KR102507490B1 - Hollow insulation including polyester foam layer - Google Patents

Abstract

The present invention relates to a hollow insulator including, based on a thickness direction of the hollow insulator, a polyester-based foam layer from the inside to the surface of the hollow insulator, and a polyolefin-based or rubber-based foam layer, sequentially. The polyester-based foam layer does not include a joint in the circumferential direction of the hollow insulator, and the polyolefin-based or rubber-based foam layer includes a joint in the circumferential direction of the hollow insulator.

Description

Hollow insulation comprising a polyester foam layer {HOLLOW INSULATION INCLUDING POLYESTER FOAM LAYER}

The present invention relates to a hollow insulation material comprising a polyester foam layer.

BACKGROUND ART Plastic resin foams having excellent performance in lightness, heat insulation, and cushioning are widely used as insulation materials for automobile air conditioning systems and the like. In addition, these foams can generally be produced continuously by extruding and foaming a molten resin, thereby simplifying the process and enabling mass production.

Urethane foam insulator is a widely used insulator because of its good expansiveness and adhesiveness, as well as excellent sound insulation and airtightness. However, urethane foam has disadvantages in that it is flammable, weak against fire, emits toxic gas (VOC), and requires a certain amount of time to cure, making it difficult to handle. Polystyrene foam insulation is widely used because it has good foaming performance, high density, low thermal conductivity, low price, sound insulation, light weight, high elasticity, and excellent workability. However, polystyrene foam is vulnerable to high temperatures of 70 ° C or higher and ultraviolet rays, has poor water resistance, and has disadvantages in terms of flammability and toxic gas emission. Phenolic foam (PF) has the advantage of having a higher density than polystyrene foam, low thermal conductivity similar to that of rigid urethane foam, and low toxic gas emissions due to its semi-incombustibility. The downside is that this is difficult.

Therefore, it is required to develop an insulator used in an automobile air conditioning system, etc., which has excellent physicochemical performance, is easy to handle in the manufacturing process, and is easy to separate/recycle by material because emission of toxic gases is suppressed.

An object of the present invention is to improve the insulation performance and sealing function under harsh conditions (high temperature conditions, repeated heat input and output conditions) by suppressing internal closed cell structure/size deformation during additional thermoforming of polyester foam.

In addition, according to the present invention, by thermally bonding (thermoforming) a polyester-based foam layer and a polyolefin-based foam layer under specific conditions, it is possible to improve interfacial adhesion between the foam layers and improve physicochemical performance of the heat insulating material.

One embodiment of the present invention is based on the thickness direction of the hollow insulator, a polyester-based foam layer from the inside to the surface of the hollow insulator; and a polyolefin-based or rubber-based foam layer, wherein the polyester-based foam layer does not include a joint portion in the circumferential direction of the hollow insulator, and the polyolefin-based or rubber-based foam layer includes a joint portion in the circumferential direction of the hollow insulator. It provides a hollow insulator comprising a.

The polyester-based foam layer may include 95% (v/v) or more of closed cells (DIN ISO4590), and may satisfy the following relational expression 1.

[Relationship 1]

|(AA _avg )/A _avg | < 10%

The relational expression 1 represents the size deviation of the closed cells in the foam layer in the circumferential direction of the hollow of the polyester foam layer as a formula, and A _avg is the average size of the closed cells inside the foam layer located at the same thickness in the polyester foam layer , and A is the size of an arbitrary closed cell inside the foam layer located at the same thickness in the polyester foam layer.

The polyester-based foam layer may further satisfy the following relations 2 and 3.

[Relationship 2] 30% < B _OS /B _C < 50%

[Relationship 3] 10% < B _IS /B _C < 30%

The relational expressions 2 and 3 above represent the size ratio of the closed cells in the foam layer in the thickness direction of the hollows of the polyester foam layer by formulas, B _c is the average size of the closed cells in the center based on the thickness direction of the hollows, and B _OS is It is the average size of closed cells on the outer surface based on the hollow thickness direction, and B _IS is the average size of closed cells on the inner surface based on the hollow thickness direction.

The outer surface (B _OS ) of the polyester-based foam layer includes area a and area b crossing each other in a direction from one side of the polyester-based foam layer to the other side based on the longitudinal direction of the hollow-type insulator, and the area a may have an average closed cell size higher than that of the b region.

