JP7357469B2 - Manufacturing method of pipe fittings and pipe fittings - Google Patents

Description

The present invention relates to a method for manufacturing a pipe joint and a pipe joint.

It is known that resin piping has the problem of warping or deterioration due to heat. In particular, when piping containing carbon black as a pigment is exposed to sunlight, carbon black tends to absorb infrared rays and accumulate heat, so the above problem is likely to occur.
General-use hard vinyl chloride resin pipes are examples of pipes containing carbon black. Hard vinyl chloride resin pipes for general use are specified to be gray in color.
Therefore, hard vinyl chloride resin pipes using organic pigments and hard vinyl chloride resin pipes using inorganic pigments have been proposed (Patent Documents 1 and 2).

On the other hand, in order to suppress deterioration of a resin-made cylindrical base material due to ultraviolet rays, an electric conduit in which a weather-resistant paint is applied to the outer periphery of the base material has been proposed (Patent Document 3).

Japanese Patent Application Publication No. 2003-329176 Japanese Patent Application Publication No. 2013-159774 International Publication No. 2011/058965

However, according to the studies of the present inventors, when attempting to manufacture a pipe joint by subjecting the hard vinyl chloride resin pipes of Patent Documents 1 and 2 to heat processing such as socket processing and bending processing, the processed portion becomes white. This may cause the appearance to deteriorate.
The hard vinyl chloride resin pipes of Patent Documents 1 and 2 use pigments that have lower heat storage properties than carbon black, so they have heat shielding properties and the temperature does not easily rise during heating. This is thought to be the cause of bleaching.
If the heating temperature is increased or the heating time is increased in order to raise the temperature sufficiently, discoloration such as burning occurs and the appearance deteriorates.

Note that Patent Document 3 describes that a weather-resistant paint contains a heat-shielding pigment. Since a coating film formed from a weather-resistant paint containing a heat-shielding pigment has heat-shielding properties, it is thought that it can suppress temperature increases when exposed to sunlight. However, when a tube coated with weather-resistant paint is processed using an oil bath, the surface coating peels off. Heat shielding properties are lost in areas where the paint film has peeled off. Furthermore, the appearance deteriorates due to peeling of the coating film.

One aspect of the present invention is that heat processing can be performed on a pipe to be processed, which is made of a gray hard vinyl chloride resin composition and has heat shielding properties, without impairing the heat shielding properties, and has excellent heat shielding properties and appearance. It is an object of the present invention to provide a method for manufacturing a pipe joint that allows the pipe joint to be obtained.
Another aspect of the present invention is to provide a pipe joint that is made of a gray hard vinyl chloride resin composition, is heat-processed, and has excellent heat shielding properties and appearance.

The present invention has the following aspects.
[1] A process of heat-processing a pipe to be processed made of a gray hard vinyl chloride resin composition containing a vinyl chloride resin and a pigment,
The pigment includes at least one selected from the group consisting of non-carbon inorganic pigments and organic pigments,
The infrared reflectance of the surface of the tube to be processed is 20% or more,
The ratio SDR of the outer diameter (mm) to the wall thickness (mm) of the pipe to be processed is 30 to 36,
The heating time when performing the heat processing is set so that the ratio T/SDR of the heating time T (seconds) converted when using an infrared heater with an output of 500 W to the ratio SDR is 40 to 150. A method for manufacturing a pipe joint characterized by:
[2] The method for manufacturing a pipe joint according to [1] above, wherein the heating process is one or both of bending and socket processing.
[3] A pipe fitting made of a gray hard vinyl chloride resin composition containing a vinyl chloride resin and a pigment, and having a processed part that has been subjected to heat processing and an unprocessed part that has not been subjected to the heat processing. And,
The pigment includes at least one selected from the group consisting of non-carbon inorganic pigments and organic pigments,
The infrared reflectance of the surface is 20% or more,
A pipe joint characterized in that the ratio SDR of the outer diameter (mm) to the wall thickness (mm) of the unprocessed portion is 30 to 36.
[4] The pipe fitting of [3] above, wherein the color difference between the processed portion and the unprocessed portion is 5 or less.
[5] The pipe fitting of [3] or [4] above, wherein the pigment does not substantially contain carbon black.
[6] The pipe fitting according to any one of [3] to [5] above, wherein the pigment consists only of a non-carbon inorganic pigment.
[7] The pipe fitting according to any one of [3] to [5] above, wherein the colored pigment among the pigments is composed only of an organic pigment.
[8] The pipe fitting according to any one of [3] to [5] above, wherein the pigment is composed of a mixture of a non-carbon inorganic pigment and an organic pigment.

According to the method for manufacturing a pipe joint of the present invention, it is possible to heat-process a pipe to be processed, which is made of a gray hard vinyl chloride resin composition and has heat-insulating properties, without impairing its heat-insulating properties. And a pipe joint with excellent appearance can be obtained.
The pipe joint of the present invention is made of a gray hard vinyl chloride resin composition, heat-processed, and has excellent heat shielding properties and appearance.

FIG. 2 is a partially cutaway side view showing an example of a pipe joint. FIG. 7 is a partially cutaway side view showing another example of a pipe joint. FIG. 7 is a partially cutaway side view showing another example of a pipe joint. 3 is a graph showing the measurement results of the spectral reflectance of the surface of the pipe fittings of Examples 1 and 3 and Comparative Example 1.

[Manufacturing method of pipe fittings]
A method for manufacturing a pipe joint according to one embodiment of the present invention includes a step of subjecting a pipe to be processed made of a gray hard vinyl chloride resin composition to heat processing (heat processing step). Therefore, the resulting pipe fitting has a processed portion that has been subjected to heating processing.
The method for manufacturing a pipe joint of this embodiment may include a step (molding step) of molding a gray hard vinyl chloride resin composition to obtain a pipe to be processed, before the heating processing step.
The method for manufacturing a pipe joint of this embodiment may include a step (preparation step) of preparing a gray hard vinyl chloride resin composition before the molding step.

(Gray hard vinyl chloride resin composition)
The gray hard vinyl chloride resin composition (hereinafter also referred to as "this resin composition") contains a vinyl chloride resin and a pigment.
The present resin composition may contain additives as necessary within a range that does not impair the effects of the present invention.

<Vinyl chloride resin>
Examples of the vinyl chloride resin include vinyl chloride homopolymers, vinyl chloride copolymers, and chlorinated products thereof. These may be used alone or in combination of two or more.
Examples of the vinyl chloride copolymer include copolymers of vinyl chloride monomers and monomers or polymers copolymerizable with the vinyl chloride monomers.

Monomers copolymerizable with vinyl chloride monomers include, for example, α-olefin compounds such as ethylene, propylene, and butylene; vinyl ester compounds such as vinyl propionate; vinyl ether compounds such as ethyl vinyl ether and butyl vinyl ether; methyl (meth)acrylate (meth)acrylate compounds such as butyl (meth)acrylate and hydroxyethyl (meth)acrylate; aromatic vinyl compounds such as styrene and α-methylstyrene; N-substituted maleimide compounds such as N-phenylmaleimide and N-cyclohexylmaleimide etc. These copolymerizable monomers may be used alone, or two or more types may be used in combination.
Examples of polymers copolymerizable with vinyl chloride monomers include acrylic copolymers made of alkyl (meth)acrylate monomers and the like. These copolymerizable polymers may be used alone or in combination of two or more.
(Meth)acrylate means acrylate or methacrylate.
In the vinyl chloride copolymer, the ratio of the vinyl chloride monomer and the above-mentioned copolymerizable monomer or polymer may be adjusted appropriately depending on the performance and purpose of the hard vinyl chloride resin pipe, and is not particularly limited. isn't it.

As the vinyl chloride resin, a commercially available one may be used, or one manufactured by a known manufacturing method may be used. In the production of a vinyl chloride homopolymer or copolymer, a conventionally known method may be used as a polymerization method for vinyl chloride, etc., such as a suspension polymerization method.

The average degree of polymerization of the vinyl chloride resin is preferably 800 to 3,000, more preferably 900 to 1,500, even more preferably 950 to 1,200, and most preferably 1,000 to 1,100. If the average degree of polymerization is 800 or more, mechanical strength will be better. When the average degree of polymerization is 3000 or less, it is easy to mold by extrusion molding and easy to heat process.
The above average degree of polymerization refers to the resin obtained by dissolving vinyl chloride resin in tetrahydrofuran (THF), removing insoluble components by filtration, and drying the THF in the filtrate. Means the average degree of polymerization measured in accordance with K 6721 "Test Method for Vinyl Chloride Resins".

<Pigment>
In the present resin composition, the pigment is used to give the present resin composition a gray tone as defined in JIS K 6741.
The pigment includes a colored (non-white) pigment in order to give the present resin composition a gray tone. Pigments typically include colored pigments and white pigments.

The pigment includes at least one type selected from the group consisting of non-carbon-based inorganic pigments and organic pigments (hereinafter also collectively referred to as "pigment (I)"). Pigment (I) has lower infrared absorption than carbon black. Therefore, when the pigment contains (I), the infrared reflectance can be increased.
The pigment may contain pigments other than pigment (I), if necessary.

Non-carbon-based inorganic pigments are compounds (oxides, etc.) obtained by chemical reactions of minerals and metals. Examples of the non-carbon-based inorganic pigment include colored (non-white) non-carbon-based inorganic pigments, white non-carbon-based inorganic pigments, and the like. These non-carbon-based inorganic pigments can be appropriately combined within a range that allows the resin composition to be toned to a gray tone.

The non-carbon-based inorganic pigment exhibiting color may contain one (single salt) or multiple metals (multiple salts) selected from the group consisting of chromium, iron, cobalt, copper, manganese, magnesium, bismuth, yttrium, aluminum, and vanadium. Examples include compounds containing salts. Specific examples of double salts include Fe-Co-Cr, Cu-Cr, Fe-Cr, Fe-Mn, Cu-Mn, Cu-Mg, Cu-Bi, Mn-Bi, Examples include Y--Mn based salts, Co--Al based salts, Fe--Co--Al--Mg based salts, and the like. Moreover, examples of the compound containing the above-mentioned metals include oxides, hydroxides, sulfides, silicates, ferrocyanide salts, etc. of the above-mentioned metals. These compounds may be used alone or in combination of two or more.
As the colored non-carbon inorganic pigment, chromium-containing compounds are preferred, and Fe--Cr compounds are more preferred, since they can lower the infrared reflectance.
As the colored non-carbon inorganic pigment, oxides are preferable because they have better color stability.

Examples of non-carbon-based inorganic pigments that exhibit white color include metal oxides such as titanium dioxide, aluminum oxide, and zinc oxide. Among these, titanium dioxide is preferred because it has a high refractive index and high whiteness.

