JPH10151682A - Production of coated formed resin tube fitted with patterns - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent patterning shape inferiority by compounding a specific amt. of a silane compd., a tin catalyst, an optical sensitizer and a crosslinking aid with a polyolefinic resin which becomes a base material to mold a foamed resin tube, and irradiating the tube with ultraviolet rays at a stage up to extruding a non-foamed resin coating layer to cover the tube. SOLUTION: 0.1-5 pts.wt. of a silane compd. and a proper amt. of a polymerization initiator are added to 100 pts.wt. of a polyolefinic resin to form resin pellets. Next, 0.01-2 pts.wt. of a tin catalyst, 0.1-5 pts.wt. of an optical sensitizer and 0.1-5 pts.wt. of a crosslinking aid are added to 100 pts.wt. of the polyolefinic resin to be kneaded therewith and a volatile org. foaming agent is introduced into the molten kneaded mixture to extrude this mixture from the leading end of an extruder 1 to foam the same to continuously mold a foamed resin tube 2. Next, the foamed resin tube 2 is cooled and the surface thereof is irradiated with ultraviolet rays and a non-foamed surface coating film layer is continuously extruded by a coating mold 7 to be applied to the outer surface of the foamed resin tube 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a coated foamed resin tube with a squeezed pattern used as a heat insulating material for piping of a hot water supply device, a solar heat utilization device, an air conditioner, and the like. The present invention relates to a method for continuously extruding and foaming a polyolefin-based resin with a foaming agent, and relates to a method for crosslinking a foamed resin tube by an ultraviolet irradiation crosslinking method and a silane crosslinking method.

[0002]

2. Description of the Related Art In general,
In order to heat and protect the piping of hot water supply equipment, solar heat utilization equipment, air conditioning equipment, etc., tube moldings made of foamed resin such as foamed polyethylene are provided, but they prevent wrinkling during bending. In order to absorb the wrinkles or wrinkles and make them inconspicuous, to prevent the tube from being broken or damaged by pulling or rubbing with the corners during construction, and to give an aesthetic appearance, the outer peripheral surface There is a demand for a foamed resin tube with a squeezed pattern having a squeezed pattern. In addition, since a heat medium is passed through a pipe for keeping and protecting the temperature, the foamed resin tube used in this field is required to have heat resistance.

[0003] In order to meet the above demand, the present applicant first kneads and mixes a polyolefin-based raw material resin and a volatile organic blowing agent at high temperature and high pressure in an extruder, and forms the mixture into a tube. Extrusion and foaming at almost the same time as extrusion, forming a foamed resin tube continuously, and continuously extruding and forming a non-foamed resin coating layer on this foamed resin tube, then cooling and applying a drawn pattern to the roll surface A method of manufacturing a coated foamed resin tube with a drawn pattern, in which a drawn pattern is continuously formed on the outer surface of the non-foamed resin coating layer of the foamed resin tube by pressing against a drawn patterning roll having irregularities, has been proposed (JP-A-Hei. JP-A-3-207639). Although not explicitly disclosed in JP-A-3-207639, in the above-mentioned manufacturing method, the outer surface temperature of the foamed resin tube is adjusted to the melting point of the non-foamed resin ± 20 before applying the drawing pattern.
Heat to about ° C to soften the non-foamed resin coating layer.

However, in the foamed resin tube with a squeezed pattern manufactured by the above-described manufacturing method, the heat resistance of the foamed resin tube before the squeezed pattern is formed is not sufficient, and the skin portion of the foamed resin tube is damaged at the time of subsequent reheating. As a result, shape defects such as heat thinning may occur. In addition, the heat resistance of the foamed resin tube with a squeezed pattern, which is the final product manufactured by the above manufacturing method, is not sufficient, and a change in wall thickness and a change in length when actually used for piping of a hot water supply device or the like become large. There was a problem.

[0005] In order to improve the heat resistance of the foamed resin, it is general to carry out crosslinking, as described in, for example, Japanese Patent Publication No. 61-34969.

As such a crosslinking method, there are a silane crosslinking method in which a silane compound is added to a resin and a condensation reaction is carried out using a catalyst, and an ultraviolet crosslinking method in which ultraviolet energy is attacked on the resin to cause crosslinking therein. General,
Each has its own technical field. The reason is that these phenomena, which can be conceptualized by the same expression of cross-linking, also differ in the target substance attacking the resin, the generation path of the attack substance, the reaction path in which cross-linking is generated, etc. by individual cross-linking methods. It is said that it is not possible to discuss the expected effect with compatibility.

On the other hand, when these cross-linking methods are applied to the modification of a polyolefin resin foam to complete a series of continuous production methods, the unique disadvantages of these cross-linking methods become apparent. It is extremely difficult to make an economical and efficient manufacturing method that satisfies the target quality.

