WO2020012784A1

WO2020012784A1 - Heat-shrinkable tube for metal pipe decoration, decorated metal pipe, and method for producing decorated metal pipe

Info

Publication number: WO2020012784A1
Application number: PCT/JP2019/020383
Authority: WO
Inventors: 遼太福本; 石橋　恵二
Original assignee: 住友電気工業株式会社; 住友電工ファインポリマー株式会社
Priority date: 2018-07-12
Filing date: 2019-05-23
Publication date: 2020-01-16
Also published as: JP2021152367A

Abstract

A heat-shrinkable tube for metal pipe decoration according to one aspect of the present disclosure comprises a single heat-shrinkable layer containing: a filler; and a base resin containing an ethylene-based copolymer and an acid-modified olefin-based resin. The mass ratio of the ethylene-based copolymer relative to the acid-modified olefin-based resin in the base resin is 40/60-95/5. The content of the filler relative to the base resin is 30 vol.% or less.

Description

Heat shrinkable tube for decorating metal tube, decorated metal tube, and method of manufacturing decorated metal tube

The present disclosure relates to a heat shrinkable tube for decorating a metal tube, a decorated metal tube, and a method for manufacturing a decorated metal tube. This application claims the priority based on Japanese Patent Application No. 2018-132731 filed on Jul. 12, 2018, and incorporates all the contents described in the Japanese application.

塗装 Conventionally, painting, printing, and the like have been performed as means for decorating metal materials such as metal tubes and food cans. Since the coating film formed by this coating is rigid and has low toughness, there is a possibility that the coating film may be chipped or peeled off by impact. In addition, the technique of applying a coating not only has a complicated baking process but also requires a large amount of processing time, and has a disadvantage of increasing the manufacturing cost.

Therefore, as an alternative to painting for surface decoration, a technique relating to a sheet-shaped decoration film that can be attached to a three-dimensional curved surface has been proposed (see JP-A-2017-205962).

JP-A-2017-205962

The heat-shrinkable tube for decorating a metal tube according to one embodiment of the present disclosure includes a single-layer heat-shrinkable layer containing a base resin and a filler including an ethylene-based copolymer and an acid-modified olefin-based resin,
The mass ratio of the ethylene-based copolymer to the acid-modified olefin-based resin in the base resin is 40/60 or more and 95/5 or less, and the content of the filler with respect to the base resin is 30% by volume or less.

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

A method for manufacturing a decorative metal tube according to still another aspect of the present disclosure is to cover the outer surface of the metal tube decorative heat-shrinkable tube on the outer surface of a decoration target portion of the metal tube, and heat shrink the coating tube to form a coating layer. Is formed.

1 is a schematic perspective view illustrating a decorative metal tube according to an embodiment of the present disclosure.

[Problems to be solved by the present disclosure]
In the conventional method of attaching a sheet-shaped decorative film to a metal material, a seam or an unnatural thickness unevenness occurs at a portion where the decorative films are joined, or a complicated shape cannot be followed, thereby deteriorating tactile sensation and design. Sometimes. Further, since the decorative film has substantially no adhesive force, it is necessary to provide an adhesive layer. However, when the adhesive layer is provided, there is a possibility that the adhesive layer may be peeled off due to the influence of humidity, and further, the tactile sensation and design properties may be reduced due to an increase in the thickness of the decorative film, and the cost may be increased.

On the other hand, there is a heat-shrinkable tube as a coating material. This heat-shrinkable tube does not require an adhesive layer when coating the base material, but the protective surface of the base material and the functional surface such as shrinkage characteristics such as shape retention during storage tend to be more important than the external appearance surface. Yes, improvement of appearance is required. Further, in the heat-shrinkable tube, further functions such as flame retardancy and cost reduction are required.

The present disclosure has been made based on the above-described circumstances, and provides a heat-shrinkable tube for decorating a metal tube capable of improving the appearance and reducing the cost while having good shrinkage characteristics, and an outer appearance. It is an object of the present invention to provide a decorative metal pipe and a method for manufacturing a decorative metal pipe that can be improved and reduced in cost.
[Effects of the present disclosure]

熱 The heat-shrinkable tube for decorating a metal tube according to one embodiment of the present disclosure can improve the appearance and reduce the cost while having good shrinkage characteristics. The decorative metal pipe according to another aspect of the present disclosure can achieve cost reduction while having a good appearance. The method for manufacturing a decorative metal pipe according to still another aspect of the present disclosure can manufacture a decorative metal pipe having a good appearance and can achieve cost reduction.

[Description of Embodiment of the Present Disclosure]
The present inventors have studied a method of decorating a metal tube using a heat-shrinkable tube that does not cause a seam problem as compared with a decorative film. By adding a filler to the heat-shrinkable layer of the heat-shrinkable tube, it is possible to reduce costs and impart flame retardancy. May occur. As a result of studying based on these problems, it was found that, when the base resin of the heat-shrinkable layer contains an acid-modified resin, the adhesion between the base resin and the filler is improved and the generation of streak-like patterns can be suppressed. . On the other hand, it is important for the heat-shrinkable tube to exhibit sufficient shrinkage when heated. For example, if the shrinkage temperature is too low, shrinkage occurs even during storage of the heat-shrinkable tube, and a sufficient diameter may not be maintained during use. Therefore, it is desired to improve shape retention during storage. The present inventors have found that, when the base resin contains an acid-modified resin, the amount of crystals of the base resin decreases, and the acid-modified resin forms pseudo-crosslinking via a filler, causing natural shrinkage during storage. It was also found that shape retention during storage may be reduced. Therefore, they have found that these problems can be solved by combining the acid-modified resin and another specific resin at a specific ratio as the base resin.

