JPH1045827A - Production of silane-crosslinked polyolefin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a silane-crosslinked polyolefin excellent in extrusion molding property, crosslinking characteristics, mechanical characteristics and heat resistance in one step by using a carrier polymer, etc., containing an organic unsaturated silane, etc., in high concentration. SOLUTION: (A) A polyolefin-based base polymer is melted, mixed and reacted with (B) a substantially water-free carrier polymer A containing an organic unsaturated silane represented by the formula RR'SiY2 (R is a monofunctional olefinic unsaturated hydrocarbon; Y is a hydrolyzable organic group; R' is a monofunctional hydrocarbon other than an aliphatic unsaturated hydrocarbon or Y) and a free radical generator and (C) a carrier polymer B comprising polypropylene containing a silanol condensation catalyst and an antioxidant at a temperature higher than melting point of the carrier polymer crystal and then, the reaction product is brought into contact with water content to carry out crosslinking. Furthermore, the component A is preferably polyethylene or a copolymer of ethylene with α-olefin.

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 polyolefin is subjected to a graft reaction with an organic unsaturated silane in the presence of a free radical generator, followed by silane grafting. The so-called silane cross-linking method of cross-linking by contact with moisture in the presence is generally known. For example, Tokiko 48-1
No. 711, 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 economical problems 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. In addition, an extruder requires an expensive and special type having a large L / D to uniformly disperse a small amount of additives, and an economical problem cannot be avoided. In addition, very high technology is required for 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 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.

[0005]

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.

[0006]

According to the present invention, there are provided (i) a polyolefin-based base polymer; 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 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 (ii)
i) Silane cross-linking in which a carrier polymer B composed of polypropylene containing a silanol condensation catalyst and an antioxidant is melt-mixed and reacted at a temperature higher than the crystal melting point of the base polymer and the carrier polymer, and then cross-linked by contact with moisture. A method for producing a polyolefin, wherein the base polymer is polyethylene, a copolymer of ethylene and α-olefin, an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl methacrylate copolymer (EMMA), Selected from the group consisting of ethylene-vinyl acetate copolymer (EVA), chlorinated polyethylene (CPE) and mixtures thereof, wherein the carrier polymer A is ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer Coalescence (EMMA) hydrogenation obtained by hydrogenating 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 Selected from the group consisting of block copolymers and mixtures thereof, wherein the carrier polymer B is a resin having a melting point higher than the melting point of the base polymer, and the carrier polymer B is a polypropylene resin having a softening point of at least 135 ° C. This is a method for producing a silane-crosslinked polyolefin having an index of 1 to 5 g / 10 min, selected from the group consisting of homopolypropylene, block polypropylene and a mixture thereof, wherein the total amount of carrier polymers A and B is 3 to 15% by weight.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The polyolefin-based base polymer of the present invention is not particularly limited, but general polyethylene, a copolymer of ethylene and an α-olefin, and α-olefins of C _{3 to} C ₁₂ such as propylene, butene-1, and pentene -1, octene-1,4-methylpentene-1,4-
Methylhexene-1,4,4-dimethylpentene-1,
Nonene-1, decene-1, undecene-1, dodecene
1 mag. Alternatively, ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-vinyl acetate copolymer (EVA), chlorinated polyethylene (CPE) and mixtures thereof can be mentioned. .

[0008] The organic unsaturated silane of the present invention is grafted onto the base resin so as to be a cross-linking point between the base resins. Examples of the organic unsaturated silane used in the present invention include compounds 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 from 0.1 to 5% by weight, preferably from 0.7 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.

[0009] 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 0.05 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 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 is usually in the form of granules or granules in the form of pellets, and the preferred form is pellets. Examples of the carrier polymer A used in the present invention include ethylene-ethyl acrylate copolymer (EEA) and ethylene-ethyl acrylate copolymer.
Hydrogenate a methyl methacrylate copolymer (EMMA), 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. And a hydrogenated styrene-isoprene block copolymer (SEPS), a hydrogenated styrene-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 softening point of the carrier polymer B must be higher than the softening point of the base polymer. This causes a silane grafting reaction and a silanol condensation reaction at the time of extrusion, but the silanol condensation catalyst and the antioxidant in the carrier polymer B decrease the crosslinking efficiency by inhibiting crosslinking in the silane grafting reaction. Accordingly, by giving a difference in the softening point, the silane grafting reaction proceeds first, and then the silanol condensation reaction proceeds, thereby preventing the inhibition of crosslinking. Carrier polymer B must also be in particulate form and be 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.

The carrier polymer B used in the present invention is preferably a polypropylene resin, and is a common homopolypropylene or block polypropylene having a softening point of 135 ° C. or more, and a mixture thereof. More preferably, the melt index is from 1 to 5 g / 10 min. If the softening point of the carrier polymer B is lower than 135 ° C., crosslinking is inhibited and the degree of crosslinking is reduced. Melt index is 1g / 10mi
If it is smaller than n, the extrudability deteriorates and 5 g / 10 mi
If it is larger than n, the degree of crosslinking is reduced.

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 3 to 15% by weight based on the total weight of the polymer. 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. As other additives, if necessary, commonly used additives such as neutralizers, ultraviolet absorbers, antistatic agents, pigments,
A dispersant, a thickener, a metal deterioration inhibitor, a fungicide, a flow regulator, other inorganic fillers, and the like, or other synthetic resins can also be contained.

[0017]

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.

The raw materials used are as follows. (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: linear low-density polyethylene (softening point: 105 ° C, density) 0.94 g / cm ³ , MI; 3.0 g / 10 min) (4) VTMOS: vinyltrimethoxysilane (5) DCP: dicumyl peroxide (6) PP (1): block polypropylene (softening point: 150 ° C., MI
(230 ° C); 2.5g / 10min) (7) PP (2): Block polypropylene (softening point: 140 ° C, MI
(230 ° C); 4.5g / 10min) (8) PP (3): homopolypropylene (softening point: 160 ° C, MI (23
0 ゜ C); 1.5g / 10min) (9) PP (4): Block polypropylene (softening point: 128 ° C, MI
(230 ° C); 15g / 10min) (10) LDPE: low density polyethylene (softening point: 100 ° C,
^{Density; 0.925g / cm 3, MI;} 1.5g / 10min) manufactured by (11) DBTDL:: dibutyltin dilaurate (12) antioxidant phenolic antioxidant / Irganox 1010 (Ciba-Geigy Corp.) (13) Lubricant: Low molecular weight polyethylene / sun wax 171P
(14) MDPE: medium density polyethylene (softening point: 105 ° C,
Density: 0.930 g / cm ³ , MI: 2.0 g / 10 min)

The evaluation method is as follows. (15) Silane impregnation: The impregnation when the VTMOS / DCP liquid mixture was heated and stirred with a supermixer was evaluated. ○: Good impregnation, ×: Impregnable (16) Tape extrusion appearance: 50mmφ extruder 120-150-170-180-170 ℃ L / D: 20 Compression ratio 3.5 Tape die: width 100mm Lip interval 1mmt Evaluation: ○> The order of △> × was set, and the level of ○ was judged as acceptable. (17) Gel fraction (%): 120 ° C., 20 hours, xylene immersion method (18) Tensile strength (MPa) and elongation (%): JIS K 6760
by. (17) Heat deformation ratio (%): According to JIS K 6723.

The polyolefin-based base polymer and the obtained carrier polymers A and B were mixed in the ratios shown in Tables 3 and 4, and a tape was extruded using an extruder, followed by immersion in warm water to perform a crosslinking treatment. Using this extruded tape, the gel fraction, tensile strength, elongation, and heat deformation were evaluated.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4] As is clear from the table, the materials shown in Examples 1 to 5 have good extrusion processability and show 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.

[0025]

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 (6)

[Claims] (1) a polyolefin base polymer; 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 a fat. A substantially water-free carrier polymer A containing an organic unsaturated silane represented by a monovalent hydrocarbon group other than a group unsaturated hydrocarbon or the same as Y) and a free radical generator, and (iii) ) Melting and reacting a carrier polymer B composed of polypropylene containing a silanol condensation catalyst and an antioxidant at a temperature higher than the crystal melting point of the base polymer and the carrier polymer, and then reacting with the carrier polymer to crosslink by contacting with moisture. For producing a silane-crosslinked polyolefin. 2. The base polymer is polyethylene, a copolymer of ethylene and α-olefin, an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl methacrylate copolymer (EMMA), and an ethylene-vinyl acetate copolymer. (EVA), chlorinated polyethylene (C
2. The method for producing a silane-crosslinked polyolefin according to claim 1, wherein the method is selected from the group consisting of PE) and a mixture thereof. 3. The method according to claim 1, wherein the carrier polymer A is ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA),
Hydrogenated block copolymer obtained by hydrogenating a block copolymer consisting of a polymer block mainly composed of two vinyl aromatic compounds and at least one polymer block mainly composed of a conjugated diene compound, and The method for producing a silane-crosslinked polyolefin according to claim 1, wherein the method is selected from the group consisting of: 4. The method for producing a silane-crosslinked polyolefin according to claim 1, wherein the carrier polymer B is a resin having a melting point higher than that of the base polymer. 5. The carrier polymer B is a polypropylene resin, and is selected from the group consisting of homopolypropylene, block polypropylene having a softening point of 135 ° C. or more and a melt index of 1 to 5 g / 10 min, and a mixture thereof. The method for producing a silane-crosslinked polyolefin according to claim 1, 2, 3, or 4. 6. The total amount of carrier polymers A and B is 3
-15% by weight.
6. The method for producing a silane-crosslinked polyolefin according to 3, 4, or 5.