JP7680948B2 - Resin composition for rib joint and rib joint - Google Patents

Description

The present invention relates to a resin composition for rib joints and a rib joint.

Although polyvinyl chloride resins are materials with a wide range of uses, when exposed to heat or light, they can cause poor appearance, such as decomposition and discoloration. To prevent such poor appearance, various stabilizers are added to polyvinyl chloride resins. For example, Patent Document 1 discloses polyvinyl chloride resins containing a tin-based stabilizer consisting of a dialkyltin compound and a monoalkyltin compound. Patent Document 2 discloses polyvinyl chloride resins for pastes containing a calcium-zinc-based stabilizer.

Japanese Unexamined Patent Publication No. 62-225546 Japanese Patent Application Publication No. 09-291118

However, polyvinyl chloride resins using tin-based compounds as stabilizers, as in Patent Document 1, place a heavy burden on the working environment, including regulations regarding the handling of hazardous materials and odor control. Furthermore, Patent Document 2 discloses a resin composition for paste use, and does not mention the use of the resin composition in rib joints.

One aspect of the present invention aims to provide a resin composition for rib joints that places a small burden on the working environment.

The present invention includes the following aspects.
＜1＞
A polyvinyl chloride resin,
A calcium-zinc stabilizer;
A resin composition for rib joints comprising:
＜2＞
The resin composition for a rib joint according to <1>, wherein the calcium-zinc stabilizer contains a calcium salt of a fatty acid and a zinc salt of a fatty acid.
＜3＞
The resin composition for a rib joint according to <1> or <2>, wherein the degree of polymerization of the vinyl chloride resin is 670 or less.
＜4＞
The resin composition for a rib joint according to any one of <1> to <3>, which is molded by injection molding.
＜5＞
A rib joint comprising the resin composition for rib joints according to any one of <1> to <4>.

According to one aspect of the present invention, a resin composition for rib joints that places little strain on the working environment is provided.

The following describes in detail the embodiments of the present invention. However, the present invention is not limited to these, and various modifications are possible within the scope described. For example, embodiments obtained by appropriately combining the technical means disclosed in the different embodiments are also included in the technical scope of the present invention. In addition, unless otherwise specified in this specification, "A to B" representing a numerical range means "greater than or equal to A and less than or equal to B."

[1. Resin composition for rib joints]
The resin composition for a rib joint according to one embodiment of the present invention contains a vinyl chloride resin and a calcium-zinc stabilizer. Each component will be described below.

[1.1. Vinyl chloride resin]
Vinyl chloride resins are used as materials for general pipe materials and are versatile and economical. In this specification, vinyl chloride resins refer to resins whose main component is a unit derived from vinyl chloride. In one embodiment, the proportion of vinyl chloride-derived units in the vinyl chloride resin molecules is 50% by weight or more, 70% by weight or more, or 90% by weight or more. Only one type of vinyl chloride resin may be used, or two or more types may be used.

Specific examples of vinyl chloride resins include homopolymers of vinyl chloride, copolymers of vinyl chloride with other monomers, and graft copolymers in which vinyl chloride monomers are graft-copolymerized onto polymers. Polymers in which the vinyl chloride units contained in these polymers have been chlorinated are also included as examples of vinyl chloride resins (such as chlorinated polyvinyl chloride).

Examples of monomers to be copolymerized with vinyl chloride include α-olefins (ethylene, propylene, butylene, etc.); vinyl esters (vinyl acetate, vinyl propionate, etc.); vinyl ethers (butyl vinyl ether, cetyl vinyl ether, etc.); methacrylic acid esters (methyl methacrylate, ethyl methacrylate, butyl acrylate, etc.); aromatic vinyls (styrene, α-methylstyrene, etc.); and N-substituted maleimides (N-phenylmaleimide, N-cyclohexylmaleimide, etc.). The monomers to be copolymerized with vinyl chloride may be one type only, or two or more types.