The reason is that in the silane crosslinking method, the time required to complete the crosslinking is as long as the date and time. For example, after forming a foamed resin tube, a non-foamed resin coating layer is extrusion-coated on the surface layer, and then heated (2 times). In the continuous molding process of forming a drawing pattern after heating (secondary heating), the thermal energy during molding of the non-foamed resin coating layer or secondary heating damages the foamed resin tube, especially the skin, and shape defects such as heat thinning occur. There are problems that are likely to occur.

Next, the ultraviolet crosslinking method has a drawback that the ultraviolet light itself has poor permeability to the resin, so that the crosslinking to the deep portion of the foam does not proceed by short-time ultraviolet irradiation, and the surface of the foamed resin tube has high crosslinking. Although the degree of cross-linking can be obtained, the degree of crosslinking inside is low, and it is difficult to obtain heat resistance of the entire foamed resin tube. It goes without saying that when the foamed resin tube is colored, the disadvantages are further increased.

[0010] The present invention is intended to solve such problems, and takes advantage of the advantages of the volatile organic foaming agent, such as high foaming properties and the continuity of uniform continuous foaming, to a molded foamed resin tube. Further, the present invention realizes an economical continuous molding process in which a non-foamed resin coating layer is formed and a drawn pattern is also provided. Specifically, the foamed resin tube extruded at a high speed is irradiated with ultraviolet rays to crosslink the foamed resin surface in a short time, impart heat resistance for subsequent processing, and form a non-foamed resin coating layer. We can manufacture coated foamed resin tubes with squeezed pattern in a consistent and continuous process without causing shape defects when applying squeezed pattern, and ensure the heat resistance of the manufactured squeezed covered foamed resin tube after installation It is intended to do so.

[0011]

According to the present invention, there is provided a method for producing a coated foamed resin tube having a squeezed pattern, comprising kneading and mixing a polyolefin-based raw material resin and a volatile organic foaming agent at a high temperature and a high pressure in an extruder. Is extruded into a tube and foamed almost at the same time as the extrusion, and a foamed resin tube is continuously formed, and a non-foamed resin coating layer is continuously formed by extrusion coating on the foamed resin tube, and then cooled. Adjust the outer surface temperature of the tube to the melting point of the non-foamed resin ± 2.
Re-heated to 0 ° C. to soften the non-foamed resin coating layer, and pressed against a squeezed pattern forming roll having irregularities for forming a squeezed pattern on the roll surface, and applied to the outer surface of the non-foamed resin coating layer of the foamed resin tube. A method for producing a coated foamed resin tube with a drawn pattern which continuously forms a drawn pattern, wherein the polyolefin-based resin as a base material is used as the polyolefin-based raw material resin.
0.1 to 5 parts by weight of a silane-based compound, 0.01 to 2 parts by weight of a tin-based catalyst,
Using a mixture of 5 parts by weight and 0.1 to 5 parts by weight of a crosslinking aid, the above foamed resin tube is molded, and then a non-foamed resin coating layer is continuously formed on the foamed resin tube by extrusion coating. In this process, the surface of the foamed resin tube is cross-linked by irradiating ultraviolet rays until the process is completed.

In the above method, the polyolefin-based resin serving as the base material of the polyolefin-based resin used includes polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, ethylene-propylene copolymer and the like. Of these, polyethylene such as low-density polyethylene, high-density polyethylene, linear polyethylene, ultra-low-density polyethylene, and ultra-high-molecular-weight polyethylene are preferred because of their high crosslinking efficiency. Of course,
These mixtures may be used.

As the silane compound, a compound represented by the general formula CH ₂ =
What can be represented by CHSi (OA) ₃ is preferable. Where A
Is a hydrocarbon group having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms, and examples thereof include vinyltrimethoxysilane, vinyltriethoxysilane, and vinyltriacetoxysilane. The silane-based compound may be used in combination of two or more kinds, and the compounding amount is appropriately determined based on the degree of crosslinking at the final stage. However, based on 100 parts by weight of the polyolefin-based resin,
It should be 0.1-5 parts by weight. If the amount is less than 0.1 part by weight, no cross-linking effect can be obtained, and if it exceeds 5 parts by weight, the amount becomes excessive, which adversely affects the physical properties and the like of the molded article after cross-linking.

The tin catalyst added to the polyolefin resin is for promoting silane crosslinking, and is used in combination with the silane compound. Examples of the tin catalyst include dibutyltin diacetate, dibutyltin dilaurate,
Dioctyltin dilaurate, tin octoate, tin oleate and the like. The amount of the tin-based catalyst may be appropriately determined, and may be 0.01 to 100 parts by weight of the polyolefin-based resin.
Should be ~ 2 parts by weight. If it is less than 0.01 part by weight, the effect of the addition cannot be sufficiently obtained, and if it exceeds 2 parts by weight, it becomes excessive and adversely affects the physical properties of the molded product after crosslinking, which is disadvantageous.