When the pigment (I) is a non-carbon inorganic pigment, the non-carbon inorganic pigment may be a colored non-carbon inorganic pigment or a white non-carbon inorganic pigment from the viewpoint of toning the present resin composition to gray. Mixed pigments with inorganic pigments are preferred.
In the mixed pigment, the non-carbon inorganic pigment exhibiting color is preferably a pigment that exhibits black color by one or more combinations of the above-mentioned non-carbon inorganic pigments exhibiting color.
Pigments that exhibit black include a mixture of two or more pigments that exhibit complementary colors or colors that are close to complementary colors; metals that constitute each of two or more pigments that exhibit complementary colors or colors that are close to complementary colors; Examples include double salt pigments containing multiple ions; and mixtures thereof.
From the perspective of obtaining high infrared reflectance and color stability, colored non-carbon inorganic pigments include green chromium oxide (Cr ₂ O ₃ ) and its complementary red pigment (e.g. chromium oxide). A mixed pigment toned to black by combining iron); a composite oxide containing chromium oxide and iron oxide; or a mixture thereof are preferred, and a composite oxide containing chromium oxide and iron oxide is more preferred.
In the mixed pigment, the content ratio of the colored non-carbon inorganic pigment to the total content of the colored non-carbon inorganic pigment and the white non-carbon inorganic pigment is such that the present resin composition becomes gray. Although it can be adjusted as appropriate within a range and is not particularly limited, it may be, for example, 18 to 58% by mass.

Organic pigments are those synthesized from petroleum and the like. Examples of the organic pigment include organic pigments that exhibit color (non-white color).
The organic pigment exhibiting color is not particularly limited, and examples thereof include azo pigments, phthalocyanine pigments (copper phthalocyanine, etc.), threne pigments, dye lake pigments, and the like. These may be used alone or in combination of two or more.
As the organic pigment exhibiting color, phthalocyanine pigments are preferable, and copper phthalocyanine is more preferable, since they have better color stability.

The pigment (I) may be a colored (non-white) pigment, a white pigment, or a mixture of a colored pigment and a white pigment.
Among the pigments (I), the white pigment is preferably a white non-carbon-based inorganic pigment.
Among the pigments (I), the colored pigment may be a colored non-carbon inorganic pigment, a colored organic pigment, or a colored non-carbon inorganic pigment and a colored pigment. It may also be a mixture of organic pigments.

When the pigment (I) is a non-carbon-based inorganic pigment, the content of the non-carbon-based inorganic pigment is 100 parts by mass of vinyl chloride resin from the viewpoint of suppressing unevenness in color tone due to uneven dispersion of the pigment. The amount is preferably 0.050 parts by mass or more. Further, the content of the non-carbon inorganic pigment is more preferably 0.050 to 0.500 parts by mass based on 100 parts by mass of the vinyl chloride resin from the viewpoint of suppressing contamination of equipment during extrusion molding. From the viewpoint of obtaining these effects better, the content of the non-carbon inorganic pigment is preferably 0.055 to 0.450 parts by mass, more preferably 0.065 to 0.350 parts by mass, and 0.070 parts by mass. More preferably 0.250 parts by mass.

When the pigment (I) is an organic pigment, the content of the organic pigment is preferably 0.01 parts by mass or more based on 100 parts by mass of the vinyl chloride resin from the viewpoint of imparting infrared reflectivity. Further, the content of the organic pigment is more preferably 0.01 to 1.0 parts by mass based on 100 parts by mass of the vinyl chloride resin from the viewpoint of providing further sufficient infrared reflectivity. From the viewpoint of obtaining these effects better, the content of the organic pigment is preferably 0.02 to 0.8 parts by mass, more preferably 0.02 to 0.6 parts by mass, and 0.02 to 0.6 parts by mass. 4 parts by mass is more preferred.

When the pigment (I) is a mixture of a non-carbon inorganic pigment and an organic pigment, the total content of the non-carbon inorganic pigment and the organic pigment is 100 parts by mass of the vinyl chloride resin from the viewpoint of providing infrared reflectivity. The amount is preferably 0.01 part by mass or more. In addition, the total content of non-carbon-based inorganic pigments and organic pigments is preferably 0.01 to 1.0 parts by mass per 100 parts by mass of vinyl chloride resin from the viewpoint of providing even more sufficient infrared reflectivity. preferable. From the viewpoint of obtaining these effects better, the total content of non-carbon inorganic pigments and organic pigments is preferably 0.02 to 0.8 parts by mass, more preferably 0.02 to 0.6 parts by mass. It is preferably 0.02 to 0.4 parts by mass, and more preferably 0.02 to 0.4 parts by mass.
The content ratio of the non-carbon inorganic pigment to the total content of the non-carbon inorganic pigment and the organic pigment is preferably 10 to 100% by mass, more preferably 50 to 99% by mass, and even more preferably 70 to 98% by mass.

Examples of other pigments include carbon black.
Preferably, the pigment in the present resin composition does not substantially contain carbon black. Since carbon black has a high infrared absorbing property, the infrared reflectance of the inner circumferential surface of the tube body 21 can easily be set to 20% or more by making the pigment substantially free of carbon black.
"Substantially free" means that the infrared reflectance is not less than 20%.
The content of carbon black is preferably 0.1 parts by mass or less, more preferably 0.01 parts by mass or less, and particularly preferably 0 parts by mass, based on 100 parts by mass of the vinyl chloride resin.

