JP3124212B2 - Method for producing silane-crosslinked polyolefin - Google Patents

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, Shoko Sho 4
Nos. 8-1711 and 57-49109. 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.

[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]

According to the present invention, there is provided (i) a linear medium-low density polyethylene (L-LDPE) 10 having a density of 0.910 to 0.945 g / cm @ 3 and a melt index of 1 to 5 g / 10 min. ~ 100% by weight, and the density is 0.1%.
Low-density polyethylene (LD: 915-0.935 g / cm3 and melt index: 0.5-4 g / 10 min)
PE) or ethylene-unsaturated ester copolymer 90-0
Weight percent base polymer; and (ii) the general formula RR'S
iY2 (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 copolymer (EMM)
A) or consists of a carrier polymer B which contains a carrier polymer A, and (iii) a silanol condensation catalyst and antioxidant agents comprising mixtures thereof, the carrier
Formulation wherein the total amount of polymers A and B is 3 to 15% by weight
Is reacted at a temperature higher than the crystal melting point of the base polymer by melt-mixing and then contacting with water to crosslink the silane, and preferably has a density of 0.910 to 0.1. 945g
/ Cm3 and melt index is 1-5g / 10min
Linear low-density polyethylene (L-LDPE) 25 to
65% by weight and a density of 0.915 to 0.935 g / cm
3 is a base polymer consisting of a mixture with 75 to 35% by weight of low density polyethylene (LDPE) having a melt index of 0.5 to 4 g / 10 min, wherein the carrier polymer A has an ethylene content of 18 to 41% by weight.
A silane-crosslinked polyolefin, which is an ethyl acrylate copolymer (EEA), wherein the carrier polymer B is a polymer selected from the group consisting of polyethylene, polypropylene, a copolymer of ethylene and an α-olefin, and a mixture thereof. It is a manufacturing method of.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. 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 according to 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. ４4 g / 10 min. Also, as the ethylene-unsaturated ester copolymer,
Ethylene-ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA),
Examples include ethylene-vinyl acetate copolymer (EVA) and mixtures thereof. The amount of the linear low-density polyethylene in the base polymer is 10% by weight or more, preferably 25 to 65% by weight. If the amount is less than 10% by weight, heat resistance such as heat deformation is reduced. The melt index of the base polymer is from 1 to 5 g / 10 min, preferably from 2 to
4 g / 10 min, and 0.1 g for low-density polyethylene.
5-4 g / 10 min, preferably 1-3 g / 10 mi
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 linear medium-low density polyethylene,
0.915 to 0.935 g / c for low density polyethylene
m ³ , but if each falls below the lower limit, heat resistance such as heat deformation is reduced. In the case of linear medium-low-density polyethylene, extrudability deteriorates when it exceeds 0.945 g / cm ³ , and in the case of low-density polyethylene produced by high-pressure radical polymerization, those exceeding 0.935 g / cm ³ are industrially produced. Difficult to do.

[0006] 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. Examples of the organic unsaturated silane used in the present invention include a compound 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. 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 represented by the general formula RSiY _{3 in} which R ′ is the same as Y, for example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltributoxysilane, allyltrimethoxysilane, allyltriethoxysilane. Examples include silane. 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. 0.1% by weight
When the amount is less than 5%, sufficient grafting does not occur. On the other hand, when the amount exceeds 5% by weight, molding failure occurs and the method is not economical.
The free radical generator of the present invention acts as an initiator for 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-
Butylcumyl peroxide, di-benzoyl peroxide, 2,5-dimethyl-2,5-bis (t-butylperoxy) hexane, t-butylperoxypivalate, t-butylperoxy-2-ethylhexano Eat 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. When the amount is less than 0.01% by weight, a sufficient silane grafting reaction does not proceed and
If it exceeds 5% by weight, the extrusion processability is reduced and the molding surface is deteriorated.

By swelling the carrier polymer A of the present invention with a liquid mixture in which a free radical generator is dissolved in silane, the free radical generator and silane can be added to the carrier polymer A. 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. What is compatibility?
It 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 an ethylene-ethyl acrylate copolymer (EEA) having a monomer content of 18 to 41% by weight, an ethylene-methyl methacrylate copolymer (EMMA), or a mixture thereof. Can be. Monomer content 18% by weight
If the amount is less than 0.1%, a desired amount of silane impregnation cannot be obtained. If the amount exceeds 41% by weight, blocking occurs during silane impregnation, resulting in poor workability. Considering workability, economy, etc., EEA alone is most preferable.

A silanol condensation catalyst, an 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. 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. As the carrier polymer B used in the present invention, for example, polyethylene, polypropylene, a copolymer of ethylene and α-olefin, and as the α-olefin, 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 or a mixture thereof. As 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,
Organic metal compounds such as cadmium stearate, barium stearate, calcium stearate and the like can be mentioned.
The amount of these additives 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 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. 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 desired, additives usually used, for example, neutralizers, ultraviolet absorbers, antistatic agents, pigments, dispersants, thickeners, metal deterioration inhibitors, antifungal agents, flow control agents , Other inorganic fillers or the like, or other synthetic resins.

[0010]

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 (1): ethylene-ethyl acrylate copolymer (EA content; 23% by weight) (2) EEA (2): ethylene-ethyl acrylate copolymer (EA content; 10 (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; 3.0 g / 10 min) (5) VTMOS: vinyltrimethoxysilane (6) DCP: dicumyl peroxide (7) LDPE (1): low-density polyethylene (density; 0.925
g / cm ³ , MI; 1.5 g / 10 min) (8) PP: polypropylene (homopolymer, MI (230 ゜)
(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 Chemical Industries) (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; (15 g) L-LDPE (5): linear medium-low density polyethylene (density: 0.950 g / cm ³ , MI; 2.7 g / 10 min) (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) Impregnation of silane: The impregnation when the VTMOS / DCP liquid mixture was heated and stirred with a super mixer was evaluated.
○: good impregnation, ×: impregnable (20) 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. (21) Gel fraction (%): 120 ° C., 20 hours, xylene immersion method (22) Tensile strength (MPa) and elongation (%): JIS K 6760
by. (23) Heat deformation ratio (%): According to JIS K 6723.

The polyolefin base polymer and the carrier polymers A and B obtained were mixed in the ratios shown in Tables 3 to 5, 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.

Table 1 Combination 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 impregnation ○ × ○ × × ○ ○ ○ Blocking ○ ○ × ○ ○ ○ ○ ○

Table 2 Combination agent 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 <Combined 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 deformation ratio 12 8 7 − × − × Overall evaluation ○ ○ ○ × × × × (Note)-indicates that measurement is not possible.

Table 4 Comparative Example 5 6 7 8 9 10 11 <Ingredients> 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 − Heat deformation rate − × − − 35 30 − Overall evaluation × × × × × × × (Note)-indicates that measurement is not possible.

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

As is clear from the table, Examples 1, 2, 3
The materials shown in Table 1 have good extrudability and 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 (4)

(57) [Claims] (1) a density of 0.910 to 0.945 g / c
Linear low-density polyethylene (L-LDPE) having a melt index of 1 to 5 g / 10 min at m3 of 10 to 10
0% by weight and a density of 0.915 to 0.935 g / cm3
A base polymer consisting of low-density polyethylene (LDPE) or an ethylene-unsaturated ester copolymer having a melt index of 0.5 to 4 g / 10 min and (ii) a general formula RR'SiY2 (where R is 1 Olefinic 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 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 containing substantially free water containing a free radical generator And (iii) a carrier polymer B containing a silanol condensation catalyst and an antioxidant.
And the total amount of carrier polymers A and B is 3 to 1
A process for producing a silane-crosslinked polyolefin, which comprises melt-mixing a 5% by weight blend at a temperature higher than the crystal melting point of the base polymer, reacting the mixture, and then contacting with water to crosslink. 2. The base polymer having a density of 0.910
0.945g / cm3 with melt index of 1-5g
/ 10 min linear medium-low density polyethylene (L-LD
PE) 25-65% by weight and a density of 0.915-0.9
The melt index is 0.5 to 4 g / at 35 g / cm3.
10min low density polyethylene (LDPE) 75-3
The method for producing a silane-crosslinked polyolefin according to claim 1, comprising 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,
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.