The method of compounding the silane compound and the tin catalyst is not specified, but it is general to graft-modify the silane compound and the tin catalyst to the polyolefin base resin.

The photosensitizer initiates ultraviolet crosslinking, and examples of such a photosensitizer include acetophenone,
Examples thereof include benzophenone, thioxanthone, benzyl, benzoyl, and Michler's ketone. Among them, a hydrogen abstraction type photosensitizer such as benzophenone and thioxanthone is preferably used. The amount of the photosensitizer should be 0.01 to 5 parts by weight based on 100 parts by weight of the polyolefin resin. If the amount is less than 0.1 part by weight, the crosslinking effect cannot be obtained.

The crosslinking aid promotes ultraviolet crosslinking. Examples of such a crosslinking aid include diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, trimethylolpropane trimethacrylate, methyl methacrylate and the like. Can be suitably used, and the amount should be 0.1 to 5 parts by weight based on 100 parts by weight of the polyolefin resin. If the amount is less than 0.1 part by weight, the crosslinking effect cannot be obtained, and if it exceeds 5 parts by weight, the amount becomes excessive and adversely affects the physical properties of the molded article after crosslinking, which is disadvantageous.

The method of compounding the photosensitizer and the crosslinking assistant is not particularly limited.

The above-mentioned polyolefin raw material resin may be blended with additives, fillers and the like, if necessary.

In the above method for producing a coated foamed resin tube having a drawn pattern, the degree of surface cross-linking of the crosslinked foamed resin tube immediately after irradiation with ultraviolet rays is 10 to 50% in terms of gel fraction at the surface of the foamed resin tube. The degree of crosslinking of the entire tube is preferably 30 to 60% as a gel fraction in the final crosslinking step. The gel fraction of the surface portion is usually
It refers to the measured value of the gel fraction of the foamed resin tube up to 1 mm from the surface.

The reason why the degree of cross-linking of the entire foamed resin tube is 30 to 60% in terms of the gel fraction in the final cross-linking step is that silane cross-linking proceeds even after irradiation with ultraviolet rays.

If the foamed resin tube is molded and the surface partial gel fraction after irradiation with ultraviolet rays is more than 10%, the surface heat resistance of the foamed resin tube cannot be obtained. The resin coating layer is damaged by thermal energy at the time of molding or applying a squeezed pattern, and is likely to cause a shape defect such as a thin skin. Conversely, it takes irradiating time to obtain a gel fraction exceeding 50%, which is uneconomical.

If the gel fraction of the whole foamed resin tube in the final cross-linking step is less than 30%, heat resistance in use after construction cannot be obtained. The heat resistance required for this type of heat insulating material is about 100 to 120 ° C. Conversely, if it exceeds 60%, the rigidity of the foamed resin tube itself is improved, and workability such as post-processing is reduced.

Here, the degree of cross-linking is evaluated by the gel fraction. In this case, the gel fraction refers to a portion of a molded article to be measured which is to be measured, and is applied to xylene at 120.degree.
It refers to the ratio (weight% ratio) of the insoluble content after immersion for a time to the molded product before dissolution.

The volatile organic blowing agent used in the present invention includes propane, butane, propylene, butene, isobutene, dichlorodifluoromethane, 1,2-dichlorotetrafluoroethane, dichlorofluoromethane, trichlorofluoromethane, monochlorofluoromethane. , 1,
There are 1,2-trichlorotrifluoroethane, monochloropentafluoroethane, octafluorocyclobutane, monochlorodifluoromethane, monochlorobromodifluoroethane, and mixtures thereof are also useful. The limit of the amount may be appropriately determined based on the target foam density.

The method for forming the foamed resin tube is not particularly limited, and is formed by a conventionally known technique.

As a method for irradiating ultraviolet rays after the foamed resin tube is formed, a high-pressure mercury lamp, a metal halide lamp, or the like can be suitably used. Regarding the arrangement of the lamp at the time of irradiation, it is preferable that the light is applied at the same distance as possible over the entire surface of the foamed resin tube, and the distance between the lamp and the foamed resin tube is preferably about 50 to 300 mm. The reason is that if the distance is shorter than 50 mm, the surface cell layer of the foamed resin tube may contract due to radiant heat of the lamp, and if it exceeds 300 mm, the irradiation efficiency may be deteriorated. The illuminance at the time of irradiating the ultraviolet rays is not particularly limited, but is usually preferably in the range of 20 to 70 mw / cm ² . Although the irradiation time is not particularly limited, for example, when molding at a line speed of 20 m / min, it is preferably 3 to 5 seconds.

