JP7122380B2 - Heat-shrinkable tube for decorating metal tube, decorated metal tube, and method for manufacturing decorated metal tube - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to a heat-shrinkable tube for decorating a metal pipe, a decorated metal pipe, and a method for manufacturing a decorated metal pipe. This application claims priority based on Japanese Application No. 2018-132730 filed on July 12, 2018, and incorporates all the content described in the above Japanese Application.

BACKGROUND ART Conventionally, painting, printing, and the like have been performed as means for decorating metal materials such as metal pipes and food cans. Since the coating film formed by this coating is rigid and has low toughness, there is a risk of chipping or peeling due to an impact. Moreover, the technique of applying a coating not only requires a complicated baking process, but also requires a long processing time, which is disadvantageous in that the manufacturing cost increases.

Therefore, as an alternative to painting for surface decoration, a technology related to a sheet-like decorative film that can be attached to a three-dimensional curved surface has been proposed (see Japanese Patent Application Laid-Open No. 2017-205962).

JP 2017-205962 A

A heat-shrinkable tube for decorating a metal pipe according to one aspect of the present disclosure is composed of a single-layer heat-shrinkable layer containing a base resin containing an acid-modified resin and a filler, and is bonded to the acid-modified resin for the base resin. The content of the acid component is 0.4% by mass or more and 1.2% by mass or less, and the arithmetic mean roughness Ra of the inner surface is 0.1 μm or more and 5.0 μm or less.

A decorated metal pipe according to another aspect of the present disclosure includes a metal pipe and a coating layer formed on an outer surface of a portion to be decorated of the metal pipe, wherein the coating layer is heat for decorating the metal pipe. It is a shrinkable body obtained by heating a shrinkable tube.

In a method for manufacturing a decorated metal pipe according to yet another aspect of the present disclosure, the heat-shrinkable tube for decorating a metal pipe is covered on the outer surface of a portion to be decorated of the metal pipe, and the coating layer is formed by heat-shrinking it. A step of forming is provided.

1 is a schematic perspective view showing a decorated metal tube according to an embodiment of the present disclosure; FIG.

[Problems to be Solved by the Present Disclosure]
In the method of attaching a sheet-shaped decorative film to a metal material, joints and unnatural thickness unevenness occur at the joints of the decorative film, and complex shapes cannot be followed, resulting in a decrease in tactile sensation and design. be. In addition, since the decorative film has substantially no adhesive strength, it is necessary to provide an adhesive layer. An increase in the thickness of the film may lead to a decrease in tactile sensation and design properties, an increase in cost, and the like.

The present disclosure has been made based on the circumstances as described above. It is an object of the present invention to provide a shrinkable tube, a decorated metal tube with good design, and a method for manufacturing the decorated metal tube.

[Effect of the present disclosure]
The heat-shrinkable tube for decorating a metal pipe according to one aspect of the present disclosure can cover the end portion of the target portion of the metal pipe to be decorated, and can obtain good design. A decorated metal tube according to another aspect of the present disclosure has good designability. A method for manufacturing a decorated metal pipe according to still another aspect of the present disclosure can manufacture a decorated metal pipe with good design and reduce variations in quality.

[Description of Embodiments of the Present Disclosure]
The present inventors have studied a method of decorating a metal pipe using a heat-shrinkable tube that does not cause the joint problem compared to a decorative film. If the heat-shrinkable tube does not have an adhesive layer, the thickness of the layer is reduced and the design is improved. It has been found that the contracted body and the metal pipe are likely to be misaligned when subjected to an impact after being coated. In addition, when the heat-shrinkable tube shrinks in the radial direction, the length of the heat-shrinkable tube changes in the longitudinal direction due to heat shrinkage due to variations in the heat shrinkage rate, and the metal tube may be exposed or the end of the heat-shrinkable tube may be exposed. was found to be left over. As a result of further studies based on these issues, we found that the arithmetic mean roughness Ra of the inner surface of the heat-shrinkable tube was optimized, and a resin that has a high affinity with the metal pipe to be coated as the base resin that constitutes the heat-shrinkable tube. We found that these problems can be solved by selecting

A heat-shrinkable tube for decorating a metal pipe according to one aspect of the present disclosure (hereinafter also referred to as a heat-shrinkable tube) is composed of a single-layer heat-shrinkable layer containing a base resin containing an acid-modified resin and a filler, The content of the acid component bonded to the acid-modified resin relative to the base resin is 0.4% by mass or more and 1.2% by mass or less, and the arithmetic mean roughness Ra of the inner surface is 0.1 μm or more and 5.0 μm It is below. The acid component bound to the acid-modified resin (hereinafter also referred to as acid component) means an acid component that contributes to the acid modification of the resin. Further, the arithmetic mean roughness Ra is a value measured according to JIS-B0601 (2013).

When the heat-shrinkable tube is heat-shrunk in the radial direction, it also shrinks in the longitudinal direction, causing a change in length in the longitudinal direction. include. When the content of the acid component with respect to the base resin is within the above range, the frictional resistance between the metal tube and the heat-shrinkable tube increases, suppressing the change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube. As a result, the end portion of the portion to be decorated of the metal pipe can be covered just enough, and a good design property can be obtained. In addition, since the base resin contains the acid-modified resin, the base resin has good polarity, and adsorption bonding is facilitated, so that the affinity with metals can be improved. As a result, the effect of suppressing positional displacement between the shrinkable body and the metal pipe when receiving an impact after covering the metal tube with the shrinkable body of the heat-shrinkable tube is excellent.
Furthermore, the arithmetic mean roughness Ra of the inner surface is 0.1 μm or more and 5.0 μm or less, so that when the tube is heat-shrunk on the metal tube, the change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube can be suppressed, and the effect of suppressing misalignment between the shrinkable body of the heat-shrinkable tube and the metal tube can be improved.
In addition, the heat-shrinkable tube for decorating a metal pipe does not suffer from delamination of the paint film, which tends to occur with decorative films, and deterioration in design due to seams. Moreover, the heat-shrinkable tube for decorating a metal pipe does not require an adhesive layer, and is composed of a single-layer heat-shrinkable layer, so that the manufacturing cost can be reduced.

As the acid-modified resin, a maleic anhydride-modified olefin resin is preferable. Since the acid-modified resin is a maleic anhydride-modified olefin resin, the affinity with the metal tube can be improved, so the effect of suppressing the positional displacement between the shrinkable body of the heat-shrinkable tube and the metal tube due to impact is enhanced. be able to.