The polyolefin-based and rubber-based foam layers each include an inner layer and an outer layer based on the center of the polyolefin-based and rubber-based foam layers in the thickness direction of the hollow insulator, and the flame retardant content (% by weight) of the inner layer is greater than that of the outer layer. may be low

During additional thermoforming of the heat insulating material including the polyester-based foam layer, deformation of the internal closed cell structure may be minimized.

The hollow heat insulator including the polyester-based foam layer of the present invention can improve dimensional change rate, interfacial adhesion and heat insulation performance.

1 is a schematic diagram showing a hollow insulator according to an embodiment of the present invention.
2 is a schematic view showing a cross section in the thickness direction of a hollow heat insulating material according to an embodiment of the present invention.
3 is a schematic diagram showing a cross section in the thickness direction of a hollow heat insulator according to another embodiment of the present invention.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. When it is said that a certain part "includes" a component throughout the specification, this means that it may further include other components, not excluding other components unless otherwise stated. In addition, singular forms also include plural forms unless specifically stated in the text.

In the present specification, "A to B" means "A or more and B or less" unless otherwise defined. In addition, "A and / or B" means at least one selected from the group consisting of A and B, unless otherwise specifically defined.

One embodiment of the present invention provides a hollow insulator. 1 is a schematic diagram showing a hollow insulator of the present invention. Referring to Figure 1, the hollow insulator (1) based on the thickness direction, a polyester-based foam layer (3) in the surface direction from the inside of the hollow insulator; and a polyolefin-based or rubber-based foam layer (5) sequentially.

Foams using polyester-based resins have excellent mechanical performance such as strength and lightness, are easy to mold and process, and have a relatively high melting point compared to conventional foams, and show stable performance even in high-temperature environments (around 100 ° C). However, when the polyester resin is extruded and foamed and thermoformed (including a cooling process), it is difficult to uniformly control the mechanical performance of the foam because the cell structure and size of each part may be deformed. Accordingly, it is an object of the present invention to provide a technology capable of maximally suppressing the deformation of the desired cell structure for each part of the foam through thermoforming and easily controlling the change in physical properties during the additional molding process.

In the hollow insulator of the present invention, the polyester-based foam layer (3) does not include a junction in the circumferential direction of the hollow, and the polyolefin or rubber-based foam layer (5) is characterized in that it includes a junction in the circumferential direction of the hollow . In the prior art, in order to manufacture a cylindrical (hollow) polyester-based foam, a foam layer (sheet) made in a sheet form is wound, and then heat is applied to the point where the foam sheets meet to partially melt and thermally bond method was applied. The junction (thermal junction) generated from such thermal bonding (thermoforming) collapses the internal closed cell structure and causes size deformation of the closed cell. Since the hollow insulator is a harsh condition in which heat is repeatedly absorbed/released from the inner hollow, when used for a long period of time, the insulation/sealing function of the insulator is deteriorated and the dimensional change rate increases, which may decrease durability. In the present invention, since no thermal welding is formed in the circumferential direction of the polyester foam layer, the rate of dimensional change is small in a repeated heat absorption/release environment, and the interfacial adhesive force between the polyester foam layer and the polyolefin (rubber) foam layer This deterioration can be improved. On the other hand, since the polyolefin-based (rubber-based) foam layer has no direct contact with the heat medium (see FIG. 1, vehicle air conditioning system pipe, etc.) located in the inner hollow of the hollow insulator due to the polyester foam layer, even if it includes a thermal junction It is analyzed that there is no significant effect on the rate of dimensional change.

The polyester-based foam layer may include 95% (v/v) or more of closed cells (DIN ISO4590), and thus, the following relational expression 1 may be satisfied.

[Relationship 1]

|(AA _avg )/A _avg | < 3%

The relational expression 1 represents the size deviation of the closed cells in the foam layer in the circumferential direction of the hollow of the polyester foam layer as a formula, and A _avg is the average size of the closed cells inside the foam layer located at the same thickness in the polyester foam layer , and A is the size of an arbitrary closed cell inside the foam layer located at the same thickness in the polyester foam layer.

