JPH01184119A - Heat-shrinkable product - Google Patents

Abstract

PURPOSE:To improve heat resistance and freeze resistance and to give a long heat aging life, by molding, crosslinking and drawing a resin compsn. wherein an ethylene-propylene block copolymer having a specified ethylene component and a specified melt index is a base polymer. CONSTITUTION:A heat-shrinkable product is obtd. by molding a resin compsn. wherein an ethylene-propylene block copolymer having 1-20wt.% ethylene component and a melt index of 0.1-10 is a base polymer in a required shape, crosslinking it by a proper means and drawing it. Crosslinking of the resin compsn. is done either by compounding a polyfunctional monomer as a crosslinking auxiliary in the resin compsn. and crosslinking it by means of an ionizing radiation or by mixing in advance a silane compd. in the resin compsn. to graft-polymerize it and crosslinking the resin compsn. brought into contact with water in the presence of a silanol condensation catalyst. Molding of a heat-shrinkable product and imparting heat-shrinkability are done by extruding a material compd. into a tube shape by means of an extruder, carrying out a crosslinking treatment and expanding the diameter of the tube by means of a continuous diameter expansion method.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a heat-shrinkable article having heat resistance, cold resistance, and heat deterioration resistance suitable for anticorrosive coating of vibrator lines for transporting liquids such as oil and gas. It is related.

(Prior art and problems to be solved by the invention) Petroleum,
Asphalt has traditionally been used to prevent corrosion of underground steel pipes used for transporting gas and water and protecting electric wires and cables, but asphalt softens at high temperatures and becomes brittle at low temperatures.
Furthermore, since there are drawbacks such as poor workability when painting, there has been a shift in recent years to the use of low-density polyethylene or epoxy powder coatings. In particular, low-density polyethylene is inexpensive and has excellent low-temperature properties, and is widely used as an anticorrosive coating on the exterior surface of pipelines.

However, recently, high-pressure transportation has been used to improve efficiency, especially in the transportation of liquids such as oil and natural gas.

In this case, the fluid may be transported at a temperature of up to 120'C, and low-density polyethylene lacks heat resistance, so a steel pipe lined with polypropylene (hereinafter abbreviated as PP), which has a higher melting point, is used. being developed. In this case, a heat-shrinkable article mainly made of PP is required for the welded joints of the steel pipes.

There are several technical problems with making heat-shrinkable articles using PP as a material. One of them is related to the crosslinking required to impart heat shrinkability.
Since PP usually contains tertiary carbon, it is difficult to cross-link to the extent that molecular cleavage takes precedence over cross-linking and imparts heat shrinkability. Furthermore, even if cross-linking is possible, molecular cleavage occurs at the same time, which tends to cause a chain reaction of deterioration, resulting in a short heat-resistant deterioration life.

Furthermore, since PP has high rigidity, it has poor workability when wound up into a roll, and its low-temperature brittleness is worse than polyethylene (hereinafter abbreviated as PE), so it cannot withstand use in cold regions. In addition, since it has a high melting point, it is necessary to heat it to a high temperature during thermal contraction, resulting in poor workability.

In order to avoid these drawbacks, for example, JP-A-60-1
45836 and JP-A No. 61-40152, a crosslinked heat-shrinkable PEj5j is provided on the outside of an uncrosslinked PP layer, and a hot melt adhesive layer is provided on the inside. According to this method, the PP layer is Since it does not have heat shrinkability, the shrinkage workability is poor, and strong heating with a burner or the like is required, resulting in the outer surface of the tube being scorched. In addition, the characteristics after shrinking into steel pipes, etc. are the indentation depth at 120℃ (DIN306
70), the needle penetrates the PE layer, so the value becomes larger by the thickness of the PE layer.

Moreover, in JP-A No. 61-64429, PP and
Polyolefin other than PP such as PE and PP is 40 to 9
A method has been proposed in which the mixture is blended to a concentration of 0% by weight and crosslinked by irradiating it with 10 Mrad of ionizing radiation in the presence of a crosslinking aid such as trimethylolpropane triacrylate.

However, according to this method, when other polyolefins such as PE are blended, the indentation depth becomes deeper as the proportion thereof increases, and the properties of PP are impaired. Furthermore, in this method, since the irradiation dose of ionizing radiation is as large as 10 Mrad, molecular scission occurs at the same time as crosslinking, and if used at high temperatures after shrinkage, cracks will occur in the surface layer in a short time.

The present invention has been made in view of the above-mentioned problems of the conventional technology, and aims to provide good workability during the manufacturing process and shrinkage, good low-temperature and high-temperature properties, and a long heat-resistant life. The purpose is to provide a long polypropylene heat-shrinkable article.

(Means for Solving the Problems) In order to achieve the above object, the heat-shrinkable article of the present invention has the following features:
A resin composition having an ethylene content of 1 to 20% by weight and an ethylene/propylene block copolymer having a melt index (hereinafter abbreviated as MI) of 0.1 to 10 as a base polymer was molded into a desired shape and crosslinked by an appropriate means. After that, it is stretched.

In the present invention, the base polymer contains 1 ethylene component.
~20% by weight, ethylene with MI of 0.1-10.
The reason for using propylene block copolymer is that polypropylene homopolymer has too high rigidity, making it difficult to work with roll winding in the processing process, and its embrittlement temperature is around room temperature, so it cannot withstand use in cold regions. Moreover, in the case of ethylene-propylene random copolymer, it is not preferable because its crystallinity is low and its mechanical properties and heat resistance are poor. Furthermore, even in the case of ethylene/propylene block copolymers, if the ethylene component exceeds 20% by weight, the heat resistance will decrease due to a decrease in the melting point, which is not preferable;
Ungrooved material has poor cold resistance, similar to polypropylene homopolymer, and is not preferred.

Furthermore, if Ml is less than 0.1, the fluidity during molding will be poor, and if it exceeds 10, the mechanical properties will be insufficient, and either case is not preferred.

In addition, for the purpose of imparting flexibility and extrusion processability to the product, a polymer such as polyethylene or polybutene-1,4-methylpentene-1 may be blended as appropriate. The amount of these polymers added is preferably within 35% by weight. This is because if the temperature exceeds this value, the indentation depth at 120° C. becomes large, and the heat resistance deteriorates.

In the present invention, the method of crosslinking the resin composition includes, for example, a method of blending a polyfunctional monomer as a crosslinking aid into the resin composition and crosslinking with ionizing radiation;
Alternatively, there is a method in which a silane compound is mixed in advance into the resin composition, graft polymerized, and then brought into contact with moisture in the presence of a silanol condensation catalyst to crosslink it. As a specific example, for example, for 100 parts by weight of the base polymer,
A compound having at least three acryloyloxy groups or methacryloyloxy groups in the molecule is 0. A method in which 1 to 20 parts by weight and 0.55 to 5.0 parts by weight of a phenolic derivative are blended, heat molded at a temperature higher than the melting point of the base polymer, and then crosslinked by irradiation with ionizing radiation, or , a radical generator selected from the group consisting of dibenzoyl peroxide and tert-butyl perbenzoate and a general formula RR'5i in the base polymer.
Y2 (wherein R is a monovalent olefinically unsaturated hydrocarbon group or hydrocarbonoxy group, Y is a hydrolyzable organic group, R' is a monovalent hydrocarbon group containing no aliphatic unsaturated bond, A resin composition to which a silane compound represented by an organic group (Y or R) is grafted is subjected to a graft reaction at a temperature higher than the thermal decomposition temperature of the radical generator, and the resulting graft copolymer is preliminarily or Examples include a method of crosslinking by contacting with moisture under the action of a silanol condensation catalyst present after the graft reaction.

Further, additives such as pigments such as carbon black, various anti-aging agents, and the like that do not inhibit crosslinking or molding processing can be added to the resin composition in the present invention.

Furthermore, in the present invention, there are roughly two methods for molding into a heat-shrinkable article and for imparting heat-shrinkable properties. One of these methods is mainly for small fields with an inner diameter of about 50 mm or less, in which the material compound is extruded into a tube shape using an extruder, crosslinked, and then expanded by a continuous diameter expansion method. diameter. As for the continuous diameter expansion method,
There are several methods, such as a method in which the tube is preheated to a temperature higher than the melting point of the resin, and a pressure difference is applied within the die so that the inside of the tube is pressurized. Another method is to extrude the compound into a sheet or film using an extruder or inflation, apply heat shrinkage by stretching after crosslinking, and then heat-seal the sheet or film after winding it around a mandrel made of iron or the like. This method is suitable for medium-sized and large-diameter products, for example, those with an inner diameter of 50 mm or more.

The heat-shrinkable article of the present invention may be provided with a bot-melt adhesive layer on the inside thereof, if necessary. As the hot melt adhesive, for example, a polyamide adhesive or a modified polyolefin adhesive can be used. Modified polyolefins include polyolefins such as polyethylene, polypropylene, ethylene/propylene copolymer, polybutene-1, poly-4-methylpentene-1, and aliphatic unsaturation such as acrylic acid, methacrylic acid, maleic acid, and maleic anhydride. Preferred are those grafted with carboxylic acid or its anhydride.

(Example) Examples of the present invention are shown below.