The content of the filler with respect to the base resin is preferably 5% by volume or more and 30% by volume or less. By setting the content of the filler in the above range, the surface roughness of the inner surface of the heat-shrinkable tube for decorating the metal pipe can be adjusted to an appropriate range. It is possible to enhance the effect of suppressing the positional deviation between the metal pipe and the metal pipe. Further, by setting the content of the filler in the above range, it is possible to suppress the generation of streaky patterns due to separation between the base resin and the filler.

The average particle size of the filler is preferably 0.5 μm or more and 20.0 μm or less. By setting the average particle size of the filler in the above range, the arithmetic mean roughness Ra of the inner surface can be controlled within a good range, so when the heat shrinkable tube is heat-shrunk on the metal tube, the heat of the heat-shrinkable tube A change in length in the longitudinal direction due to contraction can be suppressed. In addition, since the surface roughness of the inner surface of the heat-shrinkable tube for decorating the metal pipe can be adjusted to an appropriate range, it is possible to enhance the effect of suppressing positional displacement between the shrinkable body of the heat-shrinkable tube and the metal pipe due to impact. can. Furthermore, by setting the average particle size of the filler within the above range, a good matte appearance can be obtained, and the tactile sensation and design can be improved.

As the filler, inorganic particles having polarity are preferable. By using inorganic particles having polarity as the filler, bloom can be suppressed. Here, having polarity means having a polarized structure on the surface. The inorganic particles having polarity refer to, for example, inorganic particles having OH groups on their surfaces.

It is preferable that the base resin further includes a resin having an ethyl acrylate unit, and the content of the ethyl acrylate unit with respect to the base resin is 3.0% by mass or more and 20.0% by mass or less. In this way, the base resin further includes a resin having an ethyl acrylate unit, and the content of the ethyl acrylate unit is within the above range, so that affinity with the metal tube can be improved. It is possible to enhance the effect of suppressing positional deviation between the body and the metal pipe. Furthermore, by setting the content of the ethyl acrylate unit within the above range, the affinity between the base resin and the filler can be improved, so the generation of streaky patterns due to peeling between the base resin and the filler can be suppressed.

Preferably, the base resin contains an ethylene copolymer, and the mass ratio of the ethylene copolymer to the acid-modified resin in the base resin is 40/60 or more and 95/5 or less. The base resin contains an ethylene-based copolymer, and the mass ratio of the ethylene-based copolymer and the acid-modified resin in the base resin is within the above range, thereby improving the adhesion between the base resin and the filler. It is possible to suppress the generation of streaky patterns due to peeling between the base resin and the filler. In addition, since the crystallinity of the base resin and the degree of pseudo-crosslinking through the filler of the acid-modified olefin resin are in an appropriate range, the shrinkage rate at temperatures of 50 ° C. or less is suppressed, and the shape during storage is reduced. It can improve retention.

A decorated metal pipe according to another aspect of the present disclosure includes a metal pipe and a coating layer formed on an outer surface of a portion to be decorated of the metal pipe, wherein the coating layer is heat for decorating the metal pipe. It is a shrinkable body obtained by heating a shrinkable tube.

The decorative metal tube includes a metal tube and a coating layer formed on the outer surface of a portion of the metal tube to be decorated, wherein the coating layer shrinks by heating the heat-shrinkable tube for decorating the metal tube. Therefore, it has good designability.

Further, in a method for manufacturing a decorated metal pipe according to still another aspect of the present disclosure, the heat-shrinkable tube for decorating the metal pipe is covered on the outer surface of the portion to be decorated of the metal pipe, and the portion is heat-shrunk. A step of forming a coating layer is provided.

The method for manufacturing the decorated metal pipe includes the step of covering the outer surface of the portion of the metal pipe to be decorated with the heat-shrinkable tube for decorating the metal pipe, and heat-shrinking it to form a coating layer. In addition, it is possible to manufacture a decorated metal pipe having a good design and to reduce variations in quality.

The arithmetic mean roughness Ra of the outer surface of the metal tube is preferably 0.05 μm or more and 3.00 μm or less. By setting the arithmetic mean roughness Ra of the outer surface of the metal pipe within the above range, the frictional force between the outer surface of the metal pipe and the inner surface of the heat shrink tube for decorating the metal pipe is moderate. grow to As a result, when the heat-shrinkable tube is heat-shrunk on the metal tube, the effect of suppressing the change in length in the longitudinal direction due to the heat shrinkage of the heat-shrinkable tube and the position of the shrinkage body of the heat-shrinkable tube and the metal tube due to impact It is possible to manufacture a decorated metal pipe that is excellent in the effect of suppressing displacement.

[Details of the embodiment of the present disclosure]
Each embodiment of the present disclosure will be described in detail below.

<Heat-shrinkable tube for metal pipe decoration>
A heat-shrinkable tube for decorating a metal pipe according to an embodiment of the present disclosure is used as a decorative covering material for imparting design to a metal pipe. More specifically, the metal tube is decorated by heating the metal tube decorating heat-shrinkable tube into which the metal tube is inserted on the metal tube and covering the metal tube with the shrinkable body of the heat-shrinkable tube. be. The heat-shrinkable tube for decorating a metal pipe is composed of a cylindrical single-layer heat-shrinkable layer. The heat-shrinkable layer contains a base resin and a filler. The heat-shrinkable tube for decorating a metal pipe does not cause detachment of the coating film, which tends to occur with decorative films, and deterioration of designability due to seams. Moreover, the heat-shrinkable tube for decorating a metal pipe does not require an adhesive layer, and is composed of a single-layer heat-shrinkable layer, so that the manufacturing cost can be reduced.

The lower limit of the arithmetic mean roughness Ra of the inner surface of the heat-shrinkable tube for decorating a metal pipe is 0.1 μm, preferably 0.3 μm, more preferably 0.9 μm. When the arithmetic mean roughness Ra of the inner surface of the heat shrinkable tube for decorating the metal pipe is less than the above lower limit, the frictional resistance between the inner surface of the heat shrinkable tube for decorating the metal pipe and the metal pipe becomes small, There is a possibility that the effect of suppressing the positional displacement between the shrinkable body of the heat-shrinkable tube and the metal tube due to impact may be reduced. On the other hand, the upper limit of the arithmetic mean roughness Ra of the inner surface of the heat-shrinkable tube for decorating a metal pipe is 5.0 μm, preferably 3.0 μm, more preferably 2.0 μm. When the arithmetic mean roughness Ra of the inner surface of the heat absorption tube for decorating the metal pipe exceeds the above upper limit, the contact area between the heat shrinkable tube for decorating the metal pipe and the metal pipe decreases, and the heat shrinkage due to impact There is a possibility that the effect of suppressing the positional deviation between the contracted body of the tube and the metal tube may be reduced. Furthermore, when the heat-shrinkable tube is heat-shrinked in the radial direction, it also shrinks in the longitudinal direction, and the length in this longitudinal direction changes. By setting Ra within the above range, moderate frictional resistance is generated between the inner surface of the heat-shrinkable tube for decorating the metal pipe and the metal pipe. Thereby, when the heat-shrinkable tube is heat-shrunk on the metal pipe, it is possible to suppress the change in the length in the longitudinal direction due to the heat-shrinkage of the heat-shrinkable tube.