In the prior art, a melt of a polyester-based resin is extruded and foamed, and then prepared in a sheet shape using a cutter, so that some closed cells are destroyed at the cutting edge and 90% (v / v) A level of closed cells can be formed. Afterwards, when thermoforming into a cylindrical shape, the structure/size of the closed cells is destroyed and deformed in a chain around the thermal joint centered on the peripheral portion, so that the ratio of the closed cells may be lowered. On the other hand, since the cutting and welding processes are not performed in the present invention, the polyester-based foam layer has a closed cell (DIN ISO4590) of 95% (v / v) or more, preferably 95 to 99% (v / v). ), which means that a uniform closed cell structure can be formed. As a result, the dimensional change rate, interfacial adhesion, and heat insulating performance of the hollow heat insulating material including the polyester-based foam layer of the present invention may be improved.

Specifically, the polyester-based foam layer is |(AA _avg )/A _avg | < 10%, |(AA _avg )/A _avg | < 9%, |(AA _avg )/A _avg | < 7%, |(AA _avg )/A _avg | < 6%, preferably |(AA _avg )/A _avg | < 5% may be satisfied. The above formula (relational formula 1) means that the shape and size of the closed cells are uniform at any point of the cylindrical shape connecting the same point in the thickness direction of the inside of the foam layer. The effect can be further improved.

On the other hand, the A may be the result measured from the SEM image of the cross-section of the polyester-based foam layer in the thickness direction. Specifically, a circle located at the same length from the center of the hollow inside the foam layer is shown (the circle is preferably a circle located at the center of the foam layer in the thickness direction of the hollow, for example, but the present invention is not limited thereto), The circumference of the circle may be designated at least 10 points at regular intervals (each point may have an area of 3 mm * 3 mm, but the present invention is not limited thereto) and the long diameter (size) of the closed cell may be measured ( Average of closed cell sizes within each point), A _avg may be an average value calculated after excluding the maximum and minimum values of the measured closed cell sizes, but the present invention is not limited thereto.

The polyester-based foam layer may further satisfy the following relations 2 and 3.

[Relationship 2] 30% < B _OS /B _C < 50%

[Relationship 3] 10% < B _IS /B _C < 30%

The relational expressions 2 and 3 above represent the size ratio of the closed cells in the foam layer in the thickness direction of the hollows of the polyester foam layer by formulas, B _c is the average size of the closed cells in the center based on the thickness direction of the hollows, and B _OS is It is the average size of closed cells on the outer surface based on the hollow thickness direction, and B _IS is the average size of closed cells on the inner surface based on the hollow thickness direction.

Specifically, the size ratio of the closed cells in the foam layer may be 30% < B _OS / B _C < 50% or 35% < B _OS / B _C < 50%. Also, 10% < B _IS / B _C < 30% or 10% < B _IS / B _C < 25%.

When the polyester foam layer satisfies the above relational expressions 2 and 3, the outer surface has a medium closed cell size, and realizes a medium density and strength to improve interfacial adhesion with the polyolefin (rubber) foam layer. is analyzed as The center has the largest closed cell size and can improve insulation performance by realizing low density and low strength. The inner surface has the smallest closed cell size and can serve as a core material by realizing high density and high strength. The hollow insulator of the present invention protects heat/heat absorbing bodies (pipes for vehicle air conditioning systems, etc.) located in the hollow portion and can withstand harsh conditions in which heat is repeatedly absorbed/released in the hollow. Accordingly, interfacial adhesion, dimensional change, and heat insulation performance can be improved to a very high level.

On the other hand, the outer surface (B _OS ) means within 10% of the thickness from the outer surface based on the thickness direction of the hollow insulator, and the inner surface (B _IS ) is based on the thickness direction of the hollow insulator, the inner It may mean within 10% thickness of the surface.

The outer surface (B _OS ) of the polyester-based foam layer includes area a and area b crossing each other in a direction from one side of the polyester-based foam layer to the other side based on the longitudinal direction of the hollow-type insulator, and the area a may have an average closed cell size higher than that of the b region.

The effect of forming a closed-cell size pattern on the outer surface of the polyester foam layer can further improve the heat insulation performance of the hollow insulation material, and at the same time maintain an excellent level of interfacial adhesion with the polyolefin-based (rubber-based) foam layer. there is. In the present invention, when the polyester-based foam layer and the polyolefin-based (rubber-based) foam layer are thermally bonded, the area a with a relatively large closed cell size serves as a core material, and a part of the relatively small area b melts together with the polyolefin interface. can be mixed. Finally, the interfaces of the foam layers may be thermally bonded in a gear shape. Accordingly, excellent thermal insulation performance and durability can be realized because the dimensional change rate of the insulator is not large and the interfacial adhesive force is maintained under repeated heating/cooling conditions in which expansion/contraction occurs in a random direction.

The overall closed cell size of the polyester-based foam layer may be 100 to 700 μm, specifically 100 to 600 μm, 100 to 500 μm, 100 to 400 μm, or 350 to 500 μm, and more specifically, the foam layer The closed cell size of may be 200 to 350 μm or 350 to 500 μm. In addition, the closed cell size of the foam layer may be 200 to 700 μm, 300 to 700 μm, or 400 to 700 μm, and more specifically, 150 to 700 μm, 250 to 700 μm, 350 to 700 μm, or 450 to 700 μm. However, the present invention is not limited thereto.

The resin used to prepare the polyester-based foam layer may be at least one selected from the group consisting of aromatic and aliphatic polyester resins synthesized from a dicarboxylic acid component, a glycol component, or a hydroxycarboxylic acid. The polyester resin may be, for example, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly lactic acid (PLA), polyglycolic acid (PGA) At least one selected from the group consisting of polyethylene adipate (PEA), polyhydroxyalkanoate (PHA), polytrimethylene terephthalate (PTT), and polyethylene naphthalate (PEN). can Specifically, the polyester resin according to the present invention may be polyethylene terephthalate or polybutylene terephthalate, preferably polyethylene terephthalate, and the polyester foam layer of the present invention is preferably a polyethylene terephthalate (PET) foam layer. do.

In the method for producing the polyester-based foam layer of the present invention, the polyester-based resin may be melted, extruded and foamed, and the inner and outer surfaces of the discharged cylindrical foam may be cooled naturally at room temperature or cooled using a cooling member. there is. At this time, as the cooling process proceeds on the outer and inner surfaces of the foam, the foaming ratio is lowered, and the density and strength are increased. Conversely, in the center of the foam, the expansion ratio increases, and the density and strength decrease. In the present invention, after the polyester foam is extruded and foamed, immediately or after cooling under specific conditions, the entire or partial area of the surface is preheated to a specific temperature using a PE foam sheet wrapped around the outer surface of the foam and thermally bonded. The size of closed cells on the outer surface of the ester-based foam can be selectively controlled. In general, since the cell size in the thickness direction of the foam layer has a gradient sequentially or continuously without an inverted section, the closed cell structure of the inner surface and the center of the polyester foam can also be changed by the size of the outer surface closed cells. .

The polyester-based foam layer may have a thickness of 0.5T to 8T, specifically 0.5T to 7T, 0.5T to 6T, 0.5T to 5T, or 1.5T to 3T.

The polyolefin-based or rubber-based foam layer of the present invention includes a joint in the circumferential direction of the hollow, for example, by using a plate-type foam sheet preheated to a specific temperature while wrapping the outer surface of the polyester-based foam layer for thermal bonding (heat bonding) Adhesion) may proceed between interfaces to be bonded, and at the same time, adhesion between edges of the polyolefin-based foam layer may proceed. In this case, a foam layer made in the form of a sheet may be used as the polyolefin-based or rubber-based foam layer. Thus, it is not necessary to use the double annular nozzle, the fixing (adhesion) process can be simplified, and mass production of the hollow insulator can be possible. On the other hand, the polyolefin-based or rubber-based foam layer having a relatively low melting point (changes in shape at around 80° C.) can be maintained at a relatively low temperature (below 60° C.) by the polyester-based foam layer located inside the hollow.

The resin for preparing the polyolefin-based foam layer may be a polyolefin having 2 to 10 carbon atoms, preferably polyethylene, polypropylene or polybutyrene, and more preferably polyethylene or polypropylene. The polyolefin may be a homo polyolefin or a random polyolefin, and in the random polypropylene, for example, ethylene or propylene may be used as the main olefin, and olefins having 2 to 10 carbon atoms excluding the main olefin may be used as the auxiliary olefin. The resin used to prepare the polyolefin-based foam layer of the present invention may be applied with a known technique in which density, melting point, melt tension, melt index, etc. are adjusted as necessary.

The resin for preparing the rubber-based foam layer may be at least one selected from the group consisting of ethylene-propylene-diene copolymer (EPDM), isoprene rubber, silicone rubber (Silicon), nitrile rubber (NBR), and styrene rubber (SBR), and , Melting point, melt tension, melt index, etc. may be adjusted according to known techniques.

The polyolefin-based foam layer or the rubber-based foam layer may have a thickness of 1T to 50T, specifically 1T to 40T, 5T to 40T, 5T to 30T, or 5T to 20T.

The polyolefin-based foam layer or the rubber-based foam layer may include an additive, and the additive may be at least one selected from the group consisting of an antioxidant, a lubricant, a flame retardant, sulfur, a vulcanization accelerator, and a foaming agent. Materials used in the same technical field may be used as the antioxidant, lubricant, flame retardant, sulfur, vulcanization accelerator, and foaming agent, but the present invention is not limited thereto.

Meanwhile, the flame retardant may include a bromine compound, a phosphorus or phosphorus compound, and an antimony compound, but the present invention is not limited thereto. The bromine compound may include, for example, tetrabromo bisphenol A and decabromodiphenyl ether, and the phosphorus or phosphorus compound may include aromatic phosphate esters, aromatic condensed phosphate esters, halogenated phosphate esters, and the like, and antimony The compound may include antimony trioxide and antimony pentoxide, and the like.

The additives are 0.1 to 2% by weight of an antioxidant, 5 to 15% by weight of a lubricant, 0.5 to 15% by weight of a flame retardant, 0.01 to 1% by weight of sulfur, and 0.1% by weight of a vulcanization accelerator, based on the total weight of the solid content of the polyolefin-based foam layer or the rubber-based foam layer. to 5% by weight and 5 to 15% by weight of a foaming agent, but the present invention is not limited thereto.

Each of the polyolefin-based foam layer or the rubber-based foam layer may include an inner layer and an outer layer having the same thickness based on the center of the polyolefin-based or rubber-based foam layer in the thickness direction of the hollow insulator. At this time, the inner layer is a region close to the polyester-based foam layer, and the outer layer is a region far away. The inner layer of the polyolefin-based foam layer and the rubber-based foam layer may include a lower content (wt%) of the flame retardant than the outer layer. Specifically, the ratio (F ₂ /F 1 ) of the flame retardant content (F 2 , wt%) to the total weight of the solid content of the outer layer compared to the content of the flame retardant (F ₁ , _wt %) based on the total weight of the solid content of the inner layer _is 2 to 10, 2 to 7, preferably 2 to 4. In the present invention, additives such as flame retardants are added in the polyester foam layer to increase uniformity by finely controlling the closed cell structure and dimensional change of the polyester foam layer. Accordingly, when the polyester-based foam layer and the polyolefin-based (rubber-based) foam layer are thermally bonded, mixing of the flame retardant included in the polyolefin-based foam layer at the interface can be prevented. It is obvious that the above-described effects can be improved within the range, and the content ratio of the inner layer and the outer layer can be adjusted with other additives in addition to the flame retardant to achieve the same purpose.

The hollow insulator may further include a finishing material layer, and the finishing material layer may have various colors and may indicate a purpose and type of a pipe in which the insulating material is used. The finishing material layer may have a color determined according to the purpose and rules, for example, a water supply pipe (blue), a hot water supply pipe (white), a hot water pipe (yellow), a heating pipe (light red), a fire extinguishing water pipe (red), It can have a color designated as a sewage pipe or drain pipe (grey).

The finishing material layer is prepared from a coloring composition such as an inorganic pigment, an organic pigment, carbon black, a white pigment, or an aluminum pigment, and may preferably be a colored layer. The coloring composition may be a known material generally used in the related art, and examples thereof include organic pigments such as polycyclic organic compounds, azo compounds, and metal complexes; Or barium sulfate, calcium carbonate, clay, bone stone powder (Talc), silica powder (SiO ₂ ), diatomaceous earth, bentonite, titanium oxide, zinc emulsified, lead white, lithopone, iron oxide, Prussian blue, ultramarine blue, chrome rust, cobalt phosphate, aluminum It may be an inorganic pigment such as powder.

The finishing material layer may be located on the outermost surface of the hollow insulator, preferably located on the surface of the polyolefin-based foam layer and/or the rubber-based foam layer, and may be formed by a coating method known in the art. can The coating method includes, for example, a dipping method, a deep coating method, a spray coating method, a spin coating method, a roll coating method, and a die coating method. ) method, a roll court method, a gravure printing method, or a bar court, but the present invention is not limited thereto.

