JP2018104692A - Modified polyethylene, modified polyethylene composition, molded body and silane crosslinked polyethylene - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide modified polyethylene having further enhanced mechanical physical properties by modification and small in permanent compression set of obtained silane crosslinked polyethylene, a modified polyolefin composition using the modified polyethylene, a molded body and the silane crosslinked polyethylene.SOLUTION: There is provided modified polyethylene by graft modifying an unsaturated silane compound of 0.1 to 5 mass% to polyethylene satisfying that extrapolation crystal fusion finishing temperature measured in a differential scanning calorimetry at heating rate of 10°C/min. is 100°C to 130°C and A hardness by JIS K6253 is 90 or less.SELECTED DRAWING: None

Description

  The present invention relates to a modified polyethylene. The present invention also relates to a modified polyethylene composition using the modified polyethylene, a molded article using the modified polyethylene composition, and a silane-crosslinked polyethylene.

  In recent years, furniture using a three-dimensional network structure obtained by extruding a thermoplastic resin in a loop shape as a cushioning material such as a cushioning material, and bedding such as a pillow and a bed mat are becoming popular.

This three-dimensional network structure is generally manufactured as follows.
That is, a thermoplastic resin is melted in an extruder, and the melted resin is extruded from a die having a large number of holes to form a strand. A water tank is provided under the die. When the strands naturally flow down and land in the water tank, and the strands stay in the water, the resin is solidified by cooling with water, and a three-dimensional network having loop-like entanglements. A shaped structure is manufactured (Patent Document 1).
As a thermoplastic resin used for molding, an ethylene / α-olefin copolymer has been proposed.

In a cushioning material such as a bedding using a three-dimensional network structure made of a thermoplastic resin, deformation (sagging) occurs at a high temperature, and a part of the bedding is depressed or deformed. This is because the thermoplastic resin constituting the three-dimensional network structure flows or plastically deforms under a load at a high temperature, but the ethylene / α-olefin copolymer has a low melting point. Since the shape cannot be maintained above the melting point, this settling and depression are particularly problematic.

  In order to improve the heat resistance of the ethylene / α-olefin copolymer and improve the problem of sag at high temperatures, modified ethylene / α obtained by grafting an ethylenically unsaturated silane compound to the ethylene / α-olefin copolymer An olefin copolymer is disclosed in Patent Document 2.

International Publication No. 2012/035736 JP 2013-181117 A

  The modified ethylene / α-olefin copolymer described in Patent Document 2 has been studied by the inventor in detail. The melting point of the composition containing the silanol condensation catalyst is low, and the problem of sag at high temperatures is also a problem. For this reason, improvement in durability as a three-dimensional network structure and further improvement in sag are demanded.

  It is an object of the present invention to provide a modified polyethylene which has improved mechanical properties by modification and has a small compression set of the resulting crosslinked polyethylene. Another object of the present invention is to provide a modified polyolefin composition using the modified polyethylene, a molded article, and a silane-crosslinked polyethylene.

As a result of intensive studies to achieve the above object, the present inventors graft a specific amount of an unsaturated silane compound onto polyethylene having a high melting point crystal region and having a hardness of A or less according to JIS K6253. Thus, the present invention has found that it is possible to provide a three-dimensional network structure capable of recovering a distorted shape without increasing the residual strain after giving a certain strain at a high temperature, and thus, with less sag. It came to complete.
That is, the gist of the present invention is as follows [1] to [7].

[1] Unsaturated silane in polyethylene satisfying the conditions that the extrapolation crystal melting end temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. to 130 ° C. and the A hardness according to JIS K6253 is 90 or less A modified polyethylene in which a compound is 0.1 to 5% by mass graft-modified.

[2] The modified polyethylene according to [1], wherein the unsaturated silane compound is a compound represented by the following formula (1).
RSi (R ′) ₃ (1)
(However, R is an ethylenically unsaturated hydrocarbon group, R 'is mutually independently a C1-C10 hydrocarbon group or a C1-C10 alkoxy group, and is at least 1 of R'. Is an alkoxy group having 1 to 10 carbon atoms.)

[3] The modified polyethylene according to [1] or [2], wherein the polyethylene has a density of 0.850 to 0.940 g / cm ³ .

[4] The modified polyethylene according to any one of [1] to [3], wherein the polyethylene is an ethylene / α-olefin copolymer.

[5] A modified polyethylene composition comprising the modified polyethylene according to any one of [1] to [4] and a silanol condensation catalyst.

[6] A molded product obtained by molding the modified polyethylene composition according to [5].

[7] A silane-crosslinked polyethylene obtained by crosslinking the modified polyethylene composition according to [5].

  The modified polyethylene of the present invention has improved heat resistance, which is generally a major problem in ethylene / α-olefin copolymers, and is excellent in shape recoverability even if it has residual strain. For this reason, the three-dimensional network structure using the modified polyethylene of the present invention can be used at a high temperature such as an electric blanket or a hot water bottle, or exposed to a high temperature and high humidity. The generated settling can be reduced, and it is possible to efficiently restore the original shape after the settling occurs.

  Embodiments of the present invention will be described in detail below, but the following description is an example of the embodiments of the present invention, and the present invention is limited to the following description unless it exceeds the gist. is not.

