JP7704546B2 - PVC resin pipe - Google Patents

Description

The present invention relates to a vinyl chloride resin pipe using a vinyl chloride resin composition.

Vinyl chloride resins are processed into various molded articles such as joints, pipes, plates, and containers, and are used in many fields. The vinyl chloride resins are particularly suitable for use in pipes because of their excellent mechanical strength, weather resistance, heat resistance, and chemical resistance.

When producing vinyl chloride resin compositions and vinyl chloride resin pipes (vinyl chloride resin molded articles), additives such as stabilizers and lubricants are sometimes used to improve moldability. However, stabilizers and lubricants are relatively expensive, which increases the production costs. Therefore, inexpensive calcium carbonate is sometimes used as a filler to reduce the production costs of vinyl chloride resin compositions and vinyl chloride resin pipes (vinyl chloride resin molded articles).

The following Patent Document 1 discloses a vinyl chloride resin composition containing a vinyl chloride resin and cubic calcium carbonate. It also describes that the vinyl chloride resin composition preferably contains a plasticizer.

Patent Document 2 below discloses a rigid polyvinyl chloride molded product containing 100 parts by mass of a polyvinyl chloride resin having an average degree of polymerization of 500 to 1500 and 10 to 40 parts by mass of calcium carbonate. The calcium carbonate has an average primary particle size of 0.01 μm to 0.3 μm and a coefficient of variation in the number of particles of 15% or less.

JP 2002-167486 A JP 2019-038996 A

In Patent Documents 1 and 2, the production costs can be reduced to some extent by adding calcium carbonate to a vinyl chloride resin composition.

However, since calcium carbonate and vinyl chloride resin have poor compatibility, the calcium carbonate particles pulverized by mixing with vinyl chloride resin are difficult to disperse uniformly in the vinyl chloride resin composition, and tend to aggregate in the composition or during molding to form secondary particles. If secondary particles of calcium carbonate are present in a vinyl chloride resin pipe (vinyl chloride resin molded body), when the vinyl chloride resin pipe is subjected to an impact such as being dropped, cracks may occur starting from the secondary particles of calcium carbonate. In other words, there is a problem that the impact resistance of the vinyl chloride resin pipe is reduced. In addition, since the kneading capacity of extrusion molding is higher than that of injection molding, calcium carbonate particles are easily pulverized in extrusion molding. As a result, there is a problem that the pulverized particles of calcium carbonate tend to aggregate to form secondary particles in extrusion molding, which tends to further reduce the impact resistance of the vinyl chloride resin pipe.

Furthermore, in the vinyl chloride resin composition described in Patent Document 1, the heat resistance and impact resistance of the vinyl chloride resin composition may be further reduced by the plasticizer.

In addition, in Patent Document 2, the particle size of the calcium carbonate in the vinyl chloride resin composition is too small, so that the calcium carbonate is more likely to aggregate and secondary particles of calcium carbonate are more likely to form. As a result, there is a problem that the impact resistance of the vinyl chloride resin molded body is more likely to deteriorate.

The object of the present invention is to provide a polyvinyl chloride resin pipe that can reduce manufacturing costs and increase impact resistance.

According to a broad aspect of the present invention, there is provided a polyvinyl chloride resin pipe molded from a polyvinyl chloride resin composition containing a polyvinyl chloride resin, a polyoxyalkylene glycol, and calcium carbonate, the polyoxyalkylene glycol content being 0.01 parts by weight or more and 0.70 parts by weight or less, relative to 100 parts by weight of the polyvinyl chloride resin, the polyoxyalkylene glycol content being 0.01 parts by weight or more and 0.70 parts by weight or less, the polyvinyl chloride resin pipe containing secondary particles of the calcium carbonate, and the polyoxyalkylene glycol content being 15 μm or less.

In a particular aspect of the polyvinyl chloride resin pipe of the present invention, the polyoxyalkylene glycol is polyoxypropylene glycol.

In a particular aspect of the polyvinyl chloride resin pipe according to the present invention, the polyoxyalkylene glycol content in the polyvinyl chloride resin composition is 0.1 parts by weight or more and 2.0 parts by weight or less per 100 parts by weight of the calcium carbonate.

In a particular aspect of the polyvinyl chloride resin pipe according to the present invention, the polyvinyl chloride resin composition contains an organotin stabilizer.

In a particular aspect of the polyvinyl chloride resin pipe according to the present invention, the polyvinyl chloride resin pipe is an extrusion molded product of the polyvinyl chloride resin composition.

The vinyl chloride resin pipe according to the present invention is a vinyl chloride resin pipe molded from a vinyl chloride resin composition containing vinyl chloride resin, polyoxyalkylene glycol, and calcium carbonate. In the vinyl chloride resin pipe according to the present invention, the content of the calcium carbonate is 10 parts by weight or more and 35 parts by weight or less, and the content of the polyoxyalkylene glycol is 0.01 parts by weight or more and 0.70 parts by weight or less, per 100 parts by weight of the vinyl chloride resin. The vinyl chloride resin pipe according to the present invention contains secondary particles of the calcium carbonate. In the vinyl chloride resin pipe according to the present invention, the average particle diameter of the secondary particles of the calcium carbonate is 15 μm or less. Since the vinyl chloride resin pipe according to the present invention has the above configuration, it is possible to reduce manufacturing costs and increase impact resistance.

The present invention is described in detail below.

