JP7269133B2 - multilayer pipe - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer pipe suitable for use as an air conditioning drain piping material.

With the advancement of building technology, various properties are required for piping materials for air-conditioning drains that are laid around buildings. In particular, high fire resistance is required in order to use such piping materials in fireproof compartments.

Under such circumstances, as a refractory pipe material, a pipe containing thermally expandable graphite is known. In the event of a fire, the thermally expandable graphite is exposed to high temperatures, causing it to foam and expand the piping material. As a result, the inside of the piping becomes partially blocked, blocking the flow of air inside the piping and preventing the fire from spreading further, resulting in high fire resistance ( For example, see Patent Document 1).

However, while such piping materials are excellent in fire resistance, their insulation performance is insufficient, so condensation easily occurs due to the passage of waste water or environmental conditions, and condensation stains the walls and ceilings of buildings. There is a problem that arises.

In order to prevent the occurrence of such dew condensation, we are investigating a piping material that has a multi-layered structure in which a fire-resistant pipe is provided with a highly insulating foam layer. However, if too much graphite is put in the outer layer, the graphite in the outer layer will expand excessively when it burns. Leakage and fire resistance are less likely to occur. Furthermore, when the content of the thermally expandable graphite is large, the thermally expandable graphite itself tends to become a crack starting point, and the impact resistance of the outer layer tends to deteriorate.

Also, if too much heat-expandable graphite is added to the foam layer, the heat-expandable graphite tends to interfere with foaming and affect the expansion ratio. And it becomes difficult to maintain dew condensation prevention performance.
As a result, it became difficult to add a large amount of thermally expandable graphite to the foam layer, and when a fire resistance test was conducted, the desired fire resistance tended to be inferior.

Under these circumstances, when using a multi-layer pipe with a foam layer as a piping material for air conditioning drains, it is necessary to pass through the fireproof compartment in order to satisfy the fireproof performance required to pass the certification of the Minister of Land, Infrastructure, Transport and Tourism, firefighting rating, etc. Special treatment is required. As such a special treatment, it is common to wrap a refractory material around the piping to provide a refractory layer.

However, the refractory material to be wrapped around the pipe is expensive, and the work of wrapping the refractory material is also required, which poses problems in terms of both cost and labor.

As described above, piping material containing thermally expandable graphite has a problem of insufficient heat insulation, and piping material having a foam layer has a problem of insufficient fire resistance.

Japanese Patent No. 4440290

In view of the circumstances as described above, it is an object of the present invention to provide a multi-layer pipe having fire resistance and heat insulation performance and a certain level of strength.

The present inventors have made intensive studies to achieve the above object, and as a result, have found that a multi-layer pipe having an inner layer, a foamed layer and an outer layer, wherein the content of thermally expandable graphite in each of the inner layer, the foamed layer and the outer layer, Also, by setting the content of thermally expandable graphite in the entire multilayer pipe to a specific range, it was found that a multilayer pipe having fire resistance, heat insulation performance and strength can be obtained.
The inventors of the present invention conducted further studies based on such knowledge, and completed the present invention.

That is, the present invention provides the following multilayer pipe.
[1] A multilayer pipe having an inner layer, a foam layer, and an outer layer, wherein the inner layer, the foam layer, and the outer layer each contain a thermoplastic resin, the multilayer pipe contains thermally expandable graphite, and the The content of the thermally expandable graphite is 5 to 16% by mass based on the total amount of the inner layer, the content of the thermally expandable graphite is 0 to 5% by mass based on the total amount of the foam layer, and the thermally expandable graphite is based on the total amount of the outer layer. content is 0 to 2% by mass, and the content of the thermally expandable graphite is 2 to 7% by mass based on the total amount of the multilayer tube.
[2] The multilayer pipe according to [1] above, wherein the thermoplastic resin contains a polyvinyl chloride resin.
[3] The multilayer pipe according to [1] or [2] above, wherein the outer diameter (D) of the multilayer pipe is 30 mm or more and 120 mm or less.
[4] The multi-layer pipe according to any one of [1] to [3] above, wherein the expansion ratio of the foamed layer is 2 to 8 times.

The multi-layer pipe of the present invention is excellent in fire resistance, heat insulation performance and strength.

1 is an example of a cross-sectional view of a multi-layer pipe of the present invention; FIG. 1 is a plan view of an example of a multi-layer pipe manufacturing apparatus according to the present invention; FIG. 1 is a front view of an example of a multi-layer tube manufacturing apparatus of the present invention; FIG. 1 is a configuration diagram showing an example of a mold and a tube for forming the outer surface of a pipe used in the multi-layer pipe manufacturing apparatus of the present invention. FIG.

