KR840002205B1 - Pipe with a foamed cover layer - Google Patents

Abstract

For an adiabetic pipe coating, a blistering adiabetic layer is placed on a circumferential plane of pipe. The blistering adiabetic layer has a blistering rate of more than 4 times, the norm. The shape of the blister bubble has a three-layer structure, having small bubbles on both sides of a relatively large bubble, and the bubbles comprising the central blistering layer are characterized by an average bubble radius of 0.3-0.9 when measured with the diameter direction of a pipe and length μ1/μ2.

Description

Insulation pipe

1 is a cross-sectional view of an insulated pipe of the present invention.

2 is a longitudinal sectional view of the heat insulation pipe shown in FIG.

The present invention relates to insulating pipes having an insulating foam layer made of plastic foam, in particular insulating metal pipes or insulating plastic pipes made from a polyolefin high foam layer.

In accordance with the spread of hot water heating systems, a heat insulating metal pipe provided with a heat insulating layer made of expanded polyethylene having a foam ratio of about twice has been widely used.

However, in order to save energy in recent years, heat insulation pipes which are excellent in heat insulation, compressive resistance, and have low buckling resistance and water absorption are required. In addition, heat resistance is also required when using a pipe for supplying hot water or circulating heated water. For this purpose, the low-foam polyethylene insulation layer is inferior in heat insulation and heat resistance. In addition, the cross-linked high-foamed polyethylene sheet or high-foamed polypropylene sheet may be covered with a metal pipe in the form of a pipe. Not only does continuous coating require complicated handling, but also poor adhesion between the pipe and the coating layer has disadvantages of compression resistance and buckling resistance of the pipe. In addition, the compression foaming method has recently appeared to have a heat insulating layer made of expanded polyethylene having a foam ratio of about 5 times, but only a slight improvement in heat insulating properties and, on the contrary, high foaming results in continuous foaming, and therefore, compression resistance, Absorption resistance is extremely low and there are practical difficulties. Moreover, when this heat pipe is used for high temperature water or steam, since the heat insulation layer is polyethylene, heat insulation is bad, and therefore shrinkage occurs and it cannot be used for high temperature. In general, attempting to increase the degree of foaming to increase the heat insulating property tends to lower the strength and the water resistance, and heat insulating pipes having both properties have not yet appeared.

The present invention provides a structure of a heat insulating pipe having excellent heat insulating properties, high compressibility, low water absorption, and excellent heat resistance from studies on bubble structure and various physical properties.

In other words, the present invention is a heat insulation pipe in which the pipe is provided with a polypropylene foam insulation layer on the outer periphery, the insulation layer is made of foam having an average expansion ratio of 4 times or more, and both sides of the augmented foam layer having a relatively large bubble shape of the bubble shape It has a three-layer structure each having an inner foam layer and an outer foam layer having a relatively small bubble shape, and the bubble of the electric central foam layer is the average bubble diameter (μ ₁ ) measured in the radial direction of the pipe and its is a non-μ ₁ / μ ₂ of the averager uncut (μ ₂₎ when measured in the longitudinal direction of the pipe about the pipe insulation, characterized in that 0.3 to 0.9.

Then, the electric μ ₁ is typically 0.2 to 1mm, μ ₂ is the ground 0.22 3.0mm. .

Moreover, the average bubble diameter of a center foam layer is 0.2-1.0 mm, and the average bubble diameter of an inner side and an outer side foam layer is 0.2 mm or less. The thickness of the central foam layer is in the range of 40 to 90% of the thickness of the entire foam layer. The outer foam layer and the inner foam layer have almost the same thickness.

Then, the average foaming ratio of the whole is 4 times or more, the foaming ratio of the center foam layer is 5 times or more, and the inner and outer foaming ratio is a foaming ratio lower than the center foaming layer.