The content ratio of pigment (I) to the total content of pigments in the present resin composition is preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 100% by mass. That is, it is particularly preferable that the pigment of this resin composition consists only of pigment (I).

The content ratio of colored pigments to the total content of pigments is preferably 10 to 60% by mass, more preferably 15 to 50% by mass.
The content ratio of the white pigment to the total pigment content is preferably 40 to 90% by mass, more preferably 50 to 85% by mass.

In a preferred embodiment of the present invention, the pigment of the present resin composition consists only of non-carbon-based inorganic pigments. Non-carbon inorganic pigments have excellent color stability, so if the pigment consists only of non-carbon inorganic pigments, discoloration is less likely to occur.

In another preferred embodiment of the present invention, among the pigments of the present resin composition, the colored pigments consist only of organic pigments. Since organic pigments have excellent dispersibility in vinyl chloride resins, color unevenness is less likely to occur if the colored pigments are composed only of organic pigments.
In this embodiment, when the pigment includes a white pigment, the white pigment preferably consists only of a white non-carbon pigment.

In another preferred embodiment of the present invention, the pigment of the present resin composition consists of a mixture of a non-carbon inorganic pigment and an organic pigment. If the pigment is made of a mixture of a non-carbon-based inorganic pigment and an organic pigment, color unevenness is less likely to occur and fading can be suppressed.

When pigment (I) is a mixture of a non-carbon-based inorganic pigment and an organic pigment, it is preferable that the organic pigment is blue and the other colors are non-carbon-based inorganic pigments. Since the blue organic pigment is an organic pigment, it has excellent dispersibility and also has excellent color stability compared to organic pigments of other colors. Therefore, discoloration can be further suppressed while suppressing color unevenness.
Examples of blue organic pigments include copper phthalocyanine (phthalocyanine blue).
Examples of non-carbon inorganic pigments of other colors to be combined with the blue organic pigment include the above-mentioned mixture of colored non-carbon inorganic pigments (particularly black pigments) and white non-carbon inorganic pigments. Examples include pigments. By combining this mixed pigment with a blue organic pigment, color unevenness can be further suppressed and color tone stability can be further improved.

<Additives>
Examples of additives include dispersants, stabilizers, stabilizing aids, lubricants, processing aids, antioxidants, fillers, and the like. These additives may be used alone or in combination of two or more. Among these additives, dispersants, stabilizers and fillers are preferred.
The dispersant is not particularly limited, and examples thereof include silica, sodium salts and ammonium salts of polycarboxylic acids (eg, polyacrylic acid), surfactants, and the like. These may be used alone or in combination of two or more.

The stabilizer is not particularly limited and includes, for example, dimethyltin mercapto, dibutyltin mercapto, dioctyltin mercapto, dibutyltin maleate, dibutyltin maleate polymer, dioctyltin maleate, dioctyltin maleate polymer, dibutyltin laurate, dibutyltin Organotin stabilizers such as laurate polymer; lead stabilizers such as lead stearate, dibasic lead phosphite, tribasic lead sulfate, calcium-zinc stabilizers, barium-zinc stabilizers, barium- Cadmium-based stabilizers; Stearate-based stabilizers (metallic soaps) such as calcium stearate, zinc stearate, barium stearate, lead stearate; salicylate-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based, etc. Ultraviolet absorbers; hindered amine light stabilizers, and the like. These may be used alone or in combination of two or more.
Among these stabilizers, stearate (stearic acid stabilizer) is preferred, and lead stearate is more preferred.

When a stearate is included in the present resin composition, the content of stearate is 0.5 to 2 parts by mass per 100 parts by mass of vinyl chloride resin, from the viewpoint of obtaining even better color stability. parts by weight, more preferably 0.8 to 1.7 parts by weight, even more preferably 1 to 1.5 parts by weight, and particularly preferably 1.1 to 1.4 parts by weight.
When the present resin composition contains a colored non-carbon-based inorganic pigment, the content of stearate should be 1 part by mass of the colored non-carbon-based inorganic pigment from the viewpoint of obtaining even better color stability. On the other hand, it is preferably 10 to 54 parts by weight, more preferably 15 to 53 parts by weight, even more preferably 20 to 52 parts by weight, and particularly preferably 22 to 52 parts by weight.

The stabilizing aid is not particularly limited, and examples thereof include epoxidized soybean oil, epoxidized linseed bean oil, epoxidized tetrahydrophthalate, epoxidized polybutadiene, and phosphoric acid ester. These may be used alone or in combination of two or more.

Examples of the lubricant include internal lubricants, external lubricants, and the like.
The internal lubricant is used for the purpose of lowering the flow viscosity of the molten resin during molding and preventing frictional heat generation. The internal lubricant is not particularly limited, and examples thereof include butyl stearate, lauryl alcohol, stearyl stearate, epoxidized soybean oil, glycerin monostearate, stearic acid, bisamide, and the like. These may be used alone or in combination of two or more.
The external lubricant is used to increase the sliding effect between the molten resin and the metal surface during molding. The external lubricant is not particularly limited, and examples thereof include montanic acid wax, paraffin wax, polyolefin wax, and ester wax. These may be used alone or in combination of two or more.

Processing aids are not particularly limited, and include, for example, acrylic processing aids that are alkyl acrylate-alkyl methacrylate copolymers with a weight average molecular weight of 100,000 to 2,000,000, and specific examples include n-butyl acrylate- Examples include methyl methacrylate copolymer, 2-ethylhexyl acrylate-methyl methacrylate-butyl methacrylate copolymer, and the like. These may be used alone or in combination of two or more.