(Inner layer, foam layer and outer layer in multilayer pipe)
The multi-layer pipe of the present invention has an inner layer, a foam layer and an outer layer. FIG. 1 shows an example of a cross-sectional view of a multi-layer pipe of the present invention. The multi-layer pipe 10' has a multi-layer structure in which an inner layer 1, a foam layer 2 and an outer layer 3 are laminated in this order from the inside. is.

The inner layer, foam layer and outer layer each comprise a thermoplastic resin. The thermoplastic resins forming these three layers may all be the same thermoplastic resin, or may be different thermoplastic resin materials for each of the three layers.
The multi-layer pipe of the present invention has at least three layers of an inner layer, a foam layer, and an outer layer. A layer other than three layers may be provided to form four or more layers. Other layers are optionally provided between the inner layer and the foam layer, between the foam layer and the outer layer, and the like. Above all, it is preferable that the multi-layer pipe of the present invention is composed of three layers, an inner layer, a foam layer and an outer layer.

A wide range of known thermoplastic resins can be used as the thermoplastic resin, and there is no particular limitation. Specifically, polyolefin-based resins such as polyethylene-based resins, polypropylene-based resins, and polybutene-based resins, polyolefin-based copolymers such as ethylene-propylene copolymers and ethylene-ethyl acrylate copolymers, polyvinyl chloride-based resins, Polystyrene resin, polyethylene terephthalate, ABS resin, acrylic resin, etc. can be used. These may be used individually by 1 type, and may be used in mixture of 2 or more types. Among these, the thermoplastic resin preferably contains a polyvinyl chloride-based resin from the viewpoint of improving flame retardancy. The polyvinyl chloride resin may be contained in some of the inner layer, foam layer and outer layer, but is preferably contained in all layers.

Among the thermoplastic resins described above, polyvinyl chloride resins are preferably used for the outer layer and the inner layer in particular because of their excellent flame retardancy. In particular, as the material of the outer layer, it is preferable to adopt a polyvinyl chloride-based resin because it is easy to connect with a pipe joint or the like.

The polyvinyl chloride resin to be used includes not only polyvinyl chloride resin, which is a homopolymer of vinyl chloride monomers, but also other monomers that can be copolymerized with vinyl chloride monomers and vinyl chloride monomers. It is also preferred to use a copolymer of Examples of other monomers copolymerizable with vinyl chloride monomers include unsaturated hydrocarbon compounds such as ethylene and propylene; compounds having a vinyl group such as allyl chloride and acrylonitrile; Monomers of acid esters, methacrylic acid esters, acrylic acid ester compounds such as vinyl acetate, and dicarboxylic acid compounds such as maleic anhydride can be used. These may be used alone, or two or more of them may be used in combination. The copolymer may be any selected from random copolymers, block copolymers, and graft copolymers. The polyvinyl chloride resin may be used alone, or two or more of them may be used in combination.

Among polyvinyl chloride resins, it is more preferable to use a chlorinated vinyl chloride resin obtained by chlorinating a polyvinyl chloride resin. Chlorinated vinyl chloride resin has a higher chlorine content than vinyl chloride resin, and is excellent in flame retardancy and heat deformation resistance, which affect fire resistance performance.

The thermoplastic resin contained in the inner layer and the outer layer of the multi-layer pipe of the present invention may contain thermoplastic resins other than polyvinyl chloride-based resins. However, the thermoplastic resin contained in the inner layer preferably contains 60% by mass or more of polyvinyl chloride resin, more preferably 75% by mass or more, and even more preferably 85% by mass or more.
The thermoplastic resin contained in the outer layer preferably contains 85% by mass or more of a polyvinyl chloride resin, more preferably 90% by mass or more, and even more preferably 93% by mass or more.
Other thermoplastic resins include, for example, acrylic resin, polyethylene, polypropylene, polystyrene, polybutene, chlorinated polyethylene, ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, methyl methacrylate-butadiene-styrene graft. Copolymer (MBS resin), polyethylene terephthalate, ABS resin and the like can be mentioned. Among these other thermoplastic resins, from the viewpoint of improving the mechanical strength of the multilayer pipe, it is preferable to use either MBS resin or high-molecular-weight acrylic resin having a molecular weight of 3,000,000 or more, and it is more preferable to use both. .

The thermoplastic resin contained in the foam layer also preferably contains a polyvinyl chloride resin. The foam layer may contain thermoplastic resins other than polyvinyl chloride-based resins. Examples of the other thermoplastic resin are the same as those described as the other thermoplastic resin in the inner layer and the outer layer. Among these, it is desirable to contain a high-molecular-weight acrylic resin having a molecular weight of 3,000,000 or more, which is preferable for improving the melt tension and increasing the expansion ratio. These may be used alone, or two or more of them may be used in combination. The thermoplastic resin contained in the foam layer preferably contains 85% by mass or more of polyvinyl chloride resin, more preferably 90% by mass or more.
In addition, the molecular weight of the said high molecular weight acrylic resin means the weight average molecular weight of polystyrene conversion measured by a gel permeation chromatography (GPC).