[Modified polyethylene]
The modified polyethylene of the present invention is a polyethylene satisfying the conditions that the extrapolated crystal melting end temperature measured at a heating rate of 10 ° C./min in differential scanning calorimetry is 100 ° C. to 130 ° C., and the A hardness according to JIS K6253 is 90 or less. (Hereinafter referred to as “polyethylene of the present invention”) is obtained by graft-modifying 0.1 to 5 mass% of an unsaturated silane compound.

[polyethylene]
The polyethylene of the present invention is not limited as long as it contains ethylene as a raw material monomer, and a known polyethylene resin is appropriately used.
That is, the problem of heat resistance of the modified ethylene / α-olefin copolymer has been described above. However, not only the modified ethylene / α-olefin copolymer but also general polyethylene has a heat resistance problem, and these are in accordance with the present invention. To improve heat resistance by modifying polyethylene with an unsaturated silane compound using polyethylene satisfying the conditions that the extrapolation crystal melting end temperature is 100 ° C. to 130 ° C. and the A hardness according to JIS K6253 is 90 or less. Can do.

  Specific examples of polyethylene include (branched or linear) ethylene homopolymers such as low, medium and high density polyethylene; ethylene / propylene copolymers, ethylene / 1-butene copolymers, ethylene / 4 -Methyl-1-pentene copolymer, ethylene / 1-hexene copolymer, ethylene / α-olefin copolymer such as ethylene / 1-octene copolymer; ethylene / vinyl acetate copolymer, ethylene / (meta ) Ethylene copolymer resins such as acrylic acid copolymer and ethylene / (meth) acrylic acid ester copolymer. Furthermore, not only the said polymer can be used alone, but also two or more kinds of polymers can be blended and used.

  Among these, in the present invention, high-pressure method low-density polyethylene, high-density polyethylene, and ethylene / α-olefin copolymer that are excellent in the balance between heat resistance and strength are preferable, ethylene / α-olefin copolymer is more preferable, An ethylene / 1-butene copolymer, an ethylene / 1-hexene copolymer, and an ethylene / 1-octene copolymer are particularly preferred.

  The ethylene / α-olefin copolymer is a copolymer of 2 to 60% by mass of one or more α-olefins and 40 to 98% by mass of ethylene, that is, containing α-olefin units. An amount of 2 to 60% by mass and an ethylene unit content of 40 to 98% by mass are preferred.

  In the present invention, as raw material polyethylene to be subjected to graft modification with an unsaturated silane compound, an extrapolated crystal melting end temperature (hereinafter referred to simply as “melting end temperature”) measured at a heating rate of 10 ° C./min in differential scanning calorimetry. ) Is 100 ° C. or higher. When the melting end temperature is lower than 100 ° C., the residual permanent set is deteriorated. From this viewpoint, the melting end temperature of the polyethylene of the present invention is 100 ° C. or higher, preferably 105 ° C. or higher. On the other hand, the melting end temperature of the polyethylene of the present invention is 135 ° C. or lower. When the melting end temperature is 135 ° C. or lower, the load on the extruder is suppressed, and the strands tend to be fused easily, and the uniformity as a three-dimensional network structure tends to be good, and the performance and quality as a product are improved. It is preferable because it is easy to do. From this viewpoint, the melting end temperature is preferably 130 ° C. or lower.

  The melting end temperature of polyethylene is determined by measuring a peak derived from a crystal part in a differential scanning calorimeter (DSC). Specific examples of more detailed measurement methods will be shown in the examples described later.

  The polyethylene of the present invention has an A hardness according to JIS K6253 (hereinafter sometimes simply referred to as “A hardness”) of 90 or less. When the polyethylene has an A hardness of more than 90 according to JIS K6253, it has a hard feel as a three-dimensional network structure and gives an unpleasant impression as a cushion or mattress. From the viewpoint of a soft feel during use, the A hardness of the polyethylene of the present invention is preferably 89 or less. On the other hand, when the A hardness is excessively small, the three-dimensional network structure is likely to be worn out. Therefore, the A hardness of the polyethylene of the present invention is preferably 50 or more, particularly preferably 60 or more.

  In the present invention, as the raw material polyethylene used for graft modification with the unsaturated silane compound, only one type may be used, or two or more types having different monomer compositions and physical properties may be used. When two or more types of polyethylene are mixed and used, the melting end temperature and the A hardness are values measured for this polyethylene mixture.

The polyethylene of the present invention preferably has a density (measured according to JIS K6922-1, 2: 1997) of usually 0.850 to 0.940 g / cm ³ , more preferably 0.855 to 0.935 g / cm 3. ³ , more preferably 0.860 to 0.935 g / cm ³ , and particularly preferably 0.860 to 0.910 g / cm ³ . When the density is not more than the above upper limit value, the thermal adhesiveness between the strands hardly deteriorates at the time of extrusion molding, and it tends to form a loop-shaped strand. Moreover, when the density is equal to or higher than the above lower limit value, it is difficult to fuse at the die outlet, and it tends to form a loop-like strand.