Next, the continuous production method of continuously extruding and forming a non-foamed resin coating layer on the foamed resin tube, followed by cooling, reheating and drawing is not particularly limited. After air-cooling the foamed resin tube irradiated with ultraviolet rays, it is introduced into a crosshead mold, and the non-foamed resin coating layer is continuously extruded and formed, and the outer surface of the cooled coated foamed resin tube is heated with hot air. The non-foamed resin coating layer is softened by reheating to the melting point of the non-foamed resin ± 20 ° C. using an apparatus or the like.
There is a method in which the concavities and convexities for applying a squeezing pattern formed on the roll surface are transferred to a non-foamed resin coating layer and cooled by passing between the pair of squeezed patterning rolls.

As the non-foamed resin used for the surface coating, a polyolefin-based resin is generally used as in the case of the foamed resin tube. In particular, in this type of molding having a high line speed, linear low-density polyethylene having good melt drawability is used. It is suitable.

(Function) According to the method of the present invention, the foamed resin tube formed is further coated with a non-foamed resin coating layer by taking advantage of the high foaming property of the volatile organic foaming agent and the continuity of uniform continuous foaming. And an economical continuous molding process that also provides a drawn pattern can be realized. In particular,
The foamed resin tube extruded at a high speed using the compounded resin of the present invention is irradiated with ultraviolet rays to crosslink the surface of the foamed resin tube in a short time to impart heat resistance for secondary processing, and to be coated with a non-foamed resin. The layer can be easily formed and drawn, and the coated foamed resin tube with drawn pattern can be manufactured in a consistent and continuous process. Further, the required heat resistance of the manufactured coated foamed resin tube with a squeezed pattern after construction can be secured by silane crosslinking.

[0031]

Embodiments of the present invention will be described below with reference to the drawings.

Here, FIG. 1 is a schematic structural view of an apparatus for carrying out the method for manufacturing a coated foamed resin tube with a squeezed pattern according to the present invention, and FIG. Longitudinal sectional view of the coating mold to be molded,
FIG. 3 is a cross-sectional view of a foamed resin tube formed with a non-foamed surface coating film layer obtained in the course of the method of the present invention.
FIG. 5 is a schematic configuration diagram of a drawing pattern processing machine, FIG. 5 is a cross-sectional view of a non-foamed surface coating film layer, FIG. 6 is a plan view of the non-foamed surface coating film layer, and FIG. FIG. 8 is a plan view of the surface coating film layer, and FIG. 8 is a perspective view showing a modification of the squeezing patterning roll.

First, an extruder (1)
Melt kneading in the first half of the barrel, adding 0.1 to 5 parts by weight of a silane compound to 100 parts by weight of a polypropylene resin from almost the center of the barrel, adding an appropriate amount of a polymerization initiator, and kneading sufficiently to obtain a silane graft. A modified polypropylene resin pellet is produced. Then, the tin-based catalyst was added to the extruder together with the above-mentioned pellets in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the polypropylene-based resin.
Input to (1). In the tin-based catalyst, an appropriate amount of a cell nucleating agent and a cell stabilizer are mixed in advance. At the same time that the tin-based catalyst is charged into the extruder (1), a photosensitizer and a cross-linking assistant are respectively supplied from the hopper port to the polypropylene resin 10.
After adding 0.1 to 5 parts by weight to 0 parts by weight and melt-kneading, from the injection port (1a) formed in the middle of the extruder (1),
After an appropriate amount of the volatile organic foaming agent is injected and kneaded and cooled, it is extruded from a predetermined die attached to the tip of the extruder (1), and is foamed into a cylindrical shape almost simultaneously with the extrusion. 2) Form.

Then, the foamed resin tube (2) is cooled and introduced into an ultraviolet irradiator (4) by take-off rolls (3a) and (3b). UV crosslinking is applied to the surface.

Next, the foamed resin tube (2) is introduced by a take-up roll (5a) (5b) into a coating mold (crosshead die) (7) connected to the tip of a non-foamed resin extruder (6). Further, a polypropylene resin is introduced into the coating mold (7) from the injection port (6a) formed in the extruder (6), and the coating mold (7)
The non-foamed surface coating film layer (8) (non-foamed resin coating layer) is continuously extruded by
(8) is applied to the outer peripheral surface of the foamed resin tube (2) to obtain a foamed resin tube (9) with a surface coating film layer (see FIGS. 2 and 3). Immediately thereafter, the foamed resin tube (9) with the surface coating film layer is air-cooled (not shown) and introduced into the drawing machine (10).