The heat-shrinkable tube for decorating a metal tube according to one embodiment of the present disclosure includes a single-layer heat-shrinkable layer containing a filler and a base resin containing an ethylene-based copolymer and an acid-modified olefin-based resin, and the base resin In the above, the mass ratio of the ethylene-based copolymer to the acid-modified olefin-based resin is 40/60 or more and 95/5 or less, and the content of the filler with respect to the base resin is 30% by volume or less.

The base resin contains an ethylene-based copolymer, and the mass ratio between the ethylene-based copolymer and the acid-modified olefin-based resin in the base resin is in the above range, thereby improving the adhesion between the base resin and the filler. As a result, it is possible to suppress the generation of streak-like patterns due to the separation between the base resin and the filler. Further, since the degree of crystallinity of the base resin and the degree of pseudo-crosslinking via the filler of the acid-modified olefin-based resin fall within an appropriate range, the shrinkage at a temperature of 50 ° C. or lower is suppressed, and the shape during storage is reduced. Retention can be improved. As a result, it is possible to achieve both the effect of suppressing the generation of streak patterns and the contradictory effect of improving the shape retention during storage. Therefore, the appearance can be improved and the cost can be reduced while having good shrinkage characteristics.
When the content of the filler with respect to the base resin is 30% by volume or less, the effect of reducing costs and imparting flame retardancy can be obtained while suppressing generation of streak patterns. Furthermore, since the surface roughness of the inner surface of the heat-shrinkable tube can be adjusted to an appropriate range, the position of the shrinkable body and the metal tube due to the impact after the heat-shrinkable tube of the heat-shrinkable tube is coated on the metal tube is heated. The effect of suppressing displacement can be increased. If the content of the filler with respect to the base resin exceeds 30% by volume, it may be difficult to suppress whitening even when the composition of the base resin is in the above range.

(4) The gel fraction of the base resin is preferably 30% or more and 90% or less. By setting the gel fraction of the base resin in the above range, the shape retention during storage can be improved while maintaining the shape at high temperatures.

(4) The content of the acid component bonded to the acid-modified olefin-based resin with respect to the base resin is preferably from 0.2% by mass to 1.2% by mass. The heat shrinkable tube for decorating a metal pipe has an effect of suppressing the generation of a streak pattern considered to be caused by peeling of the base resin and the filler, because the content of the acid component with respect to the base resin is within the above range, and Shape retention during storage can be further improved. Here, the acid component bonded to the acid-modified olefin resin refers to an acid component that contributes to the acid modification of the olefin resin.

The ethylene copolymer contains a resin having an ethyl acrylate unit or a vinyl acetate unit, and the content of the ethyl acrylate unit or the vinyl acetate unit with respect to the base resin is not less than 3.0% by mass and not more than 23.0% by mass. Is preferred. When the content of the ethyl acrylate unit or the vinyl acetate unit with respect to the base resin is within the above range, the effect of suppressing the generation of streaky patterns can be further improved. Furthermore, when the content of the ethyl acrylate unit with respect to the base resin is in the above range, the affinity with the metal tube is increased, and the shrinkable body due to the impact after the shrinkable body of the heat shrinkable tube is coated on the metal tube. The effect of suppressing displacement between the metal pipe and the metal pipe is improved.

The filler is preferably an inorganic particle composed of an element having an atomic number of 20 or less.
Since the filler is an inorganic particle composed of an element having an atomic number of 20 or less, impurities can be reduced for use in foods, beverages, medicines, toys, and the like.

算 The arithmetic average roughness Ra of the inner surface of the heat shrinkable tube for decorating a metal tube is preferably 0.1 μm or more and 5.0 μm or less. According to this aspect, it is possible to suppress a displacement between the shrinkable body and the metal tube due to an impact after the shrinkable body of the heat shrinkable tube is coated on the metal tube. Furthermore, it is possible to suppress a change in the longitudinal length of the heat-shrinkable tube when the heat-shrinkable tube is heat-shrinked on the metal tube.

外 The arithmetic average roughness Ra of the outer surface of the heat shrinkable tube for decorating a metal tube is preferably 0.5 μm or more and 5.0 μm or less. According to this embodiment, the feel and design are excellent.

平均 The average particle diameter of the filler is preferably 0.5 μm or more and 20.0 μm or less. According to this aspect, it is possible to suppress the displacement due to the decrease in the arithmetic average roughness Ra of the inner surface of the heat shrinkable tube for decorating a metal pipe. Further, the adhesion between the metal tube decorating heat-shrinkable tube and the metal tube is improved. In addition, it is possible to suppress a change in the longitudinal length of the heat-shrinkable tube when the heat-shrinkable tube is heat-shrinked on the metal tube. Further, a good matte appearance can be obtained, and the feel and design can be improved.

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

The decorative metal tube includes a metal tube and a coating layer formed on an outer surface of a decoration target portion of the metal tube, and the coating layer is a shrinkable body formed by heating the metal tube decorating heat shrink tube. Therefore, it is possible to reduce the cost while having a good appearance.

Further, the method for manufacturing a decorative metal tube according to still another aspect of the present disclosure is to cover the outer surface of the metal tube decorative heat-shrinkable tube on the outer surface of the metal tube to be decorated, and heat-shrink it. Forming a coating layer;

The method for manufacturing a decorative metal tube includes a step of forming a coating layer by covering the outer surface of the metal tube decoration heat-shrinkable tube on the outer surface of a decoration target portion of the metal tube and heat-shrinking the heat-shrinkable tube. In addition, a decorative metal pipe having a good appearance can be manufactured, and cost can be reduced.

