JP2022149655A - Heat storage resin composition, sheet, and molding - Google Patents

Abstract

To provide a heat storage resin composition which has an excellent balance among strength in a use temperature area, heat storage performance in phase transition and moldability, and a sheet and a molding obtained by molding the heat storage resin composition.SOLUTION: A heat storage resin composition contains a paraffin compound (A) and a styrene-ethylene/propylene-styrene copolymer (B), where the heat storage resin composition has a value of a tensile elastic modulus at 25°C measured according to JIS K 7244-4 of 10 MPa or more.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a heat storage resin composition, a sheet, and a molded article.

Heat storage is a mechanism that stores heat in a substance and extracts the heat as needed. This mechanism has the advantage of being able to use energy efficiently, so it is applied to a wide range of fields such as air conditioning equipment, building materials, heat insulating containers, cold insulators, and concrete.

Examples of heat storage methods include latent heat storage using phase transition heat, sensible heat storage using specific heat, and chemical heat storage using heat absorption and heat generation during chemical reactions. Among them, the method using latent heat storage is excellent in heat storage density (efficiency), durability, cost, safety, and workability, and thus its range of use has been expanded in recent years.

Examples of latent heat storage materials include paraffin, water (ice), inorganic hydrates, and the like. Among them, paraffin has a phase transition temperature that can be set to a wide range of living environment temperatures, is non-corrosive, has a low odor, and does not deteriorate in characteristics even if the phase change is reversed (long life). Used a lot. Paraffin is a general term for aliphatic saturated hydrocarbons (alkanes), and since the melting point varies depending on the number of carbon atoms in the main chain, selecting the most suitable type of paraffin will allow the phase transition temperature to be adjusted according to the purpose of use. can be set.

Paraffin has a low viscosity in the molten state and can leak when used as part of a structure. Furthermore, since paraffin is a flammable and dangerous substance in a liquid state, it is necessary to take measures to prevent leakage when paraffin is melted.

Methods to prevent paraffin from leaking out include methods of encapsulating paraffin in microcapsules, methods of polymerizing by introducing paraffin into polymer side chains, and methods of using thermoplastic elastomers, in addition to the method of storing paraffin in a container or bag. A method of immobilizing (gelating) paraffin as a support material is known. Among them, the method of using a thermoplastic elastomer as a support material can produce a heat storage material without requiring a special device, and the heat storage capacity and strength of the heat storage material can be set widely according to the purpose by selecting the paraffin content and elastomer. becomes possible.

Thermoplastic elastomers include olefin-based elastomers, styrene-based elastomers, vinyl chloride-based elastomers, ester-based elastomers, amide-based elastomers, and urethane-based elastomers. From the viewpoint of cost and the like, many studies have been made especially on styrenic elastomers.

Styrenic elastomers have styrene blocks as hard segments, and the styrene blocks fix paraffin that has entered the soft segments, so they exhibit higher shape retention than other thermoplastic elastomers. Moreover, since it is a non-condensed polymer compound that does not have an amide bond, an ester bond, a urethane bond, a carbonate bond, or the like, it maintains stable performance even after repeated phase transitions.

As the styrene-based elastomer, a triblock copolymer having styrene blocks on both ends of the polymer chain is widely used from the viewpoint of shape retention. Specifically, styrene-butadiene-styrene copolymer Polymer (SBS), Styrene-isoprene-styrene copolymer (SIS), Styrene-isobutylene-styrene copolymer (SIBS), Styrene-butadiene/butylene-styrene copolymer (SBBS), Styrene-ethylene/butylene- Styrene copolymer (SEBS), styrene-ethylene/propylene-styrene copolymer (SEPS), styrene-ethylene/ethylene/propylene-styrene (SEEPS) copolymer. In addition to the structure having styrene blocks at both ends of the polymer chain, styrene-butadiene copolymer (SB), styrene-isoprene copolymer (SI), styrene-isobutylene copolymer (SIB), Examples include styrene-ethylene/propylene copolymer (SEP) and styrene-ethylene/butylene copolymer (SEB).

In Patent Documents 1 and 2, among styrene-based elastomers, SEBS is a triblock type copolymer having styrene blocks on both terminal sides of the polymer chain, and the conjugated diene of the soft segment of SBS is completely hydrogenated. , discloses that paraffin can be gelled only by adding about 10% by mass of SEBS due to its high shape retention and high affinity between the soft segment and paraffin.

On the other hand, in order to secure the strength of the heat storage material as a building material, it is necessary to set the strength of the heat storage material (for example, the tensile modulus value) to a predetermined value or more.

JP 2017-25184 A JP 2019-89959 A

However, when the SEBS content is about 10% by mass (the paraffin content is about 90% by mass), the heat storage material using SEBS as a supporting material exhibits heat storage performance according to the paraffin content, but the strength of the heat storage material is reduced. For example, if the SEBS content is set to 50% by mass or more in order to ensure the above, there is a problem that the heat storage performance is lower than the value predicted from the paraffin content.
As described above, with the conventional technology, it is difficult to improve the heat storage performance when the strength of the heat storage material is ensured. Met.

The present invention solves the above-mentioned conventional problems, and provides a heat storage resin composition having an excellent balance of strength in the operating temperature range, heat storage performance at the time of phase transition, and moldability, and the heat storage resin composition. It is an object to provide a sheet and a molded body obtained by molding the.

As a result of intensive studies by the present inventors, in a heat storage resin composition comprising paraffin and a styrene-based elastomer, by using a styrene-ethylene/propylene-styrene copolymer as the styrene-based elastomer, The inventors have found that a heat storage resin composition which is excellent in strength and heat storage performance at the time of phase transition and can be easily molded can be obtained, and have completed the present invention described below.

A first aspect of the present invention is a heat storage resin composition containing a paraffin compound (A) and a styrene-ethylene/propylene-styrene copolymer (B), according to JIS K 7244-4 for the heat storage resin composition. A heat storage resin composition having a measured tensile modulus at 25° C. of 10 MPa or more.

In the first invention, the styrene content in the styrene-ethylene/propylene-styrene copolymer (B) is preferably 20% by mass or more and less than 70% by mass.

In the first invention, it is preferable that the content of the styrene-ethylene/propylene-styrene copolymer (B) in the heat storage resin composition is 51% by mass or more and 90% by mass or less.

In the first aspect of the invention, the paraffin compound (A) is preferably a linear saturated hydrocarbon having 14 or more and 24 or less carbon atoms.

The second invention is a sheet formed by molding the heat storage resin composition of the first invention.

The third aspect of the present invention is a molded article obtained by injection molding the thermoplastic resin composition of the first aspect of the present invention.

The heat storage resin composition of the present invention can maintain the latent heat amount at the time of paraffin phase transition, maintain sufficient strength in the operating temperature range, and exhibit moldability.

4 is a graph showing the viscoelastic behavior of the heat storage resin compositions of Examples 1-4.

BEST MODE FOR CARRYING OUT THE INVENTION The resin composition and molded article of the present invention will be described below as an example of embodiments of the present invention. However, the scope of the present invention is not limited to the embodiments described below.

In this specification, the term "main component" indicates that the component accounts for the largest amount by mass when the total of the constituent components is 100% by mass, and is preferably 50% by mass or more, and 60% by mass. The above is more preferable, and 70% by mass or more is even more preferable.
When described as "X to Y" (X and Y are arbitrary numbers), unless otherwise specified, "X or more and Y or less" and "preferably larger than X" and "preferably smaller than Y" It contains meaning.
The upper and lower limits of the numerical range in this specification are equivalent to the present invention as long as they have the same effects as within the numerical range, even if they are slightly outside the numerical range specified by the present invention. shall be included in the scope.

In addition, in this specification, the term "sheet" has the meaning of including a thick sheet to a thin film.

<Heat storage resin composition>
The heat storage resin composition of the present invention is a heat storage resin composition containing a paraffin compound (A) and a styrene-ethylene/propylene-styrene copolymer (B).

(Paraffin compound (A))
The paraffin compound (A) used in the present invention includes saturated aliphatic hydrocarbons (alkanes). The paraffin compound (A) is not particularly limited as long as it is an aliphatic saturated hydrocarbon (alkane), but from the viewpoint of safety and use temperature, it is preferably liquid or solid at room temperature. Among them, by using a saturated hydrocarbon having a main chain of 10 to 30 carbon atoms, particularly a linear saturated hydrocarbon, the phase transition temperature can be arbitrarily selected in the practical temperature range, and it can be suitably used in a wide range of applications.

Specific examples of linear saturated hydrocarbons (number of carbon atoms/melting point) include decane (10/−30° C.), undecane (11/−26° C.), dodecane (12/−12° C.), tridecane ( 13/-5°C), tetradecane (14/6°C), pentadecane (15/10°C), hexadecane (16/18°C), heptadecane (17/21°C), octadecane (18/28) ° C), nonadecane (19/32°C), icosane (20/37°C), henicosane (21/41°C), docosane (22/44°C), tricosane (23/47°C), tetracosane ( 24/51°C), pentacosane (25/53°C), hexacosane (26/57°C), heptacosane (27/58°C), octacosane (28/62°C), nonacosane (29/64°C) ), triacontane (30/66° C.), and the like.

Among these, it is preferable to use a straight-chain saturated hydrocarbon having a phase transition temperature near normal temperature. Specifically, the paraffin compound (A) is a straight-chain saturated hydrocarbon having 14 or more and 24 or less carbon atoms. is preferred, and 16 or more and 20 or less linear saturated hydrocarbons are more preferred.

In the present invention, the above paraffin compound (A) may be used alone or in combination of two or more. Also, a branched saturated hydrocarbon having a branched chain may be used instead of the linear saturated hydrocarbon.

The latent heat (ΔHm) at the phase transition of the paraffin compound (A) is preferably 120 J/g or more, more preferably 140 J/g or more, and even more preferably 160 J/g or more. If the latent heat of the paraffin compound (A) is at least the above lower limit, it can exhibit excellent heat storage performance as a heat storage resin composition after being blended with the styrene-ethylene/propylene-styrene copolymer (B).

The proportion of the paraffin compound (A) in the heat storage resin composition of the present invention is preferably 10 to 49% by mass, preferably 15 to 45% by mass, based on the total heat storage resin composition (100% by mass). It is more preferable to have If the ratio of the paraffin compound (A) is within such a range, the latent heat performance of the heat storage material can be improved, and strength in the operating temperature range can be imparted.

(Styrene-ethylene/propylene-styrene copolymer (B))
Styrene-ethylene/propylene-styrene copolymer (B) (hereinafter sometimes referred to as "SEPS (B)") is a block copolymer having hard segments made of polystyrene at both ends of the polymer chain. be.
The soft segment of SEPS (B) is poly(ethylene/propylene), which is formed by, for example, hydrogenating after polymerizing isoprene.

The styrene content of SEPS (B) is preferably 20% by mass or more and less than 70% by mass, and more preferably 25% by mass or more and 68% by mass or less. By setting the styrene content to 20% by mass or more, the strength in the operating temperature range can be imparted to the heat storage resin composition. can improve the quality.

The number average molecular weight (Mn) of the styrene-ethylene/propylene-styrene copolymer (B) is preferably 50000 g/mol or more and 250000 g/mol or less, more preferably 60000 g/mol or more and 230000 g/mol or less. and more preferably 70000 g/mol or more and 200000 g/mol or less. When the number average molecular weight of the styrene-ethylene/propylene-styrene copolymer (B) is within the above range, the heat storage resin composition of the present invention maintains fluidity during processing and maintains strength in the operating temperature range. can be given.

The number average molecular weight (Mn) of the styrene-ethylene/propylene-styrene copolymer (B) is a value obtained by standard polystyrene conversion using GPC (gel permeation chromatography). Chloroform is used as a solvent for measurement, and HLC-8120 manufactured by Tosoh Corporation is used as a column.

The proportion of the styrene-ethylene/propylene-styrene copolymer (B) in the heat storage resin composition of the present invention is preferably 51 to 90% by mass based on the total heat storage resin composition (100% by mass). , and more preferably 55 to 85% by mass. If the ratio of the styrene-ethylene/propylene-styrene copolymer (B) is in such a range, the latent heat performance of the heat storage resin composition can be improved and strength in the operating temperature range can be imparted.

(Tensile modulus of heat storage resin composition)
The heat storage resin composition of the present invention has a tensile modulus of elasticity at 25° C. measured according to JIS K 7244-4 of 10 MPa or more, preferably 100 MPa or more. This makes it possible to impart strength in the operating temperature range to the heat storage resin composition.
The tensile modulus [Pa] of the heat storage resin composition is measured by the method described in the Examples section below.

(Composition of heat storage resin composition)
The heat storage resin composition of the present invention has the above composition and contains the paraffin compound (A) and the styrene-ethylene/propylene-styrene copolymer (B). Other ingredients can be included as long as they do not affect the effect.
Other components include, for example, lubricants, antistatic agents, antioxidants, antiblocking agents, gelling agents, thickeners, antibacterial/antifungal agents, stabilizers, dyes, flame retardants, pigments, inorganic fine particles, etc. may contain various additives. Furthermore, metal powder, metal fiber, metal oxide, carbon, carbon fiber, etc. may be contained in order to improve heat conductivity. When the heat storage resin composition of the present invention contains these other components, the content thereof, such as an antioxidant, is preferably 1% by mass or less with respect to 100% by mass of the heat storage resin composition. .

<Method for producing heat storage resin composition>
The heat storage resin composition of the present invention is prepared according to a conventional method using a conventional mixing/stirring machine such as a twin roll, an extruder, a twin-screw kneading extruder, a Banbury mixer, and a stirring mixer. , styrene-ethylene / propylene-styrene copolymer (B), and other components that are blended as necessary, are heated at a temperature higher than the softening point of SEPS (B), for example, around 200 ° C., Manufactured by mixing.

The latent heat amount at the phase transition of the paraffin-based heat storage composition of the present invention is preferably 20 J/g or more, more preferably 30 J/g or more. If the amount of latent heat at the time of phase transition of the heat storage resin composition is equal to or higher than the above lower limit, excellent heat storage performance as a heat storage material can be exhibited.
The amount of latent heat of the heat storage resin composition is measured as the amount of heat of crystal fusion (ΔHm) by the method described in the Examples section below.

It is preferable that the heat storage resin composition of the present invention sufficiently flow in the processing temperature range. This facilitates processing when used in various shapes as a heat storage material. Although the processing temperature range varies depending on the application, the processing temperature of the heat storage resin composition of the present invention is preferably 50° C. or higher and 180° C. or lower, more preferably 60° C. or higher and 170° C. or lower, and further preferably 70° C. or higher and 160° C. or lower. 80° C. or higher and 150° C. or lower are particularly preferred.

If the processing temperature of the heat storage resin composition is less than 50°C, the SEPS (B) will not be sufficiently softened and the fluidity will decrease. On the other hand, when the processing temperature exceeds 180° C., it exceeds the flash point of the paraffin compound (A), which poses a safety problem. If the processing temperature of the heat storage resin composition is within the above range, sufficient fluidity can be safely exhibited.

At this time, the viscosity [Pa·s] of the heat storage resin composition in the processing temperature range is preferably low. For example, at 120° C., it is preferably 50000 Pa·s or less, more preferably 40000 Pa·s or less, and more preferably 30000 Pa·s or less. If the viscosity [Pa·s] of the paraffin-based heat storage composition in the processing temperature range is equal to or less than the above upper limit, sufficient fluidity and good moldability can be obtained.

<Sheet, molding>
The sheet and molded article of the present invention are obtained by using the heat storage resin composition of the present invention, and are obtained by molding the heat storage resin composition of the present invention into a sheet or by injection molding into a desired shape. is.
Examples of these molding methods include a method in which each component is melted and kneaded during the production of the heat storage resin composition, and the resulting melt is extruded into a sheet or plate using an extruder. It can also be shaped into rods or pipes by an extruder and then cut into granules or pellets. Further, the obtained heat storage resin composition having a predetermined shape can be sandwiched between two metal plates, and can be formed into a sheet shape by applying a pressure of 1 to 10 MPa at the processing temperature described above. It can also be injection molded into an arbitrary shape using a metal mold or the like. Furthermore, in order to suppress bleeding out of paraffin, surface treatment such as lamination on the sheet surface layer or surface coating may be performed.

EXAMPLES The present invention will be specifically described below using Examples, but the present invention is not limited to these.

<Evaluation method>
The obtained heat storage resin composition was evaluated by the following methods.

(1) Strength in Operating Temperature Range Using a rheometer, the elastic modulus [Pa] of the heat storage resin composition was measured from −100° C. to 200° C. at a heating rate of 3° C./min during the heating process. When the elastic modulus [Pa] at 25°C was 100 MPa or more, it was evaluated as "⊚"; when it was 10 MPa or more and less than 100 MPa, it was evaluated as "◯";

(2) Heat storage performance Using a differential scanning calorimeter (DSC), the crystal melting heat amount (ΔHm) [J/g ] was measured. The ratio of ΔHm (heat storage efficiency) of the actual heat storage resin composition to the amount of heat of fusion (ΔHm) estimated from the amount of paraffin charged into the heat storage resin composition is 70% or more. It was set as "x".

<Materials used>
As the paraffin compound (A), SEPS (B), and styrene-based elastomers other than SEPS (B), the following were used.
(Paraffin compound (A))
(a)-1: PCM-18 (manufactured by Miki Riken Co., Ltd., octadecane, melting point = 28 ° C., ΔHm = 213 J / g)

(SEPS (B))
(b)-1: Septon 2104 (manufactured by Kuraray Co., Ltd., SEPS, styrene content (St) = 64% by mass)
(b)-2: Septon 2002 (manufactured by Kuraray Co., Ltd., SEPS, styrene content (St) = 30% by mass)
(Styrene-based elastomer)
(b)-3: Septon 8104 (manufactured by Kuraray Co., Ltd., SEBS, styrene content (St) = 61% by mass)
(b)-4: Tuftec H1051 (manufactured by Asahi Kasei Corporation, SEBS, styrene content (St) = 42% by mass)
(b)-5: SIBSTAR 104T (manufactured by Kaneka, SIBS, styrene content (St) = 34% by mass)

<Examples and Comparative Examples>
(Example 1)
Septon 2104 was supplied to a Plastograph mixer manufactured by Toyo Seiki Co., Ltd., and melted and kneaded for 2 minutes at a temperature of 200° C. and a rotation speed of 60 rpm. PCM-18 was supplied so as to obtain a heat storage resin composition by melting and kneading for 5 minutes at a temperature of 200° C. and a rotation speed of 60 rpm. It was sandwiched between two metal plates and press-molded under conditions of temperature = 120°C, pressure = 3 MPa, and molding time = 10 seconds to form a sheet of the heat storage resin composition with a thickness of 1.0 mm. The above evaluation was performed on the obtained heat storage resin composition. Table 1 shows the results. FIG. 1 shows the behavior of the elastic modulus with respect to temperature.

(Example 2)
A heat storage resin composition was obtained in the same manner as in Example 1 except that the mixing ratio of PCM-18 and Septon 2104 was changed to 30/70 (% by mass), and this was made into a sheet and subjected to the above evaluation. Table 1 shows the results. FIG. 1 shows the behavior of the elastic modulus with respect to temperature.

(Example 3)
A heat storage resin composition was obtained in the same manner as in Example 1, except that the mixing ratio of PCM-18 and Septon 2104 was changed to 20/80 (% by mass). Table 1 shows the results. FIG. 1 shows the behavior of the elastic modulus with respect to temperature.

(Example 4)
A heat storage resin composition was obtained in the same manner as in Example 2 except that Septon 2002 was used instead of Septon 2104, and this was formed into a sheet and subjected to the above evaluation. Table 1 shows the results. FIG. 1 shows the behavior of the elastic modulus with respect to temperature.

(Comparative example 1)
A heat storage resin composition was obtained in the same manner as in Example 1, except that the mixing ratio of PCM-18 and Septon 2104 was changed to 60/40 (% by mass). Table 1 shows the results.

(Comparative example 2)
A heat storage resin composition was obtained in the same manner as in Example 1 except that the mixing ratio of PCM-18 and Septon 2104 was changed to 5/95 (% by mass), and the composition was formed into a sheet and subjected to the above evaluation. Table 1 shows the results.

(Comparative Example 3)
A heat storage resin composition was obtained in the same manner as in Example 1 except that Septon 8104 was used instead of Septon 2104, and this was formed into a sheet and subjected to the above evaluation. Table 1 shows the results.

<Comparative Example 4>
A heat storage resin composition was obtained in the same manner as in Example 1, except that Tuftec H1051 was used instead of Septon 2104, and this was made into a sheet and subjected to the above evaluation. Table 1 shows the results.

<Comparative Example 5>
A heat storage resin composition was obtained in the same manner as in Example 1 except that SIBSTAR 104T was used instead of SEPTON 2104, and this was made into a sheet and subjected to the above evaluation. Table 1 shows the results.

From Table 1, the heat storage resin composition of the present invention, that is, the heat storage resin composition containing SEPS (B) and having a predetermined tensile elastic modulus, maintained a sufficient amount of latent heat during the paraffin phase transition. In addition, as shown in FIG. 1, the heat storage resin compositions of Examples 1 to 4 exhibit a decrease in elastic modulus as the temperature rises, exhibiting the behavior of a thermoplastic resin having moldability. As a result, it has become clear that the heat storage resin composition of the present invention is a heat storage resin composition having a high elastic modulus (excellent shape retention property) in the operating temperature range, heat storage performance, and moldability. .

On the other hand, in Comparative Example 1 in which the content of SEPS (B) is small and in Comparative Example 5 in which SIBS is used as the styrene-based elastomer, the elastic modulus is low and sufficient strength as a heat storage resin composition cannot be maintained. In Comparative Example 2, in which the content of SEPS (B) is high, and in Comparative Examples 3 and 4, in which SEBS is used as the styrene-based elastomer, the amount of latent heat relative to the charged amount of paraffin is low, and sufficient heat storage performance cannot be exhibited.

The heat storage resin composition of the present invention can maintain the latent heat amount at the time of paraffin phase transition and maintain sufficient strength in the operating temperature range, so it has strength as a material while imparting heat storage performance. It can be applied to a wide range of uses as a structural material. Examples include housing building materials, building air-conditioning materials, automotive materials, cold-insulating containers, cold-insulating agents, electronic equipment materials, and the like.

Claims (6)

A heat storage resin composition containing a paraffin compound (A) and a styrene-ethylene/propylene-styrene copolymer (B), wherein the tensile strength of the heat storage resin composition at 25°C measured according to JIS K 7244-4 A heat storage resin composition having a modulus of elasticity of 10 MPa or more. 2. The heat storage resin composition according to claim 1, wherein the styrene content in the styrene-ethylene/propylene-styrene copolymer (B) is 20% by mass or more and less than 70% by mass. 3. The heat storage resin composition according to claim 1, wherein the content of said styrene-ethylene/propylene-styrene copolymer (B) in said heat storage resin composition is 51% by mass or more and 90% by mass or less. The heat storage resin composition according to any one of claims 1 to 3, wherein the paraffin compound (A) is a linear saturated hydrocarbon having 14 or more and 24 or less carbon atoms. A sheet formed by molding the heat storage resin composition according to any one of claims 1 to 4. A molded article obtained by injection molding the thermoplastic resin composition according to any one of claims 1 to 4.

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