The vinyl chloride resin pipe according to the present invention is a vinyl chloride resin pipe molded from a vinyl chloride resin composition containing vinyl chloride resin, polyoxyalkylene glycol, and calcium carbonate. In the vinyl chloride resin pipe according to the present invention, the content of the calcium carbonate is 10 parts by weight or more and 35 parts by weight or less, and the content of the polyoxyalkylene glycol is 0.01 parts by weight or more and 0.70 parts by weight or less, per 100 parts by weight of the vinyl chloride resin.

The polyvinyl chloride resin pipe of the present invention contains secondary particles of the calcium carbonate. In the polyvinyl chloride resin pipe of the present invention, the average particle size of the secondary particles of the calcium carbonate is 15 μm or less.

The polyvinyl chloride resin pipe of the present invention has the above-mentioned configuration, which reduces manufacturing costs and improves impact resistance.

The vinyl chloride resin pipe according to the present invention is obtained by molding the vinyl chloride resin composition, and therefore contains vinyl chloride resin, polyoxyalkylene glycol, and calcium carbonate. In the vinyl chloride resin pipe according to the present invention, it is preferable that the content of the calcium carbonate is 10 parts by weight or more and 35 parts by weight or less, and the content of the polyoxyalkylene glycol is 0.01 parts by weight or more and 0.70 parts by weight or less, per 100 parts by weight of the vinyl chloride resin.

The vinyl chloride resin pipe is a molded product of the vinyl chloride resin composition. It is preferable that the vinyl chloride resin pipe is an extrusion molded product of the vinyl chloride resin composition.

The vinyl chloride resin composition is used to obtain a vinyl chloride resin pipe. The vinyl chloride resin composition is suitably used to obtain an extruded vinyl chloride resin pipe. The vinyl chloride resin composition is preferably extrusion molded. The vinyl chloride resin composition is preferably a vinyl chloride resin composition for extrusion molding.

(Vinyl chloride resin composition)
The vinyl chloride resin composition contains a vinyl chloride resin, a polyoxyalkylene glycol, and calcium carbonate.

In this specification, a single unagglomerated calcium carbonate particle in the material of the vinyl chloride resin composition is referred to as a primary particle of calcium carbonate. A pulverized product of the primary particle of calcium carbonate is referred to as a pulverized particle of calcium carbonate. An agglomerate of two or more primary particles or pulverized particles of calcium carbonate is referred to as a secondary particle of calcium carbonate.

The following describes each component contained in the vinyl chloride resin composition. In the following description of the vinyl chloride resin composition, the vinyl chloride resin pipe may also be described.

In this specification, "(meth)acrylic" means either or both of "acrylic" and "methacrylic", and "(meth)acrylate" means either or both of "acrylate" and "methacrylate".

<Vinyl chloride resin>
The vinyl chloride resin has a chlorine atom. The vinyl chloride resin may be a chlorinated vinyl chloride resin, a non-chlorinated vinyl chloride resin, or a mixture of a chlorinated vinyl chloride resin and a non-chlorinated vinyl chloride resin. From the viewpoint of enhancing flame retardancy and heat deformation resistance, the vinyl chloride resin is preferably a chlorinated vinyl chloride resin. The chlorinated vinyl chloride resin is a resin obtained by chlorinating a vinyl chloride resin. Only one type of the vinyl chloride resin may be used, or two or more types may be used in combination.

Examples of the vinyl chloride resin include homopolymers of vinyl chloride monomers, copolymers of vinyl chloride monomers and vinyl monomers copolymerizable with vinyl chloride monomers, etc.

Examples of vinyl monomers copolymerizable with the vinyl chloride monomer include vinyl esters such as vinyl acetate, vinyl propionate, and vinyl ether; cyano group-containing compounds such as acrylonitrile; halogen compounds such as vinylidene chloride and vinyl fluoride; olefins such as ethylene and propylene; carboxyl group-containing compounds such as itaconic acid, maleic acid, and fumaric acid; non-aromatic carboxylic acid anhydrides such as maleic anhydride; (meth)acrylic acid esters such as methyl (meth)acrylate and ethyl (meth)acrylate; and imide compounds such as maleimide. Only one type of vinyl monomer copolymerizable with the vinyl chloride monomer may be used, or two or more types may be used in combination.

The polymerization method of the vinyl chloride monomer or the polymerization method of the vinyl chloride monomer and a vinyl monomer copolymerizable with the vinyl chloride monomer is not particularly limited. Examples of the polymerization method include suspension polymerization, emulsion polymerization, solution polymerization, bulk polymerization, and precipitation polymerization. From the viewpoint of efficiently obtaining a vinyl chloride resin, the polymerization method is preferably suspension polymerization, emulsion polymerization, solution polymerization, or precipitation polymerization.

The chlorinated vinyl chloride resin is preferably obtained by polymerizing the vinyl chloride monomer or the vinyl chloride monomer and a vinyl monomer copolymerizable with the vinyl chloride monomer to obtain a vinyl chloride resin, and then chlorinating the vinyl chloride resin.

The method for chlorinating the vinyl chloride resin is not particularly limited. Examples of the method for chlorinating the vinyl chloride resin include a method in which the vinyl chloride resin is placed in an aqueous solvent to obtain a suspension, and then chlorine is added to react the vinyl chloride resin with chlorine. This chlorination reaction proceeds under heating conditions or light irradiation conditions.

From the viewpoint of increasing the thermal stability of the resulting chlorinated vinyl chloride resin, it is preferable that the chlorination reaction be carried out under heating conditions.

From the viewpoint of increasing the efficiency of the chlorination reaction, the temperature during the heating is preferably 65°C or higher and preferably 130°C or lower.