(Example 1) 1.4 parts of trimethylolpropane triacrylate as a crosslinking agent was added to 100 parts by weight of an ethylene/propylene block copolymer with an ethylene component of 10% and Mll of 0.
0.2 parts of a phenolic anti-aging agent and 0.5 parts of carbon black were blended, kneaded using a Banbury mixer to form pellets, and then pelletized using a 65 mmφ single-screw extruder to a thickness of 0.
．． A film having a size of 34 mm and a width of 1000 mm was prepared, and the film was further irradiated with IMRad ionizing radiation. The gel fraction of the obtained film was 43%. This film was stretched in the longitudinal direction of the film using a uniaxial stretching machine so that the stretching ratio was doubled, and then the outer diameter was 100 mm.
The film was wound in the longitudinal direction around a steel tube with a release paper in between so that the wall thickness was 1 mm, and the film was left in a constant temperature bath at an ambient temperature of 230°C for 30 minutes, then cooled and integrated into a tube shape to form a heat-shrinkable tube. did.

After heat-treating the obtained heat-shrinkable tube in a silicone oil bath at 200°C for 30 minutes, the shrinkage rate in the inner diameter direction was measured and found to be 55%.

In addition, a test piece was cut from this tube and JISK-7
The impact embrittlement temperature was measured by the method of 216.
The temperature was 8°C.

In addition, the heat-shrinkable tube obtained as described above was placed over a steel pipe with an outer diameter of 50 mm, heated with a propane gas torch,
It was evenly contracted and adhered to the steel pipe.

Using this sample, the indentation depth at 120°C was measured using the method of D I N30670 and it was 0°30I.
It was TIITl. Further, the tube that had been shrunk on the steel pipe was left in an air constant temperature bath at 160° C. for 20 days, but no change in appearance was observed.

(Comparative Example 1) The same ethylene-propylene block copolymer used in Example 1 was extruded into a film with a thickness of 0.2 mm using a 65 mmφ extruder. This film was wound around the same steel tube used in Example 1 with a release paper in between so that the wall thickness was 1 mm, and on top of this was roughly cross-linked a polyethylene film with a longitudinal shrinkage rate of 70% (film thickness 0.5 mm). 17 mm) was wound in the longitudinal direction so that the wall thickness was 1 mm, and the end of the winding was fixed to form a tube shape in the same manner as in Example 1, and the physical properties were evaluated in the same manner. The results are shown in Table 1.

(Example 2) 1.5 parts of γ-methacryloxypropyltrimethoxysilane, 0.5 parts of benzoyl peroxide, and 0.5 parts of carbon black to 100 parts by weight of ethylene-propylene block copolymer with an ethylene component of 13% and Mll of 0. Department,
0.3 part of a phenolic anti-aging agent was added and extruded into a rod shape using a 65 mm extruder to obtain a pellet-shaped graft copolymer. Separately, 4 parts of dibutyltin dilaurate and 5 parts of a phenolic antioxidant were added to 100 parts by weight of the same copolymer, and the mixture was extruded into a rod shape using a 40 mm extruder to obtain a pellet-shaped catalyst masterbatch.

After that, graft copolymer: catalyst masterbatch = 2
These were mixed at a weight ratio of 0:1, and a film with a thickness of 0.4 mm and a width of 1000 mm was obtained using a 65 mm extruder. This film was layered with a cellulose-based nonwoven fabric, wound into a roll, and immersed in warm water at 80°C for 16 hours, and then the woven fabric was removed to obtain a film with a gel fraction of 53%.

The obtained film was stretched and laminated to form a tube in the same manner as in Example 1, and the physical properties were evaluated.

The results are shown in Table 1.

(Example 3) 80 parts by weight of ethylene propylene block cobolimer with 8% ethylene content, MIo, 6 and MIo, 3 density 0.92
20 parts by weight of the medium-density polyethylene of No. 5, 1.4 parts of trimethylolpropane trimethacrylate, 0.25 parts of a phenolic antioxidant, and 0.6 parts of carbon black,
After forming into pellets, the same method as in Example 1 was used to obtain a thickness of 0.
It was formed into a film of 34 mm and irradiated with ionizing radiation of 0.7 Mrad to obtain a film with a gel fraction of 57%. This film was stretched and formed into a tube in the same manner as in Example 1, and its physical properties were evaluated. The results are shown in Table 1.

(Comparative Example 2) 48 parts by weight of ethylene-propylene block copolymer with 6% ethylene content, MIo, 5 and MIo, 7 density 0.94
After kneading 52 parts by weight of high-density polyethylene, 1.0 part of trimethylolpropane trimethacrylate, 0.25 parts of a phenolic anti-aging agent, and 0.5 parts of carbon black to form pellets, the same method as in Example 1 was carried out. thickness 0.3
It was formed into a film of 4 mm and irradiated with ionizing radiation of 10 Mrad to obtain a film with a gel fraction of 44%. This film was stretched and formed into a tube in the same manner as in Example 1, and its physical properties were evaluated. The results are shown in Table 1.

