JPS61143110A - Manufacture of crosslinked polyolefin molded body - Google Patents

Abstract

PURPOSE:To prevent a burned spot from occurring when a reaction takes place thereby improving the long run property, by causing the heat generated by shearing in a shearing extruder to elevate the temperature of material thereby allowing the silane grafting reaction to take place. CONSTITUTION:A mixture consisting of a resin and additives is fed to a hopper 10 provided to a single screw extruder, then is plasticized and kneaded by a screw 12 and is fed to a shearing extruder. The plasticized and kneaded melt is fed by the conveying action of a screw section 14 to a cylindrical orifice 15, and is subjected to a shearing action at a gap 25 between a cylinder 13 and a rotating orifice 15 so that the temperature of the melt may rise until a temperature required for the silane grafting reaction is secured, and the reaction mixture is passed through a molding die 16 to cover a conductor 3 thereby producing, for example, a covered electric wire.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a crosslinked polyolefin molded article. More specifically, the present invention involves first grafting a 710 water-decomposable organo-mechanical saturated silane compound onto an olefinic resin polymer in the presence of a free radical generator, and then grafting the silane compound to an olefinic resin polymer in the presence of a silanol condensation catalyst. Initially, the resulting graftomer was crosslinked by exposing it to a moisture atmosphere.

Frames such as extruded products such as electric wire cables and pipes 1...
The present invention relates to a method for producing a bridge polyolefin molded article.

An extrusion molded article by the conventional silane crosslinking process (method) is made by the following eight steps.

(1) Step 1 to obtain a graftomer with a flanged 2-phthalate structure.

(1) Molding the graftomer into the desired shape,
(11) The obtained molded product is exposed to moisture and crosslinked.

However, a silanol condensation catalyst is usually added in the step (II) above, and this method is usually called a two-stage process method. However, a process called a one-step process has also been developed which is even more economically effective. That is, it is as follows. A blended component consisting of a polyolefin resin, a silane compound that can be hydrolyzed by water, a free radical generator, and a silanol condensation catalyst is fed into a screw extruder at a predetermined ratio, and the extruder After the ingredients are kneaded in the cylinder and the temperature is raised to a temperature sufficient to cause the silane graft reaction, the resulting graft polymer is extruded. Next, the resulting extruded body is exposed to a moisture atmosphere to allow the crosslinking reaction to proceed.

Although such a one-stage process method is more economical than a two-stage process method, there is a first-order lower l-coupling. That is, (a) The silane craft reaction rate (■ degree of crosslinking) depends on the resin temperature and stagnation (residence) time in the extruder cylinder, so if the cylinder temperature is constant and the screw rotation speed As the cylinder rises, the residence time in the cylinder 2 also decreases, so the silane graft reaction rate decreases at high screw rotations. On the other hand, at low screw rotations, the stagnation time becomes very long, so the silane craft reaction rate is sufficient, but the cross-linking reaction between molecules, which is a side reaction, also occurs, so extrusion processability cannot be avoided. . Therefore, the screw rotation speed range during operation is generally limited. For example, when making large-sized cables, it is more efficient to use a high screw rotation speed in order to increase productivity.However, high screw rotation speeds are not possible because the grafting reaction rate, that is, the degree of crosslinking, decreases. .

On the other hand, when making small-sized cables, it is not possible to extremely increase the production line speed due to equipment limitations, so it is necessary to lower the screw rotation speed, which reduces extrusion processability. (b) In the one-stage process method, the silane graft reaction and molding process are performed simultaneously in one extruder, so the resin temperature in the extruder is generally kept at 200-2. - The temperature range is 250°C, which causes resin deterioration and burning, and the silanol condensation catalyst, which is a crosslinking reaction accelerator, is also present in such a high-temperature atmosphere, which has the following practical disadvantages. Ta.

(a) If extrusion continues for a long time, the resin will burn.
- Occurs, and scorch appears on the extruded product, causing deterioration in appearance and material properties. This requires frequent cleaning of the inside of the extruder and the screw cage, which poses a problem in the long-run performance of extrusion.

(1)) When stopping the extruder screw to replace the extrusion die nipple, etc., the inside of the cylinder must be completely replaced with polyolefin resin that does not contain silane compounds or the like before starting the first extrusion. When this is done, there is a problem that defects such as spots may occur in the extruded product. This was a problem not only in terms of IX's poor workability but also in terms of costs such as the cost of the replacement resin.

In view of the above circumstances, the inventors of the present invention conducted intensive research to solve the conventional problems, and found that 1) the silane craft reaction could be carried out using a normal external heating method, 2) in a Liu-type extruder. Mechanical shearing action is applied to the mixed resin component using a single shearing extrusion machine.

The present inventors have discovered that the above-mentioned conventional drawbacks can be significantly improved by raising the temperature of the material by the internal shear heat generated thereby and causing the silane gellast reaction.