As a foaming method for forming the foam layer, a wide range of known methods can be adopted, and there is no particular limitation. Either a chemical foaming method or a physical foaming method may be used.

(Pyrolytic foaming agent)
When employing a chemical foaming method, for example, a method of adding a thermally decomposable foaming agent to a thermoplastic resin can be exemplified. Examples of pyrolytic foaming agents include sodium bicarbonate (sodium bicarbonate) foaming agents, ADCA (azodicarbonamide), DPT (N,N'-dinitrosopentamethylenetetramine), and OBSH (4,4'-oxybis(benzene Sulfonyl hydrazides)) can be exemplified, and these may be used alone or in combination of two or more. Moreover, from the viewpoint of increasing the closed cell ratio, which will be described later, it is preferable to use ADCA as a foaming agent or to use it in combination.

When employing a physical foaming method, for example, a method of adding thermally expandable microspheres (microplastic spheres) to a thermoplastic resin can be used. The term "thermally expandable microspheres (microplastic spheres)" as used herein refers to thermoplastic polymer cells containing low-boiling-point hydrocarbons. .

(Expansion ratio)
The foaming ratio of the foam layer is preferably 2 to 8 times, more preferably 3 to 6 times, even more preferably 3.5 to 6 times, and 4 to 6 times. More preferably less than twice. By setting the foaming ratio to 3.5 times or more, the heat insulating performance of the multi-layer pipe can be improved. Further, by setting the foaming ratio to 8 times or less, the diameter of cells in the foam layer can be made uniform, and the risk of formation of open cells can be reduced. As a result, when water enters the foam layer from the end of the pipe into the open cells due to capillarity or other reasons, the risk of water permeating the entire foam layer is eliminated and the insulation performance of the multi-layer pipe is reduced. can be prevented.

The foam layer is formed by foaming the thermoplastic resin composition for foam layer containing the thermoplastic resin and the foaming agent. From the viewpoint of facilitating adjustment to the above expansion ratio, the content of the foaming agent in the thermoplastic resin composition for the foam layer is preferably 1 to 5% by mass, more preferably 2 to 4% by mass. preferable.

In this specification, the expansion ratio is defined as a value measured and calculated by the method represented by the following steps A) to C).
A) Cut the multi-layer tube to an axial length of about 50 mm, then cut axially into four quadrants approximately evenly circumferentially.
B) Cut the inner layer and the outer layer with a milling machine and process only the foam layer into a plate having a length of about 50 mm to obtain a test piece. Four test pieces are made.
C) According to JIS K 7112:1999, the apparent density of the test piece is determined to three digits after the decimal point at 23°C ± 2°C with a water displacement type specific gravity meter, and the foaming ratio is calculated by the following formula (a).
m=γo/γ (a)
[In the formula (a), m is the expansion ratio, γ is the apparent density (g/cm ³ ) of the foam layer, and γo is the unfoamed density (g/cm ³ ) of the constituent material of the foam layer. be. ]

The density of each substance may change by about 0.1 when additives are added, so the unfoamed density of the constituent material of the foam layer is the unfoamed density of the thermoplastic resin used. For example, the values described in Chemical Handbook (Applied Chemistry Edition II Materials Edition) shall be used.
The density of the unfoamed polyvinyl chloride resin is 1.54.
In addition, when using multiple types of thermoplastic resins, the density is calculated by a weighted average.

In this specification, the closed cell rate Cc (%) of the foam layer is the volume Va (cm ³ ), a value calculated using the following formula (b) from the volume Vaq (cm ³ ) of the foam layer measured using a water displacement type hydrometer at 23 ± 2 ° C. in accordance with JIS K 7112: 1999 Defined if there is.
Cc=(Va/Vaq)×100 (b)

(Thermal expandable graphite)
The thermally expandable graphite used in the present invention is obtained by mixing powders such as natural flake graphite, pyrolytic graphite, and Kish graphite with inorganic acids such as concentrated sulfuric acid, nitric acid, and selenic acid, and concentrated nitric acid, perchloric acid, perchlorate, and perchlorate. After an acid treatment that inserts an inorganic acid between graphite layers with a strong oxidizing agent such as manganate, bichromate, or hydrogen peroxide, the pH is adjusted to maintain the carbon layer structure. Crystalline compounds can be used.

In the present invention, the thermally expandable graphite preferably has a pH of 1.5 to 4.0. The pH of thermally expandable graphite is measured by a pH electrode after adding 1 g of thermally expandable graphite to 99 g of deionized water and stirring for 10 minutes.
The method for adjusting the pH of the thermally expandable graphite is not particularly limited, but usually, as described above, the pH is 1 or less in the state where the raw material graphite is acid-treated to insert an inorganic acid between the layers. Therefore, for example, a method of washing acid-treated graphite with water to remove the acid remaining on the surface of the graphite and then drying the graphite can be used. That is, in order to increase the pH of the thermally expandable graphite, washing with water and drying should be repeated.

In the present invention, the reason why it is preferable to blend thermally expandable graphite adjusted to pH 1.5 to 4.0 is that polyvinyl chloride resin repeats the hydrogen chloride elimination reaction in the presence of acid, making it difficult to To effectively carbonize a polyvinyl chloride resin at the time of combustion by utilizing the property of generating a combustible carbonized substance, thereby suppressing the combustion and improving the fire resistance performance.
That is, the polyvinyl chloride resin repeats the elimination reaction of hydrogen chloride in the presence of an acid such as a Lewis acid or hydrogen chloride to generate double bonds. When hydrogen chloride is desorbed, it itself becomes a catalyst and easily causes the next desorption reaction. Moreover, next to the generated double bond, dehydrochlorination is more likely to occur than in the original state, and double bonds are generated one after another. This is a desorption chain reaction commonly called a zipper reaction, and when the degree of the reaction is small, discoloration such as coloring and burning occurs, and as the reaction progresses, carbonization occurs.

Therefore, in order to improve the fire resistance during combustion, the carbonization reaction of the polyvinyl chloride resin is rather accelerated under certain high-temperature conditions, and a carbonized structure is created before the resin is burned to make it difficult to burn. Therefore, it is preferable to add thermally expandable graphite adjusted to pH 1.5 to 4.0 in order to promote carbonization of the polyvinyl chloride resin.

The reason why the pH of the thermally expandable graphite is in the range of 1.5 to 4.0 is that if the pH is 1.5 or more, the acidity is not too strong, and corrosion of the molding apparatus is unlikely to occur. is. On the other hand, when the pH is 4.0 or less, the effect of promoting carbonization of the polyvinyl chloride resin is high, and sufficient fire resistance can be obtained.

The particle size of the thermally expandable graphite is not particularly limited, but if the particle size is equal to or greater than a certain value, the multi-layer tube will have a high expansion coefficient. On the other hand, when the grain size is a certain value or less, the structure does not thermally expand excessively by heating, so that the shape can be easily maintained, and it is possible to prevent the residue from falling off and the fire resistance from deteriorating. Furthermore, when the particle size is below a certain value, physical properties such as tensile strength and flattening strength are improved when made into a multi-layer pipe, making it easier to obtain the mechanical strength necessary for a pipe material. Therefore, the average particle size (D50) is preferably 100-400 μm, more preferably 120-350 μm.

(Relationship between multilayer tube and thermally expandable graphite)
The multi-layer pipe of the present invention has an inner layer, a foam layer and an outer layer as shown in FIG.
In the present invention, the content of thermally expandable graphite is 2 to 7% by mass based on the total amount of the multilayer tube. Here, the content of thermally expandable graphite with respect to the total mass of the multilayer tube is obtained by 100×(mass of thermally expandable graphite contained in the multilayer tube)/(total mass of the multilayer tube).
In the present invention, the reason why the thermally expandable graphite is added in an amount of 2 to 7% by mass based on the total amount of the multilayer pipe is that if the thermally expandable graphite is less than 2% by mass, sufficient thermal expandability can be obtained during combustion. This is because the inside of the pipe cannot be sufficiently blocked, hot air rises through the inside of the pipe, and the fire resistance deteriorates. On the other hand, if the content of thermally expandable graphite exceeds 7% by mass, the structure will thermally expand too much due to heating, and the residue will drop off without being able to retain its shape, forming cavities and reducing fire resistance. . The thermally expandable graphite content is preferably 3 to 6% by mass based on the total amount of the multilayer tube.

(Relationship between inner layer and thermally expandable graphite)
In the present invention, the content of thermally expandable graphite is 5 to 16% by mass based on the total amount of the inner layer. Here, the thermally expandable graphite content relative to the total amount of the inner layer is determined by 100×(mass of thermally expandable graphite contained in the inner layer)/(total mass of the inner layer).
Since the inner layer is closest to the interior of the tube, it needs to expand aggressively with heat. On the other hand, since there is no contact with the external environment, there is no need to reduce the content of thermally expandable graphite from the viewpoint of impact resistance. Therefore, by being within the above range, it is possible to develop expansion in the event of a fire. If it is out of the above range, the expandability tends to be poor, and there is a tendency that the blockage cannot be completely closed, or the residue falls off to form cavities. The content of the thermally expandable graphite is preferably 7 to 14% by mass based on the total amount of the inner layer.

(Relationship between foam layer and thermally expandable graphite)
In the present invention, the content of thermally expandable graphite is 0 to 5% by mass based on the total amount of the foamed layer. Here, the thermally expandable graphite content relative to the foamed layer total mass is determined by 100×(mass of thermally expandable graphite contained in foamed layer)/(total mass of foamed layer).
It is preferable that the foam layer is formed in a state having a certain degree of foaming ratio and the like in order to maintain heat insulating properties (prevention of dew condensation). When the resin is foamed in the heat treatment process during molding of the foamed layer, not only the foamed layer but also the expanded graphite itself expands slightly even though it still has the expansive function in case of fire. As a result, the internal pressure inside the molding die rises, suppressing mutual foaming, and the expansion ratio and foaming ratio tend to decrease. As a result, the heat insulation is inferior, and dew condensation tends to occur. Therefore, it is preferable that the content of thermally expandable graphite in the foam layer is small. However, there is a need to actively expand with heat during fire resistance. Therefore, the content of thermally expandable graphite based on the total amount of foamed layer is preferably 4% by mass or less, more preferably 2% by mass or less, and preferably 0.1% by mass or more, It is more preferably 0.5% by mass or more.
If the thermally expandable graphite is added only to the inner layer, there is concern that a residue will be left locally and may fall off. Therefore, it is preferable to have thermally expandable graphite within the above range.
By being within the above range, it is possible to develop expansion in the event of a fire while maintaining heat insulating properties.

(Relationship between outer layer and thermally expandable graphite)
In the present invention, the content of thermally expandable graphite is 0 to 2% by mass based on the total amount of the outer layer. The content of the thermally expandable graphite based on the total amount of the outer layer is preferably 0 to 1% by mass. Here, the thermally expandable graphite content relative to the total amount of the outer layer is determined by 100×(mass of thermally expandable graphite contained in the outer layer)/(total mass of the outer layer).
Since the outer layer comes into contact with the outside, impact resistance is required. However, if too much thermally expandable graphite is added, cracks tend to occur, making it difficult to obtain the desired impact performance. Therefore, by adding the thermally expandable graphite within the above range, the gap between the ALC and the resin tube caused by the change in shape of the resin pipe in the event of a fire can be filled with the expansion of the thermally expandable graphite, and the fire resistance can be improved. can.

Although the multilayer tube of the present invention may contain thermally expandable graphite only in the inner layer, it is preferable to incorporate thermally expandable graphite in at least one of the layers other than the inner layer, that is, the outer layer and the foam layer. . That is, it is preferable to distribute the thermally expandable graphite in two or more layers. As a result, it is possible to provide a pipe that can maintain overall heat insulation and fire resistance as a multilayer pipe as a whole. The advantages of distributing thermally expandable graphite in two or more layers include the following (1) to (3).
(1) By distributing the thermally expandable graphite in at least one of the inner layer and the outer layer and the foam layer, it is possible to prevent the local formation of residues and reduce the possibility of falling off.
(2) When thermally expandable graphite is added only to the foam layer, the expansion ratio and foaming ratio tend to decrease, and the thermal insulation performance tends to deteriorate. Decrease is suppressed.
(3) If the thermally expandable graphite is added only to the outer layer, the thermally expandable graphite becomes the starting point of cracks and the impact resistance tends to deteriorate. can be prevented.

(Additive)
When forming the foam layer, it is also preferable to use a foaming agent as described above. In addition to this, it is also preferable to add other additives to each of the inner layer, the foam layer and the outer layer in the multi-layer tube of the present invention within a range that does not impair the object or effect of the present invention.

As such an additive, it is possible to use a wide range of known additives used in the constituent resin materials of multilayer pipes, and there is no particular limitation. Specific examples include stabilizers, lubricants, processing aids, fillers, flame retardants, colorants, and the like.

(Thickness and outer diameter of each layer of multi-layer pipe)
The thicknesses of the inner layer, the foamed layer, and the outer layer in the multi-layer pipe of the present invention are preferably within a certain range from the viewpoint of achieving both heat insulation performance and fire resistance performance.
The thickness of the inner layer is preferably 1-3 mm, more preferably 1.5-2.5 mm. If the thickness of the inner layer is at least these lower limits, the inner layer will expand in the event of a fire, making it easier to clog the inside of the pipe. When the thickness of the inner layer is equal to or less than these upper limits, it becomes easier to ensure constant heat insulation performance.
The thickness of the foam layer is preferably 2-4 mm, more preferably 2.5-3.5 mm. When the thickness of the foam layer is at least these lower limit values, the heat insulation performance is likely to be improved. When the thickness of the foam layer is equal to or less than these upper limits, it becomes easier to ensure a certain level of fire resistance.
The thickness of the outer layer is preferably 0.5-3 mm, more preferably 1-2.5 mm. When the thickness of the outer layer is at least these lower limit values, the mechanical strength of the multi-layer pipe increases. When the thickness of the outer layer is equal to or less than these upper limits, it becomes easier to ensure constant heat insulation performance.

The outer diameter (D) of the multilayer tube is not particularly limited, but is preferably 30 mm or more and 120 mm or less, more preferably 35 mm or more and 115 mm or less. By setting the outer diameter of the multi-layered pipe within such a range, it can be used for horizontal pipes and drainage stacks used in the field of air conditioning.

The multi-layer pipe of the present invention described above is preferably used as a building piping material, and particularly preferably as an air conditioning drain piping material. As described above, the multi-layer pipe of the present invention is excellent in heat insulation performance and fire resistance performance. It can be blocked to control the spread of fire.

The method for producing the multi-layer pipe of the present invention obtained as described above can be based on a conventional method for producing a multi-layer pipe having a multi-layer structure, and is not particularly limited. For example, it can be obtained based on the following method.

(Manufacturing method of multilayer pipe)
2 and 3 are general block diagrams of a manufacturing apparatus 20 for manufacturing a multi-layer pipe 10' having a three-layer structure. The manufacturing apparatus 20 preferably includes an inner/outer layer extruder 11 , a foamed layer extruder 12 , a mold 13 , a cooling water tank 15 , a take-up machine 16 and a cutting machine 17 . A mold 13 is connected to the inner/outer layer extruder 11 and the foamed layer extruder 12 , and a cooling water tank 15 is preferably connected to the mold 13 . A take-up machine 16 is connected to the cooling water tank 15 , and a cutting machine 17 is connected to the take-up machine 16 . Furthermore, as shown in FIGS. 2 and 3, a gas cylinder 18 and a metering pump 19 may be connected to the foamed layer extruder 12 .

A gas cylinder 18 and a metering pump 19 supply a gaseous foaming agent from a vent hole of the foam layer extruder 12 . The inner and outer layer extruder 11 melt-kneads the thermoplastic resin composition for the non-foamed layer forming the inner layer 1 and the outer layer 3 and extrudes it into the mold 13 .

The foam layer extruder 12 melts and kneads the thermoplastic resin composition for forming the foam layer 2 and extrudes it into the mold 13 . The mold 13 is made from the thermoplastic resin composition for the non-foamed layer injected from the inner and outer layer extruder 11 and the thermoplastic resin composition for the foamed layer injected from the foamed layer extruder 12, and an uncured three-layer structure. to form a multi-layer tube 100'.

The cooling water tank 15 is attached with a tube 14 for forming the outer surface of the uncured multilayer pipe 100' to a predetermined size. It is cooled while being in contact with the outer surface forming tube 14 . The take-up machine 16 receives the multi-layered pipe' cooled by the cooling water bath 15 . The cutting machine 17 cuts the multilayer pipe 10' sent from the take-up machine 16 to a predetermined length.

First, a thermoplastic resin composition for non-foamed layers containing thermally expandable graphite is supplied to the inner and outer layer extruder 11 and melt-kneaded. Separately, a foam layer thermoplastic resin composition containing thermally expandable graphite is supplied to the foam layer extruder 12 and melt-kneaded. At this time, when gas is used as a foaming agent, the gas in the gas cylinder 18 is supplied from the vent hole by the pumping operation of the metering pump 19 while the thermoplastic resin composition for the foam layer is being melted and kneaded. When a solid or liquid foaming agent is used, the foaming agent may be blended in advance with the thermoplastic resin composition for the foam layer.

Then, as shown in FIG. 4, a non-foamed layer thermoplastic resin composition 21 melt-kneaded by the inner and outer layer extruder 11 and a foamed layer thermoplastic resin composition 22 melt-kneaded by the foamed layer extruder 12. are injected into the mold 13 and merged inside the mold 13 to form an uncured multi-layer pipe 100' having a three-layer structure. The uncured multilayer pipe 100 ′ includes a non-foamed thermoplastic resin layer 31 formed from a non-foamed layer thermoplastic resin composition 21 and a foamed layer thermoplastic resin composition 22 between the inner layer 1 and the outer layer 3 . and a foamed thermoplastic resin layer 32 formed from.

Furthermore, when the uncured multi-layer pipe 100' having a three-layer structure is extruded from the mold 13, the resin of the foamed thermoplastic resin layer 32 foams. The uncured multi-layered tube 100' is inserted into the outer surface forming tube 14, and the uncured multi-layered tube 100' is molded to a predetermined size and cooled in the cooling water tank 15 to form the multi-layered tube 10'. Further, the cooled and molded air-conditioning drain pipe 10' is handed over to a take-up machine 16, sent to a cutting machine 17, and cut to a predetermined length by the cutting machine 17. - 特許庁

The temperature for molding with the mold 13 is preferably 140° C. or higher and 200° C. or lower, and more preferably 160° C. or higher and 190° C. or lower. In addition, the molding time is preferably 10 minutes or more and 30 minutes or less, more preferably 10 minutes or more and 20 minutes or less.

