Resin composition and crosslinked polyolefin molding

Abstract

To provide a resin composition exhibiting superior strength properties and enabling an increased crosslinking degree, since incorporating a moisture-releasing agent to enhance the crosslinking degree can cause reduction of strength properties.SOLUTION: A composition comprising following components: (A) a polyolefin resin, (B) a radical initiator, (C) a silane compound, and (D) a hydrate of an organic compound, wherein the melting point of the component (D) is 220°C or less, and the amount of water of hydration of the component (D) is preferably 0.005 to 0.1 pt.mass per 100 pts.mass of the component (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition and a crosslinked polyolefin molded article. [Background technology]

[0002] Crosslinked polyolefin molded articles are excellent in heat resistance, strength, flexibility, light weight, etc. Therefore, pipes made of crosslinked polyolefin molded articles (crosslinked polyolefin pipes) are used, for example, as piping for cold and hot water supply and piping for floor heating (Patent Document 1). Cross-linked polyolefin pipes are used in environments where they are exposed to high-temperature water for long periods of time, so they are required to have improved durability so that they can withstand long-term use. Generally, cross-linked polyolefin pipes require strength because they are subjected to water pressure inside the pipe. In addition, since the creep performance required for long-term use at high temperatures is correlated with the degree of cross-linking, cross-linked polyolefin pipes with a higher degree of cross-linking are in demand.

[0003] As a method for efficiently improving the degree of crosslinking, Patent Document 2 describes a method in which a moisture-releasing agent is added to a polyolefin resin. However, in the case of the moisture release agent described in Patent Document 2, the added inorganic substance does not dissolve in the resin, so in cold water and hot water supply pipes, it may become the starting point of fracture when stress is applied, leading to a decrease in strength properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4066114 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-219681 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a resin composition which is excellent in strength and has an increased degree of crosslinking. [Means for solving the problem]

[0006] The present invention has the following aspects. <1> The composition comprises: (A) component: a polyolefin resin; (B) component: a radical generator; (C) component: a silane compound; and (D) component: a hydrate of an organic compound; The resin composition, wherein the melting point of the component (D) is 220°C or lower. <2> The component (D) is an organic metal salt. <1> The resin composition according to claim 1. <3> The amount of water of hydration of the component (D) is 0.005 to 0.1 parts by mass per 100 parts by mass of the component (A). <1> or <2> The resin composition according to claim 1.

[0007] <4> <1> ~ <3> 1. A crosslinked polyolefin molded article obtained by molding the resin composition according to any one of the above items 1 to 4, and crosslinking a part or all of the component (A). <5> Density 0.900~0.950g / cm 3 That is, <4> The crosslinked polyolefin molded article according to claim 1. [Effects of the Invention]

[0008] According to the resin composition of the present invention, a crosslinked polyolefin molded article having excellent strength and a high degree of crosslinking can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0009] In this specification and claims, the use of "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] (Resin composition) The resin composition of the present invention comprises component (A): a polyolefin resin, component (B): a radical generator, component (C): a silane compound, and component (D): a hydrate of an organic compound. The resin composition of the present invention contains uncrosslinked component (A) and is a so-called crosslinkable polyolefin resin composition.

[0011] <Component (A): Polyolefin resin> Component (A) is a polyolefin resin. A "polyolefin resin" is a resin having olefin-based structural units in an amount of 50% by mass or more relative to all structural units. The olefin-based structural units in component (A) preferably account for 80% by mass or more, more preferably 90% by mass or more, and may even be 100% by mass, relative to all structural units.

[0012] Examples of component (A) include one or more resins selected from the group consisting of polyethylene-based resins such as polyethylene and ethylene-based polymers containing ethylene as the main component, and poly-α-olefin-based resins such as polypropylene resins and polybutene resins. From the viewpoint of enabling more efficient crosslinking, polyethylene-based resins are preferred as component (A).

[0013] Component (A) may be a polyolefin resin to which a silane compound has been graft-polymerized in advance, in which case there is no need to incorporate a radical generator and a silane compound during resin kneading in the method for producing a crosslinked polyolefin molded article described below.

