JP3290396B2 - Method for producing silane-crosslinked polyolefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for crosslinking a polyolefin. More specifically, an organic unsaturated silane is grafted onto a polyolefin-based polymer, and the silane grafting rate and the silane crosslink density are high.
Further, the present invention relates to a method for producing a silane crosslinked polyolefin having good heat resistance and appearance in one step.

[0002]

2. Description of the Related Art Conventionally, as a simple method for cross-linking a polyolefin, a graft reaction of an organic unsaturated silane to the polyolefin in the presence of a free radical generator is carried out, followed by silane grafting. A so-called silane cross-linking method of cross-linking by contact with water in the presence of a condensation catalyst is generally known. For example, it is disclosed in JP-B-48-1711 and JP-A-57-49109. However, this method involves at least two steps. That is, silane grafting reaction and silano-
This is a condensation reaction step. Therefore, at least two extrusion steps are required, and an economical problem as an end product cannot be avoided.

As a one-step process, there is a mono-sealing method. However, this method requires a liquid addition device for injecting the organic unsaturated silane in a liquid state into the extrusion kneader, but has problems of slippage and poor measurement. Extrusion kneaders also require expensive and special types with large L / D in order to uniformly disperse a small amount of additives, and economic problems cannot be avoided. In addition, very high technology is required for extrusion.

Further, as a one-step process, a silane crosslinking method in which an organic unsaturated silane is introduced into a resin is disclosed in Japanese Patent Laid-Open No. 3-1.
No. 67229. However, in this method, a porous polymer or EVA is used as a resin, and additives such as a silanol condensation catalyst and an antioxidant are introduced into the same resin in addition to the organic unsaturated silane and the free radical generator. are doing. For this reason, condensation of organic unsaturated silane,
There has been a problem that crosslinking efficiency and storage stability are inferior due to crosslinking inhibition due to oligomerization or radical scavenging.

[0005]

SUMMARY OF THE INVENTION The present invention has solved these problems. Extrusion and kneading in one step provide a high silane grafting ratio and a high degree of silane crosslinking, and provide excellent heat resistance and good appearance. It is intended to provide a method for producing a polyolefin.

[0006]

According to the present invention, there are provided (a) a polyolefin-based polymer and (b) 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) The organic unsaturated silane and the free radical generator are introduced from the first supply port (1) of the extruder and melt-kneaded, and (c) the silanol condensation catalyst and the antioxidant are supplied from the second supply port (2). In the step of adding and melt-kneading the extruded resin composition to crosslink it by contacting with moisture, the first supply port (1) to the second supply port (2) of the screw of the extrusion kneader to be melt-kneaded. The needing disk at the position between L /
This is a method for producing a silane-crosslinked polyolefin provided in a range of D = 3 to 4 (L is the axial length of the needing disk, and D is the diameter of the needing disk).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyolefin-based polymer of the present invention includes general polyethylene, polypropylene, a copolymer of ethylene and α-olefin, ethylene-
Ethyl acrylate copolymer (EEA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-
Examples include vinyl acetate copolymer (EVA), chlorinated polyethylene (CPE), and the like, and mixtures thereof.

The organic unsaturated silane of the present invention is one which 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, and examples thereof include vinyltrimethoxysilane and vinyltriethoxysilane.

[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, and the like. The free radical generator is preferably used by incorporating a liquid mixture dissolved in an organic unsaturated silane into a resin.
In order to contain the resin at a high concentration, the resin is preferably an ethylene-ethyl acrylate copolymer (EEA), an ethylene-methyl methacrylate copolymer (EMMA), a hydrogenated styrene copolymer or the like, or a mixture.

The silanol condensation catalyst of the present invention includes organometallic compounds such as dibutyltin dilaurate, stannous acetate, lead naphthenate, zinc stearate, cadmium stearate, barium stearate and calcium stearate. Can be The antioxidant of the present invention is generally used when processing a polyolefin, and is not particularly limited.