In the method for manufacturing a multi-layer pipe described above, an example using two types of extruders, the foam layer extruder 12 and the inner and outer layer extruders 11, is shown. extruder may be used to produce multi-layer tubes. Specifically, a multi-layer pipe may be manufactured using a manufacturing apparatus in which three types of extruders, ie, a foam layer extruder 12, an inner layer extruder, and an outer layer extruder are connected to a mold 13.

Although the embodiments of the present invention have been described above, the present invention is by no means limited to such examples, and can of course be embodied in various forms without departing from the gist of the present invention.

EXAMPLES Hereinafter, embodiments of the present invention will be described more specifically based on Examples, but the present invention is not limited to these.

(Examples 1 to 6 and Comparative Examples 1 to 7)
A non-foamed layer thermoplastic resin composition for forming an inner layer and an outer layer and a foamed layer thermoplastic resin composition for forming a foamed layer were prepared from the following materials. These compositions were used to manufacture multi-layer tubes in which an inner layer, a foam layer and an outer layer were laminated in this order. During production, a manufacturing apparatus equipped with three types of extruders, a foaming layer extruder, an inner layer extruder, and an outer layer extruder, was used, and the temperature conditions and By adjusting the extrusion rate, a multi-layer air-conditioning drain piping material was manufactured.

(Raw materials for inner and outer layers (components of thermoplastic resin composition for non-foamed layer))
Polyvinyl chloride resin (manufactured by Tokuyama Sekisui Kogyo Co., Ltd., TS-1000R)
Thermally expandable graphite pH 2.5 to 3.5, average particle size 250 μm (manufactured by Air Water, CA-60N)
Organic tin stabilizer (TVS-8832, manufactured by Nitto Kasei Co., Ltd.)
MBS resin (manufactured by Kaneka, B-564)
High molecular weight acrylic resin with a molecular weight of 3 million or more (PA-20, manufactured by Kaneka Corporation)
Lubricant (manufactured by Mitsui Chemicals, Hi-Wax 220MP)
Lubricant (Roxol 259 manufactured by Emery Oleochemicals Japan)
Calcium carbonate (manufactured by Shiraishi Kogyo Co., Ltd., CCR)
Coloring agent (manufactured by Resinocolor)

Chlorinated vinyl chloride resin (HA-58K manufactured by Tokuyama Sekisui Kogyo Co., Ltd.) was used as the raw material for the inner and outer layers of Examples 5 and 6 instead of polyvinyl chloride resin. Other than that, the materials were the same as those of Examples 1-4 and Comparative Examples 1-7.

(Raw materials for foam layer (components of thermoplastic resin composition for foam layer))
Polyvinyl chloride resin (manufactured by Tokuyama Sekisui Kogyo Co., Ltd., TS-800E)
High molecular weight acrylic resin with a molecular weight of 3 million or more (PA-40, manufactured by Kaneka Corporation)
Thermally expandable graphite pH 2.5 to 3.5, average particle size 250 μm (manufactured by Air Water, CA-60N)
Baking soda (Eiwa Kasei Kogyo Co., Ltd., Cellbon SC-855)
ADCA (manufactured by Eiwa Kasei Kogyo Co., Ltd., Vinihole AC-3)
Organic tin stabilizer (TVS-8832, manufactured by Nitto Kasei Co., Ltd.)
Lubricant (Roxol 259, manufactured by Emery Oleochemicals Japan)
Colorant (Hexachemical, D-13486)
The foam layer was manufactured based on the same composition in all the examples and comparative examples, except for the content of the thermally expandable graphite.

(Expansion ratio measurement test)
10 mm or more in the circumferential direction and 50 mm in the axial direction were cut from an air-conditioning drain pipe material, the inner and outer layers were cut with a milling machine, and only the foam layer was processed into a plate with a length of about 50 mm to obtain a test piece. In addition, four test pieces were prepared centering on points that were evenly divided into four in the inner circumferential direction.
According to JIS K 7112: 1999, the apparent density of the test piece was measured at 23°C ± 2°C with a water displacement type specific gravity meter to three digits after the decimal point, and the foaming ratio was calculated by the following formula (1). If the foaming ratio m was 3.5 times or more, it was determined that the material had sufficient heat insulating performance without dew condensation.
m=γc/γ (1)
[In formula (1), m is the foaming ratio, γ is the apparent density (g/cm ³ ) of the foamed layer, and γc is the density (g/cm ³ ) of the foamed layer when not foamed. ]