The hollow insulator may be used as an insulator for a vehicle air conditioning system, a water supply pipe, a hot water supply pipe, a hot water pipe, a heating pipe, a fire extinguishing water pipe, a sewage pipe and/or a drain pipe, but the present invention is not limited thereto.

Preferred examples and comparative examples of the present invention are described below. However, the following example is only a preferred embodiment of the present invention, but the present invention is not limited to the following example.

Example

(Example 1)

Water-removed PET resin, PMDA, talc, and Irganox (BASF Co.) were mixed at 100:1.1:1.1:0.1 parts by weight, put into the first extruder, and heated at 300°C. The prepared resin melt and a butane gas foaming agent were mixed and injected into a general die having an annular nozzle, and then extruded and foamed into a hollow PET foam.

At the same time, a PE foam sheet (Asan CS Co., Ltd.) preheated to 80 ° C. was thermally laminated on the surface of the hollow PET foam layer prepared, thereby manufacturing a hollow insulation material. At this time, the surface of the hollow PET foam layer was wrapped with a sheet-type PE foam sheet preheated to a specific temperature (80 ° C) and thermally bonded to the outer surface of the PET foam layer. .

The manufactured hollow insulation had a diameter of 54 mm, a length of 1 m, a thickness of 10 t (mm), and a thickness ratio (PET foam layer: PE foam layer = 5 t: 5 t).

evaluation example

[Evaluation Example 1]: Evaluation of interfacial adhesion between PET foam layer and PE foam layer and durability of PET foam layer

(Comparative Example 1)

A hollow insulator was manufactured by thermally laminating a PE foam sheet in the same manner as in Example 1, except that a hollow PET foam layer was manufactured by thermally bonding a plate-shaped PET foam sheet (Huvis Co., Ltd.).

(Assessment Methods)

A pipe-shaped heating member was installed inside the hollow of the hollow insulator of Example 1 and Comparative Example 1, and the inner circumferential surface of the hollow was heated to 100 ° C. and naturally cooled to room temperature. A total of 500 cycles were performed.

* Evaluation of interfacial adhesion

The hollow insulator subjected to 500 cycles was cut in the longitudinal direction (the direction in which the resin is extruded and foamed = the height direction of the cylinder) to obtain a foam sheet. The interfacial adhesive force (peel strength, kgf/cm) between the PET foam layer and the PE foam layer of the foam sheet was measured. When the interfacial adhesion of Example 1 was designated as 100%, the relative interfacial adhesion of Comparative Example 1 is shown in Table 1 below.

* Heat resistance evaluation

The heat resistance of the hollow insulator subjected to 500 cycles was measured. The volume (V ₀ , mm ³ ) and the volume after 500 cycles (V ₅₀₀ , mm ³ ) of the hollow insulator were measured, and the dimensional change rate ([V ₀ -V ₅₀₀ ]/V ₀ , %) was calculated. It is shown in Table 1 below.

In addition, the hollow insulator before/after 500 cycles was cut in the thickness direction to obtain a hollow cross section. The uniformity of closed cells inside the PET foam layer was analyzed.

* Insulation performance evaluation

The hollow inner circumferential surface of the hollow insulator that has undergone 500 cycles is heated to 100°C, and the temperature at any point inside and outside of the hollow insulator is measured 30 minutes after sealing the top and bottom of the cylinder. measured. The difference between inside/outside temperature is shown in Table 1 below.

Interfacial Adhesion (%) Dimensional change rate (%) Inside/outside temperature difference (℃) Example 1 100 1.5 51 Comparative Example 1 85 5.3 21

Referring to Table 1, it was confirmed that the hollow insulator (Example 1) of the present invention showed stable performance despite frequent internal temperature changes caused by a vehicle air conditioning system (air conditioner, etc.) located on the inner circumferential surface of the hollow. In particular, as a result of visually checking the inside of the cross section of the PET foam layer in direct contact with the heating member, it was confirmed that a uniform cross section in the thickness direction was maintained even after 500 cycles.

On the other hand, in the hollow insulator of Comparative Example 1, it was confirmed that the interfacial adhesion between the PET foam layer and the PE foam layer was deteriorated, and the dimensional change rate and insulation performance were not sufficient under harsh conditions. Inside the cross section of the insulator, the closed cells were collapsed, especially in the thermal bonding area of the PET foam sheet, suggesting that the shape deformation from the welding area is accelerated during repeated heating.

[Evaluation Example 2]: Closed cell size evaluation in PET foam layer

(Example 2-1, 2-2 and 2-3)

A hollow insulator was prepared in the same manner as in Example 1, except for using a PE foam sheet preheated to 60 ° C, 90 ° C, and 100 ° C, respectively.

(Assessment Methods)

* Measurement of whether closed cells are formed on the cross section of the PET foam layer and the size of closed cells

The hollow insulators prepared in Example 1, Comparative Example 1, and Examples 2-1 to 2-3 were cut in the thickness direction and cross-sectional SEM images of the PET foam layer were measured.

In the cross-sectional SEM images of the PET foam layer of Example 1 and Comparative Example 1, 10 points were designated at regular intervals in the circumferential direction with respect to the center of the PET foam layer in the hollow thickness direction (3mm * 3mm), and each point The average of the sizes of 10 closed cells was calculated (A ₁ to A ₁₀ ). The average closed cell size of 10 points was calculated (A _avg ) and the satisfaction of relational expression 1 (|(AA _avg )/A _avg | < 3%) was evaluated and shown in Table 2.

In the cross-sectional SEM images of the PET foam layers of Example 1 and Examples 2-1 to 2-3, inside the PET foam layer in the hollow thickness direction, the size of closed cells in the center (B _C ), the size of closed cells on the outer surface (B _OS ) and inner surface closed cell size (B _IS ) are measured to evaluate whether relational expression 2 (30% < B _OS / _BC < 50%) and relational expression 3 (10% < B _IS / _BC < 30%) are satisfied and shown in Table 2.

* Evaluation of interfacial adhesion

It proceeded in the same way as the evaluation method of Evaluation Example 1, and the results are shown in Table 2 below.

Satisfaction of relational expression 1 Satisfaction of relational expression 2 Satisfaction of relational expression 3 Interfacial adhesion (%) Example 1 O O O 100 Comparative Example 1 X - - 85 Example 2-1 O X X 91 Example 2-2 O O O 98 Example 2-3 O X X 93

Referring to Table 2, in the case of Comparative Example 1, the PET foam layer has a welding portion in the circumferential direction of the hollow circumference therein, and the size of the closed cell in that area is relatively small, so relational expression 1 is not satisfied. . This suggests that the interfacial adhesion between the PET foam layer and the PE foam layer deteriorates around the thermal junction area in a repetitive heat input/output environment, and the dimensional change rate and thermal insulation performance will not be sufficient under harsh conditions.

The preheating temperature increases during thermal bonding of the PE foam layer in the order of Example 2-1, Example 1, Example 2-2 and Example 2-3 of the hollow insulators. It was confirmed that the most preferred preheating temperature was 60 to 70 ° C. When the outer surface of the PET foam layer is covered with a PE foam layer preheated to the corresponding temperature, the closed cell size of the outer surface of the PET foam layer is reduced to the range of relational expression 2 by thermal bonding with the PE foam layer before it is sufficiently cooled after PET extrusion foaming. could be controlled However, referring to Examples 2-1 and 2-3, if the closed cell size of the outer surface of the PET foam layer is excessively reduced, the outer surface area is implemented with high density and high strength, resulting in interfacial separation from the PE foam layer, and vice versa. It is analyzed that, as the specific surface area of the outer surface of the PET foam layer decreases, the contact area decreases, resulting in a decrease in interfacial adhesive force.

[Evaluation Example 3]: Evaluation of interfacial adhesion and flame retardancy of hollow insulators

(Example 3-1)

A cooling member was installed on the inner circumferential surface of the hollow PET foam extruded and expanded in Example 1, and cooled at a temperature of 5° C. for 20 seconds. At the same time, after installing a cooling member capable of setting the temperature in the longitudinal direction on the outer circumferential surface of the PET foam, area a in FIG. 3 was set to room temperature and area b was set to 10 ° C.

A hollow insulator was manufactured in the same manner as in Example 1, except that a PE foam sheet preheated to 80° C. was thermally laminated on the surface of the cooled PET foam.

(Example 3-2)

A hollow insulator was prepared in the same manner as in Example 1, except that a PE foam sheet containing 1% by weight of a flame retardant (tetrabromo bisphenol A) was used.

(Example 3-3)

A hollow insulator was manufactured in the same manner as in Example 1, except that the first PE foam sheet containing 0.5% by weight of the flame retardant and the second PE foam sheet containing 1.5% by weight of the flame retardant were sequentially thermally bonded.