In the processing machine (10), the foamed resin tube (9) with the surface coating film layer is passed through a heating machine (12) equipped with a heating dryer (11), and the foamed tube (9) with the surface coating film layer is passed through. The surface temperature is the surface coating film layer
After reheating so that the melting point of (8) becomes ± 20 ° C., this tube (9) is passed between a pair of first drawn patterning rolls (13a) (13b) having a vertical cylindrical shape. The peripheral surface of the first drawing patterning rolls (13a) (13b), that is, irregularities for forming a drawing pattern are formed on the roll surface, and the two rolls (13a) and (13b) face each other. Are arranged as follows. Thus, the first squeezing rolls (13a) and (13b) are pressed against the surface coating film layer (8) from the front-rear direction, and the first squeezing roll (13a) is pressed against the outer surface of the foamed resin tube with the surface coating film layer (9).
The unevenness of (13b) is transferred.

Next, after heating the foamed resin tube (9) with the surface coating film layer by a plurality of heating dryers (17a) (17b), the tube (9) is heated by the first drawing rolls (13a) (13b). ) Is passed between a pair of second squeezing patterning rolls (14a) and (14b) arranged downstream from the). Second drawing patterning roll
(14a) (14b) has a horizontal cylindrical shape, and its peripheral surface, that is, a roll surface is formed with irregularities for applying a drawing pattern, and the two rolls (14a) (14b) have their peripheral surfaces facing each other. Are arranged as follows. Thus, the second drawing patterning roll (14a)
(14b) is pressed against the surface coating film layer (8) from above and below, and the second drawing pattern roll (14a) is pressed against the surface coating film layer (8).
The unevenness of (14b) is transferred.

The first and second drawing patterning rolls (13a) (13
b) (14a) (14b) store heat in each roll (13a) (13b) (1
4a) Cooling pipes provided on the axis of (14b) (15a) (15b) (16a) (16b)
And cool it at any time through cold water.

Thereafter, the foamed resin tube with the surface-coated film (9) is introduced into a cooler (18), and cooled by air cooling until the surface-coated film layer (8) is solidified. (19) and take over roll
(20a) and (20b). In this way, the coated foamed resin tube with a drawn pattern (19) is continuously manufactured. The squeezing pattern (24
5A and 5A, a large number of square pyramid-shaped projections are gathered as shown in FIGS.

The first and second squeezing patterning rolls (1
By changing the shape of the irregularities formed on the roll surfaces of 3a), (13b), (14a) and (14b), the drawn pattern (24b) of the manufactured coated foamed resin tube with drawn pattern (19) can be obtained as shown in FIG. As shown in (1), a large number of triangular pyramid-shaped protrusions may be formed.

FIG. 8 shows a modification of the first squeezing roll.

In FIG. 8, first squeezing rolls (22a) (22
The roll surface of b) is depressed in an arc shape in cross section over the entire circumference, and irregularities for forming a drawn pattern are formed in this portion. The cooling pipes (23a) (23b) are also connected to the first squeezing rolls (22a) (22b). The second squeezing roll can also have such a configuration.

Hereinafter, specific examples of the present invention will be described together with comparative examples.

[0044]

Example 1 First, a low-density polyethylene resin having a melt index of 2.1, a density of 0.92, and a melting point of 119 ° C. was melt-kneaded in the first half of the barrel of the extruder (1), and 100 weight parts of the low-density polyethylene resin was placed almost from the center of the barrel. Parts by weight, 1.5 parts by weight of vinyltrimethoxysilane, which is a silane compound, and 0.05 parts by weight of dicumyl peroxide, which is a polymerization initiator, were added and kneaded sufficiently to prepare silane-grafted modified polyethylene pellets. . Next, based on 100 parts by weight of the low-density polyethylene resin, 0.05 parts by weight of dibutyltin dilaurate as a tin-based catalyst, 0.3 parts by weight of talc as a cell nucleating agent, and stearamide 3 as a cell stabilizer. Parts of the low-density polyethylene resin and 100 parts by weight of the low-density polyethylene resin through a hopper port. 0.
5 parts by weight and 0.5 parts by weight of triallyl cyanurate as a cross-linking aid were added and melt-kneaded, and then dichlorodifluoro, a volatile organic blowing agent, was injected through an injection port (1a) of an extruder (1). Methane was press-injected in an amount equivalent to 28 times the expansion ratio, and after kneading and cooling, it was foamed into a cylindrical shape almost simultaneously with being extruded from the die of the extruder (1). (Hereinafter referred to as a foam tube) (2) was obtained.

Thereafter, the foamed tube (2) is air-cooled so that the surface temperature becomes equal to or lower than room temperature + 10 ° C.
In (4), the entire circumference of the foam tube (2) is 100
The surface was cross-linked by irradiating ultraviolet rays for 4 seconds with a high pressure mercury lamp at a distance of mm.

