JPS583818B2 - How to cover objects - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coating objects to be coated, such as pipes, rods, etc., with polymeric foam.

In recent years, various products have been used for purposes such as insulation and heat retention, which are made by coating the outer periphery of pipes with polymeric foam. Covered pipes and other products have been well received.

Conventionally, this type of coating method has been put to practical use.

Methods include extrusion molding a polymer foam layer of a required thickness around the outer periphery of a metal pipe using an extrusion molding machine, or fitting a polymer foam molded product that has been foamed and molded in advance into a metal pipe.

However, all of these methods require separate dies and forming molds for a wide variety of metal pipes with complex shapes and different diameters, which is irrational. A new and useful coating method that does not require a large number of dies or molds depending on the shape of the object, and can successfully coat the object to be coated with a polymer foam regardless of its shape. We aim to provide the following.

That is, in this invention, a foaming tube is made by extrusion molding a thermoplastic polymer mixed with a blowing agent and kneaded, and after coating various objects such as metal pipes to be coated, the softening point of the thermoplastic polymer is The method is characterized in that the foamable tube is heated and foamed at a temperature above.

In this invention, first a foamable tube is made.

The term "foamable tube" here refers to a tube that usually has an inner diameter slightly larger than the outer diameter of the object and has a wall thickness of about 0.1 to 1.5 mm so that it can be easily coated on the object to be covered. Refers to a flexible tubular polymer molded product that foams to become a polymer foam when heated above the decomposition temperature of the foaming agent.

Therefore, this type of tube is made by blending a thermoplastic polymer with a blowing agent and, if necessary, various additives such as a blowing aid, a filler, a coloring agent, an anti-aging agent, a stabilizer, a crosslinking agent, and a crosslinking accelerator. The mixture is kneaded using a mixing roll or an extruder, pelletized using a pelletizer, and then extruded using an extruder under conditions where the blowing agent is not decomposed at all or hardly.

Thermoplastic polymers used to manufacture the above-mentioned expandable tube include polyethylene, ethylene-vinyl acetate copolymer, polypropylene, polystyrene, polyvinyl chloride,
Examples include 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 dinitrone pentamethylenetetramine, and sulfonyl hydroxides such as paratoluenesulfonylhydrazide. Among them, one or more compounds whose decomposition temperature is higher than the softening point of the thermoplastic polymer and which do not decompose at all or hardly during extrusion molding are selected and used.

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

Specific examples of various additives that may be added as necessary include:
Fillers such as talc, clay, silica, alumina, barium sulfate, metal powder, and short glass fibers are used as colorants. Pigments and dyes such as titanium oxide, carbon, phthalocyanine blue, Mavico Yellow (manufactured by Titanium Kogyo Co., Ltd., trade name) and Shinryoku Charred (manufactured by DuPont, trade name) are added to 2.6 ditertiary as anti-aging agents and stabilizers. Phenol compounds such as butyl-4-methylphenol and salicylic acid, amine compounds such as phenyl-β-naphthylamine and phenyl-α-naphthylamine, etc. are used as crosslinking agents and crosslinking accelerators such as dicumyl peroxide, lauryl peroxide, and penzoyl peroxide. , peroxides such as methyl ethyl ketone peroxide, thiuram compounds such as tetramethylthiuram disulfide and tetramethylthiuram monosulfide, and dithiocarbamate compounds such as zinc dimethyldithiocarbamate and dithiocarbamate.

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.

In the present invention, such a foamed tube is coated on an object to be coated, such as a pipe or rod.

The covering means may be arbitrary, and may be carried out by, for example, inserting the object to be covered into a foam tube, or fitting the foam tube into the object depending on the shape of the object to be covered. In this case, since the foam tube has flexibility as described above, it can be easily coated even if the shape of the object to be coated is complex.

In this invention, the covered expandable tube is then heated at a temperature higher than the softening point of the thermoplastic jellymer to foam it.

Through this heat treatment, the foamable tube foams in a softened state and expands in a three-dimensional direction, and due to this expansion pressure, its inner circumferential surface first adheres to the outer circumferential surface of the object to be coated, and then it expands in a two-dimensional direction. It expands mainly in the outer diameter direction and becomes a polymer foam having a predetermined expansion ratio after a predetermined time.

