JPH09104717A - Production of silane-cross-linked polyolefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a silane-cross-liked polyolefin having high extrusibility by melt-reacting, a base polymer containing specified PEs with a carrier polymer A comprising a specified copolymer containing an organic unsaturated silane and a carrier polymer B containing a condensation catalyst. SOLUTION: An ethylene/ethyl acrylate or ethylene/methyl acrylate copolymer having a monomer content of 18-41wt.% is mixed with about 0.1-5wt.% organic unsaturated silane (e.g. vinyltrimethoxysilane) and a free radical generator to obtain a carrier polymer A. PE or the like is mixed with a silanol condensation catalyst and an antioxidant to obtain a carrier polymer B. A base polymer comprising 10-100wt.% medium to low density PE having a density of 0.910-0.945g/cm<3> and a melt index(MI) of 1-5g/10min and 90-0wt.% low-density PE having a density of 0.915-0.935g/cm<3> and an MI of 0.5-4g/10min and the carrier polymers A and B in amounts to give a total of 3-15wt.% based on the base polymer are melt-kneaded, and the obtained mixture is cross/linked with water to obtain a silane-cross-linked polyolfin.

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 for crosslinking a polyolefin, a graft reaction of an organic unsaturated silane is carried out on the polyolefin 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, Shoko Sho 4
No. 8-1711, Japanese Patent Laid-Open No. 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. 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. 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.

[0003]

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.

[0004]

The present invention provides (i) a linear medium-low density polyethylene (L-LDPE) having a density of 0.910 to 0.945 g / cm ³ and a melt index of 1 to 5 g / 10 min. 10 to 100% by weight and a density of 0.
Low density polyethylene (LD of 915 to 0.935 g / cm ³ and melt index of 0.5 to ⁴ g / 10 min)
PE) or ethylene-unsaturated ester copolymer 90-0
A base polymer consisting of wt%, and (ii) the general formula RR'S
iY ₂ (R is a monovalent olefinically unsaturated hydrocarbon group, Y is a hydrolyzable organic group, and R ′ is a monovalent hydrocarbon group other than an aliphatic unsaturated hydrocarbon or the same as Y) Substantially free of water containing an organic unsaturated silane and a free radical generator having a monomer content of 18 to 41
Wt% ethylene-ethyl acrylate copolymer (EE
A), ethylene-methyl methacrylate copolymerization (EMM
A) or a carrier polymer A composed of a mixture thereof and (iii) a carrier polymer B containing a silanol condensation catalyst and an antioxidant are melt-mixed and reacted at a temperature higher than the crystal melting point of the base polymer, and then reacted with water. A method for producing a silane-crosslinked polyolefin, which comprises contacting with and crosslinking, preferably,
Linear medium-low density polyethylene (L-LDPE) having a density of 0.910 to 0.945 g / cm ³ and a melt index of 1 to 5 g / 10 min, 25 to 65% by weight, and a density of 0.915 to 0.935 g. Is a base polymer composed of a mixture of 75 to 35% by weight of low density polyethylene (LDPE) having a melt index of 0.5 to ⁴ g / 10 min at 1 / cm ³ , and the carrier polymer A is ethylene having a monomer content of 18 to 41% by weight. -Ethyl acrylate copolymer (EEA), the carrier polymer B is a polymer selected from the group consisting of polyethylene, polypropylene, copolymers of ethylene and α-olefins and mixtures thereof, Method for producing silane-crosslinked polyolefin, characterized in that the total amount is 3 to 15% by weight It is.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The linear low-medium-density polyethylene of the base polymer of the present invention refers to a gas phase method, a solution method, a suspension polymerization method, or the like in a medium-low pressure or high pressure using various catalysts such as a Ziegler catalyst and a chromium catalyst. Is a copolymer with an α-olefin containing ethylene as a main component by various polymerization methods having a density of 0.910
0.945 g / cm ³ with melt index of 1 to ⁵ g
/ 10 min. Examples of the α-olefin include C _{3 to} C ₁₂ such as 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 and the like. Low density polyethylene is a homopolymer of low density polyethylene produced by high pressure radical polymerization by a tubular method or an autoclave method, and has a density of 0.915 to 0.935 g / cm ³ and a melt index of 0.5. ~ 4 g / 10 min. Further, as the ethylene-unsaturated ester copolymer,
Ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA),
Mention may be made of ethylene-vinyl acetate copolymer (EVA) and mixtures thereof. The amount of linear medium-low density polyethylene added to the base polymer is 10% by weight or more, preferably 25 to 65% by weight. If it is less than 10% by weight, heat resistance and other deterioration of heat resistance are caused. The linear polymer medium-low density polyethylene has a melt index of 1 to 5 g / 10 min, preferably 2 to
It is 4 g / 10 min, and is low for low density polyethylene.
5-4g / 10min, preferably 1-3g / 10mi
n. Exceeding the lower limit in each of the compositions results in poor extrudability, while exceeding the upper limit causes a decrease in the degree of crosslinking. The density of the base polymer is 0.910 to 0.945 g / cm ³ for the linear medium-low density polyethylene,
0.915 to 0.935 g / c for low density polyethylene
Although m ³ is less than the lower limit in each case, heat resistance such as heat deformation is deteriorated. Further, if the linear medium-low density polyethylene exceeds 0.945 g / cm ³ , the extrudability becomes poor, and if the low density polyethylene produced by high pressure radical polymerization exceeds 0.935 g / cm ³ , it is industrially produced. It's hard to do.

The organic unsaturated silane of the present invention is grafted onto 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 a 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. A compound represented by a monovalent hydrocarbon group other than hydrogen or the same 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 RSiY _3. For example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, allyltriethoxy. Examples include silane. The addition amount of these is 0.1 to 5% by weight, preferably 0.7 to 3% by weight, based on the total weight of the polymer. 0.1% by weight
If less than 5% by weight, sufficient grafting does not occur, and if more than 5% by weight, molding failure occurs and it is not economical.
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-ethylhexano Ato etc. can be mentioned. The amount of these added is 0.01 to 0.5% by weight, preferably 0.05 to 0.2% by weight, based on the total weight of the polymer. If the amount is less than 0.01% by weight, the silane grafting reaction does not proceed sufficiently, and the silane grafting reaction is less than 0.
If it exceeds 5% by weight, extrusion processability is deteriorated and the molding surface is deteriorated.

The free radical generator and the silane can be incorporated into the carrier polymer A by swelling the carrier polymer A of the present invention with a liquid mixture in which the free radical generator is dissolved in 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. Compatibility means
It means that the carrier polymer A must not react readily 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 is usually in the form of granules or granules in the form of pellets, the preferred form being pellets.
As the carrier polymer A used in the present invention, mention may be made of an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl methacrylate copolymer (EMMA) having a monomer content of 18 to 41% by weight, or a mixture thereof. You can 18% by weight monomer content
If it is less than 40% by weight, the desired amount of impregnated silane cannot be obtained, and if it exceeds 41% by weight, blocking occurs at the time of impregnation with silane, resulting in poor workability. Considering workability, economy, etc., EEA alone is most preferable.

The silanol condensation catalyst, antioxidant and the like can be added to the carrier polymer B by kneading and granulating with the carrier polymer B of the present invention. 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 C _{3 to} C ₁₂ such as propylene and 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., or a mixture thereof can be mentioned. The silanol condensation catalyst of the present invention,
Dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, lead naphthenate,
Zinc caprylate, cobalt naphthenate, tetrabutyl titanate, lead stearate, zinc stearate,
Organometallic compounds such as cadmium stearate, barium stearate, calcium stearate and the like can be mentioned.
The amount added of these is 0.01 to 0.2% by weight, preferably 0.02 to 0.2% by weight, based on the total weight of the polymer.
1% 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 usually used in processing a polyolefin and is not particularly limited, but it must be incorporated into 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 amount of carrier polymer added is such that the total amount of carrier polymers A and B is in the range of 3 to 15% by weight. If the amount is less than 3% by weight, sufficient grafting does not occur. If the amount is more than 15% by weight, molding failure occurs and it becomes uneconomical. If desired, other additives commonly used, for example, a neutralizer, an ultraviolet absorber, an antistatic agent, a pigment, a dispersant, a thickener, a metal deterioration inhibitor, an antifungal agent, and a flow control agent. , Other inorganic fillers, or other synthetic resins may be contained.

[0010]

EXAMPLES Examples will be described below. << 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 (1): ethylene-ethyl acrylate copolymer (EA content; 23% by weight) (2) EEA (2): ethylene-ethyl acrylate copolymer (EA content; 10 (% By weight) (3) EEA (3): ethylene-ethyl acrylate copolymer (EA content; 50% by weight) (4) L-LDPE (1): linear low density polyethylene (density: 0.924 g / cm ³ , MI; 3.0g / 10min) (5) VTMOS: vinyltrimethoxysilane (6) DCP: dicumyl peroxide (7) LDPE (1): low density polyethylene (density: 0.925
g / cm ³ , MI; 1.5g / 10min) (8) PP: polypropylene (homopolymer, MI (230 °
C); 2.0g / 10min) (9) DBTDL: dibutyltin dilaurate (10) Antioxidant: phenolic antioxidant / Irganox 1010 (manufactured by Ciba Geigy) (11) Lubricant: low molecular weight polyethylene / sun wax 171
P (manufactured by Sanyo Kasei Co., Ltd.) (12) L-LDPE (2): Linear medium-low density polyethylene (density: 0.930 g / cm ³ , MI; 0.3 g / 10 min) (13) L-LDPE (3): Linear medium-low density polyethylene (density: 0.928 g / cm ³ , MI; 10 g / 10 min) (14) L-LDPE (4): Linear medium-low density polyethylene (density: 0.900 g / cm ³ , MI; 3g / 10min) (15) L-LDPE (5): Linear medium low density polyethylene (density: 0.950g / cm ³ , MI; 2.7g / 10min) (16) LDPE (2): Low density polyethylene (density ; 0.92
5g / cm ³ , MI; 0.3g / 10min) (17) LDPE (3): Low density polyethylene (Density: 0.92
7g / cm ³ , MI; 7g / 10min) (18) LDPE (4): Low density polyethylene (Density: 0.90
5g / cm ³ , MI; 2.5g / 10min)

* Evaluation method (19) 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 (20) 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. (21) Gel fraction (%): 120 ° C, 20 hours, xylene immersion method (22) Tensile strength (MPa) and elongation (%): JIS K 6760
by. (23) Heat distortion rate (%): According to JIS K 6723.

The polyolefin base polymer and the obtained carrier polymers A and B were mixed in the ratios shown in Tables 3 to 5, the tape was extruded using an extruder, and further subjected to a crosslinking treatment by dipping in hot water. Using this extruded tape, the gel fraction, tensile strength, elongation, and heat deformation were evaluated.

Table 1 Combination drug A1 A2 A3 A4 A5 A6 A7 A8 EEA (1) 100 100 100 100 100 EEA (2) 100 EEA (3) 100 L-LDPE (1) 100 VTMOS 45 45 45 40 100 2 45 45 DCP 2.16 2.16 2.16 1.92 4.8 0.5 0.2 20 Evaluation item Silane impregnating property ○ × ○ × × ○ ○ ○ Blocking property ○ ○ × ○ ○ ○ ○ ○

Table 2 Combination drug B1 B2 B3 B4 LDPE (1) 100 100 100 PP 100 DBTDL 5 5 0.5 25 Antioxidant 16 16 16 16 Lubricant 5 5 5 5

Table 3 Example Comparative Example 1 2 3 1 2 3 4 <Compounding agent> LDPE (1) 70 50 60 55 50 L-LDPE (1) 23.5 43.5 93.5 33.5 38.5 43.5 93.5 A1 4.5 4.5 4.5 4.5 A6 4.5 A7 4.5 A8 4.5 B1 2 2 2 2 B2 2 2 B3 2 <Evaluation items> Tape extrusion ○ ○ ○ × ○ × ○ Appearance Gel fraction (%) 75 74 76 5 10 80 25 Tensile strength 19 21 23 − 18 − 18 (MPa) Elongation (%) 450 500 470 − 490 − 460 Heat distortion rate 12 8 7 − × − × Overall evaluation ○ ○ ○ × × × × (Note) -mark indicates that measurement is not possible.

Table 4 Comparative Example 5 6 7 8 9 10 11 <Compounding agent> LDPE (1) 60 45 L-LDPE (1) 93.5 37.5 36.5 L-LDPE (2) 93.5 L-LDPE (3) 93.5 L-LDPE (4) 93.5 L-LDPE (5) 93.5 A1 4.5 1 17 4.5 4.5 4.5 4.5 B1 2 2 2 B2 2 2 2 B4 2 <Evaluation items> Tape extrusion × ○ × × ○ ○ × Appearance Gel fraction (%) 78 20 82 75 50 70 73 Tensile strength (MPa) − 18 − − 12 14 − Elongation (%) − 460 − − 480 470 − Heating deformation rate − × − − 35 30 − Overall evaluation × × × × × × × (Note) -mark indicates that measurement is not possible.

[0018] (Note) -mark indicates that measurement is not possible.

As is clear from the table, Examples 1, 2, 3
The material shown in (3) has good extrusion processability and exhibits very excellent crosslinking properties, mechanical properties, and heat resistance. In contrast, all of the comparative examples do not have a balance between extrudability, cross-linking properties, mechanical properties, and heat resistance.

[0020]

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

Claims (5)

[Claims] (1) a density of 0.910 to 0.945 g /
Linear medium to low density polyethylene (L-LDPE) 10 to 1 with a melt index of 1 to 5 g / 10 min in cm ^3.
00% by weight and a density of 0.915 to 0.935 g / cm
³ , a low density polyethylene (LDPE) having a melt index of 0.5 to 4 g / 10 min or a base polymer consisting of 90 to 0% by weight of an ethylene-unsaturated ester 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), which is substantially free of water containing an organic unsaturated silane and a free radical generator.
Carrier polymer A consisting of ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA) or a mixture thereof having a monomer content of 18 to 41% by weight, and (iii) silanol condensation catalyst and antioxidant. Carrier polymer B containing
A method for producing a silane-crosslinked polyolefin, which comprises melt-mixing and reacting with each other at a temperature higher than the crystal melting point of the base polymer, and then contacting with water to crosslink. 2. The base polymer has a density of 0.910.
0.945 g / cm ³ with melt index of 1 to ⁵ g
/ 10 min linear medium-low density polyethylene (L-LD
PE) 25-65% by weight and density 0.915-0.9
The melt index at 35 g / cm ³ is 0.5-4 g /
Low density polyethylene (LDPE) 75-3 for 10 min
The method for producing a silane-crosslinked polyolefin according to claim 1, which comprises a mixture with 5% by weight. 3. The method for producing a silane-crosslinked polyolefin according to claim 1, wherein the carrier polymer A is an ethylene-ethyl acrylate copolymer (EEA) having a monomer content of 18 to 41% by weight. 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 3
It is -15 wt%, The manufacturing method of the silane bridge | crosslinking polyolefin of Claim 1, 2, 3 or 4.