The lower limit of the arithmetic mean roughness Ra of the outer surface of the heat-shrinkable tube for decorating a metal pipe is preferably 0.5 μm, more preferably 0.8 μm, and even more preferably 1.2 μm. If the arithmetic mean roughness Ra of the outer surface of the heat-shrinkable tube for decorating a metal pipe is less than the above lower limit, the surface may become smooth and glossy, and the tactile sensation and design may deteriorate. On the other hand, the upper limit of the arithmetic average roughness Ra of the outer surface of the heat-shrinkable tube for decorating a metal pipe is preferably 5.0 μm, more preferably 3.0 μm, and even more preferably 2.2 μm. If the arithmetic average roughness Ra of the outer surface of the heat shrinkable tube for decorating a metal pipe exceeds the above upper limit, the outer surface of the heat shrinkable tube for decorating a metal pipe may become rough, and the tactile sensation and design may be deteriorated. There is

When the heat-shrinkable tube for decorating a metal pipe is heat-shrunk on a metal pipe, the heat shrinkage in the radial direction is preferably 30% or more and 75% or less. When the heat shrinkage rate in the radial direction is within the above range, the stress applied to the metal pipe when covering the metal pipe can be maintained within a favorable range, so that the positional deviation between the contracted body of the heat shrinkable tube and the metal pipe due to impact can be prevented. can be suppressed. Further, if the heat shrinkage rate in the radial direction is less than 30%, the adhesion of the heat shrinkable tube for decorating the metal pipe to the metal pipe may be insufficient. On the other hand, if the heat shrinkage rate in the radial direction exceeds 75%, the thickness of the heat shrinkable layer may vary and the manufacturing cost may increase.
The heat shrinkage rate (%) in the radial direction is obtained by the following formula.
Heat shrinkage rate in the radial direction (%) = (inner diameter before heat shrinkage - inner diameter after completion of heat shrinkage) / inner diameter before heat shrinkage x 100

The lower limit of the rate of change in length in the longitudinal direction due to heat shrinkage of the heat shrinkable tube when the heat shrinkable tube for decorating the metal tube is heat shrunk on the metal tube is preferably -10%, and -5%. is more preferred. The upper limit of the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube is preferably 5%, more preferably 0%. When the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube is within the above range, it becomes easy to cover the end of the part to be decorated of the metal tube without excess or deficiency, and good designability is achieved. can be obtained.

The average thickness of the heat-shrinkable tube for decorating a metal pipe can be, for example, 0.05 mm or more and 0.8 mm or less from the viewpoint of improving designability and maintaining mechanical strength. If the average thickness of the heat-shrinkable tube is less than 0.05 mm, the strength of the tube may be reduced and the tube may be torn or broken. If the average thickness of the heat-shrinkable tube is more than 0.8 mm, the thickness of the tube at the end face may be conspicuous and the design may be deteriorated.

The average inner diameter of the heat-shrinkable tube for decorating the metal pipe is not particularly limited, and can be appropriately changed according to the application. The average inner diameter of the heat-shrinkable tube for decorating the metal pipe can be, for example, 0.5 mm or more and 110 mm or less.

The color of the heat-shrinkable tube for decorating the metal pipe can be adjusted to a desired color by adding a coloring agent. The color can be adjusted by changing the type and amount of the coloring agent. By adding the colorant as a color batch, it is possible to suppress uneven mixing and express a uniform color.

[Heat shrinkable layer]
The heat-shrinkable layer is formed as a tube that shrinks in diameter when heated. The heat-shrinkable layer contains a base resin containing an acid-modified resin and a filler.

(base resin)
The base resin contains an acid-modified resin. By including the acid-modified resin in the base resin, the base resin has good polarity, and adsorption bonding is facilitated, so that affinity with metals can be improved. As a result, the effect of suppressing displacement between the contracted body of the heat-shrinkable tube and the metal tube due to impact is excellent.

Here, the acid-modified resin is a resin having an acidic functional group in the side chain, a resin in which an acidic functional group is incorporated in the main chain, or a resin having an acidic functional group in the side chain and an acidic functional group in the main chain. Refers to the embedded resin.

Examples of resins to be acid-modified include olefin-based resins and styrene-based resins. Among these, olefinic resins are preferable from the viewpoint of being able to impart appropriate heat shrinkability and being available at relatively low cost.

Examples of the olefin resin include ethylene resins such as polyethylene, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-acrylate ester copolymer, ethylene-methacrylate ester copolymer,
Propylene-based resins such as polypropylene, propylene-acrylate copolymers, propylene-methacrylate copolymers, propylene-acrylate ester copolymers, propylene-methacrylate ester copolymers, and the like are included.
Among these, ethylene-based resins are preferred.

Examples of the ethylene resin include ultra-low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ethylene- A methyl methacrylate copolymer and the like are included. Among these, ultra-low-density polyethylene and linear low-density polyethylene are preferred from the viewpoint of resin flexibility.

The acid used for acid modification is not particularly limited as long as it does not impair the effects of the present disclosure. For example, unsaturated carboxylic acids or derivatives thereof can be used. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, itaconic acid, and fumaric acid. Examples of unsaturated carboxylic acid derivatives include maleic acid monoester, maleic anhydride, itaconic acid monoester, itaconic anhydride, fumaric acid monoester, and fumaric anhydride. Among these, by increasing the affinity with the filler, the retention of the filler is improved, and by increasing the affinity with the metal tube, it is possible to suppress the misalignment of the shrinkable body of the heat-shrinkable tube and the metal tube due to impact. From the viewpoint of improving the effect, unsaturated carboxylic acid derivatives are preferable, and maleic anhydride is more preferable.

