JPS5820775B2 - Method for manufacturing foamable heat expandable tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foamable expandable tube that easily expands and foams when heated and can form a polymeric foam with good adhesion and appearance on the inner surface of a covering object such as a pipe. .

In recent years, products made by coating the inner surface of pipes with polymeric foam for purposes such as insulation, heat retention, and cushioning have been used for powder transport pipes in pipelines. For example, products coated with urethane foam on the inner surface of steel pipes Bonded pipes are used.

Conventionally, this type of coating method has been put to practical use, such as a method in which a polymer foam molded product, which has been foamed and molded in advance, is fitted into a pipe such as 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, and are irrational.

The present invention does not have these drawbacks, that is, it does not require a large number of dies or molds depending on the shape of the object to be coated, and can be inserted into the object to be coated, easily expanded by heating, and foamed. It is an object of the present invention to provide a foamable expansion tube that can be made into a polymeric foam with excellent adhesion and appearance.

That is, the present invention provides a foamable heat-recoverable sheet obtained by stretching a foamable sheet molded product of a thermoplastic polymer blended and kneaded with a blowing agent so that the longitudinal direction of the resulting tube coincides with the stretching direction. This relates to a foamed expansion tube which is formed by bending the tube, winding it into one or more layers, and gluing the peripheral ends of the tube.

In this invention, first, a foamable sheet molded product is made.

The foamed sheet molded product mentioned here has a wall thickness of typically 0.1
It refers to a sheet-like polymer molded product of about 10 r/1 m that foams to become a polymer foam when heated above the decomposition temperature of the blowing agent.

This type of sheet molded product is made by adding a blowing agent and, if necessary, various additives such as a blowing agent, filler, colorant, anti-aging agent, stabilizer, crosslinking agent, and crosslinking aid to a thermoplastic polymer. After compounding and kneading using a mixing roll, extruder, etc., the foaming agent is molded into a sheet using an extrusion molding machine, a calender molding machine, etc. under temperature conditions that are above the softening point of the thermoplastic polymer and the blowing agent does not decompose at all or hardly. I can do it.

When using an extrusion molding machine, it is preferable to pelletize the blended and kneaded product using a pelletizer before extrusion molding.

As the above-mentioned thermoplastic polymer, polymers having a glass transition temperature, crystal melting temperature, second-order transition point, etc. of 50 to 200°C can be used alone or in combination.

Elastic materials such as rubber can also be used in combination with such thermoplastic polymers.

In this case, the content of the thermoplastic polymer in the mixture is usually 30% by weight or more. In short, a polymer is used that will remain distorted when subjected to the stretching operation.

Thermoplastic polymers used for manufacturing the above-mentioned foamable sheet molded products include polyethylene, chlorinated polyethylene,
Examples include ethylene vinyl acetate copolymer, polypropylene, polystyrene, polyvinyl chloride, ethylene propylene terpolymer, nitrile rubber, butyl rubber, acrylonitrile-butadiene-styrene rubber, and the like.

In addition, blowing agents to be incorporated into these thermoplastic polymers include azo compounds such as azodicarbonamide and azobisisobutyronitrile, nitroso compounds such as dinitrosopentamethylenetetramine, paratoluenesulfonyl hydrazide, 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 molding. Select and use.

Representative examples of foaming aids that can be used in combination with the above foaming agents include urea, metal salts of carboxylic acids, and the like.

The amount of foaming agent and foaming aid used must be determined appropriately depending on the type of the foaming expansion tube so that a predetermined expansion ratio can be obtained when foaming the foamable expansion tube.Usually, the total amount mentioned above is The amount may be 1 to 20 parts by weight per 100 parts by weight of the polymer.

Specific examples of various additives that may be added as necessary include:
Talc as a filler.

clay, silica, alumina, barium sulfate, metal powder,
Glass peas, short glass fibers, etc. are mixed with pigments and dyes such as titanium oxide, carbon, phthalocyanine blue, Mapico Yellow (manufactured by Titan Industries Co., Ltd., trade name), and Shinka Jar Red (manufactured by DuPont, trade name) as coloring agents. As anti-aging agents and stabilizers, phenolic compounds Th such as 2,6-di-tert-butyl-4-methylphenol and salicylic acid, and amine compounds such as phenyl-β-naphthylamine and phenyl-α-naphthylamine are used as crosslinkers and As a crosslinking accelerator, peroxides such as dicumyl peroxide, lauryl peroxide, benzoyl peroxide, and methyl ethyl ketone peroxide, thiuram compounds such as tetramethylthiuram monosulfide, and dithiocarbamates such as zinc dimethyl dithiocarbamate and dithiocarbamate are used. Compounds, etc. can be mentioned respectively.

The blending ratio of these various additives is usually such that the total amount thereof is about 0.1 to 5 parts by weight per 100 parts by weight of the thermoplastic polymer.

The foamable heat-recoverable sheet of the present invention is obtained by stretching the above-mentioned foamable sheet molded product, and this stretching imparts recovery properties, that is, the property of recovering dimensions by heating.

The stretching may be carried out in a conventional manner by axial stretching using a conventional stretching machine, and the stretching ratio is usually 1.2 to 10 times, preferably 1.2 to 4 times.

The foamable expandable tube of the present invention is obtained by bending the foamable heat-recoverable sheet described above and winding it into one layer or two or more layers.
It is obtained by gluing the peripheral edge.

This bending is preferably carried out so that the longitudinal direction of the resulting tube coincides with the stretching direction, thereby facilitating outward thermal expansion of the resulting tube.

The peripheral edges may be bonded, for example, by heat fusion or by using a suitable adhesive.

When winding a single layer, it is also possible to attach a pair of fasteners to both ends to tie it together.

In addition, according to the present invention, the foamable heat-recoverable sheet is bent and turned and its peripheral edges are bonded to produce the product. Therefore, it is possible to easily produce a foamable expansion tube having an arbitrary inner diameter, and the wall thickness can be freely adjusted. has.

Examples of the present invention are shown in FIGS. 1 to 4.

1 is a foamed expansion tube, and A is an adhesive portion.

In the case of a foamed expansion tube as shown in FIG. 2 or 3, an adhesive may be applied partially or entirely to the contact area between the foamable heat recovery sheets.

In addition, when forming a foamable expanded tube as shown in FIG. 3, the starting end of the foamable heat recovery sheet (the part indicated by 2 in the figure) is glued to the adjacent recovery sheet along the longitudinal direction of the tube. You can also leave it there.

Note that the arrows in the figure do not indicate the direction of stretching.The expanded foamed tube of the present invention obtained in this manner generally has a wall thickness of approximately 0.5 mm.
It has a flexibility of about 0.5 to 20 mm, and easily expands and foams when heated.The following method is used to actually coat an object using this tube.

That is, first, a foamable expansion tube is inserted into a covering object such as a pipe, and then the tube is heated to a temperature equal to or higher than the softening point of the thermoplastic polymer to cause foaming.

Due to this heating, the tube expands thermally and expands (foams) in a three-dimensional direction in a softened state, and due to the expansion pressure caused by the thermal expansion and foaming, the outer surface first adheres firmly to the inner surface of the coating object, and then Expands mostly in two-dimensional directions and in the inner radial direction, eventually forming a polymer foam having a predetermined expansion ratio with good adhesion and appearance on the inner surface of the covering object, and coating the inner surface of the covering object with the foam. become.

As detailed above, the expandable expandable foam tube of the present invention can be made into a single layer or It is made by winding two or more layers and gluing the circumferential ends.As long as the outer diameter of the tube is regulated, the tube can be heated and foamed to form a desired height on the inner surface of the object. A molecular foam layer can be formed, and the outer diameter of the tube can be easily regulated by simply determining the width of the foamable heat recovery sheet after stretching, and should be regulated because the tube itself expands thermally when heated and foamed. There is no problem in the fact that the outer diameter is much smaller than the inner diameter of the covering object, and a particularly strict outer diameter is not required. The inner surface of the coating object can be coated much more advantageously than the above-mentioned conventional method which requires many kinds of diamonds and molding dies.

Moreover, the tube of the present invention is relatively flexible, and as mentioned above, its outer diameter can be made much smaller than the inner diameter of the covering object, so it can be bent as well as ordinary covering objects such as pipes. Even various coating objects with complicated shapes such as tubes can be easily inserted into these objects, and the thermal expandability of the tube itself and the expansion force of foaming are used for heating and foaming after insertion. Since the polymer foam to be formed can be firmly adhered to the inner surface of the coating object, even when the outer diameter of the tube is much smaller than the inner diameter of the coating object, or when coating the inner surface of a coating object with a complex shape, It is possible to form a polymer foam that has good adhesion at all times, with almost no voids formed at the interface between the covering object and the polymer foam to be formed, and as a result, has an excellent appearance.

The tube of the present invention is used to cover the inner surface of a covering object with a polymeric foam having a predetermined expansion ratio, and the foam provides various functions such as heat retention, heat insulation, cushioning, and protection. It can be used for various purposes that make effective use of.

In addition, in the present invention, in order to improve the adhesion of the outer surface of the above-mentioned foamed expansion tube, and to improve the abrasion resistance and surface hardness of the inner surface, functionalities are added to the inner or outer surface or both the inner and outer surfaces of the expansion tube. A layer of material can be provided.

A foamable expanding tube with a functional material layer can be manufactured by, for example, providing a functional material layer on a previously obtained foaming expanding tube by a coating method.

In addition, the functional material layer is prepared in the form of a tube, which is fitted into a foamed expandable tube to form a layer, and then, if necessary, a portion of the tube is heated and foamed to be thermally fused. It can also be manufactured.