Next, the heat insulation pipe which concerns on this invention is demonstrated with reference to drawings. 1 shows a cross-sectional view of the heat insulation pipe of the present invention, and FIG. 2 shows a longitudinal cross-sectional view. In the figure, 1 is a pipe to be coated, 2 is a heat insulating layer, 3 is an outer foam layer, 4 is a central foam layer, and 5 is an inner foam layer. As can be seen from the figure, the diameter of the bubbles constituting the central foam layer 4 is larger than that of the bubbles constituting the outer foam layer 3 and the inner foam layer 5, respectively. In addition, in the center foam layer 4 of FIG. 2, a bubble is orientating slightly in the longitudinal direction of a pipe. That is, the average bubble diameter (μ ₂ ) measured in the longitudinal direction of the pipe is larger than the bubble diameter (μ ₁ ) measured in the radial direction of the pipe, and the ratio (μ ₂ / μ ₁ ) is 0.3 to 0.9.

By setting the structure, bubble diameter, and expansion ratio of such a heat insulation foam layer, the heat insulation layer of the heat insulation pipe adheres well to the pipe, the compressive strength is increased, the buckling resistance is excellent, and the water absorption is an independent foamed heat insulation pipe.

The reason for this is that the high density foam layer of the small bubbles of the inner and outer layers is a completely independent foam layer and is strong and thus has low water-tight. Pole, water absorption is low. In addition, the small bubble layer in close contact with the pipe acts as a protective layer against buckling that is likely to occur when a large deformation is locally applied to the pipe, thereby providing a buckling resistant heat insulating layer. The large bubble layer has a thick bubble film and is resistant to compressive stress and the like to achieve the object of the present invention starting with such a structure.

When a load is applied to a conventional high-foaming insulated copper pipe, the copper pipe is easily deformed, but the insulating-pipe of the structure of the present invention is excellent in compression resistance and hardly deformed. And since the heat insulation layer of the conventional heat insulation pipe is a foam of continuous bubble, a water absorption is large and it causes a corrosion of metal pipes, such as a copper pipe. Moreover, heat absorption also falls by absorption.

As a manufacturing method of the heat insulation pipe which has a structure as mentioned above, it is performed as follows.

That is, when extruding the polypropylene resin foam insulation layer on the pipe, the thickness t of the foam insulation layer and the expansion ratio M and the die-nipple spacing d

To have a relationship of.

In the above formula (1), when K is less than 0.20, the resin may cause drift and cannot make a heat insulating layer with a uniform thickness, or when it exceeds 0.75, the heat insulating layer becomes thick and it is difficult to trim to an accurate dimension. If the pulling speed is increased to a certain dimension beyond this, the foam of the resulting heat insulation layer is continuously bubbled to increase the absorbency and, in some cases, the foam bursts.

The heat insulating material of (micro | micron | mu) ₁ / micro <_2> = 0.3-0.9 can be obtained with the three-layered foam structure of desired magnification by the die-nipple distance of this invention. The range of K which is preferable when foaming ratio is 4-8 times is 0.3-0.4.

In the present invention, polypropylene resin is used as the foaming polymer. The main component resins preferably used are propylene-ethylene copolymers, having an ethylene content of 1 to 20% MI (melt index) of 0.1 to 4, particularly preferably 7 to 20% of ethylene and 0.1 to MI. It is two. Although it is good to use said resin independently, it is also preferable to add 1 type (s) or 2 or more types (s) of the other polymer or rubber which can be mixed, and to use it by 40 weight% or less.

In particular, for the purpose of improving the buckling resistance, it is possible to use a mixture of one or two or more kinds of ethylene-propylene rubber (EPR), polyethylene, ethylene-vinyl acetate copolymer, polybutel-1, and the like. Can be. If the amount exceeds 40% by weight, the foaming is not stable and the heat resistance is poor, which is not good.

Among the additive polymers, an EPR having an ethylene content of 20 to 60% is particularly preferable, and the insulation layer pipe coated with the polypropylene foam layer containing this polymer is not buckled even when bent to a small radius of curvature.

As described above, the propylene ethylene polymer has a high modulus of elasticity and a change in modulus of elasticity is slow even when the temperature changes in the molten state, so that a good foam can be obtained in a wide temperature range, and thus the foam layer having the three-pack structure is easily extruded It is thought that it can be obtained by foaming method.

The reason why such a good foaming structure is obtained can be explained by the crosslinking effect of the polymer.

Crosslinked polymers are suitable for foaming as they have high elasticity and low temperature dependence upon melting. The propylene-ethylene copolymer, which has not been used for crosslinking until now, is extracted for 6 hours in tetralin (135 ° C.) which is a suitable solvent for polypropylene. The copolymer also has an insoluble content of 10 to 40%, has a crosslinked structure similar to that of the crosslinked polymer, and is therefore considered to have excellent foamability. In particular, this polymer is preferably used in the form of powder as obtained in the polymerization step.

The reason for this is that the microstructure of the polymer molecule changes to the extent that it receives thermal history, and the crosslinking structure decreases. The ethylene content is limited to 1 to 20% and MI = 0.1 to 4, which means that the polymer has a large gel fraction of 10 to 40%, and the dynamic shear modulus G 'is 1.5 × at 100 Hz and 170 ° C. obtained by dynamic viscoelasticity measurement. 10 ⁶ <G '<10 × 10 ⁶ , large, the temperature change is small and suitable for foaming.

The foaming method of the present invention is a solid blowing agent such as sodium bicarbonate, ammonium bicarbonate, dinitrosopentamethylenetetraman, azodicarbonamide, oxybisbenzenesulfonylhydrazide, and the like. It is added to a polypropylene or its mixture with preparation, and is extruded and foamed outside the copper pipe etc.

It is necessary to pay attention to the decomposition temperature of the blowing agent in order to stably obtain a highly foamed three-layer polymer propylene resin insulating layer. In other words, the preferred decomposition temperature of the blowing agent is 120 to 170 ° C, particularly 130 to 160 ° C. It is particularly preferable that azodicarbonamide or dinitrosopentamethylenetetramine alone or a mixture of the azodicarbonamide or dinitrosopentamethylenetetramine is added at a decomposition temperature.

As the volatile blowing agent, for example, lower aliphatic hydrocarbons such as propane, butane and pentane, monochlorodifluoromethane, dichlorodifluoromethane, trichlorotrifluoromethane, monochlorotrifluoromethane and dichlorotetrafluoro Halogenated hydrocarbons such as methane are preferred. As a foaming agent of gas in other states, for example, nitrogen, carbon dioxide gas, oxygen, air, argon gas, etc. may be used. These blowing agents may be pressed into the copolymer or mixture in an extruder and extruded and foamed outside the copper pipe or the like. . In this case, as a press-fit method of gas or a volatile blowing agent, there are a press-fit method from a vent hole provided in a cylinder of an extruder, a press-fit method from a hopper part, and a press-fit method from a screw.

In the present invention, in the extrusion foam coating of the polymer or the mixture on the outer circumference of a metal pipe or a plastic pipe such as a copper pipe, the pipe may be provided in the nipple portion of a crosshead die or an offset die mounted on an extruder. While supplying continuously. The nipple tip (approximately 5 mm from the tip) is susceptible to heat dissipation, especially when passing through metal pipes, and below 100 ° C., the polymer or mixture becomes poor in flow and cannot be continuously coated.

Therefore, it is necessary to supply the tip part of the nipple continuously or to heat the metal pipe. For example, the heating temperature of a metal pipe is 60-120 degreeC on the pipe surface. If the temperature is too lower than 60 DEG C, the foam layer of uniform thickness will not be covered, and the unfoamed skin layer will be thick, and the pipe will be covered, and the three layers made from the foam layer aimed at this invention, ie, a small bubble layer, and an air bubble layer. A high magnification foam layer of the structure is not obtained.

If the temperature is too high than 120 ° C., the adhesion to the pipe is reduced.

In the method of the present invention, a die is usually used in the shape of a pipe, but the other end face of the foam layer is different from the circular shape, for example, an ellipse or a rectangle in the other end face of the foam. If desired, the die shape can be modified.

The foam layer extruded from the die and coated on the outer circumferential surface of the die requires cooling as close to the die as possible but should not cool the die.

Specifically, it is preferable to force-cool or water-cool so as to uniformly cool the foam layer extruded from about 2 cm away from the dioriphys. The temperature of the coolant is preferably 50 ° C or lower. If it is more than that, the small bubble surface layer made into the original purpose of cooling will not be obtained.

It is good to divide cooling into two stages.

The first stage does not cool the die and obtains a small bubble surface layer by surface cooling performed immediately after the die. Subsequent cooling of the second stage is substantial cooling for regulating the appearance, the expansion ratio and the bubble shape of the intermediate layer.

If necessary, in order to accurately maintain the required appearance, metal and resin sizing dies may be used. The required dimension of the sizing die should preferably have a dimension that is less than 0.1 to 1 mm from the desired outside diameter of the single pipe. The length of the sizing die is usually 30 cm or less, preferably 5 to 15 cm.

In addition, it is important to determine the distance from the die to the sizing die. As described above, although the surface of the foam for forming the heat insulating layer is quenched, if the distance is made too short, it is not possible to obtain a heat insulating layer having a predetermined thickness by re-expansion after the dimensioning. If the distance is too long, the surface may not be smooth.

For this reason, the distance between the die and the sizing die is usually 40 to 200 cm, preferably 80 to 150 cm.

In the case of copper pipes insulated with polypropylene foam, the polypropylene foam layer can be damaged by oxidation promotion due to copper ions. In addition, there is concern about discoloration and corrosion of the copper pipe due to the interaction of the copper pipe and the expanded polypropylene. For this reason, it is recommended to coat copper pipe resins.

Although it does not specifically limit as a coating method, The coating by an extruder, the coating by deposition, the powder coating method, etc. are easy. Coating resins include thermoplastic resins such as polyethylene, nylon and polyvinyl chloride, and thermosetting resins such as unsaturated polyester, urethane, and epoxy resins, but particularly preferred are aqueous acrylic resins, polyester resins, polyurethane resins, and the like. It adhere | attaches by a suitable method to a coating, and coat | covers with 0.1 thickness of 50 micrometers by baking process.

The single pipe of the present invention may be used with the foam insulation layer as the outermost layer, but it is preferable to use a plastic coating on the foam layer. The coating is carried out on the cooled heat insulating layer with a soft polyvinyl chloride, polyethylene, chlorinated polyethylene, a copolymer with ethylene-vinyl acetate, or the like, or by adding an inorganic additive, a flame retardant, an ultraviolet absorber, carbon black, an antioxidant, and the like.

Next, an Example and a comparative example demonstrate this invention.

Example (1) and Comparative Examples (1) to (3)

To the propylene-ethylene block copolymer powder (MI = 0.8, ethylene component 14%, melting point 163 ° C), 2.5 parts of azodicarbononeamide-based blowing agent was added and 100 parts of resin was added to the mixture. While supplying a 9.5 mm diameter copper pipe (copper pipe temperature of 70 ° C.) to the crosshead die, an extruded coating is applied to the outer periphery of the copper pipe to obtain a heat insulating pipe serving as a heat insulating layer having the following structure.

In addition, the ratio μ ₁ / μ ₂ = 0.8.

The results obtained by measuring the water absorption and the heat loss of the insulation pipe are shown in the first table.

Moreover, for comparison with the present invention, a commercially available foamed polyethylene insulation pipe, that is, an insulation pipe having a foam insulation layer having a single bubble structure (Comparative Example 3) and an insulation pipe having a foam insulation layer having a two-layer bubble structure (Comparative Examples 1, 2). The results obtained by measuring the water absorption and the heat loss as described above were specified in the first table, respectively.

However, as an inner foam layer, it is a foam layer directly contacting a copper pipe, and as an outer foam layer, a foam layer of outermost layer is said. The heat loss is the amount of heat lost in 1 m of pipe length and 1 hour when heated to an insulated pipe at an ambient temperature of 20 ° C and a water heating temperature of 80 ° C, expressed in units of KCa1 / m.hr.

As can be seen from the above table, the heat insulation pipe of the present invention has a low water absorption and heat loss, and has a low flattening of copper pipe even in bending processing.

In addition, in the case of a non-relative example, sufficient effect cannot be exhibited as a large heat insulation pipe with a water absorption rate and heat loss.

Example 2

A mixture of the same propylene ethylene block copolymer and the blowing agent as in Example 1 was used to extrude and coat the outside of the same copper pipe. In the die, a round die is used, and the distance d between the die and the nipple is 0.7 mm, the resin temperature is 175 ° C, and the dynamic shear modulus G '= 3 x 10 ⁶ dyne / cm ² . In the two cases, the tip temperature of the nipple is 155 DEG C, and the foam is blown and cooled by a blower at a distance of 5 cm from the die after extruding the mixture a, and immediately after molding by a sizing die at a distance of 90 cm from the die. Cool with water.

The insulation layer of the insulation pipe thus obtained is a foam layer of the air bubble (layer thickness 1.7mm, average bubble diameter 0.60mm) from both sides, and the air bubble layer (outer layer thickness 0.8mm, inner layer thickness 0.7mm, average thickness 0.7mm, average bubble diameter 0.15mm). ) Is a three-layered foamed layer, with μ ₁ / μ ₂ = 0.6, low water absorption and 6.2 times the average expansion ratio, where K is 0.40.

Example 3

Using a polymer incorporating the same blowing agent as in Example 1, melt plasticizing at 190 ° C. by a vent screw extruder having a screw diameter of 65 mm, injecting at a rate of 48 cc of dichlorodifluoroethanol every minute using a pump from a vent hole, 15.88mm diameter copper pipe (copper pipe temperature 60 ℃) is supplied to the crosshead die (resin temperature of 148 ° C) to maintain the nipple temperature of 128 ° C or more and is extruded and coated on the outer circumference of the pipe. Moreover, the die was set to 0.85 mm between die and nipple die using a round die, and cooled by bringing cold air into contact with the surface of the die at a place of 3 cm, and then wound while performing strong wind cooling. The average foaming ratio of the foam forming the heat insulating layer thus obtained was 22 times and the foam layer thickness of 7 mm (outer layer 1 mm, center layer 5 mm, inner layer 1 mm) μ ₁ / μ ₂ = 0.68 (μ ₁ = 0.8 mm μ ₂ = 1.18 mm) A heat insulation pipe can be obtained which is a foam layer having a high pressure resistance and buckling resistance in three layers (average bubble diameter of small bubbles in the outer layer and the inner layer), where K = 0.34.

Example 4

20% by weight of ethylene-propylene rubber (propylene content 26%) was added to the propylene ethylene block copolymer powder (MI = 0.8, ethylene content 13%, melting point 164 ° C), and the mixture was added with 1.5phr of talc. Extruded coating on the outer circumference of the copper pipe while injecting nitrogen gas at 35 kg / cm ² as a blowing agent from the vent of the extruder having a screw diameter of 35 kg / cm ² , while supplying the copper pipe at a nipple temperature of 130 ° C. or higher. Foamed. In addition, the die is extruded from a die having a resin temperature of 172 ° C, die-nipple spacing of 0.8 mm, and G '= 2.8 × 10 ⁶ dyne / cm ² using a round die, and then showered in a shower shape over a distance of 3 to 8 cm from the die. Is poured, cooled, and then water cooled, and the outer periphery is coated with polyvinyl chloride to obtain an insulated pipe.

The average foaming ratio of the foam layer which forms this heat insulation layer is about 7 times, and the foam layer thickness is 5 mm, and the outer layer (layer thickness of 1.2 mm) of the comparatively small bubble is compared with the center layer (layer thickness 3.0 mm) of a comparative air bubble from both sides. It has a three-layer structure fitted to the inner layer. In the central foam layer, μ ₁ = 0.40 mm, μ ₂ = 0.44 mm, μ ₁ / μ ₂ = 0.90, and K = 0.3.

It is excellent in water absorption and water absorption and at the same time strong against compression, and maintains the roundness without flatness even when a load of 150 kg is applied. Moreover, even if this heat insulation pipe was bent 90 degrees with a curvature of a radius of 100 mm, it did not buckle.

[Examples 5 and 6 and Comparative Example 4]

As in Example 3, the coated pipe extruded from the die is forcibly pulled up to obtain various types of bubble structures of inches. The water absorption of this heat insulation pipe was measured.

The results are shown in the second table.

[Table 2]

As can be seen from the above table, when μ ₁ / μ ₂ is outside the range of 0.3 to 0.9 in the present invention, even if the heat insulating layer has a three-layer structure, the water absorption is remarkably large and the heat insulating property is remarkably decreased.