Acid-modified resins include maleic anhydride-modified ultra-low density polyethylene, maleic anhydride-modified linear low-density polyethylene, maleic anhydride-modified ethylene-vinyl acetate copolymer, maleic anhydride-modified ethylene-ethyl acrylate copolymer, Maleic anhydride-modified ethylene-methyl methacrylate copolymer and the like are preferable. Among these, maleic anhydride-modified ultra-low density polyethylene and maleic anhydride-modified straight polyethylene are used from the viewpoint of the flexibility of the resin, the retainability of the filler, and the effect of suppressing misalignment between the heat-shrinkable tube for decorating the metal pipe and the metal pipe. Linear low density polyethylene is more preferred.

The content of the acid component bound to the acid-modified resin is preferably 0.5% by mass or more and 6% by mass or less.
Here, the content of the acid component is represented by the following formula.
Content of acid component (% by mass)=mass of functional group-containing monomer-derived portion of acid component/mass of entire acid-modified resin×100

The lower limit of the acid component content relative to the base resin is 0.4% by mass, preferably 0.6% by mass. If the content of the acid component is less than the lower limit, sufficient frictional resistance cannot be obtained between the metal tube and the heat-shrinkable tube, and the effect of suppressing changes in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube is reduced. There is a risk. On the other hand, the upper limit of the acid component content is 1.2% by mass, preferably 1.0% by mass. If the content of the acid component exceeds the upper limit, the mechanical strength of the heat-shrinkable layer is reduced and the heat-shrinkable layer is easily deformed. There is a risk that the effect of reducing the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube will be reduced. In the heat-shrinkable tube for decorating the metal tube, the content of the acid component with respect to the base resin is within the above range, so that the frictional resistance between the metal tube and the heat-shrinkable tube increases, and the heat shrinkage of the heat-shrinkable tube increases. As a result of being able to suppress the change in length in the longitudinal direction, the ends of the portion of the metal pipe to be decorated can be covered just enough, and good design can be obtained. A known method such as NMR (Nuclear Magnetic Resonance) can be used to measure the content of the acid component.

The lower limit of the content of the acid-modified resin with respect to the base resin is preferably 10% by mass. If the content of the acid-modified resin is less than the lower limit, sufficient frictional resistance cannot be obtained between the metal tube and the heat-shrinkable tube, and the effect of suppressing the change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube is small. may become On the other hand, the upper limit of the content of the acid-modified resin is preferably 60% by mass. If the content of the acid-modified resin exceeds the above upper limit, the manufacturability of the tube may deteriorate.

As the resin component of the base resin other than the acid-modified resin, an olefin resin is preferable from the viewpoint of being able to impart appropriate heat shrinkability and being available at a relatively low cost. Examples of olefinic resins include polyethylene (low-density polyethylene, medium-density polyethylene, high-density polyethylene, very-low-density polyethylene (VLDPE), linear low-density polyethylene (LLDPE), etc.), polypropylene, polybutene, polyisobutylene, and other olefins. resin,
Ethylene-propylene copolymer, ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylate ester copolymer such as ethylene-butyl acrylate copolymer (EBA), ethylene - Ethylene copolymers such as ethylene-methacrylate ester copolymers such as methyl methacrylate copolymers, ethylene-acrylate copolymers, ethylene-methacrylate copolymers, ethylene-vinyl acetate copolymers (EVA), etc. be done.
Among these, polyethylene and ethylene copolymers are preferable as the olefin resin.
In addition, the olefin resin may be used alone or in combination of two or more.

As the resin component of the base resin, among these, it has flexibility, has a small burden on the environment, and has an ethyl acrylate unit such as ethylene-ethyl acrylate copolymer (EEA) from the viewpoint of being available at a relatively low cost. It preferably contains a resin.

When the base resin contains a resin having ethyl acrylate units, the lower limit of the ethyl acrylate unit content relative to the base resin is preferably 3.0% by mass, more preferably 5.0% by mass. If the content of the ethyl acrylate unit is less than the above lower limit, the affinity with the metal tube may decrease, and the effect of suppressing the positional deviation between the shrinkable body of the heat-shrinkable tube and the metal tube due to impact may decrease. . On the other hand, the upper limit of the content of the ethyl acrylate unit is preferably 20.0% by mass, more preferably 12.0% by mass. If the content of the ethyl acrylate unit exceeds the above upper limit, the mechanical strength of the heat-shrinkable layer is reduced and the heat-shrinkable layer is easily deformed, thereby suppressing displacement between the heat-shrinkable tube and the metal tube due to impact. There is a risk that the effect of
In addition, well-known methods, such as infrared spectroscopy IR (Infrared spectroscopy), can be used for the measurement of content of an ethyl acrylate unit.

Preferably, the base resin contains an ethylene copolymer, and the mass ratio of the ethylene copolymer to the acid-modified resin in the base resin is 40/60 or more and 95/5 or less. The base resin contains an ethylene-based copolymer, and the mass ratio of the ethylene-based copolymer and the acid-modified resin in the base resin is within the above range, thereby improving the adhesion between the base resin and the filler. It is possible to suppress the generation of streaky patterns due to peeling between the base resin and the filler. In addition, since the crystallinity of the base resin and the degree of pseudo-crosslinking through the filler of the acid-modified olefin resin are in an appropriate range, the shrinkage rate at temperatures of 50 ° C. or less is suppressed, and the shape during storage is reduced. It can improve retention.

Additives may be added to the base resin as necessary. Examples of such additives include strength retention agents, antioxidants, flame retardants, copper damage inhibitors, lubricants, colorants, heat stabilizers, ultraviolet absorbers, and the like. The content of the additive in the base resin is more preferably less than 20% by mass, more preferably less than 10% by mass. If the content of the additive is more than the above upper limit, the properties of the heat-shrinkable layer may easily vary.

(filler)
The heat-shrinkable layer contains a filler, so that the surface roughness of the inner surface of the heat-shrinkable tube for decorating a metal pipe can be adjusted to an appropriate range. As the material of the filler, inorganic particles having polarity are preferable from the viewpoint of suppressing blooming of the heat-shrinkable layer. If bloom occurs in the heat shrinkable layer, there is a risk of a decrease in the arithmetic mean roughness Ra of the inner surface of the heat shrinkable tube for decorating metal pipes and a decrease in designability on the surface of the heat shrinkable tube for decorating metal pipes. .

Examples of filler materials include metal oxides such as alumina, silica, calcia, and magnesia, metal nitrides such as aluminum nitride and silicon nitride, metal hydroxides such as aluminum hydroxide and magnesium hydroxide, calcium carbonate, and magnesium carbonate. and complex compounds such as mullite, talc, and mica. A plurality of materials may be used as the filler.