The silanol condensation catalyst and the antioxidant cannot be contained in the resin containing the organic unsaturated silane and the free radical generator before extrusion kneading. When the silanol condensation catalyst is contained in the resin containing an organic unsaturated silane and a free radical generator, the condensation and oligomerization of the organic unsaturated silane by the silanol condensation catalyst occur, and the concentration of the organic unsaturated silane decreases. This is because it is not preferable. The silanol condensation catalyst is necessary when the extrudate is brought into contact with water to obtain a silane-crosslinked polyolefin and the silane-grafted portions are crosslinked with each other, but in the extrusion kneading step, the silanol condensation catalyst is not used. It does not matter which part is used. However, since the silanol condensation catalyst cannot be contained in the resin containing the organic unsaturated silane and the free radical generator before the extrusion, the resin containing the antioxidant contains the silanol condensation catalyst. A method of charging the resin into the second supply port of the extrusion kneader is preferred. Regarding the antioxidant, in the silane grafting reaction to the polyolefin base polymer of the present invention, radicals are generated from the polyolefin base polymer by a free radical generator at the time of extrusion, and the radical generation trace of the polyolefin base polymer. When the organically unsaturated silane undergoes a grafting reaction, the extrudate is brought into contact with water, whereby the silane-grafted portion is crosslinked to obtain a silane-crosslinked polyolefin. When contained in silane and free radical generator containing resin,
Radical trapping of the antioxidant by the radical generation traces of the polyolefin-based polymer during extrusion extinguishes the radical generation traces and hinders the grafting reaction of the organic unsaturated silane. . The antioxidant is preferably added after the completion of the melt-kneading of the polyolefin-based polymer, the organic unsaturated silane and the radical generator, and the melt-kneading is further performed. This antioxidant is indispensable for imparting heat resistance to the obtained silane-crosslinked polyolefin. The heat resistance in this case is J
800 in the hot internal pressure creep test of IS K6769
Clearing the 0 hour creep test.

With respect to the resin containing the silanol condensation catalyst and the antioxidant of the present invention, the silanol condensation catalyst and the antioxidant can be added to the resin by kneading and granulation. Therefore, the same kind of resin as the polyolefin base polymer can be used, and the shape is usually granules or granules, and the preferred shape is pellets.

Next, regarding the production method, a continuous extruder is used as an extruder, and a polyolefin base polymer, an organic unsaturated silane and a free radical are supplied to a first supply port (1) of the extruder. A mixture of a radical generator-containing resin must be charged, and a silanol condensation catalyst and an antioxidant-containing resin must be charged into the second supply port (2). Temporarily
A polyolefin base polymer and one of an organic unsaturated silane and a resin containing a free radical generator are charged into the supply port (1), and the polyolefin base polymer and the organic unsaturated resin are supplied into the second supply port (2). Of the resin containing a saturated silane and a free radical generator, those not charged into the first supply port (1) are charged, and the resin containing the silanol condensation catalyst and the antioxidant is charged into the third supply port. Although the characteristics of the obtained silane cross-linked polyolefin remain unchanged,
And the need to increase the L / D of the twin-screw extruder is economically undesirable.

If the silanol condensation catalyst and the resin containing the antioxidant are simultaneously introduced from the first supply port (1) together with the polyolefin base polymer and the resin containing the organic unsaturated silane and the free radical generator, Similarly, traces of radical generation of the polyolefin-based polymer at the time of extrusion disappear due to radical scavenging by an antioxidant, and silane grafting and silane crosslink density are undesirably reduced.

Further, the polyolefin-based base polymer supplied from the first supply port (1) is mixed with the silanol condensation catalyst and the resin containing an antioxidant supplied from the second supply port (2) in a molten state. Preferably, kneading is performed.
The silane grafting reaction starts when the polyolefin-based polymer is melted, and the time required for the reaction is a fraction of a second. When the resin supplied from the first supply port (1) is in a molten state, the silanol condensation catalyst and the antioxidant-containing resin supplied from the second supply port (2) are in the first state.
Since a fraction of a second has always passed before being mixed and kneaded with the resin supplied from the supply port (1), the silane grafting reaction has already been completed at this point, and the radical of the antioxidant has This is because the trapping of the silane grafting reaction does not occur.

Before the resin supplied from the first supply port (1) reaches the second supply port (2), it is melted by using a co-rotating twin-screw extruder having a large shearing force. Extrusion is performed at a temperature close to the melting point of the polymer, and with regard to the segment configuration of the screw to be used, the L / D = 3 to 4 of the needing disk at the position from the first supply port (1) to the second supply port (2). It is desirable to use screw segments of L represents the axial length of the needing disk, and D represents the longitudinal length of the needing disk, that is, the diameter. Preferably, L / D = 2 is used as a basic constitutional unit for the dinging disk, and about 10 dinging disks having the same width are used. = 2, for the first L / D = 1 from the first supply port toward the tip, the kneading disk a (6) in which the kneading disk is shifted by 45 ° in the same direction as the screw rotation direction. And the remaining L / D = 1 is 45 ° in the reverse direction.
It is preferable that the knurling disk b (7) is shifted.

Regarding the length of the needing disk, L
If / D is less than 3, the melting of the polyolefin-based polymer is insufficient, and the resulting silane-crosslinked polyolefin has insufficient silane grafting and silane crosslink density, which is not preferable. When L / D is more than 9, silane grafting and silane crosslinking density become too large, and shark skin-like wrinkles are formed on the surface of the obtained silane-crosslinked polyolefin, resulting in poor appearance.