Next, the foamed tube (2) was introduced into a coating mold (7) connected to the tip of an extruder (6) having a diameter of 70 mm, and a melt index 2 containing a pigment, a density of 0.925, Linear low-density polyethylene having a melting point of 120 ° C. was introduced into the coating mold (7) from the injection port (6a) of the extruder (6),
Linear low-density polyethylene is coated with a mold (7) for 10
Extruded as a surface-coated film layer (8) having a thickness of 0 μm, and the surface-coated film layer (8) was applied to the outer peripheral surface of the foamed tube (2).
(9) was obtained.

Then, the foamed tube (9) with the surface-coated film layer is air-cooled, and the foamed tube (9) with the surface-coated film layer is cooled in the drawing machine (10) to a temperature of 120 ° C. ± 10 ° C. ° C to soften the surface coating film layer (8) by heating to
Is passed between the pair of first squeezing rolls (13a) and (13b) so that the rolls (13a) and (13b) are compressed from the front-rear direction to the coated surface film layer (8) (outside diameter after compression / compression). Front outer diameter)
Pressing was performed under the condition of 0.70.

Then, after heating the foamed tube (9) with the surface coating film layer, the tube (9) is placed on a pair of second drawn tubes 100 mm downstream from the first drawn patterning rolls (13a) (13b). By passing between the patterning rolls (14a) and (14b), the degree of compression of the rolls (14a) and (14b) from above and below to the surface coating film layer (8) (outside diameter after compression / outside diameter before compression).
Pressing was performed under the condition of 0.70. The first and second squeezing rolls (13a) (13b) (14a) (14b) were cooled as needed.

Thereafter, the foamed tube (9) with the surface-coated film was cooled until the surface-coated film layer (8) was solidified to obtain a coated foamed resin tube (19) with a drawn pattern.

The foamed tube (2) does not have any problems such as thinning during the molding of the surface coating film layer (8) and the heating for forming the drawing pattern, and the dimensions are in the initial target range (outer diameter of 2 mm).
4.5 ± 0.5 mm), and a beautifully formed coated foamed resin tube molded product with a drawn pattern was obtained.

In the above-described production method, the surface layer of the foamed tube (2) after being irradiated with the ultraviolet ray by the ultraviolet ray irradiator (4) was cut and sampled in a peeled state to a thickness of about 1 mm, and the gel fraction thereof was obtained. Was 18%.

Further, the coated foamed resin tube with the drawn pattern was left at room temperature for 2 weeks after molding, and the coated foamed resin tube was sampled into a cross-sectional shape to measure the gel fraction of the entire coated foamed resin tube. As a result, 3
7%.

Further, as a heat resistance test, a sample having a length of 500 mm was prepared from a coated foamed resin tube having a drawn pattern two weeks after molding, and a copper tube having an outer diameter of 8 mm and a length of 1000 mm was inserted into the sample. 120 at room temperature in copper tube
After passing oil at ℃ for 168 hours continuously, the sample from which the copper tube was removed was allowed to stand at room temperature for 24 hours, and the wall thickness change after cooling was measured. The change in wall thickness was determined by the formula {(initial wall thickness before test-wall thickness after heating and cooling) / initial wall thickness}, and as a result, it was 6.5%.

Further, the change in length was measured in the same manner as described above. Then, the change in length was determined by the formula {(initial length before test−length after heating and cooling) / initial length}.
5%.

From these results, it was found that the dimensional change rate of the manufactured drawn foam coated resin foam tube was small and had the initially intended heat resistance.

[0056]

Example 2 Same low density polyethylene resin 1 as in Example 1
With respect to 00 parts by weight, 3.0 parts by weight of vinyltrimethoxysilane as a silane compound, 0.1 parts by weight of dibutyltin dilaurate as a tin-based catalyst, 1.0 parts by weight of benzophenone as a photosensitizer, and A coated foamed resin tube with a squeezed pattern was produced in the same manner as in Example 1 except that 1.0 part by weight of allyl cyanurate was used.

The foamed tube (2) does not have any problems such as thinness even when the surface-coated film is formed and when it is heated for forming a drawn pattern, and the dimensions are within the initial target range (outer diameter 24.5 ±).
0.5 mm), and a beautifully formed coated foamed resin tube molded product with a drawn pattern was obtained.

Further, the gel fraction of the surface layer of the foamed tube (2) after irradiation with ultraviolet rays was measured in the same manner as in Example 1 above, and it was found to be 21%.

The gel fraction of the entire coated foamed resin tube with a drawn pattern was measured in the same manner as in Example 1 to find that it was 39%.

Further, in the same manner as in Example 1 described above, the change in thickness and the change in length of the manufactured coated foamed resin tube with a drawn pattern were measured. As a result, the change in wall thickness is 7.
The 0% length change was 0.6%.

From these results, it was found that the dimensional change rate of the coated drawn resin foam tube with the drawn pattern was small and had the initially intended heat resistance.

[0062]

Example 3 Same low density polyethylene resin 1 as in Example 1
Based on 00 parts by weight, 1.5 parts by weight of vinyltrimethoxysilane as a silane-based compound, 0.1 parts by weight of dibutyltin diacetate as a tin-based catalyst, 1.0 part by weight of thioxanthone as a photosensitizer, and as a crosslinking aid Except for using 2.0 parts by weight of methyl methacrylate, a coated foamed resin tube with a drawn pattern was produced in the same manner as in Example 1.

The foamed tube (2) does not have any problems such as thinness even when the surface-coated film is formed and when it is heated for forming a drawn pattern, and the dimensions are within the initial target range (outer diameter 24.5 ±
0.5 mm), and a beautifully formed coated foamed resin tube molded product with a drawn pattern was obtained.

The gel fraction of the surface layer of the foamed tube (2) after irradiation with ultraviolet rays was measured in the same manner as in Example 1 to find that it was 18%.

Further, the gel fraction of the whole coated foamed resin tube with a squeezed pattern measured in the same manner as in Example 1 was 43%.

Further, in the same manner as in Example 1 described above, the change in thickness and the change in length of the manufactured coated foamed resin tube with a drawn pattern were measured. As a result, the change in wall thickness is 6.
The 0% length change was 0.5%.

From these results, it was found that the dimensional change rate of the produced coated foamed resin tube with a drawn pattern was small and had the initially intended heat resistance.

[0068]

Example 4 Low-density polyethylene resin 1 as in Example 1
With respect to 00 parts by weight, 3.0 parts by weight of vinyltriemethoxysilane as a silane-based compound, 0.1 parts by weight of dibutyltin dilaurate as a tin-based catalyst, 1.0 parts by weight of thioxanthone as a photosensitizer, and 1.0 parts by weight as a crosslinking aid. A coated foamed resin tube with a squeezed pattern was produced in the same manner as in Example 1 except that 1.0 part by weight of allyl cyanurate was used.

The foamed tube (2) does not have any problems such as thinness even when the surface-coated film is formed and when it is heated for forming a drawn pattern, and the dimensions are within the initial target range (outer diameter 24.5 ±
0.5 mm), and a beautifully formed coated foamed resin tube molded product with a drawn pattern was obtained.

The gel fraction of the surface layer of the foamed tube (2) after irradiation with ultraviolet rays was measured in the same manner as in Example 1 above, and it was 15%.

The gel fraction of the entire coated foamed resin tube with a squeezed pattern measured in the same manner as in Example 1 was 34%.

Further, in the same manner as in Example 1 described above, the change in thickness and the change in length of the manufactured coated foamed resin tube with a drawn pattern were measured. As a result, the change in wall thickness is 6.
The 0% length change was 0.5%.

From this result, it was found that the dimensional change rate of the coated drawn resin foam tube with the drawn pattern was small and had the initially intended heat resistance.

[0074]

Comparative Example 1 No silane compound and no tin catalyst were used,
Same as Example 1 except that benzophenone 1.0 part by weight as a photosensitizer and 1.0 part by weight of triallyl cyanurate as a crosslinking aid were used with respect to 100 parts by weight of the same low-density polyethylene resin as in Example 1. A coated foamed resin tube with a squeezed pattern was produced by the method described above.

The foamed tube (2) does not have any problems such as thinness even when the surface-coated film is formed and when it is heated for forming a drawn pattern, and the dimensions are within the initial target range (outer diameter 24.5 ±
0.5 mm), and a beautifully formed coated foamed resin tube molded product with a drawn pattern was obtained.

Further, the gel fraction of the surface layer of the foamed tube (2) after irradiation with ultraviolet rays was measured in the same manner as in Example 1 above. As a result, it was 20%.

The gel fraction of the whole coated foamed resin tube with a drawn pattern was measured in the same manner as in Example 1 to find that it was 24%.

Further, in the same manner as in Example 1 described above, the change in thickness and the change in length of the manufactured coated foamed resin tube with a drawn pattern were measured. As a result, the wall thickness change is 18
%, And the change in length was 3.3%.

From the results, the dimensional change rate of the coated foamed resin tube with the drawn pattern was large, the shape was poor, and there was a problem in heat resistance.

[0080]

Comparative Example 2 The same low-density polyethylene resin (100 parts by weight) as in Example 1 was used without using a photosensitizer and a crosslinking assistant.
Vinyltrimethoxysilane 1.5 as a silane compound
Parts by weight, dibutyltin dilaurate 0.0 as a tin-based catalyst
A coated foam resin tube with a drawn pattern was manufactured in the same manner as in Example 1 except that the amount was 5 parts by weight.