The polymer foam thus formed is firmly adhered to the object to be coated, such as a pipe or rod, and effectively provides various functions such as heat retention, insulation, cushioning, protection, and floating to the object. It is something that can be granted.

As detailed above, the method of this invention is to cover an object to be coated with a foamable tube made by extrusion molding, and then heat and foam the tube to form a polymer foam. If the tube is properly regulated, it can be easily coated on the object to be coated by utilizing the flexibility of the tube itself.
Moreover, regarding the regulation of the inner diameter of the tube, the inner diameter dimensions are not so strictly required, and therefore, the conventional method described above requires many types of dies and molding molds depending on the shape of the object to be coated. It can be implemented much more advantageously than .

Furthermore, in this invention, the formed polymer foam adheres to the object to be covered by the expansion force generated by the foaming of the foaming tube, which has been softened during the formation process. The gap between the plastic tube and the object is well filled with the polymer foam, resulting in good adhesion between the object to be covered and the polymer foam, and the appearance also improves. Becomes good.

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:
Sumiriki Seven F-208-1, softening point: 95°C) 100 parts, foaming agent (manufactured by Eiwa Kasei Co., Ltd., product name: Vinyhole A)
C≠1) 7 parts and crosslinking agent (dicumyl peroxide)
1 part is kneaded with a mixing roll, then pelletized with a pelletizer, and molded with an extruder at a molding temperature where the blowing agent does not decompose, for example, 160 to iso ℃, a thickness of 550μ,
Make a foam tube with an inner diameter of 22 mm.

A steel pipe with an outer diameter of 18rIrrrL1 and an inner diameter of 16mm was inserted into this tube, and the tube was covered with the steel pipe.The tube was then heated at 220°C for 10 minutes to foam, and it adhered well to the outer circumferential surface of the steel pipe. A polymer foam with excellent elasticity was formed.

The above polymer foam has a foaming ratio of 10 times and has excellent heat insulation and cushioning properties.

Example 2 100 parts of polyethylene (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumikasen L-705, softening point: 86°C), 6 parts of a foaming agent (manufactured by Sankyo Kasei Co., Ltd., trade name: Cellmic A), foaming aid (Manufactured by Sankyo Kasei Co., Ltd., product name: Selton NP) 2
1 part and a crosslinking agent (dicumyl peroxide) are kneaded with a mixing roll, pelletized with a pelletizer, and extruded at a molding temperature such as 110 to 130°C at which the blowing agent does not decompose, with a thickness of 430 μm and an inner diameter of 20 Make a foam tube.

An aluminum tube with an outer diameter of 18 mm and an inner diameter of 16 mm was inserted into this tube, and the tube was covered with the aluminum tube.The tube was then heated at 180°C for 5 minutes to foam, and the outer circumferential surface of the aluminum tube A well-adhered polymeric foam with a foaming ratio of 5 times and excellent heat insulation and cushioning properties was formed.

Example 3 Ethylene vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd., trade name: Evaflex P1907, softening point 59
°C) 100 parts, foaming agent (manufactured by Sankyo Kasei Co., Ltd.: Product name:
After kneading 10 parts of Cellmic CAP) and 1 part of a crosslinking agent (dicumyl peroxide) using a mixing roll, the molding temperature of the extruder is 100 to 110°C, at which the foaming agent does not decompose, and the thickness is 520 μm and the inner diameter is 12 mm. Make a foam tube.

A glass fiber-reinforced plastic rod with a diameter of 10 mm was inserted into this tube, and the tube was covered with the rod.The tube was then heated at 150°C for 10 minutes to foam, and it adhered well to the rod surface. A polymeric foam with an expanded expansion ratio of 8 times was formed.

The glass fiber reinforced plastic rod coated with this polymeric foam had a very light specific gravity and was able to float sufficiently on the water surface.

Claims (1)

[Claims] 1. After covering an object to be coated with a foamable tube obtained by extrusion molding a thermoplastic polymer mixed with a foaming agent and kneaded, the tube is heated and foamed at a temperature higher than the softening point of the thermoplastic polymer. A method for coating an object, characterized by: