JPH0995591A - Preparation of silane-crosslinked polyolefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a silane-crosslinked polyolefin excellent in crosslinking properties, mechanical properties and heat resistance by reacting a specific polyethylene(s) either alone or in combination with a specific ethylene copolymer with a specific org. unsatd. silane, a silanol condensation catalyst, etc., at a specific temp. SOLUTION: (I) 10-100 pts.wt. linear medium- or low-density polyethylene having a density of 0.910 to 0.945/cm<3> and a melt index of 1 to 5g/10min, and 90-0 pts.wt. low-density polyethylene or ehtylene/unsatd. ester copolymer having a density of 0.915 to 0.935/cm<3> and a melt index of 0.5 to 4g/min are melt-mixed with (II) an org. unsatd. silane of the formula: RR'SiY2 (wherein R is a univalent olefinically unsatd. hydrocarbon group; Y is a hydrolyzable org. group; and R' is a univalent hydrocarbon group other than aliph. unsatd. hydrocarbon groups, or Y) and a free radical-forming agent, and (III) a silanol condensation catalyst and an antioxidizing agent at a temp. higher than the m.p. of the polymer (I) to effect a reaction. The reaction mixture is then brought into contact with water to effect crosslinking thereof.

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, Japanese Patent Publication 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) A substantially water-free carrier polymer A containing an organic unsaturated silane and a free radical generator, and
(iii) Silane cross-linking, characterized in that the carrier polymer B containing 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 to cross-link. A method for producing a polyolefin, preferably 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 and 25 to 65% by weight. , Density 0.9
Low density polyethylene (LD of 15 to 0.935 g / cm ³ and melt index of 0.5 to ⁴ g / 10 min)
PE) is a base polymer composed of a mixture of 75 to 35% by weight, and the carrier polymer A is ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), at least one vinyl aromatic. A group consisting of a hydrogenated block copolymer obtained by hydrogenating a block copolymer composed of a polymer block containing a compound as a main component and a polymer block containing at least one conjugated diene compound as a main component, and a mixture thereof. 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, and the total amount of the carrier polymers A and B is 3 or more. A method for producing a silane-crosslinked polyolefin having a content of ˜15% by weight.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The linear medium-low-density polyethylene of the base polymer of the present invention is a gas phase method, a solution method, a suspension polymerization method or the like under various conditions such as Ziegler-based catalysts and chromium-based catalysts under medium or low pressure or high pressure. Is a copolymer with ethylene-based α-olefin by various polymerization methods, and has a density of 0.910 to
0.945 g / cm ³ with melt index of 1 to ⁵ g
/ 10 min. Examples of the α-olefin include C3 to C12, 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.

As the ethylene-unsaturated ester copolymer, ethylene-ethyl acrylate copolymer (EE
A), ethylene-methyl methacrylate copolymer (EM
MA), ethylene-vinyl acetate copolymer (EV
A) and mixtures thereof. The amount of linear low-density polyethylene in the base polymer is 1
It is 0% by weight or more, preferably 25 to 65% by weight. 1
When it is less than 0% by weight, heat resistance such as heat deformation is deteriorated. The melt index of the base polymer is 1 to 5 g / 10 min, preferably 2 to 4 g / 10 min for linear medium low density polyethylene, and 0.5 to 4 g / 10 min, preferably 1 to 3 g for low density polyethylene.
/ 10 min. 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 linear medium-low density polyethylene.
Which is 0.915 to 0.93 for low density polyethylene.
Although it is 5 g / cm ^{3, if} it is less than the lower limit in each case, heat resistance such as heat deformation is lowered. 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 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 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-ethylhexanoate and the like. 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. 0.0
If the amount is less than 1% by weight, a sufficient silane grafting reaction does not proceed. If the amount exceeds 0.5% by weight, the extrudability decreases and the molding surface deteriorates.

The free radical generator and the organic unsaturated silane can be incorporated into the carrier polymer A by swelling the carrier polymer A of the present invention with a liquid mixture of the free radical generator dissolved in the organic unsaturated 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 is usually in the form of granules or granules 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. And a hydrogenated block copolymer 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-butadiene block copolymer (SEBS) and the like, and mixtures thereof can be mentioned.

The silanol condensation catalyst, antioxidant and the like can be added to the carrier polymer B by kneading and granulating 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 C3 to C12 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, 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. Organometallic 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 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 it is less than 3% by weight, sufficient grafting does not occur,
On the other hand, if it exceeds 15% by weight, molding defects will occur and it will be 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.

[0012]

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: 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; 3.0g / 10min) (4) VTMOS: vinyltrimethoxysilane (5) DCP: dicumyl peroxide (6) LDPE (1): low density polyethylene (density: 0.925
g / cm ³ , MI; 1.5g / 10min) (7) PP: polypropylene (homopolymer, MI (230 °
C); 2.0g / 10min) (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 Co., Ltd.) (11) L-LDPE (2): Linear medium low density polyethylene (density: 0.930 g / cm ³ , MI; 0.3 g / 10 min) (12) L-LDPE (3): Linear medium-low density polyethylene (density: 0.928 g / cm ³ , MI; 10 g / 10 min) (13) L-LDPE (4): Linear medium-low density polyethylene (density: 0.900 g / cm ³ , MI; 3g / 10min) (14) L-LDPE (5): Linear medium low density polyethylene (density: 0.950g / cm ³ , MI; 2.7g / 10min) (15) LDPE (2): Low density polyethylene (density ; 0.92
5g / cm ³ , MI; 0.3g / 10min) (16) LDPE (3): Low density polyethylene (Density: 0.92
7g / cm ³ , MI; 7g / 10min) (17) LDPE (4): Low density polyethylene (Density: 0.90
5g / cm ³ , MI; 2.5g / 10min)

* Evaluation method (18) 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. (19) Tape extrusion appearance: 50 mmφ extruder 120-150-170-18
0-170 ℃ L / D: 20 Compression ratio 3.5 Tape die: Width 100mm Lip gap 1mmt Evaluation: ○>△> × in order, and the level of ○ was passed. (20) Gel fraction (%): 120 ° C, 20 hours, xylene immersion method (21) Tensile strength (MPa) and elongation (%): JIS K 6760
by. (22) 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 immersing in tape. 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 EEA 95 100 95 95 95 95 SEPS 5 5 5 5 5 L-LDPE (1) 100 VTMOS 45 40 40 100 2 45 45 DCP 2.16 1.92 1.92 4.8 0.5 0.2 20 Silane impregnation ○ ○ × × ○ ○ ○

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 Compounding agent 1 2 3 1 2 3 4 LDPE (1) 70 50 60 55 50 L-LDPE (1) 23.5 93 42.5 33.5 38.5 43.5 93.5 A1 5 5 A2 5.5 5.5 A5 5 A6 5 A7 5 B1 1.5 2 1.5 1.5 B2 1.5 1.5 B3 1.5 Evaluation item Tape extrusion ○ ○ ○ × ○ × ○ Appearance Gel fraction (%) 75 74 76 5 10 80 25 Tensile strength (MPa) 19 21 23 − 18 − 18 Elongation (%) 450 500 470 − 490 − 460 Heat deformation rate 12 8 7 − − − − Overall evaluation ○ ○ ○ × × × × (Note) -mark indicates that measurement is not possible.

Table 4 Comparative example Compounding agent 5 6 7 8 9 10 11 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 1 5 5 A2 5 17 5 5 B1 1.5 1.5 1.5 B2 1.5 1.5 1.5 B4 1.5 Evaluation item Tape extrusion appearance ○ ○ × × ○ ○ × Gel fraction (%) 78 20 82 75 50 70 73 Tensile strength (MPa) − 18 − − 12 14 − Elongation (%) − 460 − − 480 470 − Heat deformation rate − − − − 35 30 − Overall evaluation × × × × × × × (Note) -mark indicates that measurement is not possible.

[0019] (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.

[0021]

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. The density of (i) 0.910 to 0.945 g
/ Cm ³ melt index is 1-5g / 10min
Linear medium-low density polyethylene (L-LDPE) 10
100% by weight and a density of 0.915 to 0.935 g / c
Melt index at m ³ is 0.5 to 4 g / 10 min
Low density polyethylene (LDPE) or an ethylene-unsaturated ester copolymer of 90 to 0% by weight, and (ii) the 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 is a substance containing an organic unsaturated silane and a free radical generator. Water-free carrier polymer A 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 crystalline melting point of the base polymer, and then contacted with water. A method for producing a silane-crosslinked polyolefin, which comprises allowing the silane 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. 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 3
It is -15 wt%, The manufacturing method of the silane bridge | crosslinking polyolefin of Claim 1, 2, 3 or 4.