At the time of heating for forming the drawing pattern, the foam tube (2) became thin (small diameter), the shape was not stable, and the appearance was problematic. Incidentally, the dimensions were measured, and the outer diameter was 23 mm.

The gel fraction of the surface layer of the foamed tube (2) after irradiation with ultraviolet rays was measured in the same manner as in Example 1 above, and it was 0.5%.

Further, the gel fraction of the whole coated foamed resin tube with a squeezed pattern was measured in the same manner as in Example 1 above. As a result, it was 30%.

Further, in the same manner as in Example 1 described above, the change in thickness and the change in length of the manufactured coated foamed resin tube with a drawn pattern were measured. As a result, the change in wall thickness is 7.
5% and the change in length was 0.8%.

The mixing ratio of the silane compound, tin catalyst, photosensitizer and crosslinking aid to 100 parts by weight of the low-density polyethylene resin in Examples 1-4 and Comparative Examples 1-2,
Table 1 shows the results of each measurement.

[0086]

[Table 1]

[0087]

According to the production method of the present invention, the surface layer of the polyolefin-based resin foam tube is easily and highly cross-linked by irradiating ultraviolet rays before the non-foam resin is coated and molded to form a secondary layer. Heat resistance at the time of processing can be imparted, and in addition, a coated resin foam tube with a drawn pattern having the heat resistance of the entire polyolefin resin foam tube by silane crosslinking can be produced with high productivity.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of an apparatus for carrying out a method for producing a coated foamed resin tube with a drawn pattern according to the present invention.

FIG. 2 is a longitudinal sectional view of a coating mold in the apparatus of FIG.

FIG. 3 is a cross-sectional view of a foamed resin tube having a surface coating film layer obtained in the course of the method of the present invention.

FIG. 4 is a schematic configuration diagram of a drawing pattern processing machine in the apparatus of FIG. 1;

FIG. 5 is a cross-sectional view of a non-foamed surface coating film layer of the coated foamed resin tube with a drawn pattern.

FIG. 6 is a plan view of the non-foamed surface covering film layer.

FIG. 7 is a plan view of a non-foamed surface covering film layer showing a modified example of a formed squeezed pattern.

FIG. 8 is a perspective view showing a modification of the first drawing patterning roll.

[Explanation of symbols]

 (1): Extruder (2): Foamed resin tube (4): UV irradiation machine (8): Non-foamed surface coating film layer (non-foamed resin coating layer) (9): Foamed tube with surface coating film layer (13a ) (13b) (22a) (22b): First squeezed patterning roll (14a) (14b): Second squeezed patterning roll (19): Coated foamed resin tube with squeezed pattern (24a) (24b): Squeezing pattern

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C08J 3/28 CES C08J 7/00 CES 7/00 CES 304 304 9/14 CES 9/14 CES B29C 67/22 // B29K 23 : 00 105: 04 105: 24 B29L 9:00 23:00 C08L 23:00

Claims (2)

[Claims] 1. A polyolefin-based raw material resin and a volatile organic blowing agent are kneaded and mixed at a high temperature and a high pressure in an extruder, and the mixture is extruded into a tube and foamed almost simultaneously with the extrusion. While molding
The foamed resin tube is continuously extruded and molded with a non-foamed resin coating layer, cooled, and then reheated to an outer surface temperature of the non-foamed resin of ± 20 ° C. to form a non-foamed resin coating layer. Is pressed against a squeezed pattern forming roll having irregularities for forming a squeezed pattern on the roll surface to form a squeezed pattern continuously on the outer surface of the non-foamed resin coating layer of the foamed resin tube. A method for producing a foamed resin tube, wherein as the polyolefin-based raw material resin, 0.1 to 5 parts by weight of a silane-based compound and 0.01 to 2 parts of a tin-based catalyst, based on 100 parts by weight of a polyolefin-based resin as a base material. Parts by weight,
Using a mixture of 0.1 to 5 parts by weight of a photosensitizer and 0.1 to 5 parts by weight of a crosslinking aid, molding the above foamed resin tube, and then coating the foamed resin tube with a non-foamed resin A method for producing a coated foamed resin tube having a drawn pattern, comprising irradiating ultraviolet rays to crosslink the surface of the foamed resin tube until the layer is continuously subjected to extrusion coating. 2. The degree of surface cross-linking of the cross-linked foamed resin tube immediately after irradiation with ultraviolet rays is 10 to 50% in terms of gel fraction at the surface of the foamed resin tube, and the degree of cross-linking of the entire foamed resin tube is determined in the final cross-linking step. The method according to claim 1, wherein the gel fraction is 30 to 60%.