On the other hand, the manufactured hollow insulator had a diameter of 54 mm, a length of 1 m, a thickness of 10 t (mm), and a thickness ratio (PET foam layer: 2nd PE foam layer: 2 PE foam layer = 5t: 2.5t: 2.5t).

(Assessment Methods)

Evaluation of interfacial adhesion was performed in the same manner as in Evaluation Example 1, and the results are shown in Table 3 below.

The flame retardancy was evaluated by cutting the hollow insulator in the longitudinal direction to prepare a foam sheet, and then evaluating the limiting oxygen index (LOI). When the LOI (35) of Example 3-2 is designated as 100%, the relative flame retardancy of Example 4-2 is shown in Table 3 below.

Flame retardant content in PE foam layer (% by weight) Interfacial Adhesion (%) Flame retardancy (%) Example 1 0 100 - Example 3-1 0 95 - Example 3-2 One 91 100 Example 3-3 1 (inner layer 0.5% by weight / outer layer 1.5% by weight) 96 91

Referring to Table 3, the evaluation results of Example 3-1 show that the insulation performance of the hollow insulator can be further improved by forming a closed-cell size pattern on the outer circumferential surface, and at the same time, the interfacial adhesive strength is maintained at a similar level to that of Example 1. suggests that it can be

From the results of Examples 3-2 and 3-3, it was confirmed that interfacial adhesion was slightly deteriorated when the flame retardant was included in the PE foam layer. It is analyzed that when the PE foam layer is thermally bonded to the outer circumferential surface of the PET foam layer, PET and PE are partially melted and mixed at the interface. The evaluation results of Example 3-3 suggest that the interfacial adhesion can be improved while maintaining the same total amount of flame retardant (1% by weight) by reducing the content of the flame retardant at the interface between the PET foam layer and the inner layer of the PE foam layer. From this, it was confirmed that the flame retardancy and interfacial adhesion of the insulation material could be adjusted within an optimized range.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments and can be manufactured in various different forms, and those skilled in the art to which the present invention belongs can understand the technical spirit of the present invention. However, it will be understood that it may be embodied in other specific forms without changing its essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting.

1: hollow insulation
3: polyester foam layer
5: polyolefin-based or rubber-based foam layer

Claims (5)

Based on the thickness direction of the hollow insulator, a polyester-based foam layer from the inside to the surface of the hollow insulator; And a polyolefin-based or rubber-based foam layer; sequentially including,
The polyester-based foam layer does not include a junction in the circumferential direction of the hollow insulator,
The polyolefin-based or rubber-based foam layer includes a joint in the circumferential direction of the hollow insulator,
The polyester-based foam layer contains 95% (v / v) or more of closed cells (DIN ISO4590) and satisfies the following relational expression 1:
[Relationship 1]
|(AA _avg )/A _avg | < 10%
The relational expression 1 represents the size deviation of the closed cells in the foam layer in the circumferential direction of the hollow of the polyester foam layer as a formula, and A _avg is the average size of the closed cells inside the foam layer located at the same thickness in the polyester foam layer , and A is the size of an arbitrary closed cell inside the foam layer located at the same thickness in the polyester foam layer. delete According to claim 1,
The polyester-based foam layer further satisfies the following relations 2 and 3:
[Relationship 2] 30% < B _OS /B _C < 50%
[Relationship 3] 10% < B _IS /B _C < 30%
The relational expressions 2 and 3 above represent the size ratio of the closed cells in the foam layer in the thickness direction of the hollows of the polyester foam layer by formulas, B _c is the average size of the closed cells in the center based on the thickness direction of the hollows, and B _OS is It is the average size of closed cells on the outer surface based on the hollow thickness direction, and B _IS is the average size of closed cells on the inner surface based on the hollow thickness direction. According to claim 3,
The outer surface (B _OS ) of the polyester-based foam layer includes area a and area b crossing each other in a direction from one side of the polyester-based foam layer to the other side based on the longitudinal direction of the hollow-type insulator, and the area a is a hollow insulator having an average size of closed cells higher than that of the b region. According to claim 1,
The polyolefin-based and rubber-based foam layers each include an inner layer and an outer layer based on the center of the polyolefin-based and rubber-based foam layer based on the thickness direction of the hollow insulator,
The hollow insulator, characterized in that the flame retardant content (% by weight) of the inner layer is lower than that of the outer layer.

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