[0014] The density of component (A) is not particularly limited, but is preferably 0.910 to 0.955 g / cm 3 is preferable, and 0.930 to 0.950 g / cm 3 More preferably, 0.935 to 0.950 g / cm 3 is more preferable. When the density of component (A) is equal to or greater than the above lower limit, the water pressure resistance of the crosslinked polyolefin molded article described below is improved. When the density of component (A) is equal to or less than the above upper limit, the crosslinked polyolefin molded article is less likely to be excessively rigid, and is therefore easier to bend and handle during construction. The density of the raw material polyolefin resin is a value measured by the underwater displacement method in accordance with JIS K 7112 (1999).

[0015] The content of the component (A) is preferably 90 to 100% by mass relative to the total mass of the resin composition. The resin composition may contain a resin other than component (A) (e.g., polyester, polyamide, etc.). However, from the viewpoint of further increasing the strength properties of the resulting crosslinked polyolefin molded article and further increasing the degree of crosslinking, the content of component (A) relative to the total mass of resins in the resin composition is preferably 90 mass% or more, more preferably 95 mass% or more, and even more preferably substantially 100 mass%.

[0016] <Component (B): Radical generator> The component (B) is a radical generator such as an organic peroxide or an organic perester. Examples of organic peroxides include benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di(peroxybenzoate)hexyne-3,1,4-bis(tert-butylperoxyisopropyl)benzene, lauroyl peroxide, and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3,2,5-dimethyl-2,5-di(tert-butylperoxy)hexane. Organic peresters include tert-butyl peracetate, tert-butyl perbenzoate, tert-butyl perphenyl acetate, tert-butyl perisobutyrate, tert-butyl per-sec-octoate, tert-butyl perpivalate, cumyl perpivalate, and tert-butyl perdiethyl acetate. Among these components (B), alkyl type peroxides are preferred. In addition to the above, other azo compounds such as azobisisobutylnitrile and dimethylazoisobutyrate may also be used as component (B). The above-mentioned component (B) may be one type alone or a combination of two or more types.

[0017] The content of component (B) in the resin composition is preferably 0.01 to 0.3 parts by mass, more preferably 0.01 to 0.2 parts by mass, and even more preferably 0.01 to 0.15 parts by mass, per 100 parts by mass of component (A). When the content of component (B) is equal to or greater than the lower limit, the crosslinking reaction proceeds sufficiently. When the content of component (B) is equal to or less than the upper limit, the odor characteristic of crosslinked polyolefin molded articles can be suppressed.

[0018] <Component (C): Silane Compound> Component (C) is a silane compound having an olefinically unsaturated bond and a hydrolyzable organic group. An example of component (C) is vinyltrisalkoxysilane. Of these, vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltris(methoxyethoxy)silane are preferred. Alternatively, component (C) may be vinylmethyldiethoxysilane, vinylphenyldimethoxysilane, or the like. The silane compound may be used alone or in combination of two or more kinds.

[0019] The content of component (C) in the resin composition is preferably 0.1 to 3.0 parts by mass, more preferably 0.1 to 2.0 parts by mass, and even more preferably 0.1 to 1.5 parts by mass, per 100 parts by mass of component (A). When the content of component (C) is equal to or greater than the lower limit, the crosslinking reaction proceeds sufficiently. When the content of component (C) is equal to or less than the upper limit, the odor characteristic of crosslinked polyolefin molded articles can be suppressed.

[0020] <Component (D): Hydrate of organic compound> Component (D) is a hydrate of an organic compound, and examples of component (D) include organometallic salt hydrates. Organometallic salt hydrates are compounds in which an organometallic salt is stabilized by hydration water. The metals that constitute organometallic salt hydrates include, for example, alkali metals (lithium, potassium, sodium, etc.), alkaline earth metals (calcium, magnesium, etc.), and iron group elements (iron, nickel, cobalt). Preferred organic metal salt hydrates are (+)-sodium potassium tartrate tetrahydrate, magnesium acetate tetrahydrate, sodium carbonate decahydrate, sodium acetate trihydrate, sodium p-toluenesulfonchloroamide trihydrate, sodium tetraborate decahydrate, sodium N,N-diethyldithiocarbamate trihydrate, cobalt(II) acetate tetrahydrate, lithium acetate dihydrate, calcium oxalate monohydrate, sodium isoascorbate monohydrate, and trilithium citrate tetrahydrate. Examples of component (D) other than organometallic salt hydrates include organic acid hydrates, sugar hydrates, amine hydrates, etc. Examples of component (D) other than organometallic salt hydrates include oxalic acid dihydrate, citric acid monohydrate, ammonium oxalate monohydrate, p-toluenesulfonic acid monohydrate, benzenesulfonic acid monohydrate, pyridoxal phosphate monohydrate, α-L(+)-rhamnose monohydrate, ethylenediamine monohydrate, lactitol monohydrate, (2S,3S)-(+)-O,O'-dibenzoyltartaric acid monohydrate, piperazine hexahydrate, 1,10-phenanthroline monohydrate, Preferred are 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]n hydrate, D(+)-raffinose pentahydrate, sodium L(+)-aspartate monohydrate, hexadecylpyridinium chloride monohydrate, trehalose dihydrate, D(+)-maltose monohydrate, 5-sulfosalicylic acid dihydrate, maltose hydrate, and the like. These components (D) may be used alone or in combination of two or more.

[0021] Component (D) may be kneaded in advance with component (A) and other additives to form pellets, powder, or plates.

[0022] The melting point of component (D) is 220°C or lower, and preferably 200°C or lower. When the melting point of component (D) is equal to or lower than the above upper limit, component (D) can be easily melted in component (A) in the method for producing a crosslinked polyolefin molded article described below. There are no particular limitations on the lower limit of the melting point of component (D), but it is generally 30°C or higher.

[0023] The content of component (D) is not particularly limited, but is preferably 5 parts by mass or less per 100 parts by mass of component (A). When the content of component (D) is not more than the above upper limit, the strength properties of the resulting crosslinked polyolefin molded article can be further improved, and the degree of crosslinking can be further increased. The lower limit of the content of component (D) is not particularly limited, but is, for example, 0.03 parts by mass or more.

[0024] The amount of water of hydration (Wd) contained in component (D) is preferably 0.005 to 0.1 parts by mass, and more preferably 0.01 to 0.1 parts by mass, per 100 parts by mass of component (A). When Wd is equal to or greater than the lower limit, the degree of crosslinking can be increased. When the amount of Wd is equal to or less than the upper limit, defects due to over-crosslinking during molding can be suppressed.

[0025] The mass ratio of Wd to the content of component (C) (Wd / C ratio) is preferably 0.5 or less, more preferably 0.1 or less. When the Wd / C ratio is equal to or greater than the lower limit, the degree of crosslinking can be further increased. The lower limit of the Wd / C ratio is not particularly limited, but is substantially equal to or greater than 0.01.

[0026] <Optional ingredients> The resin composition may contain any optional component other than the components (A) to (D). Optional ingredients include silanol condensation catalysts, process heat stabilizers, ultraviolet absorbers, organic fillers, inorganic fillers, pigments, dyes, processing aids, and the like. The optional components may be used alone or in combination of two or more.

[0027] <Silanol condensation catalyst> When the component (A) in the resin composition is crosslinked by the silane water crosslinking method, the resin composition may contain a silanol condensation catalyst for the purpose of promoting the silanol condensation reaction. The silanol condensation catalyst is not particularly limited as long as it is any compound commonly used as a catalyst for promoting dehydration condensation between silanols.Examples of the silanol condensation catalyst include compounds such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, cobalt naphthenate, lead naphthenate, ethylamine, dibutylamine, hexylamine, and pyridine; inorganic acids such as sulfuric acid and hydrochloric acid; and organic acids such as toluenesulfonic acid, acetic acid, stearic acid, and maleic acid.Among these, dibutyltin dilaurate and dioctyltin dilaurate are preferred as the silanol condensation catalyst. The silanol condensation catalyst may be used alone or in combination of two or more.

[0028] The content of the silanol condensation catalyst in the resin composition is preferably 0.001 to 0.01 parts by mass, and more preferably 0.003 to 0.01 parts by mass, per 100 parts by mass of the component (A).

[0029] (Crosslinked polyolefin molded body) The crosslinked polyolefin molded article of the present invention is obtained by molding the resin composition of the present invention and crosslinking a part or all of the component (A). Examples of the crosslinked polyolefin molded article include plates, films, sheets, tapes, pipes, hoses, etc. The crosslinked polyolefin molded article of the present invention has excellent strength and a high degree of crosslinking, and is therefore suitable for pipes and hoses, and is particularly suitable for water and hot water supply piping and floor heating piping.

[0030] The density of the crosslinked polyolefin molded body is not particularly limited, but when used for hot and cold water supply piping, it is 0.900 to 0.950 g / cm 3 is preferable, and 0.930 to 0.950 g / cm 3 More preferably, 0.940 to 0.950 g / cm 3 is more preferable.

[0031] The density of the crosslinked polyolefin molded body is not particularly limited, but when used for hot and cold water supply piping, it is 0.900 to 0.950 g / cm3 is preferable, and 0.930 to 0.950 g / cm 3 More preferably, 0.940 to 0.950 g / cm 3 is more preferable.

[0032] (Method of manufacturing crosslinked polyolefin molded article) The method for producing a crosslinked polyolefin molded article comprises the steps of: (1) plasticizing a resin composition; (2) molding the plasticized resin composition into a desired shape to obtain an uncrosslinked polyolefin molded article; and (3) crosslinking the polyolefin resin in the uncrosslinked polyolefin molded article to obtain a crosslinked polyolefin molded article.

[0033] <Process (1)> Step (1) is a step of plasticizing the resin composition. Through step (1), a silane polymer of polyolefin resin is obtained in which component (C) (a silane compound) is graft-polymerized to component (A) (a polyolefin resin).

[0034] The plasticization is carried out by heating and kneading the resin composition. As a kneading method, for example, a method of melting the components using a Labo Plastomill or the like can be mentioned. The kneading temperature is preferably equal to or higher than the melting point of component (A) and component (D) (a hydrate of an organic compound), for example, 120 to 220°C is preferred, and 180 to 200°C is more preferred.

[0035] <Process (2)> In step (2), the resin composition (plasticized product) plasticized in step (1) is molded into any shape (e.g., a tube or a sheet), which is then cooled and solidified to obtain an uncrosslinked polyolefin molded product, in which all or part of component (A) is not crosslinked.

[0036] Examples of methods for molding the resin composition (molding methods) include press molding, extrusion molding, injection molding, and compression molding. Examples of press molding methods include kneading the mixture in a mixer such as a Labo Plastomill to obtain a plasticized product, sandwiching the resulting plasticized product between press plates that have spacers of a desired thickness between them, and shaping the plasticized product into a sheet of the spacer thickness by a heated press, and then cooling the press plates to solidify the plasticized product. The extrusion molding method includes a method in which a plasticized material is discharged from a die into a desired shape, the discharged plasticized material is taken up, and then the taken up plasticized material is cooled. Injection molding includes a method in which a plasticized material is injected into a mold having a core and a cavity, the mold is cooled, and the molded article is removed from the mold. An example of the compression molding method is a method in which a resin composition is placed in a mold cavity, sealed, and subjected to heat and pressure to plasticize the resin composition, and then the cavity is cooled. The temperature for cooling and solidifying is, for example, -10 to 50°C. After cooling and solidifying, the resulting uncrosslinked polyolefin molded article may be cured. Curing promotes crystallization and imparts strength properties. Curing conditions include, for example, 15 to 40°C and 24 to 100 hours.

[0037] <Process (3)> Step (3) is a step of crosslinking a part or all of the component (A) (which has become a silane polymer) of the uncrosslinked polyolefin molded article to obtain a crosslinked polyolefin molded article.

[0038] Examples of methods for crosslinking the component (A) of the uncrosslinked polyolefin molded article include a method of heating the uncrosslinked polyolefin molded article (thermal crosslinking method). A preferred heat crosslinking method is, for example, a method (water crosslinking) in which an uncrosslinked polyolefin molded body is subjected to a heat treatment by exposing the uncrosslinked polyolefin molded body to hot water or steam, thereby crosslinking part or all of the polyolefin resin.

[0039] The temperature during heating (heating temperature) is preferably equal to or lower than the melting point of the uncrosslinked component (A) contained in the uncrosslinked polyolefin molded article. The heating temperature is, for example, preferably 40 to 120°C, more preferably 60 to 120°C, and even more preferably 80 to 120°C. If the heating temperature is equal to or higher than the above lower limit, the crosslinking treatment of the uncrosslinked polyolefin molded article can be completed in a shorter time. If the heating temperature is equal to or lower than the above upper limit, deformation and breakage of the crosslinked polyolefin molded article can be suppressed.

[0040] The resulting crosslinked polyolefin molded article has excellent heat resistance and long-term durability because the component (A) is partially or entirely crosslinked.

[0041] The crosslinking degree of the crosslinked polyolefin molded product is preferably higher in terms of energy efficiency when crosslinked under the same conditions. The higher the crosslinking degree of the crosslinked polyolefin molded product, the higher the long-term durability. The crosslinking degree of the crosslinked polyolefin molded product is preferably 60 to 100%, more preferably 80 to 100%.

[0042] According to the resin composition of the present invention, a crosslinked polyolefin molded article having excellent strength and an increased degree of crosslinking can be obtained by containing a polyolefin resin, a radical generator, a silane compound, and an organometallic salt compound. [Example]

[0043] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0044] (Raw materials used) <Component (A): Polyolefin resin> Polyethylene resin: Creolex K4750 (trade name), manufactured by Asahi Kasei Corporation, density 0.947 g / cm 3 , MFR5.0g / 10min. <Component (B): Radical generator> 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexyne-3: Perhexyne 25B (trade name), manufactured by NOF Corporation. <Component (C): Silane Compound> Vinyltrimethoxysilane: Vinyltrimethoxysilane (trade name), manufactured by Tokyo Chemical Industry Co., Ltd. <Component (D): Hydrate of organic compound> Sodium potassium tartrate tetrahydrate: Manufactured by Fujifilm Wako Pure Chemical Industries, melting point 80°C. <Component (D'): Comparison product of component (D)> Calcium citrate tetrahydrate: Manufactured by Fujifilm Wako Pure Chemical Industries, melting point over 300°C.

[0045] (Evaluation method) <Crosslinking degree> To evaluate the degree of crosslinking, the gel fraction was measured by the following method. A higher gel fraction indicates a higher degree of crosslinking. Gel fraction measurement method: Heat to 140°C while immersed in xylene to dissolve the sol components, and calculate the gel fraction by dividing the mass of the remaining gel by the mass before immersion in xylene.

[0046] <Tensile performance> Tensile performance was evaluated by measuring the tensile yield strength and tensile elongation. The crosslinked polyolefin sheet obtained in each example was cut into a dumbbell shape No. 8 as specified in JIS K6251 to prepare test specimens. The obtained test specimens were subjected to a tensile test in accordance with JIS K7161 (2014) using an autograph manufactured by Shimadzu Corporation, and the tensile elongation was determined. The tensile test was performed at a chuck distance of 30 mm, at a temperature of 23°C, and at a tensile speed of 100 mm / min. The higher the tensile elongation, the more flexible the test piece is, and the easier it is to maintain flexibility over the long term. A tensile elongation of 300% or more was evaluated as good (○), and one less than 300% was evaluated as poor (×).

[0047] (Example 1, Comparative Examples 1 to 3)] According to the formulations in Table 1, components (A), (B), (C), and (D) (or (D')) were fed to a Labo Plastomill and melt-kneaded to form a plasticized product (step (1)). The plasticized product was molded into a sheet (length 150 mm × width 150 mm × thickness 1 mm), which was then cooled and solidified to obtain an uncrosslinked polyolefin molded product (step (2)). The obtained uncrosslinked polyolefin molded article was immersed in warm water at 80° C. for 16 hours and subjected to a heat treatment to obtain a crosslinked polyolefin molded article (step (3)). The crosslinking degree, tensile yield strength and tensile elongation of the obtained crosslinked polyolefin molded article were measured. The results are shown in Table 1.

[0048] [Table 1]

[0049] As shown in Table 1, in Example 1 to which the present invention was applied, the degree of crosslinking was 61% and the tensile elongation was 391%. In Comparative Example 2, in which component (D') was used instead of component (D), the tensile elongation was 425%, but the degree of crosslinking was 57%. In Comparative Examples 2 and 3, in which component (D') was used instead of component (D), the tensile elongation was 103 to 166%. From the above, it was confirmed that by applying the present invention, a crosslinked polyolefin molded article having excellent strength and an increased degree of crosslinking can be obtained.

Claims

1. The composition comprises: (A) component: a polyolefin resin; (B) component: a radical generator; (C) component: a silane compound; and (D) component: a hydrate of an organic compound, The resin composition, wherein the melting point of the component (D) is 220°C or lower.

2. The resin composition according to claim 1 , wherein the component (D) is an organic metal salt.

3. 2. The resin composition according to claim 1, wherein the amount of water of hydration of the component (D) is 0.005 to 0.1 parts by mass per 100 parts by mass of the component (A).

4. A crosslinked polyolefin molded article obtained by molding the resin composition according to any one of claims 1 to 3 and crosslinking a part or all of the component (A).

5. Density is 0.900 to 0.950 g / cm ３ The crosslinked polyolefin molded article according to claim 4, wherein

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