[Details of Embodiment of the Present Disclosure]
Hereinafter, each embodiment of the present disclosure will be described in detail.

<Heat-shrinkable tube for decorating metal tubes>
A heat-shrinkable tube for decorating a metal tube (hereinafter, also referred to as a heat-shrinkable tube) according to an embodiment of the present disclosure is used as a decorating coating material for imparting design properties to a metal tube. More specifically, the metal tube is decorated by heating the metal tube decoration heat-shrinkable tube into which the metal tube has been inserted, and covering the metal tube with a contracted body of the heat-shrinkable tube. You. The heat-shrinkable tube for decorating a metal tube is formed of a cylindrical single-layer heat-shrinkable layer. The heat shrink layer contains a base resin and a filler. In the heat-shrinkable tube for decorating a metal tube, there is no peeling of a coating film which is likely to occur in a decorating film, and there is no deterioration in design due to a seam. In addition, the heat shrinkable tube for decorating a metal tube does not require an adhesive layer, and is formed of a single layer of heat shrinkable layer, so that the manufacturing cost can be reduced.

下限 The lower limit of the arithmetic average roughness Ra of the inner surface of the heat-shrinkable tube for decorating a metal tube is 0.1 μm, preferably 0.3 μm, and more preferably 0.9 μm. If the arithmetic average roughness Ra of the inner surface of the metal tube decorating heat shrink tube is less than the lower limit, the frictional resistance between the inner surface of the metal tube decorating heat shrink tube and the metal tube becomes smaller, There is a possibility that the effect of suppressing the displacement between the shrinkable body and the metal tube due to the impact after coating the shrinkable body of the heat shrinkable tube on the metal tube may be reduced. On the other hand, the upper limit of the arithmetic average roughness Ra of the inner surface of the heat-shrinkable tube for decorating a metal pipe is 5.0 μm, preferably 3.0 μm, and more preferably 2.0 μm. When the arithmetic average roughness Ra of the inner surface of the metal tube decorating heat collection tube exceeds the upper limit, the contact area between the metal tube decorating heat shrink tube and the metal tube decreases, and the heat shrink tube There is a possibility that the effect of suppressing the displacement between the shrinkable body and the metal tube due to the impact after the shrinkable body is coated on the metal tube may be reduced. Further, when the heat-shrinkable tube shrinks in the longitudinal direction when it shrinks in the radial direction, the length in the longitudinal direction changes, but the arithmetic average roughness of the inner surface of the heat-shrinkable tube for decorating a metal tube is changed. By setting the Ra to the above range, an appropriate frictional resistance is generated between the inner surface of the heat shrinkable tube for decorating a metal tube and the metal tube, so that the heat shrinkable tube is thermally shrunk on the metal tube. The change in the length in the longitudinal direction of the heat-shrinkable tube at the time can be suppressed.

下限 The lower limit of the arithmetic average roughness Ra of the outer surface of the heat-shrinkable tube for decorating a metal tube is preferably 0.5 μm, more preferably 0.8 μm, and still more preferably 1.2 μm. If the arithmetic average roughness Ra of the outer surface of the heat shrinkable tube for decorating a metal tube is less than the above lower limit, the surface may be smoothed, the gloss may be increased, and the feel and design may be reduced. 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 tube is preferably 5.0 μm, more preferably 3.0 μm, and still more preferably 2.2 μm. When the arithmetic average roughness Ra of the outer surface of the heat shrinkable tube for decorating the metal tube exceeds the above upper limit, the outer surface of the heat shrinkable tube for decorating the metal tube becomes rough, and the tactile sensation and design may be reduced. There is. The arithmetic average roughness Ra is a value measured according to JIS-B0601 (2013).

The heat shrinkage rate in the radial direction when the heat shrinkable tube for decorating a metal pipe is heat shrunk on the metal pipe is preferably 30% or more and 75% or less. Since the heat shrinkage in the radial direction is in the above range, the stress applied to the metal tube during coating of the metal tube can be maintained in a favorable range, and thus, after the heat shrinkable body of the heat shrink tube is coated on the metal tube by heating. The displacement between the shrinkable body and the metal tube due to impact can be suppressed. In addition, when the heat shrinkage in the radial direction is less than 30%, the adhesion of the heat shrinkable tube for decorating a metal tube to the metal tube may be insufficient. On the other hand, if the heat shrinkage in the radial direction exceeds 75%, the thickness of the heat shrink layer may vary, or the manufacturing cost may increase.
The radial heat shrinkage [%] is determined by the following equation.
Radial heat shrinkage [%] = [(inner diameter before heat shrinkage−inner diameter after completion of heat shrinkage) / inner diameter before heat shrinkage] × 100

The lower limit of the rate of change of the length in the longitudinal direction of the heat-shrinkable tube when the heat-shrinkable tube for heat-decreasing the metal tube is shrunk on the metal tube is preferably -10%, more preferably -5%. . The upper limit of the rate of change in the length of the heat-shrinkable tube in the longitudinal direction is preferably 5%, more preferably 0%. When the rate of change in the length in the longitudinal direction of the heat-shrinkable tube is within the above range, it is easy to cover the end of the portion to be decorated of the metal tube without excess or shortage, and the metal tube has a good design property. A decorative metal tube can be obtained.

平均 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 design properties and maintaining mechanical strength. If the average thickness of the heat-shrinkable tube is smaller than 0.05 mm, the strength of the tube may be reduced and tear or tear may occur. When the average thickness of the heat-shrinkable tube is larger than 0.8 mm, the tube thickness at the end face is conspicuous, and there is a possibility that the design property may be deteriorated.

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

色 The color of the heat shrinkable tube for decorating a metal tube can be adjusted to a desired color by adding a coloring agent. The color can be adjusted by 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 shrink layer]
The heat-shrinkable layer is formed as a tube whose diameter is reduced by heating. The heat-shrinkable layer contains a base resin containing an ethylene-based copolymer and an acid-modified olefin-based resin, and a filler.

(Base resin)
The base resin includes an ethylene-based copolymer and an acid-modified olefin-based resin. The mass ratio of the ethylene-based copolymer to the acid-modified olefin-based resin in the base resin is from 40/60 to 95/5. When the mass ratio of the ethylene-based copolymer and the acid-modified olefin-based resin in the base resin is within the above range, the adhesion between the base resin and the filler is improved, and the streaks due to the separation of the base resin and the filler are improved. Can be suppressed. Further, when the mass ratio of the ethylene-based copolymer to the acid-modified olefin-based resin in the base resin is within the above range, pseudo crosslinking (degree of fine crosslinking) via the filler of the acid-modified olefin-based resin is performed. Is in an appropriate range. As a result, the shrinkage at a temperature of 50 ° C. or less is suppressed, and the shape retention during storage can be improved. Furthermore, when the base resin contains an acid-modified olefin-based resin, the base resin has good polarity and is easily bonded by adsorption, so that the affinity with the metal to be coated can be improved. Thereby, the effect of suppressing the displacement between the shrinkable body and the metal tube due to the impact after coating the shrinkable body of the heat shrinkable tube on the metal tube is excellent.

Here, the acid-modified olefin-based resin is an olefin-based resin having an acidic functional group in a side chain, an olefin-based resin having an acidic functional group incorporated in a main chain, or having an acidic functional group in a side chain. An olefin resin having an acidic functional group incorporated therein. By using an acid-modified olefin-based resin modified with an acid component, appropriate heat shrinkability can be imparted, and the resin can be obtained at relatively low cost. Furthermore, when the base resin contains an acid-modified olefin-based resin, the base resin has a good polarity, and is easily bonded by adsorption, so that the affinity with a metal can be improved. Thereby, the effect of suppressing the displacement between the shrinkable body and the metal tube due to the impact is excellent.

Examples of the olefin resin to be acid-modified include ethylene resins such as polyethylene, ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-acrylate ester copolymer, ethylene-methacrylate ester copolymer, and the like.
Examples include propylene-based resins such as polypropylene, propylene-acrylate copolymer, propylene-methacrylate copolymer, propylene-acrylate ester copolymer, and propylene-methacrylate ester copolymer.
Among these, ethylene resins are preferred.

Examples of the ethylene resin include very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), Methyl methacrylate copolymer and the like can be mentioned. Among these, ultra-low density polyethylene is preferred from the viewpoint of the flexibility of the resin.

The acid used for the acid modification is not particularly limited as long as the effects of the present disclosure are not impaired, and examples thereof include an unsaturated carboxylic acid or a derivative thereof. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid and the like.
Examples of the unsaturated carboxylic acid derivative include maleic acid monoester, maleic anhydride, itaconic acid monoester, itaconic anhydride, fumaric acid monoester, fumaric anhydride and the like. Among these, while improving the retention of the filler by increasing the affinity with the filler, the effect of suppressing the displacement between the shrinkable body and the metal tube due to the impact is improved by increasing the affinity with the metal tube. From the viewpoint of being possible, derivatives of unsaturated carboxylic acids are preferred, and maleic anhydride is more preferred.

Examples of the acid-modified olefin resin include maleic anhydride-modified ultra-low density polyethylene, maleic anhydride-modified linear low-density polyethylene, maleic anhydride-modified ethylene-vinyl acetate copolymer, and maleic anhydride-modified ethylene-ethyl acrylate copolymer. It is preferable to use a copolymer or a maleic anhydride-modified ethylene-methyl methacrylate copolymer. Among these, maleic anhydride-modified ultra-low density polyethylene and maleic anhydride-modified straight resin are used from the viewpoint of the flexibility of the resin, the retention of the filler, and the effect of suppressing the displacement between the metal tube decorating heat-shrinkable tube and the metal tube. Chain low density polyethylene is more preferred.

The content of the acid component in the acid-modified olefin resin is preferably 0.5% by mass or more and 6.0% 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 of acid component / mass of entire acid-modified olefin resin] × 100

下限 The lower limit of the content of the acid component with respect to the base resin is 0.2% by mass, and preferably 0.6% by mass. When the content of the acid component is less than the lower limit, the adhesiveness between the base resin and the filler may be reduced, and the effect of suppressing the generation of streaky patterns due to the separation of the base resin and the filler may be reduced. Further, when the value is less than the lower limit, sufficient frictional resistance between the metal tube and the heat-shrinkable tube cannot be obtained, and the effect of suppressing a change in the longitudinal length of the heat-shrinkable tube may be reduced. On the other hand, the upper limit of the content of the acid component is 1.2% by mass, and preferably 1.0% by mass. If the content of the acid component exceeds the above upper limit, the shrinkage at a temperature of 50 ° C. or lower may increase, and the shape retention during storage may decrease. In addition, the mechanical strength of the heat-shrinkable layer is reduced, and the heat-shrinkable tube is easily deformed. The effect of reducing the rate of change may be reduced.

下限 The lower limit of the content of the acid-modified olefin resin to the base resin is preferably 5% by mass. When the content of the acid-modified olefin-based resin is less than the lower limit, the frictional resistance between the metal tube and the heat-shrinkable tube is not sufficiently obtained, and the effect of suppressing the change in the longitudinal length of the heat-shrinkable tube is reduced. There is a risk. On the other hand, the upper limit of the content of the acid-modified olefin resin is preferably 60% by mass. When the content of the acid-modified olefin resin exceeds the upper limit, the productivity of the tube may be deteriorated.

The above-mentioned ethylene-based copolymer can provide appropriate heat shrinkability and can be obtained at relatively low cost. Examples of the ethylene copolymer include ethylene-propylene copolymer, ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), and ethylene-butyl acrylate copolymer (EBA). Ethylene-methacrylate ester copolymers such as ethylene-acrylate ester copolymer, ethylene-methyl methacrylate copolymer, etc., ethylene-acrylate copolymer, ethylene-methacrylate copolymer, ethylene-vinyl acetate copolymer (EVA), etc. Is mentioned.
As the ethylene-based copolymer, ethylene-ethyl acrylate copolymer (EEA) and ethylene-vinyl acetate copolymer (EVA) are preferable among these from the viewpoint of cost.
The olefin resins may be used alone or in combination of two or more.

When the ethylene-based copolymer contains a resin having an ethyl acrylate unit or a vinyl acetate unit, the lower limit of the content of the ethyl acrylate unit or the vinyl acetate unit with respect to the base resin is preferably 3.0% by mass, and more preferably 5% by mass. 0.0% by mass is more preferred. When the content of the ethyl acrylate unit is less than the lower limit, the effect of suppressing the generation of streak patterns may be reduced. In addition, the affinity for the metal tube is reduced, and the effect of suppressing the displacement between the shrinkable body and the metal tube due to the impact may be reduced. On the other hand, the upper limit of the content of the ethyl acrylate unit or the vinyl acetate unit is preferably 23.0% by mass, and more preferably 15% by mass. When the content of the ethyl acrylate unit or the vinyl acetate unit exceeds the above upper limit, the effect of suppressing the generation of streak patterns may be reduced. Further, the mechanical strength of the heat-shrinkable layer is reduced and the heat-shrinkable layer is easily deformed, so that the effect of suppressing the displacement between the shrinkable body and the metal tube due to the impact may be reduced.
For measuring the content of the ethyl acrylate unit, a known method such as infrared spectroscopy (IR) can be used.

添加 Additives may be added to the base resin as needed. Examples of such additives include a strength retaining agent, an antioxidant, a flame retardant, a copper damage inhibitor, a lubricant, a colorant, a heat stabilizer, and an ultraviolet absorber. The content of the additive in the base resin is more preferably less than 20% by mass, and further preferably less than 10% by mass. When the content of the additive is equal to or more than the above upper limit, the properties of the heat-shrinkable layer may be likely to vary.

(Filler)
When the heat-shrinkable layer contains a filler, the cost of the heat-shrinkable tube for decorating a metal tube can be reduced and the flame retardancy can be imparted. Further, the surface roughness of the heat shrinkable tube for decorating a metal tube can be adjusted to an appropriate range.

Examples of the filler material 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.

In addition, as a material of the filler, a filler composed of an element having an atomic number of 20 or less is preferable in the case of complying with the standards of the Food Sanitation Law depending on the use of food, beverage, medicine, toy, and the like. Examples of the filler composed of an element 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. Can be

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

The lower limit of the average particle diameter of the filler is preferably 0.5 μm, more preferably 1.0 μm. When the average particle diameter of the filler is less than the lower limit, the arithmetic average roughness Ra of the inner surface of the heat-shrinkable tube for decorating a metal pipe is reduced, so that the effect of suppressing the displacement may be reduced. On the other hand, the upper limit of the average particle diameter of the filler is preferably 20.0 μm, more preferably 10.0 μm. If the average particle diameter of the filler exceeds the upper limit, the adhesion between the metal tube decorating heat-shrinkable tube and the metal tube may be reduced. By setting the average particle diameter of the filler in the above range, the arithmetic average roughness Ra of the inner surface can be controlled in a favorable range, so that the length of the heat shrinkable tube when the heat shrinkable tube is heat shrunk on a metal tube is reduced. A change in the length in the direction can be suppressed. Further, by setting the average particle diameter of the filler in the above range, a good matte appearance can be obtained, and the feel and design can be improved.
In addition, the said average particle diameter means the particle diameter at the integrated value 50% in a particle size distribution which measures a particle diameter by a laser diffraction method.

は The lower limit of the content of the filler with respect to the base resin is preferably 5% by volume, more preferably 10% by volume. When the content of the filler is less than the lower limit, the arithmetic mean roughness Ra of the inner surface of the heat shrinkable tube for decorating a metal tube is reduced, and the heat shrinkable tube for decorating a metal tube is caught by the metal tube. The effect of suppressing the displacement between the shrinkable body and the metal tube due to the impact may be reduced. On the other hand, the upper limit of the carbon atom ratio is 30% by volume, preferably 20% by volume. When the content of the filler exceeds the upper limit, even when the composition of the base resin is in the above range, it may be difficult to suppress whitening. Further, the mechanical strength of the heat shrinkable tube for decorating a metal pipe may be reduced.

(4) The heat shrinkable tube for decorating a metal tube has good shrinkage characteristics and can improve the appearance and reduce the cost. Therefore, the heat shrinkable tube for decorating a metal tube can be suitably used as a decorating material for a metal tube for various industrial uses, for example, food, beverage, medicine, toys, and the like.

<Decorative metal pipe>
The decorative metal tube includes a metal tube and a coating layer formed on an outer surface of a decoration target portion of the metal tube, and the coating layer is a shrinkable body formed by heating the metal tube decorating heat shrink tube. It is. The decorative metal tube has a good appearance because the coating layer formed on the outer surface of the decoration target portion of the metal tube is a contracted body formed by heating the heat shrinkable tube for decorating the metal tube. Cost reduction can be achieved. FIG. 1 is a schematic perspective view illustrating a decorative metal tube according to an embodiment of the present disclosure. As shown in FIG. 1, the decorative metal tube 10 includes a metal tube 1 and a coating layer 2 formed on an outer surface of a portion to be decorated of the metal tube. In the present embodiment, the entire outer surface of the metal tube is a decoration target portion.

(Metal tube)
A metal tube made of, for example, stainless steel, aluminum, brass, or the like can be used as a coating target of the heat shrink tube for decorating a metal tube. In addition, the metal tube includes a cylindrical metal material, a bottomed cylindrical metal tube, and the like, in addition to the cylindrical metal tube. Further, a cylindrical shape having a step having a plurality of diameters may be used.

下限 The lower limit of the arithmetic average roughness Ra of the outer surface of the metal tube is preferably 0.05 μm, more preferably 0.30 μm. When the arithmetic average roughness Ra of the outer surface of the metal tube is less than the lower limit, the frictional force between the metal tube decorating heat-shrinkable tube and the outer surface of the metal tube is reduced, and There is a possibility that the effect of suppressing displacement from the metal tube may be reduced. On the other hand, the upper limit of the arithmetic average 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 tube exceeds the upper limit, the outer surface may be roughened by affecting the surface of the coating layer, and the design may be deteriorated.

<Production method of decorative metal tube>
The method for manufacturing a decorated metal pipe includes a step of covering the outer surface of the metal pipe decoration heat-shrinkable tube on the outer surface of a portion to be decorated of the metal pipe and heating and shrinking the outer surface to form a coating layer. According to the method for manufacturing a decorative metal tube, a decorative metal tube having a good appearance can be manufactured, and the cost can be reduced. The decoration target portion of the metal tube includes not only the entire outer surface of the metal tube but also a predetermined part of the outer surface of the metal tube. The method for manufacturing a decorative metal tube includes, for example, the following steps including other steps.
(1) A step of preparing a resin composition for a heat-shrinkable layer for forming a heat-shrinkable layer (hereinafter also referred to as a resin composition for a heat-shrinkable layer) (a step of preparing a resin composition for a heat-shrinkable layer)
(2) Step of extrusion-molding the resin composition for a heat-shrinkable layer by a melt-extrusion molding machine (extrusion-forming step) (3) Step of expanding the extruded product to obtain the heat-shrinkable tube for decorating a metal tube (expanding Diameter process)
(4) A step of forming the coating layer by covering the outer surface of the metal tube decoration target heat-shrinkable tube with the metal tube decoration heat-shrinkable tube and heat-shrinking the heat-shrinkable tube (coating layer forming step).

(1) Heat Shrinkable Layer Resin Composition Preparation Step In the heat shrinkable layer resin composition preparation step, the resin components of the heat shrinkable tube for decorating a metal tube, fillers, and additives as necessary are melt-mixed. To prepare a resin composition for a heat-shrinkable layer for forming a heat-shrinkable layer. As the melt mixer, a known mixer, for example, an open roll, a Banbury mixer, a pressure kneader, a single-shaft mixer, a multi-shaft mixer, or the like can be used.

(2) Extrusion Molding Step In the extrusion molding step, the resin composition for a heat-shrinkable layer is extrusion-molded by a melt extrusion molding machine.
Specifically, the resin composition for a 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 product corresponding to the heat-shrinkable layer is obtained.

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

(4) In this step, the base resin of the extruded product is crosslinked to impart shrinkage (shape memory effect) when heat shrinking at a high temperature after the diameter expansion step and shape retention at a high temperature after shrinkage. As a method of crosslinking the base resin, a method of irradiating the resin with radiation (irradiation crosslinking of the base resin) is preferable. Since the 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 performing radiation irradiation after the extrusion molding, the molding can be surely performed and the effect of the radiation irradiation can be sufficiently obtained.

(4) Examples of the radiation used for irradiation crosslinking of the base resin include electron beams (β rays) and γ rays. Since the electron accelerator has a low running cost, can obtain a high-power electron beam, and is easy to control, an electron beam is preferable as the radiation.

The radiation dose is preferably in the range of 80 kGy to 200 kGy. When the radiation irradiation amount is less than 80 kGy, the degree of cross-linking is reduced and the shape retention at the time of storage is improved, but the shape retention at a high temperature after shrinkage may be reduced. On the other hand, when the radiation irradiation amount is more than 200 kGy, the shrinkage at 50 ° C. or less increases, the shape retention during storage decreases, and the tube may increase in strength, making it difficult to expand the diameter.