Example 7 and Comparative Example 5

A heat insulating copper pipe of μ ₁ / μ ₂ = 0.65 having a three-layer structure of 80% of propylene-ethylene block copolymer with 20% of ethylene propylene and 20% of styrene rubber (26% of propylene). It was compared with the heat insulation copper pipe which consists of commercially available 3 times foamed polyethylene, and has a heat insulation layer of (micro | micron | mu) ₁ / micro <_2> = 0.45 as 1 layer structure.

The results are shown in the third table.

[Table 3]

(1) Insulation: It expressed by heat loss (Kcal) per 1m and 1 hour of an insulation pipe.

(2) Compressibility: The insulation pipe is placed on a parallel plate (10cm × 10cm) to apply a flat load to show a load deviating from the circle.

(3) Absorbency: The water absorption after immersing the heat insulating material in the water bath for 24 hours was measured.

(4) Heat resistance: It was left to stand in a thermostat bath at 120 degreeC for 22 hours, and the shrinkage rate after cooling was measured.

(5) Buckling: Buckling of the foamed heat insulation layer at the time of bending by 90 degrees as 150R is shown.

Example 8 and Comparative Examples 6 and 7

To the propylene-ethylene block copolymer (ethylene content 12%, MI = 0.8), 2.5 phr of azodicarbonamide-based blowing agent (decomposition temperature: 160 ° C, VINYFOR AK # 2 manufactured by Eiwa Chemical Co., Ltd.) was added and the mixture was added. Extrusion foaming is carried out by feeding an extruder having a diameter of 65 mm having a crosshead die. At this time, the copper pipe having a diameter of 15.88 mm was continuously supplied at a surface temperature of 80 ° C. and coated through the cross head die. As soon as the coated pipe came out of the die, 20 ° C. of wind was brought into contact with the uniformly coated pipe and cooled. In the above, a foamed heat insulating layer having a thickness of 3.5 mm having a three-layer structure having a foaming ratio of 5.8 times can be obtained (μ ₁ / μ ₂ = 0.52). The die-nipple spacing d was 0.75 mm. Therefore, K = 0.41.

In addition, here are shown below by changing the die gap d nipple variously foam magnification, the thickness value, K value, and μ ₁ / μ ₂ obtained.

EXAMPLE 9 AND COMPARATIVE EXAMPLE 8

In Example 8, a polyester-based emulsion paint was previously coated on a copper pipe having an outer diameter of 15.88 mm, heat treated at 220 ° C. for 30 seconds, and then cooled to cool the copper pipe temperature to 100 ° C. in Example 8 above. The same material as was used to coat the foam layer and then cooled.

As a result, a foam having a three-layer structure (μ ₁ / μ ₂ = 0.55 in the middle layer) having an average foaming ratio of 5.8 times can be obtained without a problem.

The heat insulation pipe does not show discoloration or deterioration of the foam layer even when used at 110 ° C. for a long time.

On the other hand, the heat insulation pipe which was not coated with the copper pipe in the resin showed a yellow change of the foam insulation layer (Comparative Example 8).

Examples 10 and 11 and Comparative Examples 9 and 10

In Example 8, extrusion foaming was carried out using 2.5 phr of a blowing agent having various decomposition temperatures changed by changing the mixing ratio of azodicarbonamide and dinitrosopenta ethylenetetramine. As a result, a heat insulation pipe having a foam insulation layer is obtained as follows.

As mentioned above, according to this invention, it has the outstanding effect, such as obtaining the heat insulation pipe which has the outstanding heat insulation property and the intensity | strength, the water absorption is low, and heat resistance is favorable.

Claims (1)

In a heat insulation pipe in which a foamed heat insulating layer is collapsed on the outer circumferential surface of the pipe, the foamed heat insulating layer has a foaming ratio of 4 times or more, and the bubble shape is relatively small bubble shape on both sides of the center foam layer having a relatively large bubble shape. It has a three-layer structure each having an inner foam layer and an outer foam layer having a, and the bubbles constituting the central foam layer is the average bubble diameter (μ ₁ ) measured in the radial direction of the pipe and the longitudinal direction of the pipe Insulation pipes characterized in that the ratio μ ₁ / μ ₂ of the average bubble diameter (μ ₂ ) at the time of measurement is 0.3 to 0.9.

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