(Comparative Example 3) 100 parts by weight of a polypropylene homopolymer with an MIo of 8 was kneaded with 1.0 part of trimethylolpropane trimethacrylate, 0.3 part of a phenolic antioxidant, and 0.5 part of carbon black. After pelletizing, it was made into a film with a thickness of 0.34 mm using the same method as in Example 1, and 0.8M
A film with a gel fraction of 51% was obtained by irradiation with rad ionizing radiation. This film was stretched and formed into a tube in the same manner as in Example 1, and its physical properties were evaluated. The results are shown in Table 1.

(Example 4) A 1 mm thick maleic acid-modified polypropylene adhesive was wrapped around a steel pipe with an outer mold of 100 mm via a release paper, and the stretched film prepared in Example 1 was further placed on top of this with a thickness of 1 mm. Two tubes were prepared using the same method as in Example 1. Place this tube in a silicone oil bath at 200℃ for 30 minutes.
When the shrinkage rate in the inner diameter direction was measured, it was 58%.
Met.

Another tube was placed over a steel pipe with an outer diameter of 50 mm whose surface had been polished by shot blasting, and heated with a propane gas torch to uniformly shrink and adhere the tube to the surface of the steel pipe. The temperature dependence of the adhesion of this tube to the steel pipe is
It was as shown in the figure.

(Example 5) To 100 parts by weight of an ethylene-propylene block copolymer with an ethylene component of 13% and Mll of 0, 1.6 parts of tetramethylolmethanetetraacrylate as a crosslinking aid, 0.3 parts of a phenolic antioxidant, and carbon After kneading 0.5 part of black in a panburi mixer and making it into a pellet shape, the inner diameter was 0.68 in a 30IIllTlφ single screw extruder.
+nn+, and a tube shape with a wall thickness of 0.44n+m. This tube was irradiated with ionizing radiation of 0.7 Mrad,
A tube with a gel fraction of 52% was obtained. This tube is 19
The tube is preheated in a silicone oil bath at 0°C, then expanded in the circumferential direction while applying a pressure differential that pressurizes the inside of the tube, and then cooled and solidified using a coolable outside mandrel. Made of heat shrink tubing. The inner diameter of this tube is 1.5 mm, and the wall thickness is 0.5 mm.
It was 22 mm. This tube has an outer diameter of 0.7 mm.
An insulated wire was obtained by shrinking the coating on the tin-plated conductor.

(Comparative Example 4) High-density polyethylene with MIl and O11 parts of 0.95 was formed into a tube of the same size as in Example 5, and then the tube was irradiated with ionizing radiation of 15 Mrad to obtain a gel fraction of 55%. It was made into a tube.

Place this tube in a silicone oil bath at a temperature of 150'C.
The diameter was expanded in the same manner as in Example 5 except that a heat-shrinkable tube having the same dimension as in Example 1 was obtained. This tube was coated and shrunk onto a tin-plated conductor of the same size as used in Example 5 to obtain an insulated wire.

The insulated wires obtained in Example 5 and Comparative Example 4 were subjected to a 105°C 2OkV cut-through test (■ at 105°C 30°C), and the time until short circuit was measured. It was 1.7 hours. Thus, the product of the present invention exhibited excellent high voltage cut-through characteristics.

(Example 6) The silane compound graft copolymer prepared in Example 2 and the catalyst masterbatch were mixed at a weight ratio of 20:1, and a tube shape with an inner diameter of 10 mm and a wall thickness of 1 mm was prepared using a 40 mm extruder. I pushed it out. This was immersed in warm water at 60° C. for 24 hours to obtain a tube with a gel fraction of 55%. When this tube was expanded using the same continuous diameter expansion method as in Example 5,
A heat-shrinkable tube with an inner diameter of 23 mm and a wall thickness of 0.48 mm was obtained. After treating this tube in a silicone oil bath at 200°C for 30 minutes, the shrinkage rate in the inner radial direction was measured.
It was 55%.

In addition, the gel fraction referred to in the above Examples and Comparative Examples is approximately 1
00mg in 100cc of tetralin at 135℃ for 12
This is the value obtained by dividing the weight t by the weight before extraction after time extraction and drying of the extraction residue.

1g- (Effects of the Invention) As is clear from the comparison of the characteristics of the Example and Comparative Example products, the present invention provides a heat-shrinkable article that has excellent heat resistance and cold resistance, and has a long heat-resistant aging life. It is extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the peel strength and temperature of the steel pipe-coated heat-shrinkable tube in Example 4. Patent applicant Furukawa Electric Co., Ltd. Temperature (0
C) Figure 1

Claims (1)

[Claims] Ethylene component 1-20% by weight, melt index 0
．． A heat-shrinkable article obtained by molding, crosslinking, and stretching a resin composition having an ethylene-propylene block copolymer of 1 to 10 as a base polymer.