Examples of polymers into which vinyl chloride monomers are graft-copolymerized include ethylene-vinyl acetate copolymers, ethylene-vinyl acetate-carbon monoxide copolymers, ethylene-ethyl acrylate copolymers, ethylene-butyl acrylate-carbon monoxide copolymers, ethylene-methyl methacrylate copolymers, ethylene-propylene copolymers, acrylonitrile-butadiene copolymers, polyurethanes, chlorinated polyethylenes, and chlorinated polypropylenes. The polymers into which vinyl chloride monomers are graft-copolymerized may be one type only, or two or more types.

The degree of polymerization of the vinyl chloride resin is preferably 670 or less, more preferably 660 or less. The lower limit of the degree of polymerization is preferably 600 or more, more preferably 620 or more. If the degree of polymerization is within the above range, the moldability of the resin composition is improved. Therefore, it is easy to prevent the occurrence of poor appearance of the product (yellowing of the molded body, air bubbles, etc.).

The polymerization method for the vinyl chloride resin is not particularly limited. For example, vinyl chloride resin obtained by emulsion polymerization, suspension polymerization, or bulk polymerization can be used.

1.2. Calcium-Zinc Stabilizers
The resin composition for rib joints according to one embodiment of the present invention contains a calcium-zinc based stabilizer, and since there is no need to use a tin based stabilizer or a lead based stabilizer, the burden on the working environment is small.

As the calcium-zinc stabilizer, known types of stabilizers can be used. Examples of calcium-zinc stabilizers include organic stabilizers and inorganic stabilizers. Examples of organic calcium-zinc stabilizers include metal soap stabilizers. Examples of inorganic calcium-zinc stabilizers include zeolite stabilizers, layered metal hydroxide stabilizers, and other inorganic stabilizers. Only one type of calcium-zinc stabilizer may be used, or two or more types may be used.

(Metal soap stabilizer)
The metal soap stabilizer is a stabilizer containing a calcium salt of a fatty acid and a zinc salt of a fatty acid. The number of carbon atoms of the fatty acid is preferably 10 to 22, more preferably 12 to 20, and even more preferably 14 to 18. The fatty acid may be a saturated fatty acid or an unsaturated fatty acid. Examples of saturated fatty acids include capric acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachic acid, behenic acid, and montanic acid. Examples of unsaturated fatty acids include Linderic acid, tsuzuic acid, petroselinic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid. The fatty acid may be a mixed fatty acid (beef tallow, coconut oil, palm oil, etc.). Among these, stearic acid, lauric acid, and palmitic acid are preferred, and stearic acid is more preferred.

(Zeolite stabilizer)
Examples of zeolite stabilizers include natural or synthetic zeolites (A-type zeolite, X-type zeolite, Y-type zeolite, L-type zeolite, P-type zeolite, T-type zeolite, etc.). In addition, substances having a crystal structure such as offretite, erionite, mordenite, ferrierite, clinoptilolite, chabazite, analcime, and sodalite-group aluminosilicates are also included. Furthermore, substances obtained by subjecting the above crystals to an acid treatment and then ion-exchanging them with calcium ions or zinc ions are also included.

(Layered metal hydroxide stabilizer)
Examples of layered metal hydroxide stabilizers include zinc modified hydrotalcite stabilizers, calcium silicate, and mixtures thereof.

An example of the zinc-modified hydrotalcite-based stabilizer is a composite metal hydroxide represented by the following general formula (1).
M ²⁺ _x M ³⁺ _y (OH) _2x+3y-2z (A ^2- ) _z・aH ₂ O...(1)
In formula (1), M ²⁺ is a divalent metal ion (such as Zn ²⁺ ). M ³⁺ is a trivalent metal ion (such as Al ³⁺ ). ^{A 2-} is a divalent anion (such as CO ₃ ^2- ). x, y, and z are positive numbers satisfying 8≧x/y≧1/4 and z/x+y>1/20. a is a number satisfying 0.25≦a/x+y≦1.0.

Examples of calcium silicate include tobermorite and xonotlite. In particular, microcrystalline calcium silicate is preferred. Examples of microcrystalline calcium silicate include substances represented by the following general formula (2).
CaO・_xSiO2・_nH2O ...(2)
In formula (2), x is a number from 0.5 to 2.0, and n is a number not exceeding 2.5.