The antioxidant is not particularly limited, and examples thereof include phenolic antioxidants and the like. These may be used alone or in combination of two or more.

The filler is not particularly limited, and examples thereof include calcium carbonate, talc, and the like. These may be used alone or in combination of two or more.
Among these fillers, calcium carbonate is preferred from the viewpoint of obtaining better color stability.

When calcium carbonate is included in the present resin composition, the content of calcium carbonate is preferably 5 parts by mass or more based on 100 parts by mass of the vinyl chloride resin from the viewpoint of obtaining even better color tone stability. The upper limit of the calcium carbonate content is not particularly limited, but is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, and even more preferably 8 parts by mass or less, based on 100 parts by mass of the vinyl chloride resin.

(To be processed pipe)
The pipe to be processed is a pipe made of the above-mentioned gray hard vinyl chloride resin composition.
The tube to be processed may have a single layer or multiple layers. In the case of multiple layers, the gray hard vinyl chloride resin compositions constituting each layer may be the same or different.

The infrared reflectance of the surface of the tube to be processed is 20% or more, preferably 25% or more, and more preferably 30% or more. If the infrared reflectance of the surface of the pipe to be processed is 20% or more, a pipe joint with a surface infrared reflectance of 20% or more can be obtained. If the infrared reflectance of the surface of the pipe joint is 20% or more, it has excellent heat shielding properties, and the temperature of the pipe joint is unlikely to rise when exposed to sunlight, and warpage and deterioration are unlikely to occur.
The higher the infrared reflectance of the surface of the tube to be processed is, the more preferable it is from the viewpoint of heat shielding properties, and there is no particular upper limit to the infrared reflectance, but from the viewpoint of ease of heat processing, it is preferably 60% or less.

The infrared reflectance of the surface of the tube to be processed is determined by the amount of pigment in the hard vinyl chloride resin composition that makes up the tube (if the tube is multi-layered, the infrared reflectance of the hard vinyl chloride resin composition that makes up the outermost layer). (pigment) can be adjusted. In the pigment, the higher the content of pigment (I) or the lower the content of carbon black, the higher the infrared reflectance of the surface of the tube to be processed tends to be.
The infrared reflectance is a value indicating the average value of the spectral reflectance in the wavelength range of 800 to 1600 nm, and it is particularly preferable that the average value of the spectral reflectance in the wavelength range of 800 to 1100 nm is 20% or more. Infrared reflectance is measured by an ultraviolet-visible near-infrared spectrophotometer. Details are as described in Examples.

The ratio SDR (outer diameter/thickness, hereinafter also simply referred to as "SDR") of the outer diameter (mm) to the wall thickness (mm) of the pipe to be processed is 30 to 36, preferably 31 to 34. If the SDR of the pipe to be processed is 30 or more, it will have excellent physical strength such as compressive strength and tensile strength. If the SDR of the pipe to be processed is 36 or less, the workability is excellent.

The wall thickness and outer diameter of the pipe to be processed can be appropriately selected within a range that provides an SDR of 30 to 36, depending on the pipe joint to be manufactured.
The outer diameter of the pipe to be processed is not particularly limited, but when at least one end of the pipe joint is to be inserted into the socket of another pipe joint, the outer diameter is the same as the inner diameter of the socket.

The tube to be processed may be, for example, a VU tube defined in JIS K 6741. VU pipes are mainly used for drainage pipes (drainage pipes for detached houses, buried sewer pipes, etc.) and ventilation pipes. Generally, VU tubes have an SDR of 30 to 38.

The shape of the pipe to be processed can be appropriately selected depending on the pipe joint to be manufactured.
The tube to be processed may be, for example, straight.
The cross-sectional shape of the tube to be processed may be, for example, circular, oval, square, or rectangular.

The tube to be processed is preferably an extrusion molded product from the viewpoint of manufacturing efficiency. Unlike injection molded products, processed tubes, which are extrusion molded products, have gate marks, which are marks where resin was introduced into the mold cavity (space), and points where resin that has flowed inside the mold cavity merges. Since it does not have a weld line, it does not have gate marks or weld lines even in a pipe fitting that has been heat-processed on a pipe to be processed.

(Preparation process)
In the preparation step, for example, the present resin composition is prepared by mixing a vinyl chloride resin, a pigment containing pigment (I), and additives as necessary.
As a method for mixing the vinyl chloride resin, pigment, etc., a known method such as a hot blend method or a cold blend method can be used.

(molding process)
In the molding step, the resin composition is molded to obtain a pipe to be processed.
In the molding process, a known molding method can be used to mold the resin composition. From the viewpoint of production efficiency, extrusion molding is preferred.

(heat processing process)
In the heating process, the pipe to be processed is heated. Specifically, the processed portion of the processed tube is heated and softened, thereby deforming the processed portion.

Examples of heating processing include bending processing and socket processing.
In bending, a pipe to be processed is bent to form a bent portion. Therefore, the resulting pipe fitting has a bend. In the case of bending, the part to be processed is typically a part other than the end of the pipe to be processed.
In socket machining, the diameter of the end of the pipe to be processed is expanded to form a socket. Therefore, the resulting pipe fitting has a socket.
As the heating process, both bending process and socket process may be performed on the pipe to be processed. In this case, the resulting pipe fitting has a bend and a socket.