  The melt flow rate (MFR) of the polyethylene of the present invention is a melt flow rate (MFR) measured under the conditions of a temperature of 190 ° C. and a load of 2.16 kg in accordance with JIS K7210 (1999). It is preferably 10 minutes. If the MFR is larger than the above upper limit, when a plurality of strands are extruded and molded, the melt tension is low and strand breakage occurs, so the loop is not stable, and the strand diameter varies from strand to strand. As a structure, the entanglement uniformity of strands is inferior, and the performance and quality as a product tend to deteriorate. On the other hand, if the MFR is smaller than the lower limit, the motor load and the resin pressure during extrusion molding are increased, and the melt tension is high, so that the strand diameter is increased, and the melted strand is difficult to deform and it is difficult to form a loop. Tend. From these viewpoints, the MFR of polyethylene is preferably 1 g / 10 min or more, more preferably 2 g / 10 min or more, while preferably 40 g / 10 min or less, more preferably 30 g / 10 min. It is as follows.

  Regarding the density and MFR of the above polyethylene, when two or more kinds of polyethylene are used, the density and MFR as a polyethylene mixture are applicable.

  The polyethylene of the present invention can also be obtained as a commercial product. For example, Japanese Polyethylene Kernel (registered trademark) series, Mitsui Chemicals Tuffmer (registered trademark) series, Tosoh Nipolon (registered trademark) series, Dupond Dow Elastomer Engage (registered trademark) series, ExxonMobil manufactured Applicable products can be selected from Exceed (registered trademark) and used.

  As polyethylene of this invention, 1 type may be used independently and 2 or more types from which said monomer composition and physical properties differ among said polyethylene may be mixed and used.

[Unsaturated silane compound]
Although the unsaturated silane compound used for this invention is not limited, The unsaturated silane compound represented by following formula (1) is used suitably.
RSi (R ′) ₃ (1)

  In the above formula (1), R is an ethylenically unsaturated hydrocarbon group, R ′ is independently a hydrocarbon group having 1 to 10 carbon atoms or an alkoxy group having 1 to 10 carbon atoms, and R ′ At least one of them is an alkoxy group having 1 to 10 carbon atoms.

  In the formula (1), R is preferably an ethylenically unsaturated hydrocarbon group having 2 to 10 carbon atoms, and more preferably an ethylenically unsaturated hydrocarbon group having 2 to 6 carbon atoms. Specific examples include alkenyl groups such as vinyl group, propenyl group, butenyl group, and cyclohexenyl group.

  In the formula (1), R ′ is preferably a hydrocarbon group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms or 1 to 4 carbon atoms. Of the alkoxy group. Further, at least one of R ′ is preferably an alkoxy group having 1 to 6 carbon atoms, and more preferably an alkoxy group having 1 to 4 carbon atoms.

  The hydrocarbon group having 1 to 10 carbon atoms of R ′ may be any of an aliphatic group, an alicyclic group, and an aromatic group, but is preferably an aliphatic group. In addition, the alkoxy group having 1 to 10 carbon atoms of R ′ may be linear, branched or cyclic, but is preferably linear or branched. When R ′ is a hydrocarbon group, specifically, an alkyl group represented by methyl group, ethyl group, isopropyl group, t-butyl group, n-butyl group, i-butyl group, cyclohexyl group, etc., or phenyl An aryl group typified by a group and the like can be mentioned. When R ′ is an alkoxy group, specific examples include a methoxy group, an ethoxy group, an isopropoxy group, and a β-methoxyethoxy group.

  When the unsaturated silane compound is represented by the formula (1), at least one of the three R ′ is an alkoxy group, it is preferable that two R ′ are alkoxy groups, and all R ′ are More preferably, it is an alkoxy group.

  As the unsaturated silane compound, among the compounds represented by the formula (1), vinyltrialkoxysilanes represented by vinyltrimethoxysilane, vinyltriethoxysilane, propenyltrimethoxysilane and the like are desirable. This is because the vinyl group enables modification to polyethylene, and the alkoxy group promotes the crosslinking reaction described later. In other words, an alkoxy group introduced by graft-modifying to a modified polyethylene with an unsaturated silane compound reacts with water in the presence of a silanol condensation catalyst to hydrolyze to form a silanol group, and the silanol groups dehydrate and condense with each other. As a result, the modified polyethylenes are bonded to each other to cause a crosslinking reaction.

  In addition, these unsaturated silane compounds may be used individually by 1 type, and may use 2 or more types together.

  In the modified polyethylene of the present invention, the amount of the unsaturated silane compound modified (the amount of the unsaturated silane compound introduced into the modified polyethylene by graft modification) is 0.1 to 5% by mass. When the amount of modification is less than the above lower limit, the heat resistance is poor and the three-dimensional network structure is easily deformed, which is not preferable. On the other hand, when the modification amount exceeds the above upper limit, the viscosity becomes high, the strand diameter during extrusion molding becomes thick, and the surface becomes rough, which is not preferable. From the viewpoint of making these more favorable, the amount of modification of the unsaturated silane compound is preferably 0.2% by mass or more, more preferably 0.3% by mass or more, while preferably 4.0%. It is not more than mass%, more preferably not more than 3.0 mass%.

  The amount of modification of the unsaturated silane compound is the weight ratio of the unsaturated silane compound introduced by graft modification with respect to ethylene before modification. After the sample is heated and burned, the sample is ashed, and the ash is alkali-melted and dissolved in pure water. It can be quantified and confirmed by ICP emission spectrometry using a high frequency plasma emission spectrometer.

  The modified polyethylene of the present invention may be one obtained by graft-modifying a compound other than the unsaturated silane compound within a range not impairing the effects of the present invention. Specific examples of compounds other than unsaturated silane compounds include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, and isocrotonic acid. Examples thereof include acids and acid anhydrides thereof.

[Graft modification]
The modified polyethylene of the present invention can be produced by graft-modifying the above unsaturated silane compound to the above-mentioned polyethylene of the present invention. The graft modification method is not particularly limited and can be performed according to a known method. For example, solution modification, melt modification, solid phase modification by irradiation with electron beam or ionizing radiation, modification in a supercritical fluid, and the like are preferable. Used for. Among these, melt modification excellent in equipment and cost competitiveness is preferable, and melt kneading modification using an extruder excellent in continuous productivity is more preferable. Examples of the apparatus used for melt kneading modification include a single screw extruder, a twin screw extruder, a Banbury mixer, and a roll mixer. Among these, a single screw extruder and a twin screw extruder excellent in continuous productivity are preferable.

  In general, graft modification of an unsaturated silane compound to polyethylene is performed by a graft reaction in which a carbon-hydrogen bond of polyethylene is cleaved to generate a carbon radical, and an unsaturated functional group is added thereto. As a generation source of the carbon radical, in addition to the above-described electron beam and ionizing radiation, a high temperature method or a radical generator such as an organic or inorganic peroxide can be used. It is preferable to use an organic peroxide from the viewpoint of cost and operability.

  There are no limitations on the radical generator used in producing the modified polyethylene. For example, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxyesters and organic peroxides contained in ketone peroxide groups, and azo Compounds and the like.

  Specifically, for example, the hydroperoxide group includes cumene hydroperoxide, tertiary butyl hydroperoxide, and the like, and the dialkyl peroxide group includes dicumyl peroxide, ditertiary butyl peroxide, 2,5- Dimethyl-2,5-ditertiary butyl peroxyhexane, 2,5-dimethyl-2,5-ditertiary butyl peroxyhexine-3 and the like are included, and the diacyl peroxide group includes lauryl peroxide and benzoyl peroxide. Etc. are included. The peroxyester group includes tertiary peroxyacetate, tertiary butyl peroxybenzoate, tertiary butyl peroxyisopropyl carbonate, and the like, and the ketone peroxide group includes cyclohexanone peroxide and the like. Examples of the azo compound include azobisisobutyronitrile and methyl azoisobutyrate.

  These radical generators may be used alone or in combination of two or more.

  As a generally used melt extrusion modification operation, the polyethylene of the present invention, an unsaturated silane compound, and an organic peroxide are blended, blended, put into a kneader or an extruder, and extruded while being heated and melt kneaded. The molten resin coming out from the tip die is cooled in a water tank or the like to obtain a modified polyethylene.

  Although there is no restriction | limiting in particular as a mixing | blending ratio of the polyethylene of this invention and an unsaturated silane compound, As a preferable range of a mixing | blending, an unsaturated silane compound is 1-10 mass parts with respect to 100 mass parts of polyethylene. If the amount of the unsaturated silane compound is too small relative to the polyethylene, the predetermined amount of modification necessary for obtaining the effects of the present invention may not be obtained. If the amount is too large, a large amount of unreacted unsaturated silane compound remains. However, the performance may be adversely affected.

  Although there is no restriction | limiting in particular as a mixing | blending ratio of an unsaturated silane compound and an organic peroxide, As a preferable mixing | blending range, an organic peroxide is 1-10 mass parts with respect to 100 mass parts of unsaturated silane compounds. is there. When the amount of the organic peroxide relative to the unsaturated silane compound is equal to or higher than the lower limit, a sufficient amount of radicals are generated and a necessary predetermined modification amount is easily obtained, and is equal to or lower than the upper limit. It tends to be easy to suppress deterioration of polyethylene.

  Moreover, as melt extrusion modification | denaturation conditions, it is preferable to extrude at the temperature of about 150-300 degreeC, for example in a single screw extruder and a twin screw extruder.

[Combination agent]
The modified polyethylene of the present invention can contain a compounding agent commonly used in a resin composition as long as the effects of the present invention are not impaired. Examples of such a compounding agent include a heat stabilizer, an ultraviolet absorber, a light stabilizer, an antioxidant, an antistatic agent, a crystal nucleating agent, a rust inhibitor, a viscosity modifier, and a pigment.

  Among these, it is preferable to contain an antioxidant, particularly a phenol-based, sulfur-based, or phosphorus-based antioxidant. It is preferable to contain 0.1-1 mass part of antioxidant with respect to 100 mass parts of modified polyethylene.

Moreover, you may contain a ultraviolet absorber and a viscosity modifier.
Specific examples of the ultraviolet absorber include 2-hydroxy-4-normal-octyloxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2-dihydroxy-4-methoxybenzophenone, and 2-hydroxy-4-methoxy. Benzophenone series such as -4-carboxybenzophenone and 2-hydroxy-4-N-octoxybenzophenone; 2- (2-hydroxy-3,5-di-t-butylphenyl) benzotriazole, 2- (2-hydroxy- Benzotrializoles such as 5-methylphenyl) benzotriazole; salicylic acid esters such as phenylsulcylate and p-octylphenylsulcylate are used. It is preferable to contain 1.0-0.01 mass parts of ultraviolet absorbers with respect to 100 mass parts of modified polyethylene.
The viscosity modifier is preferably a rubber compounding oil, specifically a paraffinic process oil. It is preferable to contain 0.5-5 mass parts of viscosity modifiers with respect to 100 mass parts of modified polyethylene.

[Physical properties]
The modified polyethylene of the present invention has a melt flow rate (MFR) measured at 190 ° C. under a load of 2.16 kg in accordance with JIS K7210 (1999), usually 1 g / 10 minutes or more, preferably 2 g / 10 minutes or more. More preferably, it is 3 g / 10 minutes or more, usually 100 g / 10 minutes or less, preferably 50 g / 10 minutes or less, more preferably 25 g / 10 minutes or less. If the MFR is equal to or greater than the lower limit, the die swell and melt tension are low, so the strand diameter is difficult to increase, and it is easy to form a loop along the side surface of the three-dimensional network structure. It becomes easy to do. When the MFR is equal to or less than the upper limit, when a plurality of strands are extruded, it is easy to stabilize the discharge of the strands, and it is difficult to form a resin lump in which the plurality of strands are rounded and hardened. Further, loop formation and strand fusion are stable, the strand diameter is likely to be uniform, the uniformity as a three-dimensional network structure is good, and the performance and quality as a product tend to be improved.

[Modified polyethylene composition]
A modified polyethylene composition can be obtained using the modified polyethylene of the present invention and a silanol condensation catalyst.
This modified polyethylene composition is excellent in fluidity and moldability when it is used as a composition because the modified polyethylene of the present invention is excellent in fluidity.

[Silanol condensation catalyst]
The silanol condensation catalyst that can be used in the present invention is selected from the group consisting of metal organic acid salts, titanates, borates, organic amines, ammonium salts, phosphonium salts, inorganic acids and organic acids, and inorganic acid esters. One or more compounds may be mentioned.

  Examples of metal organic acid salts include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous acetate, stannous octoate, cobalt naphthenate, lead octylate, lead naphthenate, octylic acid Examples include zinc, zinc caprylate, iron 2-ethylhexanoate, iron octylate, and iron stearate. Examples of titanates include tetrabutyl titanate, tetranonyl titanate, bis (acetylacetonitrile) di-isopropyl titanate, and the like. Examples of the organic amine include ethylamine, dibutylamine, hexylamine, triethanolamine, dimethyl soyaamine, tetramethylguanidine, pyridine and the like. Examples of the ammonium salt include ammonium carbonate and tetramethylammonium hydroxide. Examples of the phosphonium salt include tetramethylphosphonium hydroxide. Examples of the inorganic acid and the organic acid include sulfonic acids such as sulfuric acid, hydrochloric acid, acetic acid, stearic acid, maleic acid, toluenesulfonic acid, and alkylnaphthylsulfonic acid. Examples of inorganic acid esters include phosphate esters.

Of these, metal organic acid salts, sulfonic acids, and phosphoric acid esters are preferred, and tin metal carboxylates such as dioctyl tin dilaurate, alkyl naphthyl sulfonic acids, and ethylhexyl phosphoric acid esters are more preferred.
In addition, the silanol condensation catalyst mentioned above may be used alone or in combination of two or more.

  The blending amount of the silanol condensation catalyst is not particularly limited, but is preferably 0.0001 to 0.5 parts by mass, more preferably 0.0001 to 0.1 parts by mass with respect to 100 parts by mass of the modified polyethylene. Part. If the blending amount of the silanol condensation catalyst is not less than the above lower limit value, it is preferable because the crosslinking reaction proceeds sufficiently and the heat resistance tends to be good, and if it is not more than the above upper limit value, early crosslinking is unlikely to occur in the extruder. It is preferable because there is a tendency that strand breakage due to early crosslinking and resin mass due to strand breakage hardly occur.

  The silanol condensation catalyst is preferably used as a master batch in which a polyolefin and a silanol condensation catalyst are blended. Examples of polyolefins that can be used in the masterbatch include polyethylene, polypropylene, and propylene-ethylene copolymers.

  Examples of polyethylene include (branched or linear) ethylene homopolymers such as low, medium and high density polyethylene; ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 4-methyl- 1-pentene copolymer, ethylene / 1-hexene copolymer, ethylene / α-olefin copolymer such as ethylene / 1-octene copolymer; ethylene / vinyl acetate copolymer, ethylene / (meth) acrylic acid Examples thereof include ethylene copolymers such as copolymers and ethylene / (meth) acrylic acid ester copolymers.

Examples of polypropylene include random, block, and homopolypropylene. Among these, random polypropylene is preferable.
As the propylene / ethylene copolymer, a copolymer obtained by copolymerizing 5 to 20% by mass of ethylene and 95 to 80% by mass of propylene is preferable from the viewpoint of a high melting point.

  Among these, in the present invention, high-pressure method low-density polyethylene, high-density polyethylene, and ethylene / α-olefin copolymer having an excellent balance between heat resistance and strength are preferable. The ethylene / α-olefin copolymer is more preferably an ethylene / 1-butene copolymer, an ethylene / 4-methyl-1-pentene copolymer, an ethylene / 1-hexene copolymer, or an ethylene / 1-octene. It is an ethylene / α-olefin copolymer such as a copolymer, and the ethylene / α-olefin copolymer is composed of 2 to 60% by mass of one or more α-olefins and 40 to 98% by mass of ethylene. More preferably, these are copolymerized.

  In the master batch of the silanol condensation catalyst, only one kind of these polyolefins may be used, or two or more kinds may be blended and used.

  When the silanol condensation catalyst is used as a master batch in which a polyolefin and a silanol condensation catalyst are blended, the content of the silanol condensation catalyst in the master batch is not particularly limited, but is usually about 0.1 to 5.0% by mass. It is preferable to do.

  A commercially available product can be used as the silanol condensation catalyst-containing masterbatch, for example, “LZ082” manufactured by Mitsubishi Chemical Corporation.

[Other ingredients]
In the modified polyethylene composition of the present invention, in addition to the modified polyethylene and silanol condensation catalyst of the present invention, various additives, resins other than the polyolefin in the modified polyethylene and catalyst masterbatch, etc. as other components, etc. It can contain in the range which does not impair an effect.

As such an example, in order to improve adhesiveness and compatibility, a thermoplastic solid resin, a solid rubber, a liquid resin, a softening agent, a plasticizer and the like are included as a tackifier. For example, rosin and its derivatives, terpene resin or petroleum resin and its derivatives, alkyd resin, alkylphenol resin, terpene phenol resin, coumarone indene resin, synthetic terpene resin, alkylene resin, polyisobutylene, polybutadiene, polybutene, isobutylene and butadiene Polymers, mineral oils, process oils, pine oils, anthracene oils, pine root oils, plasticizers, animal and vegetable oils, polymerized oils and the like can be contained.
Moreover, the compounding agent which can be mix | blended with the above-mentioned modified polyethylene can be contained.

[Silane-crosslinked polyethylene]
Crosslinking between silanol groups by molding the modified polyethylene composition of the present invention containing the modified polyethylene of the present invention and a silanol condensation catalyst by various molding methods such as extrusion molding, injection molding, press molding, etc., and then exposing to a water atmosphere. The reaction can be advanced to give a silane-crosslinked polyethylene. Various conditions can be adopted for the method of exposure in a water atmosphere, a method of leaving in air containing moisture, a method of blowing air containing water vapor, a method of immersing in a water bath, and spraying hot water in a mist form And the like.

  In the modified polyethylene composition of the present invention, the hydrolyzable alkoxy group derived from the unsaturated silane compound used for the graft modification of polyethylene reacts with water in the presence of a silanol condensation catalyst and hydrolyzes to produce a silanol group. Further, silanol groups are dehydrated and condensed, whereby a crosslinking reaction proceeds, and modified polyethylenes are bonded to each other to produce a silane-crosslinked polyethylene.

  The rate of progress of the cross-linking reaction is determined by the conditions of exposure in a water atmosphere, but the exposure is usually in the temperature range of 20 to 130 ° C. and in the range of 10 minutes to 1 week. Particularly preferred conditions are a temperature range of 20 to 130 ° C. and a range of 1 hour to 160 hours. When air containing moisture is used, the relative humidity is selected from the range of 1 to 100%.

In order for the silane-crosslinked polyethylene to exhibit excellent characteristics over a long period of time, the silane-crosslinked polyethylene of the present invention preferably has a gel fraction (degree of crosslinking: measured in accordance with JIS K6796) of usually 30 to 90%. More preferably, it is 32 to 80%, and still more preferably 35 to 50%. If the gel fraction is less than or equal to the above upper limit, the strands are less likely to be thick during extrusion molding, and an excellent cushioning three-dimensional network structure tends to be easily formed efficiently. In addition, when the gel fraction is equal to or higher than the lower limit, silane crosslinking proceeds sufficiently, there is no problem of settling even under a high temperature load, and a three-dimensional network structure excellent in heat resistance tends to be easily formed. is there. The gel fraction of the silane-crosslinked polyethylene is adjusted by changing the graft ratio (modified amount) of the unsaturated silane compound of the modified polyethylene, the type and amount of silanol condensation catalyst, and the conditions (temperature, time) for crosslinking. can do.
The gel fraction of silane-crosslinked polyethylene can be measured by the method described in the Examples section below.

  The modified polyethylene composition of the present invention comprising the modified polyethylene of the present invention and a silanol condensation catalyst is formed into a strand by extruding the strand, and then the strands are heat-sealed and then cooled with water to obtain a three-dimensional structure. A network structure can be obtained. For example, the modified polyethylene composition can be formed into a three-dimensional network structure by a manufacturing apparatus and a forming method as described in International Publication No. 2012/035736. The three-dimensional network structure thus obtained is preferably exposed to a water atmosphere as described above and used as a silane-crosslinked polyethylene.

  In particular, the modified polyethylene composition of the present invention can be molded without cross-linking at the time of molding, so that a three-dimensional network structure that requires special moldability such as loop properties and thermal adhesiveness immediately after molding can be efficiently obtained. The molded product obtained can be molded, and since the heat resistance, which is a major issue of polyethylene such as ethylene / α-olefin copolymer, has been improved, there is a problem of stickiness even under high temperature loads. In addition, a three-dimensional network structure having excellent cushioning properties can be provided.

[Use]
The use of the modified polyethylene, modified polyethylene composition and silane-crosslinked polyethylene of the present invention is not particularly limited, but is suitably used as a cushioning material for furniture, bed mats, pillows and other beddings; be able to. In addition, when applied to these uses, it is preferably used as the aforementioned three-dimensional network structure. This three-dimensional network structure can also be used as a laminate with other materials as required.
However, the molded body of the present invention is not limited to a three-dimensional network structure.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to a following example, unless the summary is exceeded. Further, the values of various production conditions and evaluation results in the following examples have meanings as preferable values of the upper limit or the lower limit in the embodiment of the present invention, and the preferable range is the above-described upper limit or lower limit value. A range defined by a combination of values of the following examples or values of the examples may be used.

〔material〕
In the examples and comparative examples of the present invention, the following raw materials were used.

<Polyethylene>
PE-1: Nipolon (registered trademark) HM510R (manufactured by Tosoh Corporation, ethylene / 1-hexene copolymer, MFR: 12 g / 10 min (190 ° C., 2.16 kg load), density: 0.905 g / cm ³ , Melting end temperature: 98 ° C., A hardness: 92)
PE-2: Infuse (registered trademark) 9807 (manufactured by Dow Dupont Elastomer, ethylene / 1-octene copolymer, MFR: 8 g / 10 min (190 ° C., 2.16 kg load), density: 0.866 g / cm ³ , melting end temperature: 125 ° C., A hardness: 61)

[Catalyst masterbatch (MB)]
Catalyst MB: LZ082 (manufactured by Mitsubishi Chemical Corporation, containing 1% by mass of a tin catalyst (dioctyltin dilaurate) in linear low density polyethylene having the following physical properties) was used.
(Physical properties of linear low density polyethylene)
MFR: 4 g / 10 min (190 ° C., 2.16 kg load)
Density: 0.900 g / cm ³
Melting point: 90 ° C

[Measurement and evaluation method]
The measurement and evaluation methods for various physical properties and characteristics are as follows.

<Measurement of polyethylene and modified polyethylene>
(Melting end temperature)
Using a differential scanning calorimeter manufactured by Hitachi High-Tech Science Co., Ltd., trade name “DSC6220”, according to JIS K7121, about 5 mg of the sample was heated from 20 ° C. to 200 ° C. at a heating rate of 100 ° C./min. After maintaining at 200 ° C. for 3 minutes, the temperature was lowered to −10 ° C. at a cooling rate of 10 ° C./min, and then the extrapolated peak end point from the thermogram measured when the temperature was raised to 200 ° C. at a heating rate of 10 ° C./min. (° C.) was calculated as the melting end temperature.

(A hardness)
Based on JIS K6253, the measurement was performed with ASKER CL-150 manufactured by Kobunshi Keiki Co., Ltd.

(Melt flow rate (MFR))
Based on JIS K7210 (1999), the measurement was performed at 190 ° C. and a 2.16 kg load.

(Modification amount)
Silane-modified polyethylene is incinerated by heating and ashing, and the ash content is melted with alkali and dissolved in pure water for quantification, and introduced by graft modification using an ICI emission analysis method using a high-frequency plasma emission analyzer (ICPS7510 manufactured by Shimadzu Corporation). The amount of unsaturated silane compound was quantified.

<Evaluation of silane-crosslinked polyethylene>
(Gel fraction)
The mass% of insoluble matter after Soxhlet extraction at the xylene boiling point for 10 hours was measured.

(Compression set)
The manufactured sheet-like molded product is punched into a circular shape with a diameter of 30 mm, and six of these are stacked and compressed at 25% with a spacer in accordance with JIS K6262, 24 hours at 23 ° C., then shown in Table 1 Heat treatment is performed for 22 hours at the test temperature (20 ° C., 50 ° C. or 70 ° C.) and compression is performed. After the treatment, the sample is left in a constant temperature room at 23 ° C. for 30 minutes, and then the thickness is measured and compression set (CS: unit) %). A lower compression set value is better.

(Permanent distortion after shape recovery)
In the measurement of the compression set, the sample whose compression set was measured at 70 ° C. was stored for 3 hours under the conditions of 85 ° C. and 85% Rh without load, and the shape was recovered. Then, it was left in a thermostatic chamber at 23 ° C. for 30 minutes, the thickness was measured, and the permanent set (unit%) after the shape recovery was calculated. The lower the permanent set value after shape recovery, the better.

[Examples and Comparative Examples]
<Example 1>
75 parts by mass of PE-1 as polyethylene and 25 parts by mass of PE-2, 2.0 parts by mass of vinyltrimethoxysilane (VTMOS) as an unsaturated silane compound, and dicumyl peroxide 0. Two parts were stirred with a blender. After that, it was put into a twin screw extruder (PCM45, manufactured by Ikegai Co., Ltd.) set at a temperature of 220 ° C., and the strand coming out of the nozzle was cooled and solidified in a water tank, and then cut into a pellet to modify polyethylene-A Got. Table 1 shows the physical properties of the obtained modified polyethylene-A.

  5 parts by mass of LZ082 as catalyst MB was added to 100 parts by mass of the modified polyethylene-A obtained above to obtain a modified polyethylene composition-A. This was molded with an injection molding machine at 200 ° C., and immersed in warm water at 80 ° C. for 24 hours to produce a sheet-like molded product having a thickness of 2 mm made of silane-crosslinked polyethylene-A. The gel fraction, compression set, and permanent set after shape recovery of the obtained silane-crosslinked polyethylene-A were evaluated. The results are shown in Table-1.

<Example 2>
A modified polyethylene-B was obtained in the same manner as in Example 1 except that 50 parts by mass of PE-1 and 50 parts by mass of PE-2 were used as polyethylene. Using modified polyethylene-B, the same operation as in Example 1 was performed to produce modified polyethylene composition-B, and silane-crosslinked polyethylene-B was further produced.
Table 1 shows the results of evaluation of the modified polyethylene-B and the silane-crosslinked polyethylene-B.