Among the substances represented by formula (2), microcrystalline calcium silicate having X-ray diffraction patterns with interplanar spacings of 3.01 to 3.08 Å, 2.78 to 2.82 Å, and 1.81 to 1.84 Å is preferred. Also preferred is a composite of this microcrystalline calcium silicate with a polyhydric alcohol (or a partial ester of a polyhydric alcohol).

(Other inorganic stabilizers)
Other inorganic stabilizers include hydroxides of calcium and zinc, basic salts of calcium and zinc, and silicates of calcium and zinc. Hydroxides of calcium and zinc include calcium hydroxide and zinc hydroxide. Examples of basic salts of calcium and zinc include substances represented by the following general formula (3) (calcium stearate carbonate, basic zinc carbonate, basic calcium stearate, basic zinc stearate, basic calcium palmitate, etc.). Examples of silicates of calcium and zinc include substances represented by the following general formula (4) (calcium silicate, zinc silicate, etc.).
MO・qMX _z/m ...(3)
In formula (3), M is calcium or zinc. X is an inorganic acidic oxide anion or an organic anion. m is the valence of the anion X. q is 0.1 to 10, and preferably 0.5 to 5. Note that general formula (3) is expressed on an oxide basis.
MO・_kSiO2 ...(4)
In formula (4), M is calcium or zinc, and k is 0.1 to 10, and preferably 0.5 to 5. Note that general formula (4) is expressed on an oxide basis.

The calcium-zinc stabilizer contained in the resin composition may be mainly composed of a metal soap stabilizer. The proportion of the metal soap stabilizer in the total amount of calcium-zinc stabilizers may be 50% by weight or more, 70% by weight or more, 90% by weight or more, or may be 100% by weight.

The lower limit of the content of the calcium-zinc stabilizer contained in the resin composition is preferably 2 parts by weight or more, and more preferably 3 parts by weight or more, per 100 parts by weight of the vinyl chloride resin. The upper limit of the content of the calcium-zinc stabilizer contained in the resin composition is preferably 8 parts by weight or less, and more preferably 7 parts by weight or less, per 100 parts by weight of the vinyl chloride resin. If the content is within the above range, the heat resistance and pulsating water pressure resistance of the resin composition are improved.

[1.3. Other additives]
The resin composition for a rib joint according to one embodiment of the present invention may contain other additives. Examples of the other additives include a stabilizing agent, a filler, a pigment, a lubricant, a processing aid, a light stabilizer, an ultraviolet absorber, and a flame retardant. Only one type of each additive may be used, or two or more types may be used.

Examples of stabilizing agents include polyhydric alcohols, phenolic antioxidants, β-keto acid esters, and β-diketones. Specific examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, glycerin, diglycerin, dipentaerythritol, mannitol, sorbitol, trimethylolpropane, ditrimethylolpropane, trisisocyanurate, monopentaerythritol, and dipentaerythritol adipate. Examples of the phenolic antioxidant include bisphenol A, bisphenol B, bisphenol F, 2,6-diphenyl-4-octadecyloxyphenol, stearyl (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, distearyl (3,5-di-tert-butyl-4-hydroxybenzyl) phosphonate, 1,6-hexamethylene bis[(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,6-hexamethylene bis[(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], acid amide], bis[3,3-bis(4-hydroxy-3-tert-butylphenyl)butyric acid] glycol ester, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-tris(2,6-dimethyl-3-hydroxy-4-tert-butylbenzyl)isocyanurate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, triethylene glycol bis[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate]. Examples of β-keto acid esters and β-diketones include 1,3-cyclohexadione, methylenebis-1,3-cyclohexadione, 2-benzyl-1,3-cyclohexadione, acetyl tetralone, palmitoyl tetralone, stearoyl tetralone, benzoyl tetralone, 2-acetyl cyclohexanone, 2-benzoyl cyclohexanone, 2-acetyl-1,3-cyclohexanedione, bis(benzoyl)methane, benzoyl-p-chlorobenzoylmethane, bis(4-methylbenzoyl)methane, and bis(2-hydroxybenzoyl)methane. , benzoylacetone, tribenzoylmethane, diacetylbenzoylmethane, stearoylbenzoylmethane, palmitoylbenzoylmethane, lauroylbenzoylmethane, dibenzoylmethane, bis(4-chlorobenzoyl)methane, bis(methylene-3,4-dioxybenzoyl)methane, benzoylacetylphenylmethane, stearoyl(4-methoxybenzoyl)methane, butanoylacetone, distearoylmethane, acetylacetone, stearoylacetone, bis(cyclohexanoyl)-methane and dipivaloylmethane.

Examples of fillers include inorganic fillers. Examples of inorganic fillers include calcium carbonate, talc, clay, and silica.

Examples of pigments include organic pigments (azo pigments, phthalocyanine pigments, threne pigments, dye lake pigments, etc.); inorganic pigments (molybdenum chromate pigments, ferrocyanide pigments, etc.).

Examples of lubricants include fatty acids (such as stearic acid); fatty acid esters (such as butyl stearate); olefin waxes (such as polyethylene and polyethylene oxide); and hydrocarbon waxes (such as paraffin).

Examples of processing aids include homopolymers or copolymers of (meth)acrylate monomers (methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, etc.); and copolymers of (meth)acrylate monomers and vinyl monomers (styrene, vinyl toluene, acrylonitrile, etc.).

Examples of light stabilizers include hindered amine light stabilizers.

Examples of UV absorbers include salicylic acid ester-based UV absorbers, benzophenone-based UV absorbers, benzotriazole-based UV absorbers, and cyanoacrylate-based UV absorbers.

Flame retardants include halogen-based flame retardants; and oxide or hydroxide-based flame retardants (oxides or hydroxides of antimony, zircon, molybdenum, aluminum, silica, titanium, etc.).

The content of other additives is not particularly limited. In one embodiment, the content of lubricant in the resin composition is 0.1 to 2.5% by weight. In one embodiment, the content of filler or pigment in the resin composition is 5.0% by weight or less.

The resin composition may contain known additives (such as plasticizers) in addition to the additives described above. The amount of additive contained therein can be determined appropriately by a person skilled in the art.

[1.4. Physical properties of resin composition]
The Vicat softening temperature of the resin composition is preferably 76° C. or higher. The upper limit of the Vicat softening temperature can be, for example, 87° C. or lower or 85° C. or lower. Here, the Vicat softening temperature is measured based on JIS K 6816. If the Vicat softening temperature is in the above range, it can be said that the resin composition has sufficient heat resistance for producing a rib joint.

The melting point of the resin composition is preferably 230°C or less, more preferably 220°C or less, and even more preferably 215°C or less. If the melting point is within the above range, moldability in injection molding and the like is improved.

The tensile yield strength of the resin composition is preferably 45 MPa or more, and more preferably 47 MPa or more. The upper limit of the tensile yield strength can be, for example, 59 MPa or less or 57 MPa or less. Here, the tensile yield strength is measured according to the tensile yield strength measurement conditions based on JIS K 6815 and JIS K 6743. If the tensile yield strength is within the above range, it can be said that the mechanical strength required for a rib joint is provided.

[1.5. Production method and molding method of resin composition]
The resin composition for a rib joint according to one embodiment of the present invention can be produced by a method known in the art. For example, the resin composition can be produced by melt-kneading the above-mentioned components in a melt kneader (such as a single-screw extruder or a twin-screw extruder). Liquid components may be added during the melt kneading process using a liquid supply pump or the like.

The method for molding the resin composition is not particularly limited. General methods for molding thermoplastic resins can be used. Examples of such molding methods include injection molding, extrusion molding, vacuum molding, press molding, calendar molding, and blow molding. A compound obtained by mixing the components may be used as the material for molding. After pelletizing the resin composition, the obtained pellets may be used as the material for molding.

In one embodiment, the resin composition is molded by injection molding. Since the rib joint has a complex shape, molding by injection molding is suitable. A person skilled in the art can set the injection molding conditions appropriately. When injection molding the resin composition, a commercially available injection molding machine can be used.

