufficiently large MFR, good moldability, and excellent chemical resistance. In contrast, Comparative Examples 1 and 2 were insufficient in either moldability or chemical resistance. [Explanation of symbols]

[0072] 1. Pipe fittings 10 Main body 20a, 20b, 20c socket 30 Foamed resin layer 50 Non-foamed resin layer

Claims

1. A method for manufacturing a pipe joint having a plurality of sockets into which a pipe member is inserted, and having a flow path formed inside that connects the plurality of sockets, The pipe joint is made of a resin composition (I) in at least the portion that is in contact with the flow path. The resin composition (I) comprises a vinyl cyanide monomer unit, a diene monomer unit, an aromatic vinyl monomer unit, and a methacrylic monomer unit. The content of methacrylic monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 30% by mass or less relative to the total resin components of the resin composition (I). The content of vinyl cyanide monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 39% by mass or more relative to the total resin components of the resin composition (I). The content of diene monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 30% by mass or more relative to the total resin components of the resin composition (I). A method for manufacturing a pipe fitting, wherein the total content of vinyl cyanide monomer units and methacrylic monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 40% by mass or more relative to the total resin components of the resin composition (I).

2. The method for manufacturing a pipe fitting according to Claim 1, wherein the powder or pellets of the resin composition (I) are dried by hot air drying at 60 to 90°C for 2 to 6 hours, a foaming agent is mixed with the dried powder or pellets of the resin composition (I) to obtain a foaming agent resin composition, and the obtained foaming agent resin composition is injection molded.

3. A pipe joint having a plurality of sockets into which pipe members are inserted, and having a flow path formed inside that connects the plurality of sockets, At least the portion in contact with the flow path is made of resin composition (I), The resin composition (I) comprises a vinyl cyanide monomer unit, a diene monomer unit, an aromatic vinyl monomer unit, and a methacrylic monomer unit. The content of methacrylic monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 30% by mass or less relative to the total resin components of the resin composition (I). The content of vinyl cyanide monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 39% by mass or more relative to the total resin components of the resin composition (I). The content of diene monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 30% by mass or more relative to the total resin components of the resin composition (I). A pipe fitting in which the total content of vinyl cyanide monomer units and methacrylic monomer units, as determined by pyrolysis gas chromatography-mass spectrometry (PGC / MS), is 40% by mass or more relative to the total resin components of the resin composition (I).

4. The pipe fitting according to claim 3, wherein the haze of the socket portion, as measured according to JIS K 7136:2000, is 1 or more and 70 or less.

5. The pipe fitting according to claim 3 or 4, wherein the resin composition (I) comprises acrylic rubber.

6. A pipe fitting according to any one of claims 3 to 5, wherein the melt mass flow rate of the resin composition (I), measured at a test temperature of 220°C and a test load of 9.8 N in accordance with JIS K 7210:1999, is 5 g / 10 min or more.

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