The chlorine content of the vinyl chloride resin (if the vinyl chloride resin is a chlorinated vinyl chloride resin, the chlorine content of the chlorinated vinyl chloride resin) can be determined by potentiometric titration in accordance with JIS K7229.

The degree of polymerization of the vinyl chloride resin is preferably 500 or more, more preferably 800 or more, and preferably 2000 or less, more preferably 1100 or less, and even more preferably 1000 or less. If the degree of polymerization is equal to or greater than the lower limit, the durability of the vinyl chloride resin pipe can be increased, and the impact resistance can be further improved. If the degree of polymerization is equal to or less than the upper limit, the melt viscosity of the vinyl chloride resin and the vinyl chloride resin composition can be reduced, and the flowability during molding can be increased.

In 100% by weight of the vinyl chloride resin composition and 100% by weight of the vinyl chloride resin pipe, the content of the vinyl chloride resin is preferably 65% by weight or more, more preferably 70% by weight or more, even more preferably 75% by weight or more, and preferably 95% by weight or less, more preferably 92% by weight or less, even more preferably 91% by weight or less. When the content of the vinyl chloride resin is equal to or greater than the lower limit, the adhesive strength of the vinyl chloride resin pipe can be increased and the impact resistance can be further improved. When the content of the vinyl chloride resin is equal to or less than the upper limit, there is no need to raise the temperature during molding, and moldability can be improved.

The vinyl chloride resin contained in the vinyl chloride resin composition is preferably in the form of particles. The particle diameter of the vinyl chloride resin particles is preferably 0.1 μm or more and preferably 500 μm or less. If the particle diameter is equal to or more than the lower limit, the handling properties can be improved. If the particle diameter is equal to or less than the upper limit, the moldability can be improved.

The particle diameter of the vinyl chloride resin is preferably an average particle diameter, and is preferably a volume average particle diameter. The volume average particle diameter of the vinyl chloride resin is an average diameter measured on a volume basis, and is the value of the median diameter at 50% (D50). The volume average particle diameter can be measured by a laser diffraction/scattering method, etc.

<Polyoxyalkylene glycol>
By using the polyoxyalkylene glycol in combination with calcium carbonate, the primary particles and pulverized particles of the calcium carbonate can be uniformly dispersed in the vinyl chloride resin composition and the vinyl chloride resin pipe, and the formation of secondary particles of the calcium carbonate can be suppressed.

The polyoxyalkylene glycols include polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, and polyoxyethylene-polyoxypropylene copolymers. Only one type of the polyoxyalkylene glycols may be used, or two or more types may be used.

From the viewpoint of improving the appearance of the polyvinyl chloride resin pipe and further increasing the impact resistance by suppressing the formation of secondary particles of calcium carbonate, the polyoxyalkylene glycol is preferably polyoxyethylene glycol or polyoxypropylene glycol, and more preferably polyoxypropylene glycol.

From the viewpoint of improving the appearance of the polyvinyl chloride resin pipe and further increasing the impact resistance by suppressing the formation of secondary particles of calcium carbonate, the number of carbon atoms in the alkylene group in the polyoxyalkylene glycol is preferably 2 or more and preferably 4 or less. The alkylene group in the polyoxyalkylene glycol may be of only one type or of two or more types.

The alkylene group in the polyoxyalkylene glycol may or may not have a side chain. Examples of the side chain include a methyl group, an ethyl group, a propyl group, and a butyl group. The side chain of the alkylene group in the polyoxyalkylene glycol may be of only one type, or of two or more types.

From the viewpoint of dispersing the primary particles and pulverized particles of the calcium carbonate more uniformly in the vinyl chloride resin composition and the vinyl chloride resin tube and further suppressing the formation of secondary particles of the calcium carbonate, it is preferable that the polyoxyalkylene glycol has a carboxy group at its terminal, and more preferably has carboxy groups at both terminals.

The molecular weight of the polyoxyalkylene glycol is preferably 100 or more, more preferably 2000 or more, and even more preferably 3000 or more, and is preferably 10000 or less, more preferably 8000 or less, and even more preferably 6000 or less. When the molecular weight of the polyoxyalkylene glycol is equal to or more than the lower limit and equal to or less than the upper limit, the formation of secondary particles of the calcium carbonate is suppressed, thereby improving the appearance of the polyvinyl chloride resin pipe and further increasing the impact resistance. The molecular weight is preferably a number average molecular weight.

When the structural formula of the polyoxyalkylene glycol can be specified, the molecular weight of the polyoxyalkylene glycol refers to the molecular weight that can be calculated from the structural formula. When the polyoxyalkylene glycol is a polymer or the like whose structural formula cannot be specified, the molecular weight refers to the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

In the vinyl chloride resin composition, the content of the polyoxyalkylene glycol is 0.01 parts by weight or more and 0.70 parts by weight or less per 100 parts by weight of the vinyl chloride resin. In the vinyl chloride resin pipe, the content of the polyoxyalkylene glycol is preferably 0.01 parts by weight or more and preferably 0.70 parts by weight or less per 100 parts by weight of the vinyl chloride resin. In each of the vinyl chloride resin composition and the vinyl chloride resin pipe, the content of the polyoxyalkylene glycol is preferably 0.05 parts by weight or more, more preferably 0.10 parts by weight or more, and preferably 0.60 parts by weight or less, more preferably 0.56 parts by weight or less per 100 parts by weight of the vinyl chloride resin. When the content of the polyoxyalkylene glycol is equal to or more than the lower limit, the primary particles and pulverized particles of the calcium carbonate can be more uniformly dispersed in the vinyl chloride resin composition and the vinyl chloride resin pipe, and the formation of secondary particles of the calcium carbonate can be suppressed. As a result, the appearance of the polyvinyl chloride resin pipe can be improved and the impact resistance can be further improved. If the content of the polyoxyalkylene glycol is equal to or less than the upper limit, the polyoxyalkylene glycol present between the ground particles of the calcium carbonate is difficult to remove, and the aggregation of the ground particles of the calcium carbonate can be prevented, so the formation of secondary particles of the calcium carbonate can be suppressed. As a result, the appearance of the polyvinyl chloride resin pipe can be improved and the impact resistance can be further improved.

In each of the vinyl chloride resin composition and the vinyl chloride resin pipe, the content of the polyoxyalkylene glycol is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, and even more preferably 0.8 parts by weight or more, per 100 parts by weight of the calcium carbonate. In each of the vinyl chloride resin composition and the vinyl chloride resin pipe, the content of the polyoxyalkylene glycol is preferably 2.0 parts by weight or less, more preferably 1.6 parts by weight or less, and even more preferably 1.4 parts by weight or less, per 100 parts by weight of the calcium carbonate. When the content of the polyoxyalkylene glycol is equal to or more than the lower limit, the primary particles and pulverized particles of the calcium carbonate can be uniformly dispersed in the vinyl chloride resin composition and the vinyl chloride resin pipe, and the formation of secondary particles of the calcium carbonate can be suppressed. As a result, the appearance of the vinyl chloride resin pipe can be improved, and the impact resistance can be further improved. When the content of the polyoxyalkylene glycol is equal to or less than the upper limit, the polyoxyalkylene glycol present between the ground particles of the calcium carbonate is difficult to remove, and the aggregation of the calcium carbonate can be prevented, so the formation of secondary particles of the calcium carbonate can be suppressed. As a result, the appearance of the polyvinyl chloride resin pipe can be improved, and the impact resistance can be further improved.

<Calcium carbonate>
In the vinyl chloride resin composition and the vinyl chloride resin pipe, the calcium carbonate acts as a filler.

In the material of the vinyl chloride resin composition, the calcium carbonate exists as primary particles. The primary particles of calcium carbonate may be pulverized into two or more particles by mixing with vinyl chloride resin or the like during preparation of the vinyl chloride resin composition, to become pulverized particles. The pulverized particles of calcium carbonate are formed by pulverizing the primary particles of calcium carbonate. The primary particles and pulverized particles of calcium carbonate may aggregate in the vinyl chloride resin composition and during molding to become secondary particles. The secondary particles of calcium carbonate are formed by two or more primary particles or pulverized particles of calcium carbonate. The secondary particles of calcium carbonate may be formed only by the primary particles of calcium carbonate, may be formed only by the pulverized particles of calcium carbonate, or may be formed by a combination of the primary particles and pulverized particles of calcium carbonate.

The vinyl chloride resin composition may contain primary particles of the calcium carbonate, may contain crushed particles of the calcium carbonate, or may contain primary particles and crushed particles of the calcium carbonate. The vinyl chloride resin composition preferably contains crushed particles of the calcium carbonate. The calcium carbonate in the vinyl chloride resin composition is preferably crushed particles of the calcium carbonate. In the vinyl chloride resin composition, the calcium carbonate particles are preferably present as crushed particles. It is preferable that the calcium carbonate does not aggregate in the vinyl chloride resin composition. The vinyl chloride resin composition preferably does not contain secondary particles of the calcium carbonate.

From the viewpoint of exerting the effects of the present invention more effectively, the particle diameter (primary particle diameter) of the primary particles of the calcium carbonate is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, and is preferably 10 μm or less, more preferably 5.0 μm or less, even more preferably 3.0 μm or less.

From the viewpoint of exerting the effects of the present invention more effectively, the particle diameter (crushed particle diameter) of the crushed particles of the calcium carbonate is preferably 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.5 μm or more, and is preferably 5.0 μm or less, more preferably 3.0 μm or less, even more preferably 2.0 μm or less.

From the viewpoint of exerting the effects of the present invention more effectively, the particle diameter (secondary particle diameter) of the secondary particles of the calcium carbonate in the vinyl chloride resin composition is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.5 μm or more, and is preferably 15 μm or less, more preferably 14 μm or less, even more preferably 10 μm or less.

The primary particle size, crushed particle size, and secondary particle size of the calcium carbonate are preferably average particle sizes, and are preferably number average particle sizes. The particle size of the calcium carbonate is determined, for example, by observing 50 arbitrary calcium carbonate particles with an electron microscope or optical microscope and calculating the average particle size of each calcium carbonate, or by using a particle size distribution measuring device. In the observation with an electron microscope or optical microscope, the particle size of each calcium carbonate particle is determined as the particle size of a circle equivalent diameter. In the observation with an electron microscope or optical microscope, the average particle size of 50 arbitrary calcium carbonate particles with a circle equivalent diameter is almost equal to the average particle size of the sphere equivalent diameter. In the particle size distribution measuring device, the particle size of each calcium carbonate particle is determined as the particle size of a sphere equivalent diameter. The average particle size of the calcium carbonate is preferably calculated using a particle size distribution measuring device.

The primary particles, crushed particles, and secondary particles of the calcium carbonate may be spherical or may have a shape other than spherical, such as a square prism, a cylinder, or a flat shape. From the viewpoint of further increasing the impact resistance and improving the fluidity during molding, the primary particles, crushed particles, and secondary particles of the calcium carbonate are preferably spherical. The aspect ratios of the primary particles, crushed particles, and secondary particles of the calcium carbonate are preferably 2.0 or less, more preferably 1.5 or less, and even more preferably 1.2 or less.

In the vinyl chloride resin composition, the content of the calcium carbonate is 10 parts by weight or more and 35 parts by weight or less per 100 parts by weight of the vinyl chloride resin. In the vinyl chloride resin pipe, the content of the calcium carbonate is preferably 10 parts by weight or more and preferably 35 parts by weight or less per 100 parts by weight of the vinyl chloride resin. In the present invention, the above configuration is provided, so that the manufacturing costs of the vinyl chloride resin composition and the vinyl chloride resin pipe can be reduced. In addition, the fluidity during molding can be increased, and the appearance of the vinyl chloride resin pipe can be improved. In each of the vinyl chloride resin composition and the vinyl chloride resin pipe, the content of the calcium carbonate is preferably 12 parts by weight or more, more preferably 15 parts by weight or more, and preferably 30 parts by weight or less, more preferably 25 parts by weight or less per 100 parts by weight of the vinyl chloride resin. When the content of the calcium carbonate is equal to or more than the lower limit and equal to or less than the upper limit, the manufacturing costs can be further reduced and the impact resistance can be further increased.

The vinyl chloride resin composition and the vinyl chloride resin pipe may contain a filler other than the calcium carbonate. Examples of the filler other than the calcium carbonate include talc.

<Other Ingredients>
The vinyl chloride resin composition and the vinyl chloride resin pipe may contain various additives as necessary. Examples of the additives include stabilizers, heat stabilization aids, lubricants, processing aids, impact modifiers, heat resistance improvers, antioxidants, ultraviolet absorbers, antistatic agents, light stabilizers, pigments, flame retardants, and plasticizers. The additives may be used alone or in combination of two or more.

The vinyl chloride resin composition and the vinyl chloride resin pipe preferably contain a stabilizer. Examples of the stabilizer include an organotin stabilizer, a lead stabilizer, a calcium-zinc stabilizer, a barium-zinc stabilizer, and a barium-cadmium stabilizer. Only one type of the stabilizer may be used, or two or more types may be used in combination.

The stabilizer is preferably a heat stabilizer.

From the viewpoint of suppressing the decomposition of the vinyl chloride resin and capturing the hydrogen chloride generated during the decomposition of the vinyl chloride resin, the vinyl chloride resin composition and the vinyl chloride resin pipe preferably contain an organotin stabilizer, and more preferably contain an organotin heat stabilizer. In addition, the use of an organotin stabilizer improves the appearance of the vinyl chloride resin pipe.

Examples of the organic tin stabilizer include tin mercapto stabilizers, tin malate stabilizers, and tin carboxylate stabilizers. Examples of the tin mercapto stabilizers include monoalkyltin mercapto, dialkyltin mercapto, monoalkyltin mercapto polymer, dialkyltin mercapto polymer, monoalkyltin mercapto sulfide, and dialkyltin mercapto sulfide. Examples of the dialkyltin mercapto include dimethyltin mercapto, dibutyltin mercapto, and dioctyltin mercapto. Examples of the tin malate stabilizers include monoalkyltin malate, dialkyltin malate, monoalkyltin malate polymer, and dialkyltin malate polymer. Examples of the dialkyltin malate include dibutyltin malate and dioctyltin malate. Examples of the dialkyltin malate polymer include dibutyltin malate polymer and dioctyltin malate polymer. Examples of the tin carboxylate stabilizers include monoalkyltin carboxylate and dialkyltin carboxylate. Examples of the dialkyltin carboxylate include dibutyltin laurate. The organotin stabilizers may be used alone or in combination of two or more.

From the viewpoint of improving the appearance of the polyvinyl chloride resin pipe, the organotin stabilizer is preferably a tin mercapto stabilizer, more preferably a dialkyltin mercapto, and even more preferably a dioctyltin mercapto.

Examples of the lead-based stabilizers include tribasic lead sulfate, tetrabasic lead sulfate, basic lead sulfite, dibasic lead phosphite, dibasic lead phthalate, tribasic lead maleate, dibasic lead stearate, and basic sulfite and phosphite.

In each of the vinyl chloride resin composition and the vinyl chloride resin pipe, the content of the organic tin stabilizer is preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, and even more preferably 0.4 parts by weight or more, per 100 parts by weight of the vinyl chloride resin. In each of the vinyl chloride resin composition and the vinyl chloride resin pipe, the content of the organic tin stabilizer is preferably 3.0 parts by weight or less, more preferably 2.0 parts by weight or less, and even more preferably 1.8 parts by weight or less, per 100 parts by weight of the vinyl chloride resin. When the content of the organic tin stabilizer is equal to or more than the lower limit and equal to or less than the upper limit, the thermal stability can be improved and the heat resistance of the vinyl chloride resin pipe can be improved.

The heat stabilization aid is not particularly limited, and examples thereof include epoxidized soybean oil, phosphate esters, polyols, hydrotalcite, and zeolites. Only one type of the heat stabilization aid may be used, or two or more types may be used in combination.

The vinyl chloride resin composition and the vinyl chloride resin pipe may or may not contain a lubricant. It is preferable that the vinyl chloride resin composition and the vinyl chloride resin pipe contain a lubricant.

The lubricants include internal lubricants and external lubricants. The internal lubricants are used to reduce the flow viscosity of the molten resin during molding and to prevent frictional heat generation. The internal lubricants are not particularly limited, and examples thereof include butyl stearate, lauryl alcohol, stearyl alcohol, epoxy soybean oil, glycerin monostearate, stearic acid, and bisamide. The external lubricants are used to increase the sliding effect between the molten resin and the metal surface during molding. The external lubricants are not particularly limited, and examples thereof include polyethylene-based lubricants, ester-based lubricants, paraffin wax, polyolefin wax, and montanic acid wax. Only one type of the lubricants may be used, or two or more types may be used in combination.

From the viewpoint of improving the sliding between the vinyl chloride resin composition and the metal surface (mold) during molding, the vinyl chloride resin composition and the vinyl chloride resin pipe preferably contain a polyethylene-based lubricant, and more preferably contain a polyethylene-based lubricant and an ester-based lubricant.

When the vinyl chloride resin composition and the vinyl chloride resin pipe contain the polyethylene lubricant, it is preferable that the following content is satisfied. The content of the polyethylene lubricant is preferably more than 0 parts by weight, more preferably 0.1 parts by weight or more, even more preferably 0.5 parts by weight or more, and preferably 10 parts by weight or less, more preferably 2 parts by weight or less, and even more preferably 1 part by weight or less, relative to 100 parts by weight of the vinyl chloride resin. When the content of the polyethylene lubricant satisfies the above lower limit and the above upper limit, the primary particles and pulverized particles of the calcium carbonate can be uniformly dispersed in the vinyl chloride resin composition and the vinyl chloride resin pipe. As a result, the flowability during molding can be increased and the appearance of the vinyl chloride resin pipe can be improved. In addition, the sliding between the vinyl chloride resin composition and the metal surface (mold) during molding can be improved, and the appearance of the vinyl chloride resin pipe can be improved.

The vinyl chloride resin composition and the vinyl chloride resin pipe may contain the polyethylene lubricant and a lubricant other than the polyethylene lubricant.

When the vinyl chloride resin composition and the vinyl chloride resin pipe contain the polyethylene lubricant and a lubricant other than the polyethylene lubricant, it is preferable to satisfy the following contents. The total content of the polyethylene lubricant and the lubricant other than the polyethylene lubricant (total content of lubricants) relative to 100 parts by weight of the vinyl chloride resin is preferably more than 0 parts by weight, more preferably 0.2 parts by weight or more, and even more preferably 0.4 parts by weight or more. The total content of the polyethylene lubricant and the lubricant other than the polyethylene lubricant (total content of lubricants) relative to 100 parts by weight of the vinyl chloride resin is preferably 2.0 parts by weight or less, more preferably 1.5 parts by weight or less, and even more preferably 1.2 parts by weight or less. When the total content of the polyethylene lubricant and the lubricant other than the polyethylene lubricant satisfies the lower limit and the upper limit, the primary particles and pulverized particles of the calcium carbonate can be uniformly dispersed in the vinyl chloride resin composition and the vinyl chloride resin pipe, and the formation of secondary particles of the calcium carbonate can be suppressed. As a result, the flowability during molding can be improved and the appearance of the vinyl chloride resin pipe can be improved. In addition, the sliding between the vinyl chloride resin composition and the metal surface (mold) during molding can be improved, and the appearance of the vinyl chloride resin pipe can be improved.

The processing aid is not particularly limited. Examples of the processing aid include acrylic processing aids. Examples of the acrylic processing aid include alkyl acrylate-alkyl methacrylate copolymers having a weight average molecular weight of 100,000 to 2,000,000, and specific examples thereof include n-butyl acrylate-methyl methacrylate copolymers and 2-ethylhexyl acrylate-methyl methacrylate-butyl methacrylate copolymers. Only one type of the processing aid may be used, or two or more types may be used in combination.

The impact modifier is not particularly limited, and examples thereof include methyl methacrylate-butadiene-styrene copolymer (MBS), chlorinated polyethylene, and acrylic rubber. The impact modifier may be used alone or in combination of two or more kinds.

The heat resistance improver is not particularly limited, and examples thereof include α-methylstyrene-based and N-phenylmaleimide-based resins. Only one type of the heat resistance improver may be used, or two or more types may be used in combination.

The antioxidant is not particularly limited, and examples thereof include phenol-based antioxidants. The antioxidants may be used alone or in combination of two or more.

The above-mentioned UV absorbers are not particularly limited, and examples thereof include salicylic acid ester-based UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and cyanoacrylate-based UV absorbers. The above-mentioned UV absorbers may be used alone or in combination of two or more kinds.

The light stabilizer is not particularly limited, and examples thereof include hindered amine light stabilizers. Only one type of the light stabilizer may be used, or two or more types may be used in combination.

The pigment is not particularly limited, and examples thereof include organic pigments and inorganic pigments. Examples of the organic pigments include azo-based organic pigments, phthalocyanine-based organic pigments, threne-based organic pigments, and dye lake-based organic pigments. Examples of the inorganic pigments include oxide-based inorganic pigments, molybdenum chromate-based inorganic pigments, sulfide/selenide-based inorganic pigments, and ferrocyanide-based inorganic pigments. From the viewpoint of further increasing transparency, it is preferable that the vinyl chloride resin composition does not contain the above pigments.

The plasticizer may be added to improve processability during molding. The addition of a plasticizer may reduce the heat resistance of the molded product, so it is preferable to add a small amount of plasticizer. The plasticizer is not particularly limited, and examples include dibutyl phthalate, di-2-ethylhexyl phthalate, and di-2-ethylhexyl adipate. Only one type of the plasticizer may be used, or two or more types may be used in combination.

(Other details of polyvinyl chloride resin pipes)
The vinyl chloride resin pipe is formed using the vinyl chloride resin composition. The vinyl chloride resin composition can be used to obtain the vinyl chloride resin pipe. The vinyl chloride resin pipe is obtained by molding the vinyl chloride resin composition. The vinyl chloride resin pipe is a molded article of the vinyl chloride resin composition. The vinyl chloride resin pipe is preferably an extrusion molded article of the vinyl chloride resin composition.

In the polyvinyl chloride resin pipe, the primary particles and crushed particles of the calcium carbonate can be uniformly dispersed. As a result, the appearance of the polyvinyl chloride resin pipe can be improved.

Note that some of the primary particles and pulverized particles of the calcium carbonate in the vinyl chloride resin composition may aggregate in the composition or during molding. In the vinyl chloride resin pipe, some of the primary particles and pulverized particles of the calcium carbonate are aggregated. The vinyl chloride resin pipe (molded body of the vinyl chloride resin composition) contains secondary particles of the calcium carbonate. In the vinyl chloride resin pipe, primary particles, pulverized particles, and secondary particles of the calcium carbonate may be present. The vinyl chloride resin pipe may contain only secondary particles of the calcium carbonate, may contain primary particles and secondary particles, may contain pulverized particles and secondary particles, or may contain primary particles, pulverized particles, and secondary particles.

In the polyvinyl chloride resin pipe, the particle diameter (secondary particle diameter) of the secondary particles of the calcium carbonate is 15 μm or less. The particle diameter of the secondary particles of the calcium carbonate in the polyvinyl chloride resin pipe is preferably 1.0 μm or more, more preferably 1.5 μm or more, even more preferably 2.0 μm or more, and preferably 13 μm or less, more preferably 10 μm or less, even more preferably 8.0 μm or less, and particularly preferably 5.0 μm or less. When the particle diameter of the secondary particles of the calcium carbonate is equal to or more than the lower limit and equal to or less than the upper limit, the appearance of the polyvinyl chloride resin pipe can be improved and the impact resistance can be further improved.

The particle size of the secondary particles of calcium carbonate is preferably a number average particle size. The particle size of the secondary particles of calcium carbonate can be measured, for example, by the following method. The polyvinyl chloride resin pipe is cut using a diamond cutter, and the cross section is observed using a scanning electron microscope. The average particle size of the secondary particles of calcium carbonate present in a unit area is obtained using image analysis software. An example of the diamond cutter is Makita's "Circular Saw Model 2711".

For example, if one secondary particle is composed of three primary particles of calcium carbonate, the number of primary particles of calcium carbonate that are secondary particles in this secondary particle is counted as 3. For example, if one secondary particle is composed of three pulverized particles of calcium carbonate, the number of pulverized particles of calcium carbonate that are secondary particles in this secondary particle is counted as 3.

The polyvinyl chloride resin pipe may be a single-layer pipe or a multi-layer pipe.

The method of mixing the vinyl chloride resin composition and the material of the vinyl chloride resin pipe is not particularly limited. The vinyl chloride resin composition and the material of the vinyl chloride resin pipe may be mixed together, or a plurality of materials may be mixed in advance. In the manufacturing method of the vinyl chloride resin composition and the vinyl chloride resin pipe, it is preferable that the calcium carbonate (primary particles) and the polyoxyalkylene glycol are mixed in advance. When the calcium carbonate and the polyoxyalkylene glycol are mixed in advance, the polyoxyalkylene glycol is dispersed on the surface of the calcium carbonate, and the aggregation of the primary particles and crushed particles of the calcium carbonate can be prevented. As a result, the calcium carbonate can be prevented from becoming secondary particles in the vinyl chloride resin composition and during molding, so that the appearance of the vinyl chloride resin pipe can be improved and the impact resistance can be further improved. The calcium carbonate and the polyoxyalkylene glycol can be mixed using, for example, a mixer.

The molding machine used for molding is not particularly limited, and examples thereof include a screw-type extruder, a single-screw extruder, a twin-screw counter-rotating parallel extruder, a twin-screw counter-rotating conical extruder, and a twin-screw co-rotating extruder. In the above-mentioned screw-type extruder, the vinyl chloride resin composition filled in the cylinder is molded in a metal mold, extruded from the tip of the screw, and cooled in a water tank to form a vinyl chloride resin pipe (vinyl chloride resin molded product). When molding is performed using the above-mentioned molding machine, the mold for forming and the resin temperature, etc. are not particularly limited.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to the following examples.

The following materials were prepared:

(Vinyl chloride resin)
Polyvinyl chloride resin ("TS-1000R" manufactured by Taiyo Vinyl Corporation, polymerization degree: 1000)

(Polyoxyalkylene glycol)
Polyoxypropylene glycol (BYK "DISPERPLAST 1180", molecular weight: 3.2 x 10 ³ )

(Calcium Carbonate)
Calcium carbonate (Maruo Calcium Co., Ltd. "Super #1700", average particle size of primary particles: 1.9 μm)

(Lubricant)
Polyethylene lubricant (Mitsui Chemicals "HW2203A", acid value: 30)
Ester lubricant (Emery Oleo's "G15")

(Stabilizer)
Organotin stabilizer (Katsuta Chemical Industries, Ltd. "KM-19D-2")

Example 1
10 parts by weight of calcium carbonate and 0.15 parts by weight of polyoxypropylene glycol were added to a small crusher ("Rotary Crusher NR-04A" manufactured by Sansho Industry Co., Ltd.) and mixed at 30,000 rpm for 5 minutes to obtain a premixed composition. In the premixed composition, crushed particles of calcium carbonate were formed. The obtained premixed composition, 100 parts by weight of vinyl chloride resin, 1.6 parts by weight of organotin stabilizer, 0.5 parts by weight of polyethylene lubricant, and 0.5 parts by weight of ester lubricant were added to a rotary mixer ("20L Super Mixer" manufactured by Kawata Co., Ltd.). Next, steam was added and the mixture was rotated and mixed at a rotation speed of 1500 rpm, and the temperature was raised to 105°C, after which the steam was stopped, cooling water was flowed and the mixture was rotated and mixed, and the mixture was cooled to 50°C to obtain a vinyl chloride resin composition.

A polyvinyl chloride resin pipe (extrusion molded product) was produced from the obtained polyvinyl chloride resin composition using a twin-screw counter-rotating parallel extruder ("SLM50" manufactured by Nagata Manufacturing Co., Ltd.) under the following conditions. The obtained polyvinyl chloride resin pipe had a length of 40 cm, an outer diameter of 60 mm, and a thickness of 4.3 mm. Secondary particles of calcium carbonate were formed in the polyvinyl chloride resin pipe.

[Extrusion conditions]
Mold: Pipe mold (diameter 50A)
Total output: 20 kg/h
Resin temperature: 190°C (temperature at the mold inlet)

(Examples 2 to 4, Comparative Examples 1 to 4, and Reference Example 1)
A vinyl chloride resin composition and a vinyl chloride resin pipe were prepared in the same manner as in Example 1, except that the types and amounts of the blended components were as shown in Tables 1 and 2 below.

(evaluation)
(1) Average particle size of secondary particles of calcium carbonate The obtained polyvinyl chloride resin pipe was cut into a length of 3 mm using a diamond cutter (Makita Corporation, "Circular Saw Model 2711"), and the cross section was observed using a scanning electron microscope (JEOL Corporation, "JSM-6510A"). Using image analysis software (ImageJ), the average circle equivalent diameter of secondary particles of calcium carbonate present in any 1 ^cm2 was calculated, and this was taken as the average particle size of the secondary particles.

(2) Impact resistance A drop weight impact test (impact resistance test) was carried out on the obtained polyvinyl chloride resin pipe in accordance with Annex JA of JIS K6743 using a drop weight tester ("TS-001" manufactured by Nidec-Shimpo Corporation) and a flat-bottomed weight with a mass of 3 kg. The 50% impact fracture height at 0°C was calculated in accordance with JIS K7211, and the ratio (%) of the 50% impact fracture height of Reference Example 1 containing no calcium carbonate was taken as the impact strength retention rate. The impact resistance of the polyvinyl chloride resin pipe was judged according to the following criteria. It is preferable that the following impact strength retention rate is 50% or more.

[Impact resistance evaluation criteria]
○○: Impact strength retention rate is 80% or more. ○: Impact strength retention rate is 60% or more and less than 80%. △: Impact strength retention rate is 50% or more and less than 60%. ×: Impact strength retention rate is less than 50%.

The compounding composition and results are shown in Tables 1 and 2 below.

In the polyvinyl chloride resin pipes of Examples 1 to 4, the average particle size of the secondary particles of calcium carbonate was 15 μm or less. As a result, the polyvinyl chloride resin pipes of Examples 1 to 4 can prevent a decrease in the impact strength retention rate and have excellent impact resistance. In addition, since the polyvinyl chloride resin pipes of Examples 1 to 4 contain calcium carbonate at a specific content, the manufacturing costs can be reduced.

In addition, in Reference Example 1, which does not contain calcium carbonate, secondary particles of calcium carbonate are not formed, so it has excellent impact resistance, but the production cost is higher than in Examples 1 to 4, which contain calcium carbonate.

Claims (5)

A vinyl chloride resin pipe molded from a vinyl chloride resin composition containing a vinyl chloride resin, a polyoxyalkylene glycol, and calcium carbonate,
In the vinyl chloride resin composition, the content of the calcium carbonate is 10 parts by weight or more and 35 parts by weight or less, and the content of the polyoxyalkylene glycol is 0.01 parts by weight or more and 0.70 parts by weight or less, relative to 100 parts by weight of the vinyl chloride resin,
The polyoxyalkylene glycol has carboxy groups at both ends,
the polyvinyl chloride resin pipe contains secondary particles of the calcium carbonate,
A polyvinyl chloride resin pipe, wherein, when a cross section of the polyvinyl chloride resin pipe is observed with a scanning electron microscope, the average circle equivalent diameter of the secondary particles of the calcium carbonate is 15 μm or less. The polyvinyl chloride resin pipe according to claim 1, wherein the polyoxyalkylene glycol is polyoxypropylene glycol. The polyvinyl chloride resin pipe according to claim 1 or 2, wherein the polyoxyalkylene glycol content in the polyvinyl chloride resin composition is 0.1 parts by weight or more and 2.0 parts by weight or less per 100 parts by weight of the calcium carbonate. The polyvinyl chloride resin pipe according to any one of claims 1 to 3, wherein the polyvinyl chloride resin composition contains an organotin stabilizer. The polyvinyl chloride resin pipe according to any one of claims 1 to 4, which is an extrusion molded product of the polyvinyl chloride resin composition.