JP3377742B2 - Method for producing silane-crosslinked polyolefin - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a silane cross-linking polyolefin in one step in the silane cross-linking of a polyolefin by a carrier polymer A containing a high concentration of an organic unsaturated silane and the like and a carrier polymer B containing a silanol condensation catalyst and the like. The present invention relates to a silane crosslinking method to be produced.

[0002]

2. Description of the Related Art Conventionally, as a simple method for crosslinking a polyolefin, an organic unsaturated silane is graft-reacted on the polyolefin in the presence of a free radical generator to effect silane grafting, and then the silane grafter is used as a silanol condensation catalyst. The so-called silane cross-linking method is generally known in which the substance is brought into contact with water to crosslink in the presence of silane. For example, Japanese Patent Publication Sho 48
-1711, JP-A-57-49109, etc. However, this method involves at least two steps. That is, a silane grafting reaction step and a silanol condensation reaction step. Therefore, the extrusion process must be performed at least twice, and the economic problem of the final product cannot be avoided.

Further, there is a mono-seal method as a one-step process. However, this method requires a liquid addition device for injecting the organic unsaturated silane in a liquid state into the extruder, but has a problem of slippage and poor metering. Also, the extruder requires a special type with a large L / D, in order to uniformly disperse a small amount of additives.
Financial problems are inevitable. Furthermore, very high technology is required in extrusion. Further, as a one-step process, a silane cross-linking method in which silane is introduced into a solid carrier polymer is disclosed in JP-A-3-167229. However, in this method, the solid carrier polymer is a porous polymer or EVA, and in addition to the silane and the free radical generator, additives such as a silanol condensation catalyst and an antioxidant are also introduced into the solid carrier polymer. Therefore, there has been a problem that the crosslinking efficiency and the storage stability are deteriorated due to the oligomerization by the condensation of silane or the inhibition of the crosslinking by the radical trapping.

[0004]

DISCLOSURE OF THE INVENTION The present invention has solved these problems and, in the silane crosslinking of polyolefin, contains a carrier polymer A containing a high concentration of an organic unsaturated silane and the like and a silanol condensation catalyst. The purpose of the present invention is to provide a silane cross-linking method for producing a silane cross-linked polyolefin in one step by using a carrier polymer B.

[0005]

According to the present invention, (i) the density is 0.85 to 0.89 g / cm ³ , the melt index is 0.3 to 20 g / 10 min, and 1-octene is used as a comonomer during polymerization. 0.04 long chain branches per 1000 carbons along the polymer backbone, used and polymerized using a single site catalyst as catalyst.
Substantially linear polyethylene having one or more / 1-
A base polymer composed of an octene copolymer, and (ii) the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R'is other than an aliphatic unsaturated hydrocarbon. Monovalent hydrocarbon groups or the same as Y) to obtain an organic unsaturated silane whose addition amount is 0.1 to 5% by weight based on the total weight of the polymer and a half-life of 1 minute. Decomposition temperature of 170 ℃ or more 250 ℃
A substantially water-free carrier containing a free radical generator having the following content and an active oxygen content of 8% or more and an addition amount of 0.01 to 0.5% by weight based on the total weight of the polymer. Polymer A, and (iii) a carrier polymer B containing a silanol condensation catalyst and an antioxidant in an amount of 0.01 to 0.2% by weight based on the total weight of the polymer, and a crystalline melting point of the base polymer. A method for producing a silane-crosslinked polyolefin, which comprises melt-mixing and reacting at a higher temperature, and then contacting with water to crosslink, preferably having a density of 0.86 to 0.89 g / cm3.
The polymer was polymerized by using 1-octene as a comonomer and a single-site catalyst as a catalyst at the time of polymerization with a melt index of 0.5 to 5 g / 10 min.
It is a base polymer comprising a substantially linear polyethylene / 1-octene copolymer having 0.01 or more per 000, and the carrier polymer A is ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer. Combined (EMMA), water obtained by hydrogenating a block copolymer comprising at least one vinyl aromatic compound-based polymer block and at least one conjugated diene compound-based polymer block Is a polymer selected from the group consisting of an additive block copolymer and a mixture thereof, and the carrier polymer B is a polymer selected from the group consisting of polyethylene, polypropylene, a copolymer of ethylene and α-olefin, and a mixture thereof. , Carrier polymers A and B
Is a method for producing a silane-crosslinked polyolefin having a total amount of 2 to 15% by weight.

DETAILED DESCRIPTION OF THE INVENTION A substantially linear polyethylene / 1-octene copolymer of the base polymer of the present invention means that 1-octene is used as a comonomer at the time of polymerization and is an appropriate constraint among single-site catalysts. Geometric catalyst (con
Strained geometrycatalyst
s) is used. US Pat. No. 5,026,798
The olefin polymerization catalysts of monocyclopentadienyl transition metals taught in US Pat. No. 4,096,036 are also suitable for use in the preparation of polyethylene / 1-octene copolymers which are substantially linear of the base polymers of the present invention. Suitable cocatalysts for use in the production of polyethylene / 1-octene copolymers that are substantially linear of the base polymers of the present invention include:
Examples include, but are not limited to, polymeric or oligomeric aluminoxanes, especially methylaluminoxane, as well as inert, compatible, non-coordinating, ion-forming compounds. Suitable cocatalysts are inert, non-coordinating boron compounds. Suitable polymerization conditions for producing a substantially linear polyethylene / 1-octene copolymer of the base polymer of the present invention are those which are generally effective in solution polymerization processes,
The application of the present invention is not limited thereto. Slurry and gas phase polymerization methods are also effective, provided that appropriate catalysts and polymerization conditions are used.

In the production of the substantially linear polyethylene / 1-octene copolymer of the base polymer of the present invention, a multi-reactor polymerization process such as US Pat.
The polymerization method disclosed in No. 342 can also be used. It is possible to operate these reactors in series or in parallel with at least one constrained geometry catalyst in one of the multiple reactors. By "substantially linear" polyethylene / 1-octene copolymer is meant that the backbone of the polymer is substituted with 0.01 or more long chain branches per 1000 carbons, A substantially linear polyethylene / base polymer of
The reason why the 1-octene copolymer has 0.01 or more long chain branches per 1000 carbons along the polymer backbone is to ensure a certain level of melt viscosity, thereby substantially eliminating the base polymer of the present invention. This is because the polyethylene / 1-octene copolymer, which is linear, has good moldability. In contrast, the term "linear" polyethylene / C ₃ -C ₂₀ α- olefin copolymers, the olefin copolymer is meant that it does not contain long chain branching.

In embodiments of the present invention, it is of course contemplated to blend other ethylene polymers into the substantially linear polyethylene / 1-octene copolymer in the base resin of the present invention, in which case the blended ethylene. Examples of the copolymer include low density polyethylene (LDPE) polymerized by a high pressure polymerization method, medium density polyethylene (MDPE), very low density polyethylene (VLDPE) polymerized by a multi-site catalyst, linear low density polyethylene (LLDPE), High density polyethylene (HD
One or more of homopolymer types such as PE) and various ethylene copolymers obtained by copolymerizing a majority of ethylene with a comonomer such as propylene, vinyl acetate and ethyl acrylate are used. The density of the polyethylene / 1-octene copolymer, which is substantially linear of the base polymer, is 0.85 to 0.89 g / cm ³ . Those less than 0.85 g / cm ³ are difficult to industrially manufacture. If it exceeds 0.92 g / cm ³ , desired flexibility cannot be obtained. The melt index of the polyethylene / 1-octene copolymer which is substantially linear of the base polymer is 0.3 to 20 g / 10 min, preferably 0.5 to 5
It is g / 10min. If it is less than 0.3 g / 10 min, the extrusion processability will be poor, and if it exceeds 20 g / 10 min, the degree of crosslinking will be lowered.

The organic unsaturated silane of the present invention is grafted to the base resin so as to serve as a cross-linking point between the base resins. The organic unsaturated silane used in the present invention has the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R'is an aliphatic unsaturated carbon group. Monovalent hydrocarbon group other than hydrogen or
The same compound as Y) is used. It is desirable to use an organic unsaturated silane in which R'is the same as Y and is represented by the general formula RSiY3, such as vinyltrimethoxysilane,
Examples thereof include vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, and allyltriethoxysilane. The addition amount of these is 0.1 to 5% by weight, preferably 0.4 to 3% by weight, based on the total weight of the polymer. If it is less than 0.1% by weight, sufficient grafting does not occur, and if it exceeds 5% by weight, molding defects will occur and it will be uneconomical.