In addition, as an example of a method in which an antioxidant is added after the completion of the melt-kneading of the polyolefin-based polymer, the organic unsaturated silane, and the free radical generator, and further melt-kneaded, two continuous kneaders are used. The first kneader was used to melt-knead the polyolefin base polymer and the resin containing the organic unsaturated silane and the free radical generator,
It is conceivable to add a silanol condensation catalyst and an antioxidant-containing resin to the first extrudate by a second continuous kneading machine and further melt-knead the mixture. However, it is not preferable because an economic problem as a final product cannot be avoided.

If the silanol condensation catalyst and the antioxidant-containing resin charged through the second supply port (2) are not completely melted after the charging, the obtained silane-crosslinked polyolefin is not preferable because the appearance becomes poor. In order to completely melt the resin charged from the second supply port (2), the resin is extruded at a temperature close to the melting point of the polyolefin base polymer even from the second supply port (2) to the tip, and further into a screw segment. It is preferable to provide a zone for the nipping disk.

At the time of extrusion, a volatilized gas of the additive and the reaction composition is generated from the kneader. If this gas is not removed from the inside of the extruder, the gas may cause the thickness of the extrudate to become unstable, and in some cases, the extrudate may be cut off by the generation of gas bubbles. For this reason, it is desirable to remove the gas, but it is usually preferable to suck the gas through the vent hole (3) near the die of the twin-screw extruder. If desired, other additives may be added. Commonly used additives include, for example, neutralizers, ultraviolet absorbers, antistatic agents, pigments, dispersants, thickeners, metal deterioration inhibitors, fungicides, flow regulators, and other inorganic fillers. Or other synthetic resin.

[0021]

Embodiments will be described below with reference to embodiments. << Production of Resin Containing Organic Unsaturated Silane and Free Radical Generating Agent >> In a blending amount as shown in Table 1, first, a resin 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 organic unsaturated silane was charged into a super mixer, and the resin was impregnated with stirring for 10 minutes.

<< Production of Silanol Condensation Catalyst and Antioxidant-Containing Resin >> Resins, silanol condensation catalyst, antioxidant and the like are blended in the amounts shown in Table 2 using a pressure kneader. Kneaded and granulated. << Raw Materials Used >> (1) EEA (1): Ethylene-ethyl acrylate copolymer (EA content: 23% by weight) (2) EMMA: Ethylene-methyl methacrylate copolymer (MMA content: 30% by weight) (3) SEPS (1): hydrogenated styrene-isoprene block copolymer (styrene content: 30% by weight) (4) L-LDPE: linear low-density polyethylene (density: 0.924 g / cm ³ , MI ： 3.0g / 10min)

(5) VTMOS: vinyltrimethoxysilane (organic unsaturated silane) (6) DCP: dicumyl peroxide (free radical generator) (7) LDPE: low density polyethylene (density: 0.925 g / c)
(m ³ , MI: 1.5 g / 10 min) (8) DBTDL: dibutyltin laurate (silano-
(9) Antioxidant: phenol-based antioxidant / Irganox 1010 (manufactured by Ciba Geigy Corporation) (10) Lubricant: low molecular weight polyethylene / sun wax 1
71P (manufactured by Sanyo Chemical Industries, Ltd.)

<< Segment Configuration of Screw >> Regarding the screws of type a to d shown in FIG. 2, the kneading disk at the position between the first supply port and the second supply port is a type: L / D = 2 b type: L / D = 4 c type: L / D = 8 d type: L / D = 10

The kneading disks used for the screws a to d have L / D = 2 as a basic constitutional unit, and 10 kneading disks having the same width are used. 1 First L / D from supply port toward tip
= 1 for the needing disk a (6) shifted by 45 ° in the same direction as the screw rotation direction (the number of needing disks is 5). ・ The remaining L / D = 1 is 45 in the reverse direction. This is the shifting disc b (7) (the number of the cutting discs is five) shifted. Needing disk a which is shifted by 45 ° in the same direction as the screw rotation direction by L / D = 1 between the second supply port and the tip for screws a to d.
(6) was provided.

<< Extrusion Kneading >> (1) Examples 1-2 : A polyolefin-based base polymer, an organic unsaturated silane and a free radical generator were charged from the first supply port (1), and the mixture was supplied to the second supply port (2). ) To silano-
And an antioxidant. Extrusion is b or c
This was done using a type screw. (2) Comparative Examples 1-2: All compounds containing a polyolefin-based polymer were introduced from the first supply port (1). At that time, the second supply port (2) was sealed. Extrusion was performed using a b or c type screw. (3) Comparative examples 3 to 9: a polyolefin-based base polymer, an organic unsaturated silane and a free radical generator were introduced from the first supply port (1), and silanol was supplied from the second supply port (2).
And an antioxidant. Extrusion is a, c
Alternatively, the test was performed using a d-type screw.

