JPS5935343B2 - Heat-shrinkable multilayer foam tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a heat-shrinkable multilayer that easily shrinks and foams when heated to form a polymeric foam with good adhesion and good appearance on the surface of articles to be coated, such as pipes and rods. Regarding foamable sheets.

In recent years, a variety of products have been used for purposes such as heat insulation and heat retention, which are made by coating the outer periphery of pipes and the like with polymeric foam.

Conventionally, this type of coating method has been put to practical use by extruding a polymer foam layer of a required thickness around the outer periphery of a metal pipe using an extrusion molding machine, or by using a pre-foamed and molded polymer foam molded product. One method is to fit it into a metal pipe. However, all of these methods require separate dies and molds for a wide variety of metal pipes with complex shapes and different diameters, which is irrational.
Further, in order to impart functions such as abrasion resistance, flame retardance, and adhesion to the foam layer, more complicated and difficult work is required. In light of the above circumstances, the present inventors have already filed a patent application in 1970-
In Japanese Patent No. 63788, a method of covering a foamed article was discovered by covering the article to be coated with a sheet-like material that can be shrunk and foamed by heating, and then heating and foaming.

According to this method, the efficiency of manufacturing foam-coated pipes, head throats, etc. is greatly improved compared to the conventional method. However, depending on the usage method and location, when abrasion resistance, flame retardance, adhesion, etc. are required, the above-mentioned foamable plastic sheet that can shrink when heated cannot be used, for example, to improve abrasion resistance. However, it is necessary to improve the abrasion resistance of the sheet itself, and there are many difficulties in improving the abrasion resistance without reducing the foaming properties, such as the selection of the basic resin. The same applies to flame retardancy, adhesion, etc. This invention does not have the above-mentioned drawbacks, that is, does not require a large number of dies or molds depending on the shape of the article to be coated, and can be coated on the article to be coated and easily shrink and shrink by heating. Not only can it be covered with foamed polymer foam, but it also has wear resistance,
The object of the present invention is to provide a heat-shrinkable multilayer foam sheet that can easily impart functions such as flame retardancy and adhesion.

That is, the present invention relates to a heat-shrinkable multilayer foamable sheet, which is formed by providing a functional plastic layer on at least one side of a heat-shrinkable foamable plastic sheet.

The heat-shrinkable multilayer foamable sheet according to the present invention is a foamable sheet obtained by extruding or calendering a thermoplastic polymer mixed with a blowing agent and kneaded at a temperature below the decomposition temperature of the blowing agent. Plastic sheets with features such as hardness, flame retardancy, and adhesion are laminated using a laminating roll, hot press, etc. to create a multilayer structure.
After that, it can be stretched and manufactured.

In addition, the heat-shrinkable multilayer foam sheet of the present invention is produced by separately melting and extruding a foamable composition obtained by blending and kneading a foaming agent into a thermoplastic polymer and a functional plastic as two streams (foamable composition The temperature is adjusted to prevent the foaming agent inside from decomposing.

) and these two flows are guided into a single die, and an unstretched product is obtained by a melt extrusion method consisting of a step of thermally bonding them in a molten state, and a step of extruding this bonded material from the die, and then stretched. It can also be obtained by Stretching may be carried out using a normal stretching machine, preferably uniaxial stretching, and the stretching ratio is usually 1.2 to 5 times, preferably 1.5.
It is said to be ~3 times as much.

Of course, biaxial stretching may be used depending on the case. This stretching imparts heat shrinkability. Examples of heat-shrinkable multilayer foamable sheets obtained according to the present invention are shown in FIGS. 1 and 2.

In the figure, 1 is a stretched foamed plastic sheet, 2
, 2' are functional plastic layers.

The arrow line in the figure indicates the stretching direction. In order to cover an article (for example, a rod-shaped object) with the heat-shrinkable multilayer foam sheet of the present invention, for example, when a twist-resistant polymer such as chlorinated polyethylene is used as the functional plastic layer shown in FIG. After wrapping the polymer layer on the outside in a sushi roll as shown in Figure 3 and welding the peripheral ends, it shrinks and foams to cover the rod when heated above the decomposition temperature of the foaming agent. do.

Note that instead of welding, adhesive tape may be used for temporary fixing. Further, when the heat-shrinkable multilayer foam sheet is spirally wound around the rod-shaped object, the ends may be welded or adhered with adhesive tape or the like and then heated.

At this time, it is preferable that the functional plastic layer softens or softens and flows at the foaming temperature of the expandable plastic in the heat-shrinkable multilayer foamable sheet. In FIG. 3, R is a rod-shaped body, and 10 is a heat-shrinkable multilayer foam sheet.

Thermoplastic polymers used in the production of the expandable plastic sheet in the present invention include polyethylene, chlorinated polyethylene, ethylene vinyl acetate copolymer, polypropylene, polystyrene, polyvinyl chloride, ethylene propylene terpolymer, nitrile rubber, butyl rubber,
Examples include polymers whose strain can be frozen by stretching, such as and mixtures thereof.

In addition, blowing agents to be added to these thermoplastic polymers include azo compounds such as azodicarbonamide and azobisisobutyronitrile, nitroso compounds such as dinitrosopentamethylenetetramine, paratoluenesulfonylhydrazide, 4.4 Examples include sulfonyl hydrazide compounds such as '-oxybisbenzenesulfonyl hydrazide, whose decomposition temperature is higher than the softening point of the thermoplastic polymer, and which do not decompose at all or hardly during molding such as extrusion. Select and use things.
Typical examples of foaming aids that can be used in combination with the above foaming agents include urea and metal salts of carboxylic acids. The amount of foaming agent and foaming aid used must be determined appropriately depending on the type of heat-shrinkable multilayer foaming sheet so that a predetermined expansion ratio can be obtained when the sheet is foamed. The amount may be 0.1 to 20 parts by weight per 100 parts by weight of the plastic polymer. Specific examples of various additives that may be added as necessary include fillers such as talc, clay, silica, alumina, barium sulfate, metal powder, glass beads, and short glass fibers, and colorants such as titanium oxide, carbon, and phthalocyanine. Pigments and dyes such as Blue, Mapikoi Eroichi (manufactured by Titan Kogyo Co., Ltd., trade name), Shinka Shaared (manufactured by DuPont, trade name), etc.
As anti-aging agents and stabilizers, phenolic compounds such as 2,6-ditertiarybutyl-4-methylphenol and salicylic acid, and amine compounds such as phenyl-β-naphthylamine and phenyl-α-naphthylamine are used as crosslinking agents. and peroxides such as dicumyl peroxide, lauryl peroxide, benzoyl peroxide, and methyl ethyl ketone peroxide, thiuram compounds such as tetramethylthiuram monosulfide, zinc dimethyl dithiocarbamate, pipecoline piperium, and dithiocarbamate as crosslinking accelerators. Examples include dithiocarbamate compounds such as carbamates. The blending ratio of these various additives is usually about 0.1 to 3 parts by weight in total per 100 parts by weight of the thermoplastic polymer.
It is preferable that the amount be in parts by weight. The thickness of the foamable plastic sheet used in the present invention is usually about 0.
It has a relative flexibility of about 0.05 to 2.0 mm, and easily shrinks and foams when heated.

The crosslinking treatment described above may be performed by irradiation with ionizing radiation such as electron beams or gamma rays, and the irradiation can also be performed after laminating (or adhering) the foamable plastic sheet and the functional plastic layer. be able to.

In the present invention, a functional plastic layer is provided on at least one side of the foamable plastic sheet in order to impart various functions such as abrasion resistance, twist resistance, weather resistance, adhesiveness, and surface hardness.

Plastics used to provide the functional plastic layer include polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, polyvinyl chloride, chlorinated polyethylene, polyester, acrylonitrile-butylene-styrene copolymer, ethylene-acrylic acid. Examples include ionomers, ethylene-ethyl acrylate copolymers, and the like.

Particularly when imparting an adhesive function, it is preferable to add a tackifying agent such as a terpene resin to the resin. Furthermore, in order to impart functions such as wear resistance and surface hardness, it is preferable to add a filler or the like to the resin. In addition, in order to impart a flame retardant function, a flame retardant, a filler, etc. are added to the resin, preferably a halogen-containing polymer such as polyvinyl chloride or chlorinated polyethylene. The heat-shrinkable multilayer foam sheet of the present invention is cut to a predetermined length as necessary, and is applied to the article to be covered in the form of a tube.

This coating is carried out by bending the sheet, for example, in a sushi roll shape, along the surface of the article to be coated, winding it in one or more layers, and gluing the peripheral edges. The above bending is preferably carried out along the stretching direction of the heat-shrinkable multilayer foam sheet, so that the heated sheet after wrapping will cause the wound sheet to turn inward. Heat shrinks easily. The peripheral edges may be bonded, for example, by heat fusion or by using a suitable adhesive. At this time, when using a heat-shrinkable multilayer foam sheet made of a material with excellent abrasion resistance, twist resistance, and weather resistance as the functional plastic layer, it is sufficient to wind the sheet so that the plastic layer is on the outer surface. When a functional plastic layer with excellent adhesive properties is used, it is sufficient to wind it so that the plastic layer is on the inside, and the selection can be made depending on the purpose.

It goes without saying that the article may be wound in a spiral manner.

Next, the covered heat-shrinkable multilayer foam sheet is heated at a temperature higher than the softening point of the thermoplastic polymer to cause it to shrink and foam.

Due to this heating, the sheet thermally shrinks and expands in a three-dimensional direction in a softened state, and the expansion pressure caused by the thermal contraction and foaming causes the inner circumferential surface of the sheet to adhere to the surface of the object to be coated, and then The two-dimensional direction also expands in the outer diameter direction,
The surface of the object to be coated can eventually be provided with a foamed coating layer. At this time, for example, if both adhesion and abrasion resistance are required, a functional plastic layer with excellent adhesion is provided on one side of the foamed plastic sheet.
It is preferable to provide a functional plastic layer with excellent abrasion resistance on the other side, and provide a foam coating layer in the same manner as described above.

When the sheet of the present invention is used, a foamed coating layer can be applied to the surface of the article to be coated, and functions such as heat retention, insulation, cushioning, protection, sealing, and buoyancy can be imparted to the surface of the article.

Further, the surface of the foamed coating layer can be imparted with characteristics of wear resistance, surface hardness, and flame retardancy, and adhesion to the article to be coated can also be improved. On the other hand, a method of covering the outer periphery of pipes, etc. with resin wire containing a foaming agent was published in
Although it is described in No. 09, this uses unstretched resin wire, and with this method, during heating coating,
Since foaming occurs after it is detached from the surface of the wire pipe due to its own weight, a foamed layer with a good appearance cannot be obtained.

As described above, the heat-shrinkable multilayer foamable sheet of the present invention is made into a polymer foam by covering the article to be coated in a tube shape and then shrinking and foaming it by heating. Therefore, there is no need for various types of dies and molds depending on the shape of the article to be coated as in the conventional method, and therefore, the method is much more advantageous than the conventional method. .

Moreover, since the heat-shrinkable multilayer foam sheet is relatively flexible, it can be easily coated regardless of the shape of the article to be coated, and the sheet itself can be easily coated during heating after coating. The polymer foam to be formed can be firmly attached to the surface of the article to be coated by utilizing the heat shrinkability and the expansion force of foaming, so it can be used not only for ordinary articles to be coated such as pipes and rods but also for objects with complex shapes. A foam coating layer can be easily applied to pipes (T-shaped, elbow-shaped, vent-shaped, etc.) and their accessories (valve, strainer, etc.). In addition, in the present invention, the heat-shrinkable multilayer foam sheet described above is bent so that its stretching direction (usually the larger stretching ratio in the case of a biaxially stretched product) becomes the circumferential direction.
It is also possible to form a heat-shrinkable multilayer foam tube by winding the tube into a layer or two or more layers and bonding (welding, etc.) the peripheral edges.

When this tube is used to coat an article, a foamed coating layer can be obtained by simply inserting it into the article and heating and foaming it.

Examples of heat-shrinkable multilayer foam tubes are shown in FIGS. 4 to 6.

In the drawing, 21 is a functional plastic layer with good flame retardancy, 22 is a functional plastic layer with good heat adhesion, and 23 is a functional plastic layer with good flame retardancy.
3 is a functional plastic layer with good abrasion resistance, and 31 is a dotted line indicating a welded portion.

The present invention will be specifically described below using examples. In addition, parts in the examples are parts by weight. In addition, in the following Examples, Examples 2, 3, 4, 6, 7, and 8 indicate that at least one
Two functional plastic layers have the ability to shrink when heated. Example 1 Polyethylene (Milason 11, manufactured by Mitsui Polychemical Co., Ltd.)
100 parts, foaming agent (manufactured by Eiwa Kasei Co., Ltd., Spansel DS#2
5) A foamable resin composition consisting of 8 parts and 1 part of a crosslinking agent (dicumyl peroxide), and an ethylene vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd., Evaflex #220)
) and an adhesive resin composition consisting of 20 parts of a terpene resin (YS Resin P-1000, manufactured by Yasushi Oil Co., Ltd.) were respectively heated and melted and simultaneously extruded using a two-layer extruder to obtain a 0.8 mm thick adhesive resin composition. It is made into a foamable two-layer sheet.

The thickness of the foamable plastic sheet was 0.7 mm, and the thickness of the adhesive resin layer was 0.17 nm. The obtained foamable two-layer sheet was uniaxially stretched in the length direction at a roll temperature of 60° C. using a roll stretching machine (stretching ratio: 2 times) to produce a heat-shrinkable multilayer foamable sheet.

This heat-shrinkable multilayer foam sheet is 5mm long in length. Cut the steel pipe to a width of (outer diameter 3 (S-J mo V!, inner diameter 2.5
) was spirally half-wrapped with the adhesive resin layer on the inside, the edges of the sheet were fixed with adhesive tape, and then heated at 200° C. for 5 minutes to cause contraction and foaming.

As a result, a foam-coated steel pipe was obtained that had good elasticity and heat insulation properties, and also had very good adhesion to the steel pipe. Note that the heat-shrinkable multilayer foam sheet was not wound in a spiral shape as described above, but was bent into a sushi-waki shape and wound around a steel pipe, the peripheral end was heat-sealed, and then heated at 200 ° C. for 5 minutes. After shrinking and foaming, a foam-coated steel pipe with good adhesion similar to the above was obtained.

Example 2 Ethylene vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd.,
A foamable plastic sheet (thickness: 0.5TILTL) was made by extrusion molding from 100 parts of EVAFLEX P-1405), 10 parts of a foaming agent (manufactured by Eiwa Kasei Co., Ltd., Vinyhole DW#6), and 1 part of a crosslinking agent (dicumyl peroxide). was manufactured.

On the other hand, polypropylene (Mitsui Petrochemical Co., Ltd., F4Ol)
was formed into a sheet using an extrusion molding machine (thickness: 0.1 mm), and laminated with the foamable plastic sheet using a laminating roll. The obtained foamable two-layer sheet was uniaxially stretched in the length direction using a stretching machine (stretching ratio: 1.5 times) to produce a heat-shrinkable multilayer foamable sheet (thickness: 0.4 mm). The obtained heat-shrinkable multilayer foam sheet was cut into a width of 3 CTrL in the length direction, and a 90-degree elbow for water pipes (outer diameter 33 mm, inner diameter 2
A foam-coated 90-degree elbow was manufactured by spirally winding the polypropylene layer around 9m0 and heating it at 190° C. for 5 minutes. Generally, it is difficult to cover objects with complex shapes with foam, but by using a heat-shrinkable multilayer foam sheet, it is possible to manufacture foam-covered elbows that are both easy to work with and have a good appearance. Summer.

The foam layer obtained had a foaming ratio of about 12 times, had good heat insulation properties and cushioning properties, and had a polypropylene layer on the skin side, so it had good abrasion resistance and surface hardness. Example 3 Polyethylene (manufactured by Sumitomo Chemical Co., Ltd., Sumikasen G2Ol) 1
00 parts and foaming agent (manufactured by Eiwa Kasei Co., Ltd., Vinyhole AC#1)
After melt-kneading 8 parts, use an extruder to form a sheet (thickness 0
．． 67nm) and using an electron beam accelerator to
A foamable plastic sheet was produced by crosslinking treatment by irradiating 4 Mrad with an electron beam of 15 mmA.

On the other hand, a flame retardant sheet (thickness 0.2
m0 was prepared, and this and the above-mentioned foamable plastic sheet were laminated using a laminating roll to produce a foamable two-layer sheet. The obtained foamable two-layer sheet was uniaxially stretched in the length direction at a roll temperature of 80°C using a roll stretching machine (stretching ratio: 1.8 times) to obtain a heat-shrinkable multilayer foaming sheet (thickness: 0.44
mm) was manufactured. This heat-shrinkable multilayer foam sheet was cut into a size of 4crrL in width in the length direction, and a flame-retardant sheet layer was placed on an aluminum tube (outer diameter 2 (1-J mo V1, inner diameter 1.6C!RL)). After wrapping it in a spiral shape so that it is on the outside, fix the wrapped end with adhesive tape,
A foam-coated aluminum tube was produced by heating at .degree. C. for 5 minutes.

The foam layer thus obtained had a foaming ratio of about 11 times and had good heat insulation and cushioning properties. In addition, the skin layer had a flame-retardant resin layer, making it flame-retardant as a whole. The polyethylene foam-coated aluminum tube whose surface had been flame-retardant treated in this manner was exposed to a flame using a burner in accordance with ASTM D1692-74, and the time until ignition was measured, and it was 110 seconds. On the other hand, a foam-coated aluminum tube obtained by the same method as in this example except that no flame-retardant sheet was used was exposed to a flame and the time required for ignition was measured in the same manner. It was hot in seconds.

As is clear from the above, it can be seen that the flame retardant properties are greatly improved by forming the two-layer structure with the flame retardant sheet layer.

Example 4 High-density polyethylene (manufactured by Mitsui Petrochemical Co., Ltd., Hi-Zex 3300F) was formed into a sheet by extrusion molding (thickness 0.
1 mm), this sheet and the polyethylene foam sheet side of the foamable two-layer sheet obtained in Example 1 were brought into contact and adhered using a laminating roll to produce a foamable three-layer sheet.

The obtained foamable three-layer sheet was stretched in the length direction using a roll stretching machine (stretching ratio: 2 times) to produce a heat-shrinkable multilayer foamable sheet. This heat-shrinkable multilayer foam sheet was cut lengthwise into a width of 5CTIL and wound in a spiral shape around a steel tube (outer diameter 3CTIL, inner diameter 2.5CTIL) with the adhesive resin layer on the inside and the high-density polyethylene layer on the outside. The terminals were temporarily fixed with adhesive tape and heated at 200° C. for 5 minutes to cause shrinkage and foaming.

As a result, foam-coated steel pipes with good cushioning and thermal insulation properties, as well as very good adhesion to steel pipes, have a layer of high-density polyethylene on the skin side, and have good wear resistance and surface hardness. I was able to get it. Example 5 The heat-shrinkable multilayer foam sheet obtained in Example 1 was placed so that the adhesive resin layer was on the inside, and one end was bent along the stretching direction to the corresponding other end, and the above-mentioned both ends were Adhered by heat fusion to an inner diameter of 5.0 cm. Thickness 0.4 mm, length 4
A heat-shrinkable multilayer foam tube as shown in FIG. 5 of 0(1-JMoV!) was obtained.

The resulting heat-shrinkable multilayer foam tube has an outer diameter of 4.0 CT.
When a steel pipe with fL1 inner diameter of 3.5Cr1L1 and length of 50CTrL was searched and heated at 200TC for 5 minutes to shrink and foam, a polymer foam layer with very good adhesion to the steel pipe surface and excellent appearance was formed. It was done.

Example 6 Using the heat-shrinkable multilayer foam sheet obtained in Example 2, in the same manner as described in Example 5,
With the polypropylene layer on the outside, the inner diameter is 5.5
CT! A heat-shrinkable multilayer foam tube with a length of 40 cm and a thickness of 0.4 m was obtained.

The obtained tube was cut to a length of 10 CTn, and a 90-degree elbow for water pipes (outer diameter 33 mm, inner diameter 29 mm) was attached to it.
They investigated and covered the 90 degree elbow with the tube.

The tube was then heated at 1900C for 5 minutes to produce a foam coated 90 degree elbow. Generally, it is difficult to cover articles with complicated shapes with foam, but by using the heat-shrinkable multilayer foam tube of the present invention, a foam-coated elbow with good workability and a good appearance can be manufactured. became possible. The resulting foam-covered elbow had good heat insulation and cushioning properties, and because it had a polypropylene layer on the skin side, it had good abrasion resistance and surface hardness. Example 7 Using the heat-shrinkable multilayer foam sheet obtained in Example 3, the inner diameter was 2.5° in the same manner as described in Example 5, with the flame-retardant sheet side facing outward. A heat-shrinkable multilayer foam tube with a thickness of 0.44 cm and a length of 40 (V7 l) was obtained.

Insert an aluminum tube (outer diameter 2 (1-J model) into the obtained tube.
V! , inner diameter 1.6 cIrL, length 50 cm), and the aluminum tube was covered with the tube. Thereafter, the mixture was heated at 220° C. for 5 minutes to produce a foam-coated aluminum tube. The foam layer thus obtained had a foaming ratio of about 11 times and had good heat insulation and cushioning properties. In addition, the skin layer had a flame-retardant resin layer, making it flame-retardant as a whole. The polyethylene foam-coated aluminum tube whose surface had been flame-retardant treated in this manner was exposed to a flame using a burner in accordance with ASTM D169274, and the time it took to ignite was measured, which was a good 110 seconds. Example 8 Using the heat-shrinkable multilayer foam sheet obtained in Example 4, the adhesive resin layer was placed on the inside in the same manner as described in Example 5, and the inner diameter was 5.0? , thickness 0.457
F! 77! A heat-shrinkable multilayer foam tube with a length of 40 CTIL was obtained.

The resulting heat-shrinkable multilayer foam tube has an outer diameter of 4.0C!
RLl inner diameter 3.5CT! A steel pipe with an L1 length of 50 CfL was found and the tube was fitted onto the steel pipe.

Thereafter, it was heated at 200° C. for 5 minutes to shrink and foam. The resulting foam-coated steel pipe has good cushioning and heat insulation properties, and has very good adhesion to the steel pipe.Furthermore, since it has a layer of high-density polyethylene on the skin side, it has excellent wear resistance and
Both surface hardness was good.

[Brief explanation of drawings]

1 and 2 are partially cutaway perspective views of a heat-shrinkable multilayer foam sheet showing an example of the present invention. FIG. 3 is an explanatory diagram for explaining an example of covering an article using the heat-shrinkable multilayer foamable sheet of the present invention. 4 to 6 are partially cutaway perspective views of a heat-shrinkable multilayer foam tube showing an example of the present invention. 1...Stretched foamable plastic sheet, 2, 2', 21, 22,
23...Functional plastic layer.

Claims (1)

[Scope of Claims] 1. A heat-shrinkable multilayer foamable sheet consisting of a heat-shrinkable foamable plastic sheet provided with a functional plastic layer on at least one side thereof is bent so that its stretching direction is in the circumferential direction. A heat-shrinkable multilayer foam tube made by winding one layer or two or more layers and gluing the edges. 2. The heat-shrinkable multilayer foam tube according to claim 1, wherein the functional plastic layer is shrinkable when heated.