The free radical generator of the present invention acts as an initiator of the silane grafting reaction. The free radical generator used in the present invention has a decomposition temperature for obtaining a half-life of 1 minute of 170 ° C. or more and 250 ° C. or less and an active oxygen amount of 8% or more, has a strong polymerization initiation action, and decomposes and forms. Various organic peroxides that do not generate odor are used.
These organic peroxides include 2,5-dimethyl-2,
5-di (t-butylperoxy) hexane, α, α′-
One or more organic peroxides selected from bis (t-butylperoxy-m-isopropyl) benzene, di-t-butylperoxide, di-t-butylperoxyisophthalate, etc. are used. To be done. If the decomposition temperature for obtaining a half-life of 1 minute is less than 170 ° C, the reaction becomes violent and it is difficult to control it. If it exceeds 250 ° C, the reaction does not occur under appropriate conditions. If the amount of active oxygen is less than 8%, it is necessary to add a large amount of a free radical generator, resulting in poor appearance and reduced strength. The amount of these added is 0.01 to 0.5% by weight, preferably 0.015 to 0.2% by weight, based on the total weight of the polymer. 0.01% by weight
If it is less than 0.5% by weight, the silane grafting reaction does not proceed sufficiently, and if it exceeds 0.5% by weight, the extrusion processability is deteriorated and the molding surface is deteriorated.

The carrier polymer A of the present invention can be incorporated by swelling a liquid mixture of a free radical generator in a silane with the liquid mixture of the silane. At this time, the carrier polymer A must be preheated in order to add silane to a high concentration, but the temperature must be below the crystalline melting point so that the polymer does not melt. The carrier polymer A must also be in particulate form and be solid with the cross-linking base polymer and silane. By compatible is meant that the carrier polymer A must not readily react with the silane and must be dispersible or soluble in the base polymer. Suitable carrier polymers A are non-hygroscopic. That is, it is preferred that the absorption of water be relatively slow in order to minimize the possibility of premature hydrolysis and condensation of the silane. In any case, the carrier polymer A should be substantially free of water. The carrier polymer A of the present invention is a granule,
Alternatively, it is usually in the form of pellets, the preferred form being pellets. Examples of the carrier polymer A used in the present invention include ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), and a polymer block mainly containing at least one vinyl aromatic compound. When,
Hydrogenated block copolymers obtained by hydrogenating a block copolymer composed of a polymer block mainly composed of at least one conjugated diene compound, for example, hydrogenated styrene-isoprene block copolymer (SEPS), hydrogenated Styrene
Examples thereof include butadiene block copolymer (SEBS), and a mixture thereof.

The carrier polymer B of the present invention can be added by kneading and granulating a silanol condensation catalyst, an antioxidant and the like. The carrier polymer B must also be in particulate form and be a solid compatible with the cross-linking base polymer. The carrier polymer B of the present invention is usually in the form of granules or granules in the form of pellets, the preferred form being pellets. The carrier polymer B used in the present invention is, for example, polyethylene, polypropylene, a copolymer of ethylene and α-olefin, and the α-olefin is C3 to C12.
Of propylene, butene-1, pentene-1, octene-1, 4-methylpentene-1, 4-methylhexene-1,4,4-dimethylpentene-1, nonene-1,
Decene-1, undecene-1, dodecene-1, etc.,
And mixtures thereof.

The silanol condensation catalyst of the present invention includes dibutyltin dilaurate, dioctyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, lead naphthenate, zinc caprylate, cobalt naphthenate, tetrabutyl titanate. Examples thereof include organic metal compounds such as esters, lead stearate, zinc stearate, cadmium stearate, barium stearate, and calcium stearate. The amount of these added is 0.01 to 0.2% by weight based on the total weight of the polymer,
It is preferably 0.02 to 0.1% by weight. If the amount is less than 0.01% by weight, a sufficient crosslinking reaction does not proceed, and if the amount is more than 0.2% by weight, crosslinking locally progresses in the extruder at the time of extrusion and the appearance is significantly deteriorated. Also, the silanol condensation catalyst must be incorporated into the carrier polymer B. This is because the addition of the carrier polymer A promotes oligomerization due to condensation of silane and causes deterioration of appearance.

The antioxidant of the present invention is usually used in processing a polyolefin and is not particularly limited, but it must be incorporated into the carrier polymer B. This is because when the carrier polymer A is added, crosslinking is hindered by radical scavenging. Additives that may inhibit crosslinking even when other additives are added must be added to the carrier polymer B.

The amount of carrier polymer added is such that the total amount of carrier polymers A and B is in the range of 2 to 15% by weight. If it is less than 2% by weight, sufficient grafting does not occur, and if it exceeds 15% by weight, molding failure occurs and it becomes uneconomical.