<Example 3>
A modified polyethylene-C was obtained in the same manner as in Example 1 except that 25 parts by mass of PE-1 and 75 parts by mass of PE-2 were used as polyethylene. The modified polyethylene-B was used in the same manner as in Example 1 to produce a modified polyethylene composition-C, and a silane-crosslinked polyethylene-C was further produced.
Table 1 shows the results of evaluation of the modified polyethylene-C and the silane-crosslinked polyethylene-C.

<Example 4>
A modified polyethylene-D was obtained in the same manner as in Example 1 except that 100 parts by mass of PE-2 was used as polyethylene. A modified polyethylene composition-D was produced using the modified polyethylene-D in the same manner as in Example 1, and a silane-crosslinked polyethylene-D was further produced.
Table 1 shows the results of evaluation of modified polyethylene-D and silane-crosslinked polyethylene-D.

<Comparative Example 1>
Non-modified polyethylene-E was obtained in the same manner as in Example 1 except that 100 parts by mass of PE-1 was used as polyethylene and VTMOS and organic peroxide were not used. A non-crosslinked polyethylene composition-E was produced in the same manner as in Example 1 except that non-modified polyethylene-E was used and catalyst MB: LZ082 was not used, and non-crosslinked polyethylene-E was further produced.
Table 1 shows the results of evaluation of non-modified polyethylene-E and non-crosslinked polyethylene-E.

<Comparative example 2>
A modified polyethylene-F was obtained in the same manner as in Example 1 except that 100 parts by mass of PE-1 was used as polyethylene. A modified polyethylene composition-F was produced by using the modified polyethylene-F in the same manner as in Example 1, and a silane-crosslinked polyethylene-F was further produced.
Table 1 shows the results of evaluation of modified polyethylene-F and silane-crosslinked polyethylene-F.

  The following can be seen from the above results.

As shown in Examples 1 to 4, modified polyethylene using polyethylene having a melting end temperature of 100 to 130 ° C. and A hardness of 90 or less shows high MFR, and silane-crosslinked polyethylene using these modified polyethylenes is 20 ° C. Low compression set was exhibited at 50 ° C. and 70 ° C., and the permanent set after shape recovery was also low. Since the modified polyethylenes of Examples 1 to 4 are excellent in fluidity, excellent moldability such as low resin pressure can be expected. In addition, since the silane-crosslinked polyethylene of Examples 1 to 4 has a low compression set, it can form a three-dimensional network structure that is difficult to set and further has a low permanent set after shape recovery, so that hydrothermal treatment such as hot water disinfection However, it can be seen that the three-dimensional network structure is easy to recover.
The modified polyethylenes of Examples 1 to 4 have excellent durability, heat resistance, and shape recoverability because they have a small compression set and a small permanent set after shape recovery.

On the other hand, in the case of non-modified polyethylene using polyethylene having a melting point of less than 100 ° C. and an A hardness of more than 90 as in Comparative Example 1, both the compression set and the permanent set after shape recovery are large.
The modified polyethylene of Comparative Example 1 obtained by modifying the polyethylene with silane also has a large compression set and permanent set after shape recovery.
For this reason, these are easy to remain distortion and are inferior to durability and heat resistance.

  From the above, it can be seen that a silane-crosslinked polyethylene having a small compression set and excellent shape restoring property can be produced from a silane-modified polyethylene using a polyethylene having a high melting point and a low hardness.

  Since the modified polyethylene of the present invention is excellent in durability and heat resistance, it is possible to give a silane-crosslinked polyethylene that has a small compression set even under a heating condition and is unlikely to cause depression or settling due to use. In addition, since the modified polyethylene of the present invention is excellent in shape recoverability, it is possible to produce a three-dimensional network structure that can be easily recovered by hot water treatment such as a disinfection process. For this reason, the modified polyethylene, modified polyethylene composition and silane-crosslinked polyethylene of the present invention can be suitably used as a constituent material of cushion materials for furniture, bed mats, pillows, etc .; vehicles, boat seats, etc. .

Claims (7)

  In the differential scanning calorimetry, the unsaturated silane compound is 0 in the polyethylene satisfying the conditions that the extrapolation crystal melting end temperature measured at a heating rate of 10 ° C./min is 100 ° C. to 130 ° C. and the A hardness according to JIS K6253 is 90 or less. .1-5% by weight graft-modified polyethylene. The modified polyethylene according to claim 1, wherein the unsaturated silane compound is a compound represented by the following formula (1).
RSi (R ′) ₃ (1)
(However, R is an ethylenically unsaturated hydrocarbon group, R 'is mutually independently a C1-C10 hydrocarbon group or a C1-C10 alkoxy group, and is at least 1 of R'. Is an alkoxy group having 1 to 10 carbon atoms.) The modified polyethylene according to claim 1 or 2, wherein the density of the polyethylene is 0.850 to 0.940 g / cm ³ .   The modified polyethylene according to any one of claims 1 to 3, wherein the polyethylene is an ethylene / α-olefin copolymer.   A modified polyethylene composition comprising the modified polyethylene according to any one of claims 1 to 4 and a silanol condensation catalyst.   The molded object formed by shape | molding the modified polyethylene composition of Claim 5.   Silane cross-linked polyethylene obtained by cross-linking reaction of the modified polyethylene composition according to claim 5.