The lower limit of the gel fraction which is an index of the degree of crosslinking of the base resin is preferably 30%, more preferably 40%. When the gel fraction is less than the lower limit, the shape retention at the time of storage can be improved, but the shape retention at a high temperature may be reduced. On the other hand, the upper limit of the gel fraction is preferably 90%, more preferably 80%. If the gel fraction exceeds the above upper limit, the shape retention during storage may decrease. The gel fraction refers to the mass of the solid content after immersing the heat-shrinkable layer in xylene (100%) and heating and dissolving it at 120 ° C. for 24 hours to W1 [g], and setting the heat-shrinkable layer before immersion in xylene. Is the value obtained from the following formula, when the mass of the sample is W2 [g].
Gel fraction [% by mass] = [W1 / W2] × 100 (1)

(3) Diameter expansion step In the diameter expansion step, the diameter of the extruded product is expanded. As a method of expanding the diameter of the extruded product, a known method of expanding the diameter which is usually used for manufacturing a conventional heat-shrinkable tube can be used. For example, a method of introducing compressed air into an extruded product while the extruded product is heated to a temperature equal to or higher than the melting point, a method of reducing the pressure from the outside, a method of inserting a metal rod, or the like is used to expand the diameter to a predetermined inner diameter. Then, a method of cooling and fixing the shape is used. The diameter expansion of such an extruded product is performed, for example, so that the inner diameter of the extruded product is 1.2 times or more and 4 times or less. By fixing the shape of the extruded product whose diameter has been increased, the heat-shrinkable tube for decorating a metal pipe can be obtained. As the fixing method, for example, a method of cooling to a temperature equal to or lower than the melting point of the base resin component and the like can be mentioned. In the diameter-expanding step, in order to reduce the influence on the surface roughness of the inner surface of the heat-shrinkable tube, the roughness of the metal rod can be reduced, and a coating or a lubricant can be applied. Further, by reducing the speed of the diameter expansion, 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 tube is inserted into the heat shrinkable tube for decorating the metal tube, and the heat shrinkable tube for decorating the metal tube is placed outside the portion to be decorated of the metal tube. A decorative metal pipe is manufactured by covering the surface and shrinking it by heating to form a coating layer. The heat shrink temperature in the coating layer forming step is preferably from 80 ° C to 200 ° C. In addition, at the time of the coating layer forming step, the length of the heat-shrinkable tube relative to the metal tube is taken into account in consideration of the rate of change in the longitudinal length of the heat-shrinkable tube during the heat-shrinkage of the decorative heat-shrinkable tube. Can be adjusted.

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

Next, the present disclosure will be described in more detail based on embodiments. However, the examples do not limit the scope of the present invention.

<Heat shrinkable tube No. for decorative metal tube 1 to No. 17>
No. 1 consisting of a single heat-shrinkable layer was obtained by the following procedure. 1 to No. Seventeen heat shrink tubes for decorating metal tubes were formed. Hereinafter, EA indicates ethyl acrylate, and VA indicates vinyl acetate.

(Base resin)
Examples of the ethylene-based copolymer include an ethylene-acrylate ethyl copolymer having an EA unit content of 15% by mass (EEA, density: 0.930 g / cm ³ ) and an ethylene-acrylate ethyl copolymer having an EA unit content of 25% by mass. It was used from a coalesced product (EEA, density 0.930 g / cm ³ ) and an ethylene-vinyl acetate copolymer (EVA, density 0.930 g / cm ³ ) having a VA unit content of 15% by mass.
Further, as the acid-modified olefin-based resin, a maleic anhydride-modified ultra-low-density polyethylene (maleic anhydride-modified VLDPE, density 0.873 g / cm ³ ) having a maleic anhydride component content of 2% and a maleic anhydride component One of maleic anhydride-modified linear low-density polyethylene (maleic anhydride-modified LLDPE, density 0.906 g / cm ³ ) having an amount of 2% was used.
As other resins, linear low-density polyethylene (LLDPE, density 0.920 g / cm ³ ) was used.

(Filler)
The filler was selected from calcium carbonate, aluminum hydroxide and magnesium hydroxide.

(4) A resin composition for a heat-shrinkable layer was prepared using the above base resin and filler. Table 1 shows the composition of the base resin, the content of the acid component with respect to the base resin, the average particle size and the content of the filler. "-" 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.

(4) After preparing the resin composition for a heat shrinkable layer, a mold was set, and the resin composition for a heat shrinkable layer was pressed and extruded from the mold to obtain a molded tube. Next, this molded tube was irradiated with radiation under the irradiation conditions shown in Table 1. The outer diameter of the molded tube was 5 mm and the inner diameter was 4 mm. Next, a heat-shrinkable tube for decorating a metal pipe having an outer diameter of 10 mm and an inner diameter of 9.5 mm was obtained by expanding the extruded tube with a diameter expanding device.

[Evaluation]
Heat shrinkable tube No. for decorative metal tube 1 to No. For No. 17, the gel fraction, the suppression of the generation of streak-like patterns, the shape retention during storage, and the shape retention at high temperatures were evaluated.

(Gel fraction)
A sample of 1 g of the heat-shrinkable tube for decorating a metal tube was immersed in 20 g of xylene and heated at 120 ° C. for 24 hours. After the heating, the xylene solution was collected and filtered, and the insoluble matter remaining on the filter paper was collected.
Next, this insoluble matter was dried, and the mass of the insoluble matter after drying was defined as W1 [g]. Then, the gel fraction [% by mass] was determined from the following equation.
Gel fraction [% by mass] = [W1 / 1] × 100

(Inhibition of streak pattern generation)
The appearance was evaluated for the appearance of streak-like patterns on the surface of the heat-shrinkable tube for decorating each metal tube after the diameter-expanding step. The occurrence of the streak-like pattern was evaluated in two stages of A and B. The evaluation criteria for the generation of the streak pattern were as follows.
A: No streak pattern on tube surface B: Streak pattern on tube surface

(Shape retention during storage)
Each of the heat-shrinkable tubes for decorating a metal pipe after the above-described diameter expansion step was stored under a constant temperature condition of 50 ° C., and the shrinkage rate after one month was measured was used as an index of shape retention during storage. . Then, the shrinkage ratio [%] was determined from the following equation.
Shrinkage [%] = ｛[(tube inner diameter before storage at 50 ° C.) − (Tube inner diameter after storage at 50 ° C.)] / [(Tube inner diameter before storage at 50 ° C.) − (Each metal tube The inner diameter of the heat-shrinkable tube for decoration before the diameter expansion step)] 工程 100.
If the shrinkage after storage at 50 ° C. for one month is 10% or less, it is judged as acceptable.