As a method of heating the part to be processed, from the viewpoint of productivity, a method of irradiating the part to be processed with infrared rays using an infrared heater is preferable. The output of the infrared heater can be, for example, in the range of 250 to 1000W. Examples of the shape of the infrared heater include a rod shape and a plate shape. The distance between the part to be processed and the infrared heater can be adjusted within a range of, for example, 5 cm to 50 cm. When irradiating infrared rays, the tube to be processed and the infrared heater may be rotated relative to each other in order to uniformly heat the part to be processed. In this case, only the tube to be processed may be rotated, only the infrared heater may be rotated, or both of them may be rotated. The rotation speed can be adjusted as appropriate depending on the output of the infrared heater and the distance between the workpiece and the infrared heater.
However, the heating method is not limited to the above method, and other heating methods may be employed.

The heating time when performing heat processing is determined by the ratio T/SDR (hereinafter also simply "T/SDR") of the heating time T (seconds) converted when using an infrared heater with an output of 500W to the SDR of the pipe to be processed. ) is set to be 40 to 150, preferably 50 to 140, and more preferably 60 to 130. In other words, the value of "heat amount per unit time x heating time (seconds)" when actually performing heat processing, and the value of "heat amount per unit time x heating time T (seconds)" when using an infrared heater with an output of 500W. The heating time (seconds) is set in consideration of the amount of heat per unit time when actually performing heat processing so that the values are equal. When T/SDR is 40 or more, processability is excellent and whitening is less likely to occur. When T/SDR is 150 or less, productivity is excellent and discoloration (scorch) is less likely to occur.

When heating using an infrared heater, the amount of heat is proportional to the output, so the heating time (seconds) when performing heating processing is calculated by "T x 500 (W) / output of the infrared heater (W)" . For example, when the output of the infrared heater is 500 W, the heating time when performing heating processing is T (seconds). When the output of the infrared heater is 1000 W, the heating time during heating processing is T×500/1000 (seconds). When the output of the infrared heater is 250 W, the heating time during heating processing is T×500/250 (seconds).
For example, when the SDR of the tube to be processed is 33 and the output of the infrared heater is 500 W, the heating time (infrared irradiation time) is 1300 to 5000 seconds, preferably 1600 to 4500 seconds.

The heating time during the heating process is preferably set so that the surface temperature after heating is 115 to 160°C, more preferably 125 to 150°C. If the surface temperature after heating is equal to or higher than the lower limit value, even if the tube to be processed is thick, the temperature of the tube to be processed will be sufficiently high, and the tube to be processed can be successfully heat-processed. Whitening is less likely to occur. If the surface temperature after heating is below the upper limit, discoloration (burning) and unintended deformation are unlikely to occur in the portion to be bent.

The bending process can be performed by a known method, except that the heating conditions when performing the bending process are as described above.
The radius of curvature R of the bent portion formed by bending may be, for example, 450 to 2100 mm. The bending angle of the bent portion may be, for example, 15 to 90°.

The socket processing can be carried out by a known method, except that the heating conditions when performing the socket processing are as described above.
The inner diameter of the socket portion formed by socket processing may be, for example, 114 to 630 mm. In addition, the inner diameter of the socket should be larger than the above inner diameter in the range of 1 to 10 mm in cases where the inner diameter of the socket is tapered, such as with a TS socket, or to create a gap between the inserted pipe and the inner surface of the socket for clearance. In some cases, such cases are also included.
The inner diameter of the socket is preferably 114 mm or more, more preferably 165 mm or more, and particularly preferably 216 mm or more. For pipe fittings with large diameter sockets with an inner diameter of 114 mm or more, it is difficult to evenly fill the mold cavity (space) with resin using the injection molding method, and the resin injection pressure by the injection molding machine is extremely high. Therefore, it is difficult to manufacture. According to the present invention, a pipe joint having such a large diameter socket can also be manufactured.

[Pipe fitting]
The pipe joint of the present invention is made of a gray hard vinyl chloride resin composition, and has a processed portion that has been subjected to heat processing and an unprocessed portion that has not been subjected to the heat processing.
The gray hard vinyl chloride resin composition is as described above.
The heat processing is as described above. Examples of the processed portion include a socket portion and a bent portion. The unprocessed portion typically has a straight tubular shape.
The pipe fitting of the present invention may have a single layer or a multilayer structure. In the case of multiple layers, the gray hard vinyl chloride resin compositions constituting each layer may be the same or different.

The infrared reflectance of the surface of the pipe joint of the present invention is 20% or more, preferably 25% or more, and more preferably 30% or more. If the infrared reflectance of the surface is 20% or more, it has excellent heat shielding properties, and the temperature of the pipe joint is unlikely to rise when exposed to sunlight, and warpage and deterioration are unlikely to occur.
The higher the infrared reflectance of the surface of the pipe joint of the present invention is, the more preferable it is from the viewpoint of heat shielding properties, and there is no particular upper limit to the infrared reflectance, but the ease of performing socket processing or bending processing when manufacturing the pipe joint of the present invention is preferable. From this point of view, it is preferably 60% or less.

The SDR of the unprocessed portion is 30 to 36, preferably 31 to 34.

In the pipe fitting of the present invention, the color difference between the processed part and the unprocessed part is preferably 5 or less, more preferably 3 or less, even more preferably 2 or less, and even more preferably 1 or less. It is particularly preferable. If the color difference between the processed part and the unprocessed part is 5 or less, the appearance will be better.
The color difference can be adjusted by the heating conditions when heat-processing the pipe to be processed. The lower the heating temperature or the shorter the heating time, the smaller the color difference tends to be.
Note that the color difference refers to the color difference (ΔE) in the L*a*b* color system defined in JIS Z8781-4:2013.

The shape of the pipe joint of the present invention can be selected as appropriate.
A pipe joint according to one aspect of the present invention includes a main body portion and a socket portion.
The main body portion is formed into a cylindrical shape having the same diameter. The main body portion may have a straight tubular shape or may have a bent portion. The cross-sectional shape of the main body may be, for example, circular, oval, square, or rectangular. The outer diameter of the main body is the same as the outer diameter of the tube to be processed.
The socket portion is formed at the end of the pipe joint so as to have a larger diameter than the main body portion. The socket portion is typically thinner than the main body portion. The cross-sectional shape of the socket may be, for example, circular or oval. The preferred inner diameter of the socket is as described above. The number of sockets may be one or more.

A pipe joint according to another aspect of the present invention includes a main body portion having a straight pipe portion and a bent portion.
The main body portion is similar to the main body portion of the pipe joint of the above-described embodiment except that it has a bent portion.
The pipe joint of this embodiment may include a socket. The socket part is similar to the socket part of the pipe joint of the embodiment described above.

FIG. 1 shows an example of a pipe joint. The pipe joint 1 of this example includes a straight pipe part 2 (main body part) formed in a cylindrical shape having the same diameter, and a socket part 3 formed with an enlarged diameter at one end of the straight pipe part 2. . The straight pipe part 2 and the socket part 3 are connected by a tapered pipe part 4.
The other end of the straight pipe section 2 is an insertion section 5 that is inserted into a socket section 3 of another pipe joint 1 . The outer peripheral surface of the distal end of the insertion portion 5 is an inclined surface 5a that is inclined so that the diameter gradually decreases toward the distal end. An insertion mark 6 is provided on the outer circumferential surface of the straight pipe section 2 to define the insertion depth of another pipe fitting 1 into the socket section 3 .
In the socket part 3, an enlarged diameter part 3a for accommodating a rubber ring 11 as a water stop material is formed on the inner peripheral surface of the socket part 3 over the entire circumference. The portions of the socket portion 3 other than the enlarged diameter portion 3a are formed to have the same diameter. The inner diameter (minimum inner diameter) of the socket part 3 is the same as the outer diameter of the insertion part 5.

FIG. 2 shows another example of a pipe joint. The pipe joint 1 of this example is the same as the pipe joint 1 of FIG. 1 except that the shape of the socket part 3 is different. In this example, the socket portion 3 has a shape whose diameter decreases from the tapered pipe portion 4 to the enlarged diameter portion 3a.

FIG. 3 shows another example of a pipe joint. The pipe joint 1 of this example includes a main body part 7 formed in a cylindrical shape having the same diameter, and a socket part 3 formed with an enlarged diameter at one end of the main body part 7. The main body part 7 and the socket part 3 are connected by a tapered pipe part 4.
The main body portion 7 has a bent portion 7a, a first straight tube portion 7b located on the other end side of the bent portion 7a, and a second straight tube portion 7c located on one end side of the bent portion 7a. In this example, the bending angle of the bent portion 7a (the inclination angle of the axis _l2 of the second straight pipe portion 7c with respect to the axis _l1 of the first straight pipe portion 7b) is 15°.
The other end of the first straight pipe part 7b is an insertion part 5 that is inserted into the socket part 3 of another pipe joint 1, like the pipe joint in FIG. is an inclined surface 5a which is inclined so that its diameter gradually decreases toward the tip.
The inner diameter of the socket part 3 is the same as the outer diameter of the insertion part 5.

Preferably, the pipe joint of the present invention does not have gate marks or weld lines. Such pipe joints are typically made by heat-processing a pipe to be processed that has been formed by extrusion molding.
It is particularly preferable that the pipe joint of the present invention has a socket having an inner diameter of 114 mm or more and has no gate marks or weld lines. The more preferable inner diameter of the socket is as described above.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

(Examples 1 to 8, Comparative Examples 1 to 3)
<Preparation of hard vinyl chloride resin composition>
A pigment composition was prepared by mixing pigments and dispersants according to the formulations shown in Tables 1 to 3, and the resulting pigment composition, vinyl chloride resin, and additives were mixed in a super mixer (100 L, manufactured by Kawata Co., Ltd.). The mixture was stirred and mixed using a cold blend method to obtain a hard vinyl chloride resin composition.
Details of each component shown in Tables 1 to 3 are as follows.

- Vinyl chloride resin: vinyl chloride homopolymer (trade name "TS-1000R", manufactured by Tokuyama Sekisui Kogyo Co., Ltd., average degree of polymerization 1000).
・Lead stearate: Product name: "SAK-NSBN", manufactured by Sun Ace Co., Ltd.
- Calcium carbonate: Product name: "Whiten 305S", manufactured by Shiroishi Calcium Co., Ltd.
- Titanium oxide: white inorganic pigment, trade name "R-3L", manufactured by Sakai Chemical Co., Ltd.
・Chromium compound: Composite oxide of chromium oxide and iron oxide, black inorganic pigment.
・Cobalt Blue: Blue inorganic pigment.
・Copper phthalocyanine: Blue organic pigment.
・Diketopyrrolopyrrole: Red organic pigment.
・Monoazo Yellow: Yellow organic pigment.
・Carbon black: Product name "Toka Black #7350", manufactured by Tokai Carbon Co., Ltd.
・Dispersant: Silica.