The method for producing a crosslinked polyolefin molded article of the present invention is prepared by adding and blending a hydrolyzable unsaturated silane, a free radical generator, and a silanol condensation catalyst in predetermined proportions to a polyolefin resin. The resin mixture is fed into a screw type extruder and plasticized and kneaded in the extruder cylinder, and the resulting resin mixture is then fed to the screw extruder and molding die without being exposed to the atmosphere. The resin temperature is raised to a temperature sufficient to cause the silane graft reaction by further applying mechanical shearing force to the resin kneaded product. The method is characterized by comprising a step of extruding the obtained resin reaction kneaded product from the molding gou, and then crosslinking it by the action of moisture.

The polyolefins used in the present invention include polyethylene, polypropylene, ethylene vinyl acetate copolymer, ethylene ethyl acrylate copolymer, chlorinated polyethylene, or a binary or ternary copolymer of ethylene and -α-olefin (sometimes α-olefin is 08-010)
etc., and blends of these polymers are also included.

Next, the organic silane used in the BAvc of the present invention is 1.
・For more details, see 2RR'SiYg (where R is, for example, vinyl, allyl, butenyl, or cyclohexenyl.

Cyclopentagel, cyclohexadiel, OH, -0
(OH2)Coo(OH2)8-, 0H2-0(OH8
)OOOOH,0H20(an,)8-t○H2-0(
OH8)0000H,OHg(OH)(OH)OH20
=(OHg) -valent olefinic unsaturated hydrocarbon group such as 8- or hydrocarboxyl group, Y is an alkoxy group such as methoxy, ethoxy, butotoxy group, acyloxy group such as formyloxy, acetoxy group, or propioxy group Group, -0N-0,.

CCH2), -〇N-0(OH2)08H5, -0N
Oximo group such as -0(06H5)2, -NHO
Alkylamino/groups such as 2H, -NH(0,H8)
% R' is a hydrolyzable organic group such as an arylamine group such as methyl, ethyl, propyl, tetradecyl, octadecyl, phenyl, benzyl, tolyl group, etc. group or the same thing as Y). In particular, it is desirable to use an organic hexarane represented by R81Y2 in which R' is the same as Y, such as vinyltrimethoxy(□
Disilane, vinyltriethoxysilane, etc. are suitable.

The amount of organic silane used is 1 to 5 parts, preferably 1.5 to 2.5 parts, per 100 parts by weight (hereinafter referred to as "parts") of the mixture with the polyolefin. The reason for this is that if the amount is less than 1 part, sufficient grafting will not occur, whereas if it is more than 5 parts, molding becomes difficult and uneconomical.

Next, the free radical generator used when grafting the above-mentioned organic silane to the polyolefin includes, for example, benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide,
2.5-di(peroxybenzoate)hexyne-8,
1,8-bis(t-butylperoxyisopropyl)benzene, lauroyl peroxide, butyl peracetate, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-8,2,5- Organic peroxides such as dimethyl-2,5-di(t-butylperoxy)hexane, t-butylperbenzoate, or 1(-perester), or azo compounds such as azobisisobutytetranitrile and dimethylazodiisobutyrate are used. The free radical generator may be a compound that generates a free radical site in polyolefin at a temperature of 100°C or higher, such as di-1-milperoxide 41,8-bis(t-butylperoxyisopropyl)benzene. It is preferable to use the free radical generator in an amount of
The amount is -1 part of OQl per 100 parts of the above mixture, preferably 0.005 to 0.25 part. If the upper limit exceeds 2.1, the extrusion properties of the obtained graft polymer will deteriorate and the surface texture of the molded article will become poor, and if the length is too small, the graft reaction will be insufficient. Furthermore, examples of silanol condensation catalysts include dibutyltin silaurylate, stannous acetate, and dibutyltin diacetate.

Dibutyltin octoate, lead naphthenate, zinc caprylate, cobalt naphthenate, tetrabutyl titanate, tetranonyl titanate, lead stearate,
Organometallic compounds such as zinc stearate, cadmium stearate, barium stearate, and calcium stearate are used. The amount used is similarly 0.08 to 0.5 parts per 109 parts of the mixture; if the amount is less than this, the degree of crosslinking will be low, while if it is more than 9 tlc, the surface of the molded product will become rough.

Next, the resin and each additive are measured in advance in a predetermined ratio, premixed, and fed into the extruder hopper, but each additive can be made into a masterbatch in advance.

For example, the silanol condensation catalyst, antioxidant, etc. may be kneaded with the resin component in advance to form a masterbatch. Further, a diaphragm type pump can be used as an adjustable plunger for measuring and supplying liquid components.

The resin mixture is first fed into a screw extruder, where it is plasticized and melt-kneaded. The screw type extruder used here does not need to be a special one, and a single screw extruder with L/D=18 to 24, which is usually used for coating electric wires such as polyethylene or PVC, can be used. In this screw-type extruder, the resin and additive components are melt-kneaded.

Since the main function is to homogenize the material and quantitatively transport it to the primary shear extrusion section, there is no need to actively raise the material temperature, and generally silane craft reaction does not occur. Preferably, extrusion is carried out at a temperature of 1X degrees below 170°C. Even if the temperature of the material increases further in the screw extruder, it will not cause a fatal situation, but it may hinder workability such as changing the size or cleaning when the equipment is stopped.

Next, the molten material 2 conveyed from the screw extruder is supplied to a shear extruder. This shear extruder consists of a shear heating section which is a cylindrical rotary oryswiss formed by a threaded section for conveying the melt, a rotating shaft for imparting a shearing action to the tip, and a surrounding cylinder wall. It has become. Furthermore, when covering a conductor such as a wire to be covered with electricity, a through hole is provided in the rotating @ and a stationary protective tube is provided to protect the running conductor, and the tip of this protective tube is There is a replaceable conductor guide nipple. The space between this nipple and the molding die becomes a resin passage, and the covered electric wire l.
・The structure is such that it can be manufactured. In the case of hollow molded products such as pipes, there is no conductor, etc.

A quiet protection tube is not required. In addition, the rotating shaft that rotates concentrically within the cylinder of the shear extruder is
The screw type extruder is equipped with a separate variable x-speed drive device, and has a structure that can be easily connected to the tip of a conventional extruder. In a shear extruder with such a structure, molten resin containing additives supplied from a screw extruder is conveyed toward the molding die through a threaded section.
The molten material is fed into the shear heating section of the cylindrical circular orifice, where the molten material generates heat due to the high shear action, the temperature of the material decreases rapidly, and a silane craft reaction occurs. The exothermic section is subjected to a higher level of shear than that experienced in the screw extruder, with a shear rate in the range of about 100 to 600/sec.

The silane-crafted polyolefin molded product extruded under such conditions can be crosslinked by exposing it to water or a humid atmosphere at an appropriate temperature.

The present invention will be further described below with reference to the accompanying drawings. In the case of coated wires, the coated wire manufacturing equipment (FIG. 1) is fed from a conductor supply device 1, preheated if necessary through a conductor preheating device 2, and passed through a shear extruder 4 to flanges 2.
The foamed resin is coated on the conductor 11, and the cooling device 5
The wire is passed through the wire and wound into the wire take-up and winding device 6. Two extrusion devices? and 4 can be driven independently by the drive devices 8 and 9, but it is also possible to control 8 and 9 in conjunction at a certain ratio.

FIG. 2 is a detailed view of the two extrusion devices 4 and 7. A mixture of resin and additives is supplied to a hopper 10 provided in a single-screw extruder, and the mixture is plasticized and kneaded by a screw 12, and sent to a shear extruder. The plasticized and kneaded melt is transferred by the conveying action of the first threaded part 14.
The melt is fed into the cylindrical orifice 15, where a shearing action is applied to the melt in the gap 25 between the cylinder 18 and the rotating orifice 15, and the temperature of the melt rises to the point required for the silane grafting reaction, causing a reaction. The mixture is molded through a molding die 1t1
16 and coated on the conductor B to obtain a coated wire.

The effects of the present invention are as follows. Instead of carrying out the silane grafting reaction in a normal screw-type extruder, the silane grafting reaction is carried out by applying a mechanical shearing action to the molten resin temperature compound in a shearing extruder. In order to obtain a silane craft polyolefin molded article by raising the temperature to a sufficient temperature, there are the following practical advantages.
2. (b) Because the material temperature rises quickly due to the shear heat generation of the resin, it has excellent long-run properties because there is almost no discoloration during the reaction phase during Silanggraph) X%%% reaction. .

(b) The temperature required for silane crafting is determined by changing the rotation speed of the rotating shaft of the shear extruder/extruder.

Since the temperature can be set to any desired value, the extrusion rate can be freely selected at any point within the equipment capacity range, allowing for a wide range of insulated wire sizes that can be manufactured and the most efficient conditions for productivity. You can choose. (1) It is excellent in workability and productivity because there is no need to replace the inside of the extruder with a resin that does not contain a crosslinking agent when changing the size of the coated wire to be manufactured or when stopping the extrusion operation. Also, there is less waste of materials.

(in) No seams occur in the insulation layer.

Examples of the present invention are shown below.

Examples (Parts indicate parts by weight) (4) 95 parts of polyethylene (density 0.92 r/z, melt index 8.1710 minutes) and a separately prepared masterbatch [to 100 parts of the polyethylene,...
・35 parts of a masterbatch prepared by blending 1 part of dibutyltin silaurylate and 4 parts of Irganox 1010 (product name manufactured by Nippon Ciba Geigy) as an antioxidant and kneading with two rolls, and 2 parts of vinyltrimethoxysilane. 0.18 part of dicumyl peroxide was dissolved in □ and mixed with the mixture using a Henschel Migisser.