The material of the filler is preferably a filler composed of an element with an atomic number of 20 or less in order to meet the specifications and standards of the Food Sanitation Act depending on the application such as food, beverage, medicine, and toy. Examples of fillers composed of elements having an atomic number of 20 or less include alumina, silica, calcia, magnesia, aluminum nitride, silicon nitride, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, mullite, and talc. be done.

The shape of the filler is not limited as long as the surface roughness of the inner surface can be controlled, and may be particulate, flat, or rod-like. In the case of long fibers having an extremely large filler aspect ratio, it may be difficult to uniformly disperse the filler in the base resin.

The arithmetic mean roughness Ra of the inner surface of the heat-shrinkable tube for decorating metal pipes can also be adjusted by the average particle size of the filler, and the lower limit of the average particle size of the filler is preferably 0.5 μm, more preferably 1.0 μm. preferable. If the average particle size of the filler is less than the above lower limit, the arithmetic mean roughness Ra of the inner surface of the heat-shrinkable tube for decorating the metal pipe is lowered, which may reduce the effect of suppressing positional deviation. On the other hand, the upper limit of the average particle size of the filler is preferably 20.0 µm, more preferably 10.0 µm. If the average particle size of the filler exceeds the above upper limit, the adhesion between the metal pipe decorating heat shrinkable tube and the metal pipe may deteriorate. By setting the average particle size of the filler in the above range, the arithmetic mean roughness Ra of the inner surface can be controlled within a good range, so when the heat shrinkable tube is heat-shrunk on the metal tube, the heat of the heat-shrinkable tube A change in length in the longitudinal direction due to contraction can be suppressed. Furthermore, by setting the average particle size of the filler within the above range, a good matte appearance can be obtained, and the tactile sensation and design can be improved.

The lower limit of the filler content relative to the base resin is preferably 5% by volume, more preferably 10% by volume. When the content of the filler is less than the above lower limit, the arithmetic mean roughness Ra of the inner surface of the heat shrinkable tube for decorating the metal pipe is reduced, and the heat shrinkable tube for decorating the metal pipe is not caught by the metal pipe. As a result, there is a risk that the effect of suppressing positional displacement between the shrinkable body of the heat-shrinkable tube and the metal tube due to impact will be reduced. On the other hand, the upper limit of the carbon atom ratio is preferably 30% by volume, more preferably 20% by volume. If the content of the filler exceeds the upper limit, the mechanical strength of the heat-shrinkable tube for decorating a metal pipe may decrease. Further, by setting the content of the filler in the above range, it is possible to suppress the generation of streaky patterns due to separation between the base resin and the filler.

(Application)
The heat-shrinkable tube for decorating metal pipes can be suitably used as a decorative material for metal pipes, for example, for various industrial uses, foods, beverages, medicines, toys, and the like. In applications where cleanliness is required, it is important that the raw material contains few impurities. An appropriate one can be selected according to the cleanliness of the base resin, filler, and colorant.

<Decorative metal tube>
The decorative metal tube includes a metal tube and a coating layer formed on the outer surface of a portion of the metal tube to be decorated, wherein the coating layer shrinks by heating the heat-shrinkable tube for decorating the metal tube. is. In the decorative metal pipe, the coating layer formed on the outer surface of the portion to be decorated of the metal pipe is a shrinkable body obtained by heating the heat-shrinkable tube for decorating the metal pipe, so that it has good tactile sensation and designability. have. FIG. 1 is a schematic perspective view showing a decorated metal tube according to one embodiment of the present disclosure. As shown in FIG. 1, a decorated metal tube 10 includes a metal tube 1 and a coating layer 2 formed on the outer surface of a portion of the metal tube to be decorated. In the present embodiment, the entire outer surface of the metal pipe is the portion to be decorated.

(metal tube)
Metal pipes made of, for example, stainless steel, aluminum, brass, or the like can be used as objects to be coated with the heat-shrinkable tube for decorating metal pipes. In addition to the cylindrical metal pipe, the metal pipe includes a cylindrical metal material, a bottomed cylindrical metal pipe, and the like. It may also have a stepped cylindrical shape with a plurality of diameters.

The lower limit of the arithmetic mean roughness Ra of the outer surface of the metal tube is preferably 0.05 μm, more preferably 0.30 μm. When the arithmetic mean roughness Ra of the outer surface of the metal tube is less than the above lower limit, the frictional force between the heat shrinkable tube for decorating the metal tube and the outer surface of the metal tube becomes small, and the heat shrinkable tube is damaged by impact. There is a possibility that the effect of suppressing the positional deviation between the contraction body and the metal pipe may be reduced. On the other hand, the upper limit of the arithmetic mean roughness Ra of the outer surface of the metal tube is preferably 3.00 μm, more preferably 1.00 μm. If the arithmetic average roughness Ra of the outer surface of the metal pipe exceeds the upper limit, the surface of the heat-shrinkable tube for decorating the metal pipe after coating may be affected, resulting in a rough appearance and a reduced design. .

<Manufacturing method of decorated metal tube>
The method for manufacturing the decorated metal pipe includes the step of covering the outer surface of the portion to be decorated of the metal pipe with the heat-shrinkable tube for decorating the metal pipe, and heat-shrinking it to form a coating layer. The method for producing a decorated metal tube can produce a decorated metal tube with a good design and can reduce variations in quality. Note that the decoration target portion of the metal pipe includes not only the entire outer surface of the metal pipe, but also a predetermined partial range of the outer surface of the metal pipe. The method for manufacturing the decorated metal pipe includes other steps, for example, the following steps.
(1) A step of preparing a heat-shrinkable layer resin composition for forming a heat-shrinkable layer (hereinafter also referred to as a heat-shrinkable layer resin composition) (heat-shrinkable layer resin composition preparation step)
(2) Step of extruding the resin composition for the heat-shrinkable layer with a melt extruder (extrusion molding step) diameter process)
(4) A step of covering the outer surface of the portion of the metal pipe to be decorated with the heat-shrinkable tube for decorating the metal pipe, and heat-shrinking the heat-shrinkable tube to form a coating layer (coating layer forming step).

(1) Heat-shrinkable layer resin composition preparation step In the heat-shrinkable layer resin composition preparation step, a heat-shrinkable layer is formed by mixing each resin component, filler and, if necessary, additives with a melt mixer or the like. A resin composition for a heat-shrinkable layer is prepared. As the melt mixer, a known one such as an open roll mixer, a Banbury mixer, a pressure kneader, a single screw mixer, a multi-screw mixer and the like can be used.

(2) Extrusion molding process In the extrusion molding process, the resin composition for the heat-shrinkable layer is extruded using a melt extruder. Specifically, the resin composition for the heat-shrinkable layer is extruded using an extrusion die having a cylindrical space for extruding a layer corresponding to the heat-shrinkable layer. Thereby, an extruded article corresponding to the heat-shrinkable layer is obtained.

The dimensions of the extruded product can be designed according to the application. The average inner diameter of the extruded article is, for example, 0.3 mm or more and 100 mm or less, and the average thickness of the extruded article is, for example, 0.1 mm or more and 1.5 mm or less.

In this step, by cross-linking the base resin of the extruded product, the shape memory effect of the heat-shrinkable tube can be exhibited and the heat resistance can be improved. As a method for cross-linking the base resin, a method of irradiating the resin with radiation (radiation cross-linking of the base resin) is preferable. Since molding becomes difficult after the base resin is crosslinked by irradiation with radiation, irradiation with radiation (crosslinking step) is performed after the extrusion molding step. By irradiating radiation after extrusion molding, molding can be carried out reliably and the effects of radiation irradiation can be sufficiently obtained.

Radiation used for irradiation crosslinking of the base resin includes electron beams (β-rays), γ-rays, and the like. Electron beams are preferable as the radiation because electron accelerators have low running costs, can produce high-power electron beams, and are easy to control.

The radiation dose is not particularly limited, but when the radiation dose is too large, the strength of the tube may increase and the diameter expansion may become difficult. On the other hand, when the irradiation dose is too small, the degree of cross-linking necessary for exhibiting shrinkage properties as a heat-shrinkable tube may not be obtained. Therefore, it is preferable to select a radiation dose that is as small as possible within a range in which the contraction property is sufficiently exhibited, and the range of 80 kGy or more and 200 kGy or less is preferable.

The lower limit of the gel fraction, which is an index of the degree of crosslinking of the base resin, is preferably 40%, more preferably 50%. On the other hand, the upper limit of the gel fraction is preferably 80%, more preferably 70%. When the gel fraction is within the above range, the shrinkage characteristics of the heat-shrinkable tube for decorating a metal pipe can be set within a favorable range. The gel fraction is defined as W1 [g], which is the mass of the solid content after the heat-shrinkable layer is immersed in xylene and heated and dissolved at 120° C. for 24 hours, and W2, which is the mass of the heat-shrinkable layer before the heat-shrinkable layer is soaked in xylene. When [g] is used, it means the value obtained from the following formula.
Gel fraction [% by mass]=[W1/W2]×100 (1)

(3) Diameter-expanding step In the diameter-expanding step, the diameter of the extruded product is expanded. As a method for expanding the diameter of the extruded product, a known diameter-expanding method that is commonly used for producing conventional heat-shrinkable tubes can be used. For example, the extruded product is heated to a temperature above its melting point and then compressed air is introduced into the interior, the pressure is reduced from the outside, or a metal rod is inserted to expand the diameter to a predetermined inner diameter. After that, it is cooled to fix the shape. Such expansion of the diameter of the extruded product is performed, for example, so that the inner diameter of the extruded product becomes, for example, 1.2 times or more and 4 times or less. By fixing the shape of the diameter-expanded extruded product, the heat-shrinkable tube for decorating the metal pipe can be obtained. Examples of this fixing method include a method of cooling to a temperature below the melting point of the base resin component. In order to reduce the influence on the surface roughness of the inner surface of the heat-shrinkable tube in the diameter-expanding process, the roughness of the metal rod can be reduced, or coating or lubricant can be applied. Also, by reducing the expansion speed, the influence on the surface roughness of the inner surface of the heat-shrinkable tube can be reduced.

(4) Coating layer forming step In the coating layer forming step, a metal pipe is inserted into the heat shrinkable tube for decorating the metal pipe, and the heat shrinkable tube for decorating the metal pipe is placed outside the portion to be decorated of the metal pipe. The coated metal pipe is produced by covering the surface and heat-shrinking it to form a coating layer. The heat shrink temperature in the coating layer forming step is preferably 80° C. or higher and 200° C. or lower. In addition, in the coating layer forming process, the rate of change in the length in the longitudinal direction due to the heat shrinkage of the heat shrinkable tube is taken into account when the heat shrinkable tube for decoration is heat-shrunk. length can be adjusted.

[Other embodiments]
It should be considered that the embodiments disclosed this time are illustrative in all respects and not restrictive. The scope of the present disclosure is not limited to the configurations of the above-described embodiments, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. be.

Next, the present disclosure will be described in further detail based on examples. However, the examples are not intended to limit the scope of the present disclosure.

<Heat-shrinkable tube for metal pipe decoration No. 1 to No. 18>
No. 4 consisting of a single-layer heat-shrinkable layer was formed by the following procedure. 1 to No. 18 heat-shrinkable tubes for decorating metal pipes were formed.

Linear low-density polyethylene and maleic anhydride-modified ultra-low-density polyethylene (maleic anhydride-modified VLDPE) with a maleic anhydride component content of 2% by mass are used as the base resin, and calcium carbonate is used as the filler to form a heat-shrinkable layer. A resin composition for was prepared. Table 1 shows the composition of the base resin, the content of the above acid component relative to the base resin, and the average particle size and content of the filler. EA indicates ethyl acrylate. "-" indicates that the corresponding component was not used. The content of the acid component was adjusted by the mixing ratio of the resin components constituting the base resin. Further, as a coloring agent, a black color batch having a pigment concentration of 32% by mass corresponding to the voluntary standards of the Polyolefin Sanitation Council was added so as to be 1% by mass with respect to the base resin.

After preparing the resin composition for the heat-shrinkable layer, a mold was set, and the resin composition for the heat-shrinkable layer was pressurized and extruded from the mold to obtain a molded tube. Next, this molded tube was irradiated with radiation at 120 kGy. The gel fraction of the base resin was 65%. The molded tube had an outer diameter of 6.6 mm and an inner diameter of 6 mm. Next, by expanding the diameter of the extruded tube with a diameter expanding device, a heat-shrinkable tube for metal pipe decoration having an outer diameter of 12.3 mm and an inner diameter of 12 mm was obtained.

Next, after passing a metal pipe through the obtained heat-shrinkable tube for decorating a metal pipe, the heat-shrinkable tube is shrunk by heating at 150° C. for 5 minutes, and the heat-shrinkable tube for decorating a metal pipe shrinks the metal. The entire outer surface of the tube was coated. A stainless steel pipe having an outer diameter of 10 mm and a thickness of 0.2 mm was used as the metal pipe.

(Arithmetic mean roughness of the inner surface of the heat-shrinkable tube for metal pipe decoration)
The arithmetic mean roughness Ra of the inner surface of the heat-shrinkable tube for decorating metal pipes was measured using a stylus-type surface roughness meter, and the inner surface of the heat-shrinkable tube for decorating metal pipes was measured in accordance with JIS-B0601 (2013). Measurements were taken over a surface length of 15 mm.

(Longitudinal length change rate due to heat shrinkage of heat shrinkable tube for metal tube decoration)
The length change rate due to heat shrinkage of the heat shrinkable tube on the metal tube is affected by the length change rate due to heat shrinkage of the heat shrinkable tube alone, so the length of the heat shrinkable tube after complete shrinkage The rate of change is based on the heat-shrinkable tube No. for decorating metal pipes in Table 1 below. 1 to No. For 18, it was set to -15%. The rate of change in length of the heat-shrinkable tube after complete shrinkage can be adjusted by the supply speed and take-up speed in the diameter-expanding process. The rate of change in the length of the heat-shrinkable tube after complete shrinkage is calculated from the longitudinal length of the heat-shrinkable tube before and after shrinkage by shrinking the heat-shrinkable tube cut to a length of 100 mm at 150°C for 5 minutes. did.
The length change rate is defined by the following formula.
Length change rate (%) = (length after heat shrinkage - length before heat shrinkage) / length before heat shrinkage x 100

Next, the length change rate in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube after covering the entire outer surface of the metal tube was calculated. Evaluation was made on a four-grade scale from A to D based on the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube. The evaluation criteria for the length change rate in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube were as follows.
A: Especially excellent B: Excellent C: Good D: Inferior Test No. In Nos. 11 and 18, the strength of the tube was lowered and it became easy to deform, and the strength of the tube was weak against the frictional resistance with the metal tube, so that the tube did not shrink uniformly.

(Positional deviation of shrinkable body of heat-shrinkable tube for base material decoration)
It was evaluated whether the position of the heat-shrinkable tube, which is the coating layer of the decorative metal tube, is displaced by applying a stress in the longitudinal direction to the heat-shrinkable tube. The misalignment was evaluated in three grades from A to C. The evaluation criteria for the misalignment are as follows.
A: No shift at 50N stress, particularly excellent B: No shift at 20N stress, good C: 20N stress, poor

Table 1 shows the evaluation results of the arithmetic average roughness of the inner surface of the heat-shrinkable tube, the rate of change in length in the longitudinal direction due to heat shrinkage, and the displacement of the heat-shrinkable body of the heat-shrinkable tube.

As shown in Table 1, the content of the acid component with respect to the base resin is 0.4% by mass or more and 1.2% by mass or less, and the arithmetic mean roughness Ra of the inner surface is 0.1 μm or more and 5.0 μm or less. No. 1 to No. The heat-shrinkable tube for decorating the metal pipe of No. 10 has the effect of reducing the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube for decorating the metal pipe when the heat-shrinkable tube for decorating the metal pipe is heat-shrunk on the metal pipe. And the effect of suppressing the positional deviation of the contraction body was good. On the other hand, the content of the acid component with respect to the base resin is less than 0.4% by mass or more than 1.2% by mass, or the arithmetic average roughness Ra of the inner surface is less than 0.1 μm or more than 5.0 μm No. 11 to No. The heat-shrinkable tube for metal pipe decoration of No. 18 was inferior in the effect of reducing the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube and in the effect of suppressing displacement of the shrinkable body.
No. 4 using calcium carbonate as a filler. 1 to No. No. 18 metal tube decorative heat-shrinkable tube is tested for both the elution amount of heavy metals based on the heavy metal test method specified in the Food Sanitation Act and the potassium permanganate consumption amount based on the potassium permanganate consumption test method. complied with sanitary laws.

<Heat-shrinkable tube for metal pipe decoration No. 19 to No. 29>
As the base resin, in addition to the above-mentioned linear low-density polyethylene and acid-modified ultra-low-density polyethylene having an acid component content of 2% by mass, an ethylene-acrylate ethyl copolymer (EEA) having an ethyl acrylate unit content of 15% ), except that No. 1 to No. A heat-shrinkable tube for decorating a metal pipe was formed in the same manner as the heat-shrinkable tube for decorating a metal pipe of No. 18. Table 2 shows the composition of the base resin, the content of the acid component relative to the base resin, the content of ethyl acrylate units relative to the base resin, and the average particle size and content of the filler. The content of the acid component and the content of the ethyl acrylate unit were adjusted by the mixing ratio of the base resin. In addition, EA 15% in the table indicates that the content of ethyl acrylate units is 15% by mass. In addition, EA 25% in the table indicates that the content of ethyl acrylate units is 25% by mass.

Obtained No. 19 to No. No. 29 except that the rate of change in length after complete shrinkage of the tube was set to -10%. 1 to No. When the heat shrink tube is heat shrunk on the metal tube in the same manner as the heat shrink tube for decorating the metal tube in 18, the length change rate in the longitudinal direction due to heat shrinkage of the heat shrink tube, the positional deviation, the arithmetic mean roughness of the inner surface and The inhibitory property against the generation of streaky patterns shown below was evaluated.

(Inhibitory property against generation of streaky pattern)
Appearance evaluation was performed with respect to the ability to suppress the occurrence of streaky patterns on the surface of each metal pipe decorative heat shrinkable tube after the diameter expansion step. Occurrence of streaky patterns on the outer surface of the heat-shrinkable tube for decorating the base material was determined visually under a fluorescent lamp. The ability to suppress the occurrence of streaky patterns was evaluated according to the following two-level evaluation criteria of A and B.
A: No streaky pattern on tube surface B: Streaky pattern on tube surface

Table 2 shows the evaluation results of the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube, misalignment, arithmetic mean roughness of the inner surface, and inhibitory effect on the occurrence of streaky patterns.