(4) Extrusion kneading conditions: Extrusion kneader: 30 mmφ biaxial extruder (co-meshing type, co-directional non-meshing type, di-directional meshing type, di-directional non-meshing type) L / D: 30 Extrusion temperature : 120-150-170-180-180-
180-180-180-180-180-180 ° C. (5) Table showing polyolefin-based polymer, obtained resin containing organic unsaturated silane and free radical generator, and resin containing silanol condensation catalyst and antioxidant. The mixture was mixed at the ratios shown in Tables 3 to 6, the tape and the pipe were extruded using a twin-screw extruder, and further subjected to crosslinking treatment by immersion in warm water. Using this extruded tape, the gel fraction, tensile strength, elongation, and heat deformation were evaluated, and heat resistance was evaluated using a pipe.

For all types of twin-screw extruders, a second feeder (1) was placed at a position of L / D = 16 from the first feed port (1) of the extruder.
A supply port (2) is provided, and in Examples 1 and 2 and Comparative Examples 3 to 9, a silanol condensation catalyst and an antioxidant-containing resin are charged from the second supply port (2), and the first supply port ( In 1), the remaining mixture of the resin containing the organic unsaturated silane and the free radical generator and the polyolefin base polymer was charged. Regarding the supply amount of the raw materials, the silanol condensation catalyst and the antioxidant-containing resin are supplied to the second supply port (2) at a supply amount of 0.15 kg / hr, and the remaining organic unsaturated silane and free radical generator are supplied. After mixing the containing resin and the polyolefin base polymer, 9.85 was added to the first supply port (1).
The feed rate was kg / hr. When all the raw materials are put into the first supply port (1) at a time as in Comparative Examples 1 and 2, after mixing all the raw materials, 10 k is supplied to the first supply port (1).
g / hr was supplied.

<< Evaluation Method >> (1) Silane impregnation: The impregnation when the VTMOS / DCP liquid mixture was heated and stirred by a super mixer was evaluated. ：: good impregnation, ×: impregnable (2) Blocking: VTMOS / DCP with super mixer
The blocking properties of the pellets when the liquid mixture was heated and stirred were evaluated. ：: No blocking, X: Blocking (3) Tape extrusion appearance: Tape die: width 100 mm, lip interval 1 mmt Evaluation: ○>△> ×, and ○ is a pass level. (4) Gel fraction (%): 120 ° C., 20 hours, xylene immersion method (5) Tensile strength (MPa) and elongation (%): JIS K
6760. (6) Heat deformation ratio (%): according to JIS K 6723. (7) Heat resistance: JIS K6769, 8000 hour creep of hot internal pressure creep performance. Sample creation is PN15
Uses one type of pipe die with a nominal diameter of 13. Evaluation: After the test, samples having no cracks and other defects were evaluated as ○, and samples having those defects were evaluated as ×. The evaluation results are shown in Tables 3 to 6.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

As is clear from the table, the materials shown in the examples have good extrusion processability and appearance, and show very excellent crosslinking properties, mechanical properties and heat resistance. On the other hand, all of the comparative examples do not have a balance between extrudability, appearance, crosslinking properties, mechanical properties, and heat resistance.

[0037]

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

[Brief description of the drawings]

FIG. 1A is a longitudinal sectional view of an extrusion kneader of the present invention, and FIG. 1B is an enlarged sectional view taken along line II-II ′.

FIG. 2 is a diagram showing a segment configuration of a screw used in Examples and Comparative Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st supply port 2 2nd supply port 3 Vent hole 4 Needing disk a 5 Needing disk b 6 Article 2 needs disk a 7 Article 2 needs disk b

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Claims (2)

(57) [Claims] 1. A polyolefin-based base polymer
And (b) a general formula RR'SiY2 (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 an organic unsaturated silane and a free radical generator are introduced from the first supply port of the extrusion kneader and melt-kneaded. And (c) a step of introducing a silanol condensation catalyst and an antioxidant from the second supply port to further melt-knead, and extruding and kneading in a step of bringing the extruded resin composition into contact with moisture and crosslinking. L / D = 3 to 4 (L is the axial length of the kneading disk, D is the kneading disk) at a position between the first supply port and the second supply port of the screw of the machine. (Diameter) of the silane-crosslinked polyolefin. 2. The method for producing a silane-crosslinked polyolefin according to claim 1, wherein the extrusion kneader is a co-rotating twin screw extruder.