(Expansion ratio measurement test)
A circular test piece approximately 3 mm thick is cut from the tube. The thickness and width of the test piece are measured with vernier calipers at four arbitrary points in the circumferential direction of the test piece. This test piece is placed in an electric furnace heated to 950° C. and expanded for 4 minutes. After that, the test piece is taken out from the electric furnace and allowed to cool at room temperature. The thickness (height) and width of the expanded test piece were measured at four locations in the circumferential direction with vernier calipers, and the expansion ratio R was calculated by the following formula. If the expansion ratio R was 4.0 times or more, it was judged that the fire resistance performance was sufficient to pass the fire resistance test.
Expansion ratio R=(a ₁ ×b ₁ ×3.14/4)/(a ₀ ×b ₀ )
a ₀ : Specimen thickness before expansion (mm)
b ₀ : Specimen width before expansion (mm)
a ₁ : test piece thickness after expansion (mm)
b ₁ : test piece width after expansion (mm)

(Tensile strength evaluation test)
According to the tensile test method for plastics (JIS K7113), a dumbbell-shaped test piece having a length of 100 mm, a width of 15 mm, and a center width of 10 mm was measured at 5 mm/min for the tensile yield strength of each example and comparative example. The measurement atmosphere at this time was 23°C. The maximum load until the test piece breaks is P (N), the cross-sectional area of the test piece is S (mm ² ), and the tensile yield strength f (MPa) is calculated by the following formula. was 45 (MPa) or more, it was determined that the strength was sufficient for practical use.
Tensile yield strength: f = P/S

It was confirmed that Examples 1 to 6 had excellent performance in expansion ratio, expansion ratio and tensile yield strength. Therefore, it is possible to provide an air-conditioning drain piping material having desired heat insulation performance, fire resistance performance and strength.
In Comparative Example 1, the evaluation of the expansion ratio was 4.0 times or less, so it was judged that the heat insulation performance and strength were obtained, but the fire resistance performance was not obtained.
In Comparative Example 2, the evaluation of the expansion ratio was 4.0 times or less, so it was judged that the heat insulation performance and strength were obtained, but the fire resistance performance was not obtained.
In Comparative Example 3, the evaluation of the expansion ratio was 4.0 times or less, so it was judged that the heat insulation performance and strength were obtained, but the fire resistance performance was not obtained.
In Comparative Example 4, the evaluation item of the foaming ratio was less than 3.5 times and the evaluation item of the expansion ratio was 4.0 times or less, so it was determined that although the strength was obtained, the heat insulating performance and the fire resistance performance could not be obtained.
In Comparative Example 5, the evaluation of the expansion ratio was 4.0 times or less, so it was judged that the heat insulation performance and strength were obtained, but the fire resistance performance was not obtained.
In Comparative Example 6, the evaluation of the tensile yield strength was 45.0 MPa or less, so it was judged that the strength could not be obtained although the heat insulation performance and the fire resistance performance could be obtained.
In Comparative Example 7, the evaluation of the expansion ratio was 4.0 times or less, so it was judged that the heat insulation performance and strength were obtained, but the fire resistance performance was not obtained.

1 inner layer 2 foam layer 3 outer layer 10' multi-layer pipe 11 inner and outer layer extruder 12 foam layer extruder 13 mold 14 tube for outer surface molding of pipe 15 cooling water tank 16 take-up machine 17 cutting machine 18 gas cylinder 19 metering pump 20 manufacturing apparatus 21 non-foaming Thermoplastic resin composition for layer 22 Thermoplastic resin composition for foam layer 31 Non-foamed thermoplastic resin layer 32 Foamed thermoplastic resin layer 100' Uncured multilayer pipe

Claims (4)

A multi-layer tube having an inner layer, a foam layer and an outer layer,
The inner layer, the foam layer, and the outer layer each contain a thermoplastic resin,
The multilayer tube contains thermally expandable graphite,
The content of the thermally expandable graphite with respect to the total amount of the inner layer is 5 to 16% by mass,
The content of the thermally expandable graphite based on the total amount of the foamed layer is 0 to 5% by mass,
The content of the thermally expandable graphite relative to the total amount of the outer layer is 0 to 2% by mass,
The content of the thermally expandable graphite is 2 to 7% by mass based on the total amount of the multilayer tube,
multi-layer tube. 2. The multi-layer pipe according to claim 1, wherein said thermoplastic resin contains a polyvinyl chloride resin. 3. The multilayer pipe according to claim 1, wherein the multilayer pipe has an outer diameter (D) of 30 mm or more and 120 mm or less. The multi-layer pipe according to any one of claims 1 to 3, wherein the foaming layer has an expansion ratio of 2 times or more and 8 times or less.

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