<Forming the pipe to be processed>
The hard vinyl chloride resin composition obtained above was supplied to a two-axis counterrotating extruder (trade name "SLM-50", manufactured by Nagata Seisakusho Co., Ltd.), and the outer diameter and wall thickness shown in Tables 1 to 3 were A straight pipe to be processed having a length of 1 m was formed. The SDR of the pipe to be processed is also listed in Tables 1 to 3.

<Processing of pipe to be processed>
The obtained pipe to be processed was bent (heated) according to the following procedure to obtain a pipe joint.
Using a rod-shaped infrared heater (quartz tube) with an output of 500 W and a reflector attached, the tube to be processed was heated while rotating under the conditions shown in Tables 1 to 3 (infrared heater output, heating time). The T/SDR at this time and the surface temperature after heating are also listed in Tables 1 to 3. Immediately after heating was completed, the tube to be processed was fixed to a bending mold set at an angle of 90° and the heated portion was bent to form a bent portion with a bending angle of 90° and a radius of curvature R of 1200 mm. After cooling, the pipe fitting was taken out from the bending mold.

The following measurements were performed on the obtained pipe fitting.

<Infrared reflectance measurement>
Using an ultraviolet-visible near-infrared spectrophotometer ("UV-3600Plus" manufactured by Shimadzu Corporation), measure the spectral reflectance of the surface of the pipe joint in the wavelength range of 800 to 1100 nm, and calculate the average value as the infrared reflection of the surface of the pipe joint. percentage. The results are shown in Tables 1 to 3. Moreover, the spectral reflectance curves of Examples 1 and 3 and Comparative Example 1 are shown in FIG.

<Color difference measurement>
The chromaticity of the surface of the processed part (bent part or socket part) and the unprocessed part (straight pipe part) of the pipe joint was measured in a dark room using a spectrophotometer (handheld spectrophotometer "NF333" Nippon Denshoku). (manufactured by Kogyo Co., Ltd.). The results are shown in Tables 1 to 3.
Here, the color difference (ΔE) is calculated using the following equation (1).
ΔE=√((L1-L2) ² +(a1-a2) ² +(b1-b2) ² )...(1)
In addition, in formula (1), L1, a1, and b1 represent the brightness L of the processed part, chromaticity a in the red direction, and chromaticity b in the yellow direction, and L2, a2, and b2 respectively represent the brightness L of the unprocessed part. , represents chromaticity a in the red direction and chromaticity b in the yellow direction.

In Examples 1 to 8, a tube to be processed containing pigment (I) and having a surface infrared reflectance of 20% or more and an SDR of 40 to 150 was heat-processed by heating under predetermined heating conditions. The pipe was successfully machined. Further, the color difference between the processed part and the unprocessed part was less than 5.

1 Pipe joint 2 Straight pipe part 3 Socket part 4 Tapered pipe part 5 Insertion part 6 Insertion mark line 7 Main body part 7a Bent part 7b First straight pipe part 7c Second straight pipe part 11 Rubber ring

Claims (11)

The method includes the step of subjecting a pipe to be processed made of a hard gray vinyl chloride resin composition containing a vinyl chloride resin and a pigment to heat processing,
The step of applying heat processing is a step of heating, softening and deforming the processed portion of the processed tube by irradiating infrared rays with an infrared heater,
The pigment includes at least one selected from the group consisting of non-carbon inorganic pigments and organic pigments,
The infrared reflectance of the surface of the tube to be processed is 20% or more,
The ratio SDR of the outer diameter (mm) to the wall thickness (mm) of the pipe to be processed is 30 to 36,
The heating time when performing the heating processing is such that the ratio T/SDR of the heating time T (seconds) converted when using an infrared heater with an output of 500 W as the infrared heater to the ratio SDR is 40 to 150. A method for manufacturing a pipe joint, characterized in that: The method for manufacturing a pipe joint according to claim 1, wherein the heat processing is one or both of bending and socket processing. A pipe joint that is made of a gray hard vinyl chloride resin composition containing a vinyl chloride resin and a pigment, and has a processed part that has been subjected to heat processing and an unprocessed part that has not been subjected to the heat processing. ,
The pigment includes at least one selected from the group consisting of non-carbon inorganic pigments and organic pigments,
The infrared reflectance of the surface is 20% or more,
The ratio SDR of the outer diameter (mm) to the wall thickness (mm) of the unprocessed part is 30 to 36,
A pipe joint characterized in that the color difference between the processed part and the unprocessed part is 5 or less . The pipe joint according to claim 3, wherein the processed portion is one or both of a bent portion and a socket portion . The pipe joint according to claim 4, wherein the radius of curvature of the bent portion is 450 to 2100 mm. The pipe joint according to claim 4 or 5, wherein the inner diameter of the socket portion is 114 to 630 mm. A pipe fitting according to any one of claims 3 to 6 , wherein the pigment is substantially free of carbon black. The pipe fitting according to any one of claims 3 to 7 , wherein the pigment consists only of a non-carbon inorganic pigment. The pipe fitting according to any one of claims 3 to 7 , wherein the pigment exhibiting color among the pigments consists only of organic pigments. The pipe fitting according to any one of claims 3 to 7 , wherein the pigment consists of a mixture of a non-carbon inorganic pigment and an organic pigment. The pipe fitting according to any one of claims 3 to 10, having no gate marks and no weld lines.

Images