As other additives, if desired, additives usually used, for example, a neutralizer, an ultraviolet absorber, an antistatic agent, a pigment, a dispersant, a thickener, a metal deterioration inhibitor, an antifungal agent, A flow regulator, other inorganic filler, etc., or other synthetic resin may be contained.

[0018]

EXAMPLES Examples will be described below. << Production of Carrier Polymer A >> According to the blending ratio as shown in Table 1, first, the carrier polymer A is put into a super mixer, stirred and mixed, and preheated to 80 ° C. Next, the liquid mixture in which the free radical generator was dissolved in unsaturated silane was charged into a super mixer and impregnated with the carrier polymer A for 10 minutes while stirring. << Production of Carrier Polymer B >> Carrier polymer B, silanol condensation catalyst, antioxidant and the like were kneaded and granulated using a pressure kneader in accordance with the blending ratios shown in Table 2.

* Raw materials used (1) EEA: ethylene-ethyl acrylate copolymer (E
(A content; 23% by weight) (2) SEPS: hydrogenated styrene-isoprene block copolymer (styrene content; 30% by weight) (3) L-LDPE (1): linear low density polyethylene (density: 0.924 g (/ cm ³ , MI; 3.0 g / 10 min) (4) VTMOS: vinyltrimethoxysilane (5) organic peroxide (1): α, α'-bis (t-butylperoxy-m-isopropyl) benzene ( Decomposition temperature for obtaining a half-life of 1 minute; 175.4 ℃, amount of active oxygen; 9.4
5%) (6) Organic peroxide (2): 2,5-dimethyl-2,5-
Di (t-butylperoxy) hexane (decomposition temperature for obtaining a half-life of 1 minute; 179.8 ° C, amount of active oxygen; 11.02
%) (7) Organic peroxide (3): Dicumyl peroxide (1
Decomposition temperature for obtaining half-life of minutes; 175.2 ℃, active oxygen amount; 5.92%) (8) LDPE (1): low density polyethylene (density: 0.925
g / cm ³ , MI; 1.5g / 10min) (9) PP: polypropylene (homopolymer, MI (230 °
C); 2.0g / 10min) (10) DOTDL: Dioctyltin dilaurate (11) Antioxidant: Phenolic antioxidant / Irganox 1010 (manufactured by Ciba Geigy) (12) Lubricant: Low molecular weight polyethylene / sun wax 171
P (manufactured by Sanyo Kasei Co., Ltd.) (13) Ethylene / 1-octene copolymer (1): Substantially linear ethylene / 1-octene copolymer (density: 0.910) obtained by continuous polymerization using a constrained geometry catalyst. g / cm ³ , M
I; 3.5 g / 10 min) (14) Ethylene / 1-octene copolymer (2): Substantially linear ethylene / 1-octene copolymer (density; 0.868 g / cm2) obtained by continuous polymerization using a constrained geometry catalyst. ³ , M
I; 0.5 g / 10 min) (15) Ethylene / 1-octene copolymer (3): Substantially linear ethylene / 1-octene copolymer (density: 0.880 g / cm3) obtained by continuous polymerization using a constrained geometry catalyst. ³ , M
I; 18g / 10min) (16) LDPE (2): Low density polyethylene (Density: 0.91
9g / cm ³ , MI; 2.0g / 10min) (17) Ethylene / 1-octene copolymer (4): Substantially linear ethylene / 1-octene copolymer (density obtained by continuous polymerization using a constrained geometry catalyst) ; 0.935g / cm ³ , M
I; 2.5 g / 10 min) (18) Ethylene / 1-octene copolymer (5): Substantially linear ethylene / 1-octene copolymer (density; 0.868 g / cm) obtained by continuous polymerization using a constrained geometry catalyst. ³ , M
I; 0.2 g / 10 min) (19) Ethylene / 1-octene copolymer (6): Ethylene / 1-octene copolymer (density: 0.885 g / cm2) which is substantially linear and which is obtained by continuous polymerization using a constrained geometry catalyst. ³ , M
I; 30g / 10min)

* Evaluation method (20) Silane impregnating property: The impregnating property when the VTMOS / DCP liquid mixture was heated and stirred with a super mixer was evaluated. ○: Good impregnation, ×: Impregnation is not possible (21) Tape extrusion appearance: 50mmφ extruder 120-150-170-180-170 ℃ L / D: 20 Compression ratio 3.5 Tape die: Width 100mm Lip spacing 1mmt Rating: ○> The order was Δ> ×, and the level of ◯ was passed. (22) Gel fraction (%): 120 ° C, 20 hours, xylene immersion method (23) Tensile strength (MPa) and elongation (%): JIS K 6760
by. (24) Heat distortion rate (%): According to JIS K 6723. (25) Shore D hardness (-): According to ASTM D-2240. (26) Tube extrusion appearance: 50mmφ extruder 120-150-170-180-170 ℃ L / D: 20 Compression ratio 3.5 Tube die: Outer diameter 15mm Inner diameter 1
Evaluation of 2 mm: ○>△> × in this order, and the level of ○ was passed. (27) Odor and taste (-): According to JIS K 6769. (28) Potassium permanganate consumption (mg / l): JIS K
According to 6769. The polyolefin base polymer and the obtained carrier polymers A and B were mixed in the ratios shown in Tables 3 to 7, tapes and tubes were extruded using an extruder, and further subjected to a crosslinking treatment by dipping in hot water. The extruded tape was used to evaluate the gel fraction, tensile strength, elongation, heat deformation rate and Shore D hardness, and this extruded tube was used to evaluate the odor and taste and the elution of potassium permanganate consumption. went.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

[Table 5]

[0026]

[Table 6]

[0027]

[Table 7]

As is apparent from the table, Examples 1, 2,
The materials shown in Nos. 3 and 4 have good extrusion processability and also have very excellent crosslinking properties, mechanical strength, heat resistance, flexibility and hygiene. On the other hand, in all the comparative examples, the extrudability, the crosslinking property, the mechanical property, the heat resistance, the flexibility and the hygienic property are not balanced.

[0029]

According to the present invention, it is possible to obtain a silane-crosslinked polyolefin which is excellent in extrusion processability, crosslinkability, mechanical properties, heat resistance, flexibility and hygiene.

Claims (5)

(57) [Claims] 1. (i) Density of 0.85 to 0.89 g / c
m ³ , the melt index is 0.3 to 20 g / 10 mi
n having substantially 0.01 or more long chain branches per 1000 carbons along the backbone of the polymer, which was polymerized by using 1-octene as a comonomer at the time of polymerization and a single-site catalyst as a catalyst. A base polymer comprising a linear polyethylene / 1-octene copolymer, and (ii) the general formula RR'SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, R is 'Is represented by a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y), and the addition amount is 0.1 to 5% by weight based on the total weight of the polymer. And the decomposition temperature for obtaining a half-life of 1 minute is 170 ° C. or higher and 250 ° C. or lower and the amount of active oxygen is 8
% Or more, the addition amount is 0. 0 based on the total weight of the polymer.
Substantially water-free carrier polymer A containing a free radical generator of from 01 to 0.5% by weight, and (iii) an addition amount of 0.0 based on the total weight of the polymer.
A carrier polymer B containing 1 to 0.2% by weight of a silanol condensation catalyst and an antioxidant is melt-mixed and reacted at a temperature higher than the crystalline melting point of the base polymer, and then contacted with water for crosslinking. A method for producing a silane-crosslinked polyolefin, comprising: 2. The base polymer has a density of 0.86 to
Melt index is 0.5 to 5 at 0.89 g / cm ^3.
A substance having 0.01 or more long chain branches per 1000 carbons along the backbone of the polymer, which was polymerized using 1-octene as a comonomer and a single-site catalyst as a catalyst at the time of polymerization of g / 10 min. The method for producing a silane-crosslinked polyolefin according to claim 1, comprising a polyethylene / 1-octene copolymer that is linear in nature. 3. A carrier polymer A comprising an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl methacrylate copolymer (EMMA), and a polymer block containing at least one vinyl aromatic compound as a main component.
The silane according to claim 1 or 2, which is selected from the group consisting of a hydrogenated block copolymer obtained by hydrogenating a block copolymer composed of a polymer block mainly containing at least one conjugated diene compound, and a mixture thereof. Method for producing crosslinked polyolefin. 4. The carrier polymer B is polyethylene,
The method for producing a silane-crosslinked polyolefin according to claim 1, 2 or 3, which is selected from the group consisting of polypropylene, a copolymer of ethylene and α-olefin, and a mixture thereof. 5. The total amount of carrier polymers A and B is 2
It is -15 wt%, The manufacturing method of the silane bridge | crosslinking polyolefin of Claim 1, 2, 3 or 4.