(Shape retention at high temperature)
The heat-shrinkable tubes for decorating metal pipes after the above-mentioned diameter expansion step were observed under a constant temperature condition of 150 ° C. for a change in shape after a lapse of 24 hours. The evaluation was made in two stages of A and B based on the change in the shape of the heat shrinkable tube for decorating each metal tube. The evaluation criteria for the change in the shape of the heat-shrinkable tube for decorating a metal tube were as follows.
A: There is no problem in shape change.
B: Change in shape is observed.

Table 1 shows the evaluation results of the gel fraction of the heat-shrinkable tube, the suppression of generation of streak patterns, the shape retention during storage, and the shape retention at high temperatures.

As shown in Table 1, a single-layer heat-shrinkable layer containing a base resin containing an ethylene-based copolymer and an acid-modified olefin-based resin and a filler, wherein the acid-modified ethylene-based copolymer in the base resin was used. The mass ratio of the olefin-based resin to the olefin-based resin is 40/60 or more and 95/5 or less, and the content of the filler to the base resin is 30% by volume or less. 1 to No. The heat-shrinkable tube for decorating a metal tube of No. 11 was excellent in all of the suppression of generation of streak-like patterns, the shape retention during storage, and the shape retention at high temperatures.

On the other hand, the mass ratio of the ethylene-based copolymer to the acid-modified olefin-based resin in the base resin is less than 40/60 or more than 95/5. 12-No. The heat-shrinkable tube for decorating a metal tube of No. 16 was inferior in any of suppressiveness against generation of a streak-like pattern, shape retention during storage, and shape retention at high temperatures. In addition, as the present inventors guessed, No. 1 containing only an acid-modified olefin-based resin. The heat-shrinkable tube for decorating a metal tube of No. 14 did not show any streak-like pattern due to the improved adhesiveness between the filler and the resin, but pseudo-crosslinking was formed by the acid-modified olefin-based resin, Since the amount of crystals in the base resin was reduced, shape retention during storage at 50 ° C. was poor. On the other hand, in the same manner, No. 1 containing only the acid-modified olefin resin was used. The heat-shrinkable tube for decorating a metal tube of No. 15 improved the shape retention during storage by lowering the irradiation amount to the base resin, reducing the gel fraction and lowering the degree of cross-linking. Retention was poor.
In addition, in the case of No. 3 in which the content of the filler with respect to the base resin was more than 30% by volume. In the heat-shrinkable tube for decorating a metal tube of No. 17, a streak-like pattern was generated.

The above results show that the heat-shrinkable tube for decorating a metal tube has a high effect on all aspects of suppressing the generation of streak patterns, maintaining shape during storage, and maintaining shape at high temperatures.

DESCRIPTION OF SYMBOLS 1 Metal tube 2 Coating layer 10 Decorative metal tube

Claims

Consisting of a single-layer heat-shrinkable layer containing a base resin and a filler including an ethylene-based copolymer and an acid-modified olefin-based resin,
A mass ratio of the ethylene-based copolymer to the acid-modified olefin-based resin in the base resin is 40/60 or more and 95/5 or less;
A heat-shrinkable tube for decorating a metal tube, wherein the content of the filler with respect to the base resin is 30% by volume or less.
The heat-shrinkable tube for decorating a metal tube according to claim 1, wherein the gel fraction of the base resin is 30% or more and 90% or less.
The metal tube decoration according to claim 1 or 2, wherein the content of the acid component bonded to the acid-modified olefin-based resin with respect to the base resin is 0.2% by mass or more and 1.2% by mass or less. Heat shrink tubing.
The ethylene-based copolymer contains a resin having an ethyl acrylate unit or a vinyl acetate unit,
The heat shrinkage for decorating a metal pipe according to claim 1, wherein the content of the ethyl acrylate unit or the vinyl acetate unit with respect to the base resin is from 3.0% by mass to 23.0% by mass. tube.
The heat-shrinkable tube for decorating a metal tube according to any one of claims 1 to 4, wherein the filler is an inorganic particle composed of an element having an atomic number of 20 or less.
The arithmetic mean roughness Ra of the inner surface of the heat shrinkable tube for decorating a metal tube is 0.1 μm or more and 5.0 μm or less, and the metal tube decorating tube according to any one of claims 1 to 5. Heat shrink tubing.
The arithmetic mean roughness Ra of the outer surface of the heat shrinkable tube for decorating a metal tube is 0.5 μm or more and 5.0 μm or less, the metal tube decorating tube according to any one of claims 1 to 6. Heat shrink tubing.
The heat-shrinkable tube for decorating a metal pipe according to any one of claims 1 to 7, wherein the filler has an average particle diameter of 0.5 µm or more and 20.0 µm or less.
Metal tubes,
And a coating layer formed on an outer surface of a decoration target portion of the metal tube.
A decorated metal pipe, wherein the coating layer is a shrinkable body of the heat shrinkable tube for decorating a metal pipe according to claim 1.
A step of forming the coating layer by covering the heat-shrinkable tube for decorating a metal tube according to any one of claims 1 to 8 on an outer surface of a portion to be decorated of the metal tube and heat-shrinking the tube. A method for manufacturing a decorated metal tube comprising: