JPH11172001A - Production of silane-crosslinked polyolefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silane-crosslinked polyolefin in one step by melt-blending a base polymer comprising a substantially linear polyethylene/1-octene copolymer, a carrier polymer containing an unsaturated organosilane or the like in a high concentration, and a carrier polymer containing a silanol condensation catalyst, etc., and bringing the blend into contact with water. SOLUTION: The following components A to C are melt-blended at a temperature higher than the crystalline melting point of component A, and the blend is brought into contact with water: (A) a base polymer comprising a substantially linear polyehylene/1-octene copolymer having a density of 0.85-0.92 g/cm and a melt index of 0.3-20 g/10 min, (B) a carrier polymer A containing 0.1-5 wt.% unsaturated organosilane of the formula: RR'SiY2 (wherein Y is a hydrolyzable organic group) and 0.01-0.5 wt.% free radical generator and substantially freed from water, and (C) a carrier polymer B containing 0.01-0.2 wt.% silanol condensation catalyst and an antioxidant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a simple method of crosslinking a polyolefin, a polysilane is graft-reacted with an organic unsaturated silane in the presence of a free radical generator, followed by silane grafting. A so-called silane cross-linking method of cross-linking by contacting with moisture in the presence of is generally known. For example, Tokiko 48
-1711, JP-A-57-49109 and the like. However, this method involves at least two steps. That is, a silane grafting reaction step and a silanol condensation reaction step. Therefore, at least two extrusion steps are required, and an economic problem as an end product cannot be avoided.

As a one-step process, there is a mono-seal method. However, this method requires a liquid addition device for injecting the organic unsaturated silane in a liquid state into the extruder, but has problems of slippage and poor measurement. Extruders also require expensive and special types with large L / D to uniformly disperse small amounts of additives.
Economic problems are inevitable. In addition, very high technology is required for extrusion. Further, as a one-step process, a silane crosslinking 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 additives such as a silanol condensation catalyst and an antioxidant are introduced into the solid carrier polymer in addition to the silane and the free radical generator. For this reason, there has been a problem that crosslinking efficiency and storage stability are inferior due to oligomerization by silane condensation or crosslinking inhibition by radical scavenging.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve these problems. In the silane cross-linking of polyolefin, a carrier polymer A containing a high concentration of an organic unsaturated silane and the like, a silanol condensation catalyst and the like are contained. An object of the present invention is to provide a silane crosslinking method for producing a silane-crosslinked polyolefin in one step by using a carrier polymer B.

[0005]

According to the present invention, (i) a density of 0.85 to 0.92 g / cm ³ , a melt index of 0.3 to 20 g / 10 min, and 1-octene is used as a comonomer during polymerization. And long chain branches along the backbone of the polymer, polymerized using a single site catalyst as a catalyst, at 0.0 / 1000 carbons.
A substantially linear polyethylene / 1- having one or more
A base polymer consisting of an octene copolymer, and (ii) a 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. A monovalent hydrocarbon group or the same as Y), the amount of the organic unsaturated silane added is 0.1 to 5% by weight based on the total weight of the polymer, and the amount added is the total weight of the polymer. Substantially water-free carrier polymer A containing from 0.01 to 0.5% by weight of a free radical generator, based on the total weight of the polymer, and (iii) the amount added is based on the total weight of the polymer. 01-0.2% by weight
A silane-crosslinked polyolefin, characterized by melt-mixing and reacting a carrier polymer B containing a silanol condensation catalyst and an antioxidant at a temperature higher than the crystal melting point of the base polymer, and then contacting with water to effect crosslinking. Preferably, 1-octene is used as a comonomer at the time of polymerization with a density of 0.86 to 0.89 g / cm ³ and a melt index of 0.5 to 5 g / 10 min, and a single-site catalyst is used as a catalyst. A base polymer comprising a substantially linear polyethylene / 1-octene copolymer having at least 0.01 long chain branches per 1000 carbons along the backbone of the polymer as polymerized. A is ethylene-ethyl acrylate copolymer (EEA), Hydrogenation of a block copolymer consisting of at least one polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound. A polymer selected from the group consisting of hydrogenated block copolymers and mixtures thereof, wherein the carrier polymer B is selected from the group consisting of polyethylene, polypropylene, copolymers of ethylene and α-olefins, and mixtures thereof. And a total amount of the carrier polymers A and B is 2 to 15% by weight.

DETAILED DESCRIPTION OF THE INVENTION The substantially linear polyethylene / 1-octene copolymer of the base polymer of the present invention is defined as a copolymer which uses 1-octene as a comonomer at the time of polymerization and has a suitable restriction among single-site catalysts. Geometric catalyst (con
strained geometry catalyst
s). US Patent 5,026,798
The olefin polymerization catalysts of the monocyclopentadienyl transition metal taught in US Pat. No. 5,077,077 are also suitable for use in the preparation of the substantially linear polyethylene / 1-octene copolymer of the base polymer of the present invention. Suitable co-catalysts for use in preparing the substantially linear polyethylene / 1-octene copolymer of the base polymer of the present invention include, but are not limited to, polymeric or oligomeric aluminoxanes, especially Includes methylaluminoxane, as well as inert, compatible, non-coordinating, ion-generating compounds. Suitable cocatalysts are non-coordinating inert boron compounds. Polymerization conditions suitable for producing a substantially linear polyethylene / 1-octene copolymer of the base polymer of the present invention are generally, but are not limited to, those conditions that are effective in a solution polymerization process. Slurry and gas phase polymerization methods are also effective, subject to the use of appropriate catalysts and polymerization conditions.

In the preparation of the substantially linear polyethylene / 1-octene copolymer of the base polymer of the present invention, a multiple reactor polymerization process, such as US Pat.
No. 342 can also be used. The reactors can be operated in series or in parallel using 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, and A substantially linear polyethylene of the base polymer of
The reason that the 1-octene copolymer has 0.01 or more long chain branches per 1000 carbons along the backbone of the polymer is to ensure a given level of melt viscosity and thereby substantially reduce the base polymer of the present invention. This is for giving good moldability to the polyethylene / 1-octene copolymer which is linear. In contrast, the term “linear” polyethylene / C ₃ -C ₂₀ α-olefin copolymer means that the olefin copolymer does not contain long-chain branches.

In an embodiment of the present invention, it is of course conceivable to blend another ethylene polymer with 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 with a multi-site catalyst, linear low-density polyethylene (LLDPE), High density polyethylene (HD
One or two or more of a homopolymer type such as PE) or various ethylene copolymers obtained by copolymerizing a monomer such as propylene, vinyl acetate and ethyl acrylate with ethylene, which accounts for the majority, are used. Density polyethylene / 1-octene copolymer is a substantially linear base polymer 0.85~0.92g / cm ^3, preferably 0.86~0.89g / cm ^3. 0.8
If the amount is less than 5 g / cm ³ , it is difficult to produce industrially. 0.
If it exceeds 92 g / cm3, the desired flexibility cannot be obtained.
Substantially linear polyethylene / 1 base polymer
The melt index of the octene copolymer is from 0.3 to
20 g / 10 min, preferably 0.5 to 5 g / 10 m
in. If it is less than 0.3 g / 10 min, the extrudability deteriorates, and if it exceeds 20 g / 10 min, the degree of crosslinking is reduced.

[0009] The organic unsaturated silane of the present invention is grafted to the base resin so as to be a cross-linking point between the base resins. The organic unsaturated silane used in the present invention is represented by 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 hydrocarbon group. Monovalent hydrocarbon groups other than hydrogen or
The same compound as used for Y) is used. It is desirable to use an organic unsaturated silane represented by the general formula RSiY _{3 in} which R ′ is the same as Y, for example, vinyltrimethoxysilane,
Vinyl triethoxy silane, vinyl tributoxy silane, allyl trimethoxy silane, allyl triethoxy silane and the like can be mentioned. The amount of these additives is 0.1 to 5% by weight, preferably 0.4 to 3% by weight, based on the total weight of the polymer. If the amount is less than 0.1% by weight, sufficient grafting does not occur, and if the amount exceeds 5% by weight, molding failure occurs and it becomes uneconomical.

[0010] 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 includes various organic peroxides and peresters having a strong polymerization initiating action, such as dicumyl peroxide, α, α'-bis (t-butylperoxydiisopropyl) benzene, Di-t-butyl peroxide, t-butyl cumyl peroxide, di-benzoyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylperoxypivalate, t -Butylperoxy-2-ethylhexanoate and the like. The amount of these additives 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.
When the amount is less than 01% by weight, a sufficient silane grafting reaction does not proceed. When the amount is more than 0.5% by weight, the extrudability deteriorates and the molding surface deteriorates.

The carrier polymer A of the present invention can be added by swelling a liquid mixture in which a free radical generator is dissolved in a silane with the liquid mixture of the silane. At this time, in order to add silane at a high concentration, preheating of the carrier polymer A is necessary, but the temperature must be lower than the crystal melting point so that the polymer does not melt. Also, the carrier polymer A must be in solid form and be solid and compatible with the crosslinkable base polymer and silane. Compatible means 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 water absorption be relatively slow to minimize the potential for 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 comprises granules,
Alternatively, granules are usually in the form of pellets, the preferred form being pellets.

The carrier polymer A used in the present invention is mainly composed of, for example, ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), and at least one vinyl aromatic compound. A hydrogenated block copolymer obtained by hydrogenating a block copolymer composed of a polymer block and a polymer block mainly composed of at least one conjugated diene compound, for example, a hydrogenated styrene-isoprene block copolymer ( SEPS), hydrogenated styrene-butadiene block copolymer (SEBS), and the like, and mixtures 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. Also, the carrier polymer B must be in particulate form and a solid compatible with the base polymer to be crosslinked. 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. Examples of the carrier polymer B used in the present invention include polyethylene, polypropylene, a copolymer of ethylene and an α-olefin, and examples of the α-olefin include C3 to C12.
For example, 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, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, lead naphthenate, zinc caprylate, cobalt naphthenate, tetrabutyl titanate, and stearic acid. Organic metal compounds such as lead, zinc stearate, cadmium stearate, barium stearate, calcium stearate and the like can be mentioned. These additives may be added in an amount of 0.01 to 0.2% by weight, preferably 0.02 to 0.1% by weight, based on the total weight of the polymer.
% By weight. If the amount is less than 0.01% by weight, a sufficient crosslinking reaction does not proceed. If the amount exceeds 0.2% by weight, crosslinking occurs locally in the extruder at the time of extrusion, and the appearance is significantly deteriorated. Also, a silanol condensation catalyst must be added to the carrier polymer B. This is because the addition to the carrier polymer A promotes oligomerization by condensation of silane and causes deterioration in appearance.

The antioxidant of the present invention is generally used when processing a polyolefin and is not particularly limited, but must be added to the carrier polymer B. This is because the addition to the carrier polymer A inhibits crosslinking by scavenging radicals. Even when other additives are added, additives that may inhibit crosslinking must be added to the carrier polymer B.

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

As other additives, if desired, commonly used additives such as a neutralizer, an ultraviolet absorber, an antistatic agent, a pigment, a dispersant, a thickener, a metal deterioration inhibitor, a fungicide, A flow regulator, other inorganic fillers, or the like, or other synthetic resins can also be contained.

[0018]

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

* 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) DCP:
Dicumyl peroxide (6) LDPE (1): low density polyethylene (density; 0.925
g / cm ³ , MI; 1.5 g / 10 min) (7) PP: polypropylene (homopolymer, MI (230 ゜)
(8) DBTDL: dibutyltin dilaurate (9) Antioxidant: phenolic antioxidant / Irganox 1010 (manufactured by Ciba Geigy) (10) Lubricant: low molecular weight polyethylene / sun wax 171
P (manufactured by Sanyo Chemical Industries, Ltd.) (11) Ethylene / 1-octene copolymer (1): A substantially linear ethylene / 1-octene copolymer obtained by continuous polymerization using a constrained geometry catalyst (density: 0.910 g / cm ³ , M
I; 3.5 g / 10 min) (12) Ethylene / 1-octene copolymer (2): a substantially linear ethylene / 1-octene copolymer obtained by continuous polymerization using a constrained geometric catalyst (density: 0.868 g / cm) ³ , M
I; 0.5 g / 10 min) (13) Ethylene / 1-octene copolymer (3): A substantially linear ethylene / 1-octene copolymer obtained by continuous polymerization using a constrained geometric catalyst (density: 0.880 g / cm) ³ , M
I; 18 g / 10 min) (14) LDPE (2): low density polyethylene (density: 0.91
(9 g / cm ³ , MI; 2.0 g / 10 min) (15) Ethylene / 1-octene copolymer (4): A substantially linear ethylene / 1-octene copolymer obtained by continuous polymerization using a constrained geometry catalyst (density) ; 0.935 g / cm ³ , M
I; 2.5 g / 10 min) (16) Ethylene / 1-octene copolymer (5): A substantially linear ethylene / 1-octene copolymer obtained by continuous polymerization using a constrained geometric catalyst (density: 0.868 g / cm) ³ , M
I; 0.2 g / 10 min) (17) Ethylene / 1-octene copolymer (6): A substantially linear ethylene / 1-octene copolymer obtained by continuous polymerization using a constrained geometric catalyst (density: 0.885 g / cm) ³ , M
I; 30g / 10min)

* Evaluation method (18) Silane impregnation: The impregnation when the VTMOS / DCP liquid mixture was heated and stirred with a super mixer was evaluated. ○: good impregnation, ×: impregnable (19) Tape extrusion appearance: 50mmφ extruder 120-150-170-180-170 ℃ L / D: 20 Compression ratio 3.5 Tape die: width 100mm Rip interval 1mmt Evaluation: ○> The order of △> × was set, and the level of ○ was judged as acceptable. (20) Gel fraction (%): 120 ° C., 20 hours, xylene immersion method (21) Tensile strength (MPa) and elongation (%): JIS K 6760
by. (22) Heat deformation ratio (%): According to JIS K 6723. (23) Shore D hardness (-): According to ASTM D-2240. The polyolefin-based base polymer and the obtained carrier polymers A and B were mixed at a ratio shown in Tables 3 to 5, a tape was extruded using an extruder, and further subjected to a crosslinking treatment by immersion in warm water. Using this extruded tape, the gel fraction, tensile strength, elongation, heat deformation rate and Shore D hardness were evaluated.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

[Table 5]

As is clear from the table, Examples 1, 2 and
The materials shown in Nos. 3 and 4 have good extrusion processability and show very excellent crosslinking properties, mechanical properties, heat resistance and flexibility. On the other hand, in all of the comparative examples, the balance between the extrudability, the crosslinking properties, the mechanical properties, the heat resistance and the flexibility is not achieved.

[0027]

According to the present invention, it is possible to obtain a silane-crosslinked polyolefin having excellent extrudability and excellent crosslinking properties, mechanical properties, heat resistance and flexibility.

Claims (5)

[Claims] (I) a density of 0.85 to 0.92 g / c;
m ³ , melt index 0.3 to 20 g / 10 mi
n, substantially 0.01 or more long chain branches per 1000 carbons along the polymer backbone, as polymerized using 1-octene as a comonomer and a single-site catalyst as a catalyst during polymerization. A base polymer comprising a linear polyethylene / 1-octene copolymer, and (ii) a general formula RR′SiY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, R Is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y), and the amount of addition is 0.1 to 5% by weight based on the total weight of the polymer. And a substantially water-free carrier polymer A containing a free radical generator in an amount of 0.01 to 0.5% by weight, based on the total weight of the polymer, and (iii) the addition. Is melt-mixed with 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 at a temperature higher than the crystal melting point of the base polymer. And then contacting with water to crosslink the silane-crosslinked polyolefin. 2. The base polymer having a density of 0.86 to 0.86.
0.89 g / cm ³ with a melt index of 0.5 to 5
g / min with 1-octene as a comonomer and a single-site catalyst as a catalyst, the polymer having 0.01 or more long chain branches per 1000 carbon atoms along the backbone of the polymer. The method for producing a silane-crosslinked polyolefin according to claim 1, comprising a polyethylene / 1-octene copolymer which is linear in nature. 3. A polymer block mainly composed of an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl methacrylate copolymer (EMMA), and at least one vinyl aromatic compound.
3. The silane according to claim 1, wherein the silane is selected from the group consisting of a hydrogenated block copolymer obtained by hydrogenating a block copolymer consisting of a polymer block mainly composed of at least one conjugated diene compound and a mixture thereof. A method for producing a crosslinked polyolefin. 4. The carrier polymer B is polyethylene,
4. The method for producing a silane-crosslinked polyolefin according to claim 1, wherein the method is selected from the group consisting of polypropylene, a copolymer of ethylene and an α-olefin, and a mixture thereof. 5. The total amount of the carrier polymers A and B is 2
The method for producing a silane-crosslinked polyolefin according to claim 1, 2, 3 or 4, wherein the amount is from 15 to 15% by weight.