[2. Rib joints]
A rib joint according to one aspect of the present invention includes the above-mentioned resin composition for a rib joint. Since this rib joint contains the above-mentioned resin composition for a rib joint, it places less strain on the working environment.

The proportion of the resin composition for rib joints in the total weight of the rib joint is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. In one embodiment, the rib joint consists only of the resin composition for rib joints.

The shape of the rib joint is not particularly limited. It may be any shape that is commonly used for a rib joint (socket, elbow, tee, etc.). The thickness of the rib joint and the presence or absence of a socket can be appropriately determined by a person skilled in the art.

The rib joint can be used as a rib joint for water pipes (waterworks pipes, sewer pipes, etc.), gas pipes, and any other piping. It is preferably used as a rib joint for sewer pipes.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[Evaluation test method]
[1. Tensile Yield Strength]
Test pieces were prepared from the prepared rib joints, and the tensile yield strength was measured according to the test conditions for tensile yield strength based on JIS K 6815 and JIS K 6743. A screw-type uniaxial test machine AGS-10kNX (Shimadzu Corporation) was used as the test machine.

[2. Formability]
The appearance of the rib joints produced by injection molding was visually observed and the evaluation criteria were as follows:
○: No bubbles, short shots, or other abnormalities in the appearance △: Almost no bubbles, short shots, or other abnormalities in the appearance ×: There are bubbles, short shots, or other abnormalities in the appearance

Comparative Example 1
100 parts by weight of polyvinyl chloride A (degree of polymerization: 700, TH-700, Taiyo PVC) and 5 to 6 parts by weight of a lead-based stabilizer (including tribasic lead sulfate, lead stearate, and other lubricants) were kneaded in a Henschel mixer. Using the resulting compound as a raw material, a T-shaped rib joint (diameter: 200 mm) was manufactured by injection molding. In the injection molding, the time from plasticizing the compound to weighing was 65 seconds, and the time for filling the molten resin into the mold was 77 seconds.

Comparative Example 2
A rib joint was produced in the same manner as in Comparative Example 1, except that polyvinyl chloride A was changed to polyvinyl chloride B (polymerization degree: 650, S1006, manufactured by Kaneka).

Example 1
A rib joint was produced in the same manner as in Comparative Example 1, except that the lead-based stabilizer was changed to a calcium-zinc-based stabilizer (a mixture of calcium metal soap and zinc metal soap, Mizusawa Chemicals).

Example 2
A rib joint was produced in the same manner as in Comparative Example 2, except that the lead-based stabilizer was changed to a calcium-zinc-based stabilizer (a mixture of calcium metal soap and zinc metal soap, Mizusawa Chemicals).

The resin composition according to the embodiment does not use lead-based stabilizers and places less strain on the working environment. In addition, the resin composition according to the embodiment has a tensile yield strength equal to or greater than that of the resin composition according to the comparative example. Therefore, the resin composition according to the embodiment places less strain on the working environment and has mechanical strength equal to or greater than that of conventional products.

The resin composition of Example 2 also had a superior appearance to the resin compositions of Example 1 and Comparative Example 1 in terms of the rib joint appearance. This suggests that by using a calcium-zinc stabilizer and lowering the degree of polymerization of polyvinyl chloride to a certain degree (for example, by setting it to 670 or less), moldability is improved and a product with excellent appearance can be obtained.

The resin composition of the present invention can be suitably used, for example, as a raw material for rib joints.

Claims (4)

The composition includes a polyvinyl chloride resin and a calcium-zinc stabilizer ,
Does not contain β-diketones
A resin composition for a ribbed joint for a sewer pipe, comprising:
A resin composition, wherein the degree of polymerization of the vinyl chloride resin is 670 or less. 2. The resin composition of claim 1, wherein the calcium-zinc stabilizer comprises a calcium salt of a fatty acid and a zinc salt of a fatty acid. The resin composition according to claim 1 or 2 , which is molded by injection molding. A ribbed joint comprising the resin composition according to any one of claims 1 to 3 .