(8) D: 9 ommφ, L/D: 5 (1) Shear P
Connect IJT extrusion c'A (see Figures 1 and 2).

The above component (A) is supplied to this single screw extruder hopper lo]
- First, a 60 mm copper conductor was extruded and coated with a wall thickness of 1 and 5 mm under the extrusion conditions shown in the examples in Table 1 to produce an insulated wire. (Example 1 in Table 1) To continue changing the conductor size to 22 mm.

After stopping the extrusion and changing the size, extrusion coating was performed again on a 22 tnm copper conductor under the conditions of 1 and Example 2 (see Table 1). Extruded appearance of 22 mm insulated wire H6t)
It was as good as the mm wire.

Further, long-run properties were investigated under the conditions of Example 2, and even after continuous extrusion for 86 hours, there was no change in appearance after extrusion.

Example 8 is after continuous extrusion for 86 hours.

Subsequently, under the extrusion conditions shown in Example 8, 2 B yar
Create a n” insulated wire and proceed as follows.

The insulated wires prepared in each Example 1.2.8 were treated in hot water at 80°C for 24 hours, and the gel fraction and tensile properties were investigated, and the results are shown in Table 1.

Comparative Example The same component (1) as in Example was used in a single-screw extruder with D = 90 mm and T-yD: 28, as shown in Comparative Example 1.2.8! The same experiment as in the example was conducted under extrusion conditions such that In addition, when changing the size from 60m to 21mm as in the example, the inside of the extruder was not replaced with polyethylene. ,60rnm
After completing extrusion, the inside of the extruder was completely replaced with polyethylene.
2.) I had no choice but to use the extremely inefficient method of replacing the nozzles and starting extruding BZmtm again.

As for the long run performance, I started to notice some burning and discoloration after about 80 hours! Therefore, the appearance of the extruded product could not be improved unless the extrusion operation was stopped and cleaned.

From Table 1, the extruder screw rotation speed is from 10 to -70r.
, p, m, fc Example 1 using a shear extruder
．． In No. 2.8, by adjusting the rotational speed of the shear extruder, the external appearance of the extruded products was good and the gel fraction was all 60 (%) or more, which was a good result. on the other hand,
Comparative example 1.2.8 using a long single screw extruder
Then, when the screw rotation speed is low (10 r, p, m,), the gel fraction is good but the appearance of the extruded product is poor;
When the screw rotation speed is high (70 r, p, m, ), the appearance of the extruded product is good, but the gel fraction is low,
Suitable extrusion conditions: ・Screw rotation speed 40 (r
, p, m, ) can only be selected, which is a big problem in practice.

In addition, long-run performance and size changeability (by using a shear extruder) were significantly improved compared to the conventional method (Comparative Example 1゜2.8) (see Table 1). The industrial value of the present invention is extremely significant.

Table 1 Measurement conditions * 4zt, 'yB°vx24 (hr) after extrusion, 8
oeX12 honey ※※ According to JIS G 8005.

***Tatsunaka (-) has a long run and did not experiment with size changes.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of electric wire manufacturing equipment using a shear extruder according to an embodiment of the present invention, and FIG. 2 is a detailed diagram of a screw type extruder and a shear extruder according to an embodiment of the present invention. It is. 1... Conductor supply device 2... Conductor preheating device 8.
...Conductor 4...Shearing extruder 5...Cooling water tank 6...Take-up and winding device 7...Screw type extruder 8, 9...Drive device 10...Hopper 11... Extruder cylinder l1l12... Extruder screw 1B... Shear extruder cylinder 14... Threaded part of shear extruder rotating shaft 15... Shear extruder rotation orifice part 16... Molding die 17... Die holder 18...insulation chamber a19...extruder drive device 20, 21...gear
Wholesale... Shearing extruder drive device 28... Heater 24/Pa rotation shaft 25... Shearing heat generating part

Claims (1)

[Claims] 1. A resin mixture prepared by adding and blending a hydrolyzable unsaturated silane, a free radical generator, and a silanol condensation catalyst in predetermined proportions to a polyolefin resin is introduced into a screw extruder. and plasticizing and kneading in the extruder cylinder, followed by a step of supplying the resulting resin kneaded material to the high shear extruder installed between the screw extruder and the molding die without exposing it to the atmosphere. further applying a mechanical shearing force to the resin kneaded product to raise the resin temperature to a temperature sufficient to cause the silane graft reaction; 1. A method for producing a crosslinked polyolefin molded article, comprising the steps of extruding it from a die and then crosslinking it by the action of moisture.