As the functional material layer, it is preferable to use a material that softens and adapts when the expandable expandable tube is heated and expanded.

The material used for the functional material layer naturally differs depending on the function to be imparted, and can be selected as appropriate in combination with the material of the foamable expansion tube. For example, it imparts functions such as surface hardness and abrasion resistance to the foam layer. When using various resins such as polyethylene, polypropylene, polyester, polyamide, polyimide, etc., or mixtures of these resins with fillers, etc., when adding flame retardant function, use halogen-containing polymers such as polyvinyl chloride and chlorinated polyethylene. It is preferable to use ethylene-vinyl acetate copolymer, ethylene-acrylic acid ionomer, ethylene-acrylic acid ionomer, etc. to improve adhesion to the inner surface of the coating object. Examples include various resins with good adhesiveness such as ethyl acid copolymers, or resins to which adhesion agents such as terpene resins and rosin resins are added.

Whether such a functional material layer is provided on the inner surface or the outer surface of the foamed expansion tube depends on each function. If you want weather resistance, flame retardancy, etc., you can usually provide it on the inner surface, and if you want to provide both of these functions, you can provide it on both the inside and outside surfaces.

Next, the present invention will be explained in more detail with reference to Examples.

In addition, in the following, parts indicate parts by weight.

Example 1 Polyethylene pellets (manufactured by Sumitomo Chemical Co., Ltd., product name:
After kneading 100 parts of Sumikasen F-208-1), 7 foaming agents (Vinihole AC#1 manufactured by Eiwa Kasei Co., Ltd.) and 1 part of a crosslinking agent (dicumyl peroxide) using a mixing roll, pellets were formed using a pelletizer. and use an extrusion molding machine (T-type die) at a die temperature of 160 to 180°C where the blowing agent does not decompose, with a thickness of 0.1 mm and a width of 40 CrrL.
Create foam sheet molded products.

This sheet molded product is processed by a roll stretching machine at a roll temperature of 80°C.
It is uniaxially stretched in the longitudinal direction at a stretching ratio of 2 times at °C to obtain a foamable heat-recoverable sheet having a thickness of 0.7 mm and a width of 28 crrL.

After cutting the above sheet to an appropriate length, bend one end to the corresponding other end, and adhere both ends by heat fusion to form a sheet with an outer diameter of 90 mm and a thickness of 0.7 mm. Figure 1) A foamable expansion tube as shown.

Obtained.

The obtained expanded foam tube was cut into 50 pieces, each having an outer diameter of 114.3 cfrL, a wall thickness of 4.5 mm, and a length of 4 mm.
After inserting the tube into a steel tube of 0.00℃, heat the tube to 220℃.
When heated for 10 minutes to foam, a polymer foam with excellent adhesiveness and appearance was formed on the inner surface of the steel pipe.

This foam had an expansion ratio of 9 times and had excellent heat insulation and cushioning properties.

Example 2 Ethylene vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd., trade name: Evaflex P190+7) 100
After kneading 10 parts of a blowing agent (manufactured by Sankyo Kasei Co., Ltd., trade name: Cellmic CAP) and 1 part of a crosslinking agent (dicumyl peroxide) using a mixing roll, the mixture was kneaded using a mixing roll. A foamed sheet molded product with a thickness of 1.5 mm and a width of 40 mm is made at a temperature of 110°C.

This sheet molded product is processed by a roll stretching machine at a roll temperature of 60°C.
Uniaxially stretched at ℃ to a stretching ratio of 25 times to a thickness of 0.
．． A foamable heat-recoverable sheet with a width of 6 mm and a width of 25.3 CrrL was prepared.

The sheet was bent so that the length direction of the obtained tube coincided with the stretching direction, and the side ends were heat-sealed, and the outer diameter was 38 mm.
A foamed expanding tube as shown in FIG. 2 with a wall thickness of 1.2 mm and a wall thickness of 1.2 mm was obtained.

The length of the obtained foamed expansion tube was 150 WtrIL.
When the tube was cut into pieces and inserted into a reducer (nominal diameter: 2X1-) specified in JIS B 2304, the tube was heated at 150°C for 10 minutes to foam, and the foaming ratio was 10 times the inner surface of the reducer. A polymer foam with good heat insulation and cushioning properties, excellent adhesion and appearance was formed.

[Brief explanation of the drawing]

1 to 4 are perspective views of a foamable expansion tube showing an example of the present invention. 1... Foaming expansion tube, A...
Adhesive part.

Claims (1)

[Claims] 1 A foamable heat-recoverable sheet obtained by stretching a foamable sheet molded product of a thermoplastic polymer blended and kneaded with a blowing agent is bent so that the longitudinal direction of the obtained tube coincides with the stretching direction. A method for producing a foamable expanding tube, which is formed by winding the tube into one layer or two or more layers and gluing the peripheral edges of the tube.