As shown in Table 2, in addition to the acid-modified resin having an acid component content of 0.4% by mass or more and 1.2% by mass or less based on the base resin, the ethyl acrylate unit content is 3.0% by mass or more. No. 0.0 mass % or less of a resin having an ethyl acrylate unit and an inner surface arithmetic mean roughness Ra of 0.1 μm or more and 5.0 μm or less. 19 to No. 22 and no. 24 to No. The heat shrink tube for decorating the metal pipe of 29 has the effect of reducing the rate of change in length in the longitudinal direction due to heat shrinkage of the heat shrink tube for decorating the metal pipe when the heat shrink tube for decorating the metal pipe is heat shrunk on the metal pipe. And the effect of suppressing the displacement of the contraction body was better.
Furthermore, the base resin contains an ethylene copolymer, and the mass ratio of the ethylene copolymer in the base resin to the acid-modified resin is 40/60 or more and 95/5 or less. 19 to No. 22 and no. 24 to No. The heat-shrinkable tube for metal pipe decoration of No. 29 was also excellent in suppressing the occurrence of streaky patterns.
No. 4 using calcium carbonate as a filler. 19 to No. No. 29 heat-shrinkable tube for metal pipe decoration is also available. 1 to No. As with the 18 metal tube decorative heat shrinkable tubes, in either the elution amount of heavy metals based on the heavy metal test method of the standards of the Food Sanitation Act and the potassium permanganate consumption based on the potassium permanganate consumption test method also complied with the Food Sanitation Act.

<Heat-shrinkable tube for metal pipe decoration No. 30 to No. 39>
Ethylene-acrylate ethyl copolymer (EEA) with an ethyl acrylate unit content of 15% and an acid-modified linear low-density polyethylene (acid-modified LLDPE) with an acid component content of 2% by mass as a base resin. , except that fillers having various polarities with different average particle sizes and contents were used. 1 to No. A heat-shrinkable tube for decorating a metal pipe was formed in the same manner as the heat-shrinkable tube for decorating a metal pipe of No. 18. Table 3 shows the composition of the base resin, the content of the acid component with respect to the base resin, the composition of the filler, the average particle size and the content. The content of the acid component and the content of the ethyl acrylate unit were adjusted by the mixing ratio of the base resin. In addition, EA 15% in the table indicates that the content of ethyl acrylate units is 15% by mass.

Obtained No. 30 to No. No. 39 except that the rate of change in length after complete contraction of the tube was -5%. 1 to No. In the same manner as the heat-shrinkable tube for decorating the metal tube of 18, when the heat-shrinkable tube is heat-shrunk on the metal tube, the length change rate in the longitudinal direction due to heat shrinkage, the positional deviation and the arithmetic mean roughness of the inner surface are measured. evaluated. Table 3 shows the evaluation results of the length change rate in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube, positional deviation, and arithmetic mean roughness of the inner surface.

As shown in Table 3, acid-modified resins having an acid component content of 0.4 mass % or more and 1.2 mass % or less and ethyl acrylate content of 3.0 mass % or more and 20.0 mass % or less of the base resin. A resin having an ethyl acrylate unit of 0% by mass or less, and a polar filler whose content is 5% by volume or more and 30% by volume or less and whose average particle diameter is 0.5 μm or more and 20.0 μm or less, No. 1 having a surface arithmetic mean roughness Ra of 0.1 μm or more and 5.0 μm or less. 30 to No. The heat-shrinkable tube for decorating the metal pipe of No. 39 has the effect of reducing the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube for decorating the metal pipe when the heat-shrinkable tube for decorating the metal pipe is heat-shrunk on the metal pipe. And the effect of suppressing the positional deviation of the contraction body was good.
In addition, No. 1 using a filler composed of an element having an atomic number of 20 or less as a filler. 30 to No. No. 39 heat-shrinkable tube for metal pipe decoration is also available. 1 to No. As with the 18 decorative heat-shrinkable tubes for metal tubes, in either the elution amount of heavy metals based on the heavy metal test method of the standards of the Food Sanitation Act and the potassium permanganate consumption based on the potassium permanganate consumption test method also complied with the Food Sanitation Act.

From the above results, the heat-shrinkable tube for decorating a metal pipe is composed of a single-layer heat-shrinkable layer containing a base resin containing an acid-modified resin and a filler, and the content of the acid component with respect to the base resin is 0. .4% by mass or more and 1.2% by mass or less, and the arithmetic mean roughness Ra of the inner surface is 0.1 μm or more and 5.0 μm or less, so that the metal pipe decorating heat shrinkable tube can be placed on the metal pipe. It was shown that the effect of reducing the rate of change in length in the longitudinal direction due to heat shrinkage of the heat-shrinkable tube when heat-shrunk and the effect of suppressing displacement of the shrinkable body are high. Therefore, it is considered that the heat-shrinkable tube for decorating a metal pipe can reduce variations in the quality of the decorated metal pipe and contribute to improving the production efficiency of the decorated metal pipe.

1 metal tube 2 coating layer 10 decorated metal tube

Claims (10)

Consists of a single-layer heat-shrinkable layer containing a base resin containing an acid-modified resin and a filler,
The content of the acid component bonded to the acid-modified resin relative to the base resin is 0.4% by mass or more and 1.2% by mass or less,
A heat-shrinkable tube for decorating a metal pipe, the inner surface of which has an arithmetic mean roughness Ra of 0.1 μm or more and 5.0 μm or less. 2. The heat-shrinkable tube for metal pipe decoration according to claim 1, wherein the acid-modified resin is a maleic anhydride-modified olefin resin. 3. The heat-shrinkable tube for decorating a metal pipe according to claim 1, wherein a content of said filler with respect to said base resin is 5% by volume or more and 30% by volume or less. 4. The heat-shrinkable tube for metal pipe decoration according to claim 1, 2 or 3, wherein the filler has an average particle size of 0.5 [mu]m or more and 20.0 [mu]m or less. 5. The heat-shrinkable tube for metal pipe decoration according to any one of claims 1 to 4, wherein the filler is inorganic particles having polarity. The base resin further comprises a resin having ethyl acrylate units,
The heat-shrinkable tube for decorating a metal pipe according to any one of claims 1 to 5, wherein the ethyl acrylate unit content relative to the base resin is 3.0% by mass or more and 20.0% by mass or less. The base resin contains an ethylene-based copolymer,
7. The heat-shrinkable tube for metal pipe decoration according to claim 6, wherein the mass ratio of the ethylene copolymer to the acid-modified resin in the base resin is 40/60 or more and 95/5 or less. a metal tube;
a coating layer formed on the outer surface of the portion to be decorated of the metal pipe,
A decorated metal pipe, wherein the coating layer is a shrinkable body obtained by heating the heat-shrinkable tube for decorating a metal pipe according to any one of claims 1 to 7. A step of covering the outer surface of a portion of a metal pipe to be decorated with the heat-shrinkable tube for decorating a metal pipe according to any one of claims 1 to 7, and heat-shrinking it to form a coating layer. A method for manufacturing a decorated metal tube. 10. The method for manufacturing a decorated metal tube according to claim 9 , wherein the outer surface of said metal tube has an arithmetic mean roughness Ra of 0.05 [mu